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Sample records for asymmetric allylic alkylation

  1. Pd and Mo Catalyzed Asymmetric Allylic Alkylation

    PubMed Central

    Trost, Barry M.

    2012-01-01

    The ability to control the alkylation of organic substrates becomes ever more powerful by using metal catalysts. Among the major benefits of metal catalysis is the possibility to perform such processes asymmetrically using only catalytic amounts of the chiral inducing agent which is a ligand to the metal of the catalyst. A unique aspect of asymmetric metal catalyzed processes is the fact that many mechanisms exist for stereoinduction. Furthermore, using the same catalyst system, many types of bonds including but not limited to C-C, C-N, C-O, C-S, C-P, and C-H can be formed asymmetrically. An overview of this process using palladium and molybdenum based metals being developed in my laboratories and how they influence strategy in synthesizing bioactive molecular targets is presented. PMID:22736934

  2. Asymmetric Allylic Alkylation of β-Ketoesters with Allylic Alcohols by a Nickel/Diphosphine Catalyst.

    PubMed

    Kita, Yusuke; Kavthe, Rahul D; Oda, Hiroaki; Mashima, Kazushi

    2016-01-18

    Asymmetric allylic alkylation of β-ketoesters with allylic alcohols catalyzed by [Ni(cod)2]/(S)-H8-BINAP was found to be a superior synthetic protocol for constructing quaternary chiral centers at the α-position of β-ketoesters. The reaction proceeded in high yield and with high enantioselectivity using various β-ketoesters and allylic alcohols, without any additional activators. The versatility of this methodology for accessing useful and enantioenriched products was demonstrated. PMID:26637131

  3. Total Synthesis of Enantiopure (+)-γ -Lycorane Using Highly Efficient Pd-Catalyzed Asymmetric Allylic Alkylation

    PubMed Central

    Chapsal, Bruno D.; Ojima, Iwao

    2008-01-01

    Highly efficient short total synthesis of γ -lycorane (>99% ee, 41% overall yield) was achieved by using the asymmetric allylic alkylation in the key step catalyzed by palladium complexes with novel chiral biphenol-based monodentate phosphoramidite ligands. PMID:16562900

  4. Catalyst-controlled switch of regioselectivity in the asymmetric allylic alkylation of oxazolones with MBHCs.

    PubMed

    Zhu, Gongming; Yang, Junxian; Bao, Guangjun; Zhang, Ming; Li, Jing; Li, Yiping; Sun, Wangsheng; Hong, Liang; Wang, Rui

    2016-06-14

    A catalyst-controlled switch of regioselectivity in asymmetric allylic alkylation of oxazolones with MBHCs was described. The SN2'-SN2' reaction catalysed by a quinine-derived base produced γ-selective secondary allylic oxazolone derivatives, whereas the addition-elimination reaction catalysed by an amino acid-derived bifunctional urea catalyst provided β-selective primary adducts. PMID:27250517

  5. Highly Enantioselective Formation of α-Allyl-α-Arylcyclopentanones via Pd-Catalysed Decarboxylative Asymmetric Allylic Alkylation.

    PubMed

    Akula, Ramulu; Doran, Robert; Guiry, Patrick J

    2016-07-11

    A highly enantioselective Pd-catalysed decarboxylative asymmetric allylic alkylation of cyclopentanone derived α-aryl-β-keto esters employing the (R,R)-ANDEN-phenyl Trost ligand has been developed. The product (S)-α-allyl-α-arylcyclopentanones were obtained in excellent yields and enantioselectivities (up to >99.9 % ee). This represents one of the most highly enantioselective formations of an all-carbon quaternary stereogenic center reported to date. This reaction was demonstrated on a 4.0 mmol scale without any deterioration of enantioselectivity and was exploited as the key enantioselective transformation in an asymmetric formal synthesis of the natural product (+)-tanikolide. PMID:27191198

  6. Expanding insight into asymmetric palladium-catalyzed allylic alkylation of N-heterocyclic molecules and cyclic ketones.

    PubMed

    Bennett, Nathan B; Duquette, Douglas C; Kim, Jimin; Liu, Wen-Bo; Marziale, Alexander N; Behenna, Douglas C; Virgil, Scott C; Stoltz, Brian M

    2013-04-01

    Eeny, meeny, miny ... enaminones! Lactams and imides have been shown to consistently provide enantioselectivities substantially higher than other substrate classes previously investigated in the palladium-catalyzed asymmetric decarboxylative allylic alkylation. Several new substrates have been designed to probe the contributions of electronic, steric, and stereoelectronic factors that distinguish the lactam/imide series as superior alkylation substrates (see scheme). These studies culminated in marked improvements on carbocyclic allylic alkylation substrates. PMID:23447555

  7. Asymmetric allylic alkylation of Morita–Baylis–Hillman carbonates with α-fluoro-β-keto esters

    PubMed Central

    Yan, Lin; Han, Zhiqiang; Zhu, Bo; Yang, Caiyun

    2013-01-01

    Summary In the presence of a commercially available Cinchona alkaloid as catalyst, the asymmetric allylic alkylation of Morita–Baylis–Hillman carbonates, with α-fluoro-β-keto esters as nucleophiles, have been successfully developed. A series of important fluorinated adducts, with chiral quaternary carbon centres containing a fluorine atom, was achieved in good yields (up to 93%), with good to excellent enantioselectivities (up to 96% ee) and moderate diastereoselectivities (up to 4:1 dr). PMID:24062852

  8. Non-stabilized nucleophiles in Cu-catalysed dynamic kinetic asymmetric allylic alkylation.

    PubMed

    You, Hengzhi; Rideau, Emeline; Sidera, Mireia; Fletcher, Stephen P

    2015-01-15

    The development of new reactions forming asymmetric carbon-carbon bonds has enabled chemists to synthesize a broad range of important carbon-containing molecules, including pharmaceutical agents, fragrances and polymers. Most strategies to obtain enantiomerically enriched molecules rely on either generating new stereogenic centres from prochiral substrates or resolving racemic mixtures of enantiomers. An alternative strategy--dynamic kinetic asymmetric transformation--involves the transformation of a racemic starting material into a single enantiomer product, with greater than 50 per cent maximum yield. The use of stabilized nucleophiles (pKa < 25, where Ka is the acid dissociation constant) in palladium-catalysed asymmetric allylic alkylation reactions has proved to be extremely versatile in these processes. Conversely, the use of non-stabilized nucleophiles in such reactions is difficult and remains a key challenge. Here we report a copper-catalysed dynamic kinetic asymmetric transformation using racemic substrates and alkyl nucleophiles. These nucleophiles have a pKa of ≥50, more than 25 orders of magnitude more basic than the nucleophiles that are typically used in such transformations. Organometallic reagents are generated in situ from alkenes by hydrometallation and give highly enantioenriched products under mild reaction conditions. The method is used to synthesize natural products that possess activity against tuberculosis and leprosy, and an inhibitor of para-aminobenzoate biosynthesis. Mechanistic studies indicate that the reaction proceeds through a rapidly isomerizing intermediate. We anticipate that this approach will be a valuable complement to existing asymmetric catalytic methods. PMID:25592541

  9. Non-stabilized nucleophiles in Cu-catalysed dynamic kinetic asymmetric allylic alkylation

    NASA Astrophysics Data System (ADS)

    You, Hengzhi; Rideau, Emeline; Sidera, Mireia; Fletcher, Stephen P.

    2015-01-01

    The development of new reactions forming asymmetric carbon-carbon bonds has enabled chemists to synthesize a broad range of important carbon-containing molecules, including pharmaceutical agents, fragrances and polymers. Most strategies to obtain enantiomerically enriched molecules rely on either generating new stereogenic centres from prochiral substrates or resolving racemic mixtures of enantiomers. An alternative strategy--dynamic kinetic asymmetric transformation--involves the transformation of a racemic starting material into a single enantiomer product, with greater than 50 per cent maximum yield. The use of stabilized nucleophiles (pKa < 25, where Ka is the acid dissociation constant) in palladium-catalysed asymmetric allylic alkylation reactions has proved to be extremely versatile in these processes. Conversely, the use of non-stabilized nucleophiles in such reactions is difficult and remains a key challenge. Here we report a copper-catalysed dynamic kinetic asymmetric transformation using racemic substrates and alkyl nucleophiles. These nucleophiles have a pKa of >=50, more than 25 orders of magnitude more basic than the nucleophiles that are typically used in such transformations. Organometallic reagents are generated in situ from alkenes by hydrometallation and give highly enantioenriched products under mild reaction conditions. The method is used to synthesize natural products that possess activity against tuberculosis and leprosy, and an inhibitor of para-aminobenzoate biosynthesis. Mechanistic studies indicate that the reaction proceeds through a rapidly isomerizing intermediate. We anticipate that this approach will be a valuable complement to existing asymmetric catalytic methods.

  10. Catalytic asymmetric carbon-carbon bond formation via allylic alkylations with organolithium compounds

    NASA Astrophysics Data System (ADS)

    Pérez, Manuel; Fañanás-Mastral, Martín; Bos, Pieter H.; Rudolph, Alena; Harutyunyan, Syuzanna R.; Feringa, Ben L.

    2011-05-01

    Carbon-carbon bond formation is the basis for the biogenesis of nature's essential molecules. Consequently, it lies at the heart of the chemical sciences. Chiral catalysts have been developed for asymmetric C-C bond formation to yield single enantiomers from several organometallic reagents. Remarkably, for extremely reactive organolithium compounds, which are among the most broadly used reagents in chemical synthesis, a general catalytic methodology for enantioselective C-C formation has proven elusive, until now. Here, we report a copper-based chiral catalytic system that allows carbon-carbon bond formation via allylic alkylation with alkyllithium reagents, with extremely high enantioselectivities and able to tolerate several functional groups. We have found that both the solvent used and the structure of the active chiral catalyst are the most critical factors in achieving successful asymmetric catalysis with alkyllithium reagents. The active form of the chiral catalyst has been identified through spectroscopic studies as a diphosphine copper monoalkyl species.

  11. Copper-catalysed asymmetric allylic alkylation of alkylzirconocenes to racemic 3,6-dihydro-2H-pyrans

    PubMed Central

    Rideau, Emeline

    2015-01-01

    Summary Asymmetric allylic alkylation is a powerful reaction that allows the enantioselective formation of C–C bonds. Here we describe the asymmetric alkylation of alkylzirconium species to racemic 3,6-dihydro-2H-pyrans. Two systems were examined: 3-chloro-3,6-dihydro-2H-pyran using linear optimization (45–93% ee, up to 33% yield, 5 examples) and 3,6-dihydro-2H-pyran-3-yl diethyl phosphate with the assistance of a design of experiments statistical approach (83% ee, 12% yield). 1H NMR spectroscopy was used to gain insight into the reaction mechanisms. PMID:26734091

  12. Enantioselective Synthesis of α-Secondary and α-Tertiary Piperazin-2-ones and Piperazines by Catalytic Asymmetric Allylic Alkylation

    PubMed Central

    Korch, Katerina M.; Eidamshaus, Christian; Behenna, Douglas C.; Nam, Sangkil; Horne, David

    2014-01-01

    The asymmetric Pd-catalyzed decarboxylative allylic alkylation of differentially N-protected piperazin-2-ones allows for the synthesis of a variety of highly enantioenriched tertiary piperazine-2-ones. Deprotection and reduction affords the corresponding tertiary piperazines, which can be employed for the synthesis of medicinally important analogs. The introduction of these chiral tertiary piperazines resulted in imatinib analogs that exhibited comparable antiproliferative activity to that of their corresponding imatinib counterparts. PMID:25382664

  13. Hydrogen-Bond Directed Regioselective Pd-Catalyzed Asymmetric Allylic Alkylation: The Construction of Chiral α-Amino Acids with Vicinal Tertiary and Quaternary Stereocenters.

    PubMed

    Wei, Xuan; Liu, Delong; An, Qianjin; Zhang, Wanbin

    2015-12-01

    A Pd-catalyzed asymmetric allylic alkylation of azlactones with 4-arylvinyl-1,3-dioxolan-2-ones was developed, providing "branched" chiral α-amino acids with vicinal tertiary and quaternary stereocenters, in high yields and with excellent selectivities. Mechanistic studies revealed that the formation of a hydrogen bond between the Pd-allylic complex and azlactone isomer is responsible for the excellent regioselectivities. This asymmetric alkylation can be carried out on a gram scale without a loss of catalytic efficiency, and the resulting product can be further transformed to a chiral azetidine in two simple steps. PMID:26575242

  14. Chiral N-1-adamantyl-N-trans-cinnamylaniline type ligands: synthesis and application to palladium-catalyzed asymmetric allylic alkylation of indoles.

    PubMed

    Mino, Takashi; Nishikawa, Kenji; Asano, Moeko; Shima, Yamato; Ebisawa, Toshibumi; Yoshida, Yasushi; Sakamoto, Masami

    2016-08-21

    Such chiral phosphine-internal olefin hybrid type ligands as N-1-adamantyl-N-cinnamylaniline derivatives 1 with C(aryl)-N(amine) bond axial chirality were synthesized and utilized for the palladium-catalyzed asymmetric allylic alkylation of indoles to afford the desired products in high enantioselectivities (up to 98% ee). PMID:27425209

  15. Spiro-fused carbohydrate oxazoline ligands: Synthesis and application as enantio-discrimination agents in asymmetric allylic alkylation

    PubMed Central

    Kraft, Jochen; Golkowski, Martin

    2016-01-01

    Summary In the present work, we describe a convenient synthesis of spiro-fused D-fructo- and D-psico-configurated oxazoline ligands and their application in asymmetric catalysis. The ligands were synthesized from readily available 3,4,5-tri-O-benzyl-1,2-O-isopropylidene-β-D-fructopyranose and 3,4,5-tri-O-benzyl-1,2-O-isopropylidene-β-D-psicopyranose, respectively. The latter compounds were partially deprotected under acidic conditions followed by condensation with thiocyanic acid to give an anomeric mixture of the corresponding 1,3-oxazolidine-2-thiones. The anomeric 1,3-oxazolidine-2-thiones were separated after successive benzylation, fully characterized and subjected to palladium catalyzed Suzuki–Miyaura coupling with 2-pyridineboronic acid N-phenyldiethanolamine ester to give the corresponding 2-pyridyl spiro-oxazoline (PyOx) ligands. The spiro-oxazoline ligands showed high asymmetric induction (up to 93% ee) when applied as chiral ligands in palladium-catalyzed allylic alkylation of 1,3-diphenylallyl acetate with dimethyl malonate. The D-fructo-PyOx ligand provided mainly the (R)-enantiomer while the D-psico-configurated ligand gave the (S)-enantiomer with a lower enantiomeric excess. PMID:26877819

  16. Spiro-fused carbohydrate oxazoline ligands: Synthesis and application as enantio-discrimination agents in asymmetric allylic alkylation.

    PubMed

    Kraft, Jochen; Golkowski, Martin; Ziegler, Thomas

    2016-01-01

    In the present work, we describe a convenient synthesis of spiro-fused D-fructo- and D-psico-configurated oxazoline ligands and their application in asymmetric catalysis. The ligands were synthesized from readily available 3,4,5-tri-O-benzyl-1,2-O-isopropylidene-β-D-fructopyranose and 3,4,5-tri-O-benzyl-1,2-O-isopropylidene-β-D-psicopyranose, respectively. The latter compounds were partially deprotected under acidic conditions followed by condensation with thiocyanic acid to give an anomeric mixture of the corresponding 1,3-oxazolidine-2-thiones. The anomeric 1,3-oxazolidine-2-thiones were separated after successive benzylation, fully characterized and subjected to palladium catalyzed Suzuki-Miyaura coupling with 2-pyridineboronic acid N-phenyldiethanolamine ester to give the corresponding 2-pyridyl spiro-oxazoline (PyOx) ligands. The spiro-oxazoline ligands showed high asymmetric induction (up to 93% ee) when applied as chiral ligands in palladium-catalyzed allylic alkylation of 1,3-diphenylallyl acetate with dimethyl malonate. The D-fructo-PyOx ligand provided mainly the (R)-enantiomer while the D-psico-configurated ligand gave the (S)-enantiomer with a lower enantiomeric excess. PMID:26877819

  17. Kinetic resolution of 2-substituted 2,3-dihydro-4-pyridones by palladium-catalyzed asymmetric allylic alkylation: catalytic asymmetric total synthesis of indolizidine (-)-209I.

    PubMed

    Lei, Bai-Lin; Zhang, Qing-Song; Yu, Wei-Hua; Ding, Qiu-Ping; Ding, Chang-Hua; Hou, Xue-Long

    2014-04-01

    The kinetic resolution of 2-substituted-2,3-dihydro-4-pyridones was realized via a Pd-catalyzed allylic substitution reaction using a commercially available (S)-P-Phos as a ligand, affording optically active dihydropyridones and C-allylated dihydropyridones in high yields and good enantioselectivities with the S-factor up to 43. With this protocol, a catalytic asymmetric total synthesis of indolizidine (-)-209I was realized for the first time. PMID:24661080

  18. Catalytic enantioselective synthesis of naturally occurring butenolides via hetero-allylic alkylation and ring closing metathesis.

    PubMed

    Mao, Bin; Geurts, Koen; Fañanás-Mastral, Martín; van Zijl, Anthoni W; Fletcher, Stephen P; Minnaard, Adriaan J; Feringa, Ben L

    2011-03-01

    An efficient catalytic asymmetric synthesis of chiral γ-butenolides was developed based on the hetero-allylic asymmetric alkylation (h-AAA) in combination with ring closing metathesis (RCM). The synthetic potential of the h-AAA-RCM protocol was illustrated with the facile synthesis of (-)-whiskey lactone, (-)-cognac lactone, (-)-nephrosteranic acid, and (-)-roccellaric acid. PMID:21268603

  19. Kinetic Resolution of Racemic Allylic Alcohols by Catalytic Asymmetric Substitution of the OH Group with Monosubstituted Hydrazines.

    PubMed

    Yan, Liang; Xu, Jing-Kun; Huang, Chao-Fan; He, Zeng-Yang; Xu, Ya-Nan; Tian, Shi-Kai

    2016-09-01

    A new strategy has been established for the kinetic resolution of racemic allylic alcohols through a palladium/sulfonyl-hydrazide-catalyzed asymmetric OH-substitution under mild conditions. In the presence of 1 mol % [Pd(allyl)Cl]2 , 4 mol % (S)-SegPhos, and 10 mol % 2,5-dichlorobenzenesulfonyl hydrazide, a range of racemic allylic alcohols were smoothly resolved with selectivity factors of more than 400 through an asymmetric allylic alkylation of monosubstituted hydrazines under air at room temperature. Importantly, this kinetic resolution process provided various allylic alcohols and allylic hydrazine derivatives with high enantiopurity. PMID:27339655

  20. Catalytic Asymmetric Synthesis of Chiral Allylic Esters

    PubMed Central

    Cannon, Jeffrey S.; Kirsch, Stefan F.; Overman, Larry E.

    2010-01-01

    A broadly useful catalytic enantioselective synthesis of branched allylic esters from prochiral (Z)-2-alkene-1-ols has been developed. The starting allylic alcohol is converted to its trichloroacetimidate intermediate by reaction with trichloroacetonitrile, either in situ or in a separate step, and this intermediate undergoes clean enantioselective SN2′ substitution with a variety of carboxylic acids in the presence of the palladium(II) catalyst (Rp,S)-di-μ -acetatobis[(η5-2-(2'-(4'-methylethyl)oxazolinyl)cyclopentadienyl,1-C,3'-N)(η4-tetraphenylcyclobutadiene)cobalt]dipalladium, (Rp,S)-[COP-OAc]2 or its enantiomer. The scope and limitations of this useful catalytic asymmetric allylic esterification are defined. PMID:15740118

  1. Nickel-Catalyzed Allylic Alkylation with Diarylmethane Pronucleophiles: Reaction Development and Mechanistic Insights.

    PubMed

    Sha, Sheng-Chun; Jiang, Hui; Mao, Jianyou; Bellomo, Ana; Jeong, Soo A; Walsh, Patrick J

    2016-01-18

    Palladium-catalyzed allylic substitution reactions are among the most efficient methods to construct C-C bonds between sp(3)-hybridized carbon atoms. In contrast, much less work has been done with nickel catalysts, perhaps because of the different mechanisms of the allylic substitution reactions. Palladium catalysts generally undergo substitution by a "soft"-nucleophile pathway, wherein the nucleophile attacks the allyl group externally. Nickel catalysts are usually paired with "hard" nucleophiles, which attack the metal before C-C bond formation. Introduced herein is a rare nickel-based catalyst which promotes substitution with diarylmethane pronucleophiles by the soft-nucleophile pathway. Preliminary studies on the asymmetric allylic alkylation are promising. PMID:26756444

  2. Asymmetric synthesis of N-allylic indoles via regio- and enantioselective allylation of aryl hydrazines

    PubMed Central

    Xu, Kun; Gilles, Thomas; Breit, Bernhard

    2015-01-01

    The asymmetric synthesis of N-allylic indoles is important for natural product synthesis and pharmaceutical research. The regio- and enantioselective N-allylation of indoles is a true challenge due to the favourable C3-allylation. We develop here a new strategy to the asymmetric synthesis of N-allylic indoles via rhodium-catalysed N-selective coupling of aryl hydrazines with allenes followed by Fischer indolization. The exclusive N-selectivities and good to excellent enantioselectivities are achieved applying a rhodium(I)/DTBM-Segphos or rhodium(I)/DTBM-Binap catalyst. This method permits the practical synthesis of valuable chiral N-allylated indoles, and avoids the N- or C-selectivity issue. PMID:26137886

  3. Asymmetric synthesis of N-allylic indoles via regio- and enantioselective allylation of aryl hydrazines.

    PubMed

    Xu, Kun; Gilles, Thomas; Breit, Bernhard

    2015-01-01

    The asymmetric synthesis of N-allylic indoles is important for natural product synthesis and pharmaceutical research. The regio- and enantioselective N-allylation of indoles is a true challenge due to the favourable C3-allylation. We develop here a new strategy to the asymmetric synthesis of N-allylic indoles via rhodium-catalysed N-selective coupling of aryl hydrazines with allenes followed by Fischer indolization. The exclusive N-selectivities and good to excellent enantioselectivities are achieved applying a rhodium(I)/DTBM-Segphos or rhodium(I)/DTBM-Binap catalyst. This method permits the practical synthesis of valuable chiral N-allylated indoles, and avoids the N- or C-selectivity issue. PMID:26137886

  4. α-Allyl-α-aryl α-Amino Esters in the Asymmetric Synthesis of Acyclic and Cyclic Amino Acid Derivatives by Alkene Metathesis

    PubMed Central

    2015-01-01

    Allylating agents were explored for the asymmetric synthesis of α-allyl-α-aryl α-amino acids by tandem N-alkylation/π-allylation. Cross-metathesis of the tandem product was developed to provide allylic diversity not afforded in the parent reaction; the synthesis of homotyrosine and homoglutamate analogues was completed. Cyclic α-amino acid derivatives could be accessed by ring-closing metathesis presenting a viable strategy to higher ring homologue of enantioenriched α-substituted proline. The eight-membered proline analogue was successfully converted to the pyrrolizidine natural product backbone. PMID:24828423

  5. Asymmetric synthesis of α-chiral allylic silanes by enantioconvergent γ-selective copper(I)-catalyzed allylic silylation.

    PubMed

    Delvos, Lukas B; Vyas, Devendra J; Oestreich, Martin

    2013-04-22

    Gamma way: Regio- and enantioselective allylic substitution with a silicon nucleophile generated by copper(I)-catalyzed Si-B bond activation provides direct access to α-chiral allylic silanes from linear acceptors. The enantioconvergent catalysis employing McQuade's six-membered N-heterocyclic-carbene-copper(I) catalyst is applicable to aryl- and alkyl-substituted allylic phosphates (see scheme). PMID:23512610

  6. Enantioselective Synthesis of α-Quaternary Mannich Adducts by Palladium-Catalyzed Allylic Alkylation: Total Synthesis of (+)-Sibirinine

    PubMed Central

    2016-01-01

    A catalytic enantioselective method for the synthesis of α-quaternary Mannich-type products is reported. The two-step sequence of (1) Mannich reaction followed by (2) decarboxylative enantioselective allylic alkylation serves as a novel strategy to in effect access asymmetric Mannich-type products of “thermodynamic” enolates of substrates possessing additional enolizable positions and acidic protons. Palladium-catalyzed decarboxylative allylic alkylation enables the enantioselective synthesis of five-, six-, and seven-membered ketone, lactam, and other heterocyclic systems. The mild reaction conditions are notable given the acidic free N–H groups and high functional group tolerance in each of the substrates. The utility of this method is highlighted in the first total synthesis of (+)-sibirinine. PMID:25578104

  7. Construction of vicinal tertiary and all-carbon quaternary stereocenters via Ir-catalyzed regio-, diastereo-, and enantioselective allylic alkylation and applications in sequential Pd catalysis.

    PubMed

    Liu, Wen-Bo; Reeves, Corey M; Virgil, Scott C; Stoltz, Brian M

    2013-07-24

    Highly congested vicinal stereocenters comprised of tertiary and all-carbon quaternary centers were generated via Ir-catalyzed asymmetric allylic alkylation of β-ketoesters. These catalytic reactions proceed in excellent yields with a broad scope on either reaction partner and with outstanding regio-, diastereo-, and enantiocontrol. Implementation of a subsequent Pd-catalyzed alkylation affords dialkylated products with pinpoint stereochemical control of both chiral centers. PMID:23829704

  8. Catalytic Asymmetric Generation of (Z)-Disubstituted Allylic Alcohols

    PubMed Central

    Salvi, Luca; Jeon, Sang-Jin; Fisher, Ethan L.; Carroll, Patrick J.; Walsh, Patrick J.

    2008-01-01

    A one-pot method for the direct preparation of enantioenriched (Z)-disubstituted allylic alcohols is introduced. Hydroboration of 1-halo-1-alkynes with dicyclohexylborane, reaction with t-BuLi, and transmetallation with dialkylzinc reagents generates (Z)-disubstituted vinylzinc intermediates. In situ reaction of these reagents with aldehydes in the presence of a catalyst derived from (−)-MIB generates (Z)-disubstituted allylic alcohols. It was found that the resulting allylic alcohols were racemic, most likely due to a rapid addition reaction promoted by LiX (X = Br and Cl). To suppress the LiX promoted reaction, a series of inhibitors was screened. It was found that 20–30 mol % tetraethylethylene diamine (TEEDA) inhibited LiCl without inhibiting the chiral zinc-based Lewis acid. In this fashion, (Z)-disubstituted allylic alcohols were obtained with up to 98% ee. The asymmetric (Z)-vinylation could be coupled with tandem diastereoselective epoxidation reactions to provide epoxy alcohols and allylic epoxy alcohols with up to three contiguous stereogenic centers, enabling the rapid construction of complex building blocks with high levels of enantio- and diastereoselectivity. PMID:18052173

  9. Enantioselective construction of quaternary N-heterocycles by palladium-catalysed decarboxylative allylic alkylation of lactams.

    PubMed

    Behenna, Douglas C; Liu, Yiyang; Yurino, Taiga; Kim, Jimin; White, David E; Virgil, Scott C; Stoltz, Brian M

    2012-02-01

    The enantioselective synthesis of nitrogen-containing heterocycles (N-heterocycles) represents a substantial chemical research effort and resonates across numerous disciplines, including the total synthesis of natural products and medicinal chemistry. In this Article, we describe the highly enantioselective palladium-catalysed decarboxylative allylic alkylation of readily available lactams to form 3,3-disubstituted pyrrolidinones, piperidinones, caprolactams and structurally related lactams. Given the prevalence of quaternary N-heterocycles in biologically active alkaloids and pharmaceutical agents, we envisage that our method will provide a synthetic entry into the de novo asymmetric synthesis of such structures. As an entry for these investigations we demonstrate how the described catalysis affords enantiopure quaternary lactams that intercept synthetic intermediates previously used in the synthesis of the Aspidosperma alkaloids quebrachamine and rhazinilam, but that were previously only available by chiral auxiliary approaches or as racemic mixtures. PMID:22270628

  10. Enantioselective construction of quaternary N-heterocycles by palladium-catalysed decarboxylative allylic alkylation of lactams

    NASA Astrophysics Data System (ADS)

    Behenna, Douglas C.; Liu, Yiyang; Yurino, Taiga; Kim, Jimin; White, David E.; Virgil, Scott C.; Stoltz, Brian M.

    2012-02-01

    The enantioselective synthesis of nitrogen-containing heterocycles (N-heterocycles) represents a substantial chemical research effort and resonates across numerous disciplines, including the total synthesis of natural products and medicinal chemistry. In this Article, we describe the highly enantioselective palladium-catalysed decarboxylative allylic alkylation of readily available lactams to form 3,3-disubstituted pyrrolidinones, piperidinones, caprolactams and structurally related lactams. Given the prevalence of quaternary N-heterocycles in biologically active alkaloids and pharmaceutical agents, we envisage that our method will provide a synthetic entry into the de novo asymmetric synthesis of such structures. As an entry for these investigations we demonstrate how the described catalysis affords enantiopure quaternary lactams that intercept synthetic intermediates previously used in the synthesis of the Aspidosperma alkaloids quebrachamine and rhazinilam, but that were previously only available by chiral auxiliary approaches or as racemic mixtures.

  11. Mutagenic properties of allylic and alpha, beta-unsaturated compounds: consideration of alkylating mechanisms.

    PubMed

    Eder, E; Henschler, D; Neudecker, T

    1982-12-01

    1. Allyl and allylic compounds may exert alkylating activities by SN1, SN2 and SN2' mechanisms. This direct alkylating potential can be determined quantitatively by a modified 4-NBP (4-nitrobenzyl pyridine) test. 2. The alkylating activities in a systematically selected series of allyl and allylic compounds correlate well with the direct mutagenic potential as determined in the Ames test using Salmonella typhimurium TA 100 as tester strain. 3. The allylic structure is a prerequisite for these types of activities since structurally related molecules lacking the allylic moiety are inactive in this respect. 4. The potency of both the alkylating and mutagenic activity is determined by the strength of the leaving group: --OSO2CH3 greater than I greater than Br greater than Cl greater than--NCS. 5. Indirect mutagenicity, through metabolic activation of the olefinic bond (by addition of S9 mix to the tester medium), can be ruled out for practically all compounds, the only exception found being 2,3-dichloro-1-propene where an increase of mutagenicity is encountered after addition of S9 mix; mechanistic explanations for this exception are provided. 6. Analogous activation is demonstrated for benzyl halides, the alkylating potency of which is even higher than that of genuine allylic compounds. 7. A variety of methyl- and chlorine-substituted allyl compounds has been included in the study: both groups increase activity, either by +I (CH3) or by +M effects (Cl). 8. alpha, beta-Unsaturated carbonyl compounds, e.g. acrolein and crotonaldehyde, also display direct mutagenic activity which is due to a completely different mechanism: covalent binding to nucleophilic sites of DNA bases by Michael addition. Methyl and other alkyl substitutions decrease the mutagenic potential in this type of compound. The corresponding alcohols, also displaying mutagenic activity but to a lesser degree, are metabolically activated by ADH (alcohol dehydrogenase) of the tester strain microbes to the

  12. Palladium-Catalyzed Dearomative Allylic Alkylation of Indoles with Alkynes To Synthesize Indolenines with C3-Quarternary Centers.

    PubMed

    Gao, Shang; Wu, Zijun; Fang, Xinxin; Lin, Aijun; Yao, Hequan

    2016-08-01

    A palladium-catalyzed dearomative allylic alkylation of indoles with alkynes to construct indolenines with C3-quarternary centers was reported. The in situ formed arylallene intermediate omitted the need to install leaving groups on the allylic compounds and employ extra oxidants to oxidize the allylic C-H bonds. The reaction exhibited good functional group tolerance and high atom economy. Moreover, the reaction was further expanded to synthesize pyrroloindolines and furanoindolines. PMID:27442021

  13. Unusual Allylpalladium Carboxylate Complexes: Identification of the Resting State of Catalytic Enantioselective Decarboxylative Ketone Allylic Alkylation Reactions**

    PubMed Central

    Sherden, Nathaniel H.; Behenna, Douglas C.; Virgil, Scott C.

    2010-01-01

    Palladium poprocks: Hold on to your CO2! Enantioselective Pd-catalyzed decarboxylative alkylation of ketone enolates proceeds via η1-σ-allyl Pd-carboxylate complexes by slow loss of CO2. PMID:19672907

  14. Asymmetric Catalysis with CO2 : The Direct α-Allylation of Ketones.

    PubMed

    Pupo, Gabriele; Properzi, Roberta; List, Benjamin

    2016-05-10

    Quaternary stereocenters are found in numerous bioactive molecules. The Tsuji-Trost reaction has proven to be a powerful C-C bond forming process, and, at least in principle, should be well suited to access quaternary stereocenters via the α-allylation of ketones. However, while indirect approaches are known, the direct, catalytic asymmetric α-allylation of branched ketones has been elusive until today. By combining "enol catalysis" with the use of CO2 as a formal catalyst for asymmetric catalysis, we have now developed a solution to this problem: we report a direct, highly enantioselective and highly atom-economic Tsuji-Trost allylation of branched ketones with allylic alcohol. Our reaction delivers products bearing quaternary stereocenters with high enantioselectivity and water as the sole by-product. We expect our methodology to be of utility in asymmetric catalysis and inspire the design of other highly atom-economic transformations. PMID:27071633

  15. Expanding the scope of Metal-Free enantioselective allylic substitutions: Anthrones

    PubMed Central

    Ceban, Victor; Tauchman, Jiří; Meazza, Marta; Gallagher, Greg; Light, Mark E.; Gergelitsová, Ivana; Veselý, Jan; Rios, Ramon

    2015-01-01

    The highly enantioselective asymmetric allylic alkylation of Morita–Baylis–Hillman carbonates with anthrones is presented. The reaction is simply catalyzed by cinchona alkaloid derivatives affording the final alkylated products in good yields and excellent enantioselectivities. PMID:26592555

  16. Enantioselective synthesis of dialkylated N-heterocycles by palladium-catalyzed allylic alkylation.

    PubMed

    Numajiri, Yoshitaka; Jiménez-Osés, Gonzalo; Wang, Bo; Houk, K N; Stoltz, Brian M

    2015-03-01

    The enantioselective synthesis of α-disubstituted N-heterocyclic carbonyl compounds has been accomplished using palladium-catalyzed allylic alkylation. These catalytic conditions enable access to various heterocycles, such as morpholinone, thiomorpholinone, oxazolidin-4-one, 1,2-oxazepan-3-one, 1,3-oxazinan-4-one, and structurally related lactams, all bearing fully substituted α-positions. Broad functional group tolerance was explored at the α-position in the morpholinone series. We demonstrate the utility of this method by performing various transformations on our useful products to readily access a number of enantioenriched compounds. PMID:25714704

  17. Asymmetric Enzymatic Synthesis of Allylic Amines: A Sigmatropic Rearrangement Strategy.

    PubMed

    Prier, Christopher K; Hyster, Todd K; Farwell, Christopher C; Huang, Audrey; Arnold, Frances H

    2016-04-01

    Sigmatropic rearrangements, while rare in biology, offer opportunities for the efficient and selective synthesis of complex chemical motifs. A "P411" serine-ligated variant of cytochrome P450BM3 has been engineered to initiate a sulfimidation/[2,3]-sigmatropic rearrangement sequence in whole E. coli cells, a non-natural function for any enzyme, providing access to enantioenriched, protected allylic amines. Five mutations in the enzyme substantially enhance its activity toward this new function, demonstrating the evolvability of the catalyst toward challenging nitrene transfer reactions. The evolved catalyst additionally performs the highly enantioselective imidation of non-allylic sulfides. PMID:26970325

  18. Mechanistically Driven Development of Iridium Catalysts for Asymmetric Allylic Substitution

    PubMed Central

    Hartwig, John F.; Stanley, Levi M.

    2010-01-01

    Conspectus Enantioselective allylic substitution reactions comprise some of the most versatile methods for preparing enantiomerically enriched materials. These reactions form products that contain multiple functionalities by creating carbon–nitrogen, carbon–oxygen, carbon–carbon, and carbon–sulfur bonds. For many years, the development of catalysts for allylic substitution focused on palladium complexes. However, studies of complexes of other metals have revealed selectivities that often complement those of palladium systems. Most striking is the observation that reactions with unsymmetrical allylic electrophiles that typically occur with palladium catalysts at the less hindered site of an allylic electrophile occur at the more hindered site with catalysts based on other metals. In this Account, we describe an iridium precursor and a phosphoramidite ligand that catalyze reactions with a particularly broad scope of nucleophiles. The active form of this iridium catalyst is not generated by the simple binding of the phosphoramidite ligand to the metal precursor. Instead, the initial phosphoramidite and iridium precursor react in the presence of base to form a metallacyclic species that is the active catalyst. This species is generated either in situ or separately in isolated form by reactions with added base. The identification of the structure of the active catalyst led to the development of simplified catalysts as well as the most active form of the catalyst now available, which is stabilized by a loosely bound ethylene. Most recently, this structure was used to prepare intermediates containing allyl ligands, the structures of which provide a model for the enantioselectivities discussed here. Initial studies from our laboratory on the scope of iridium-catalyzed allylic substitution showed that reactions of primary and secondary amines, including alkylamines, benzylamines, and allylamines, and reactions of phenoxides and alkoxides occurred in high yields

  19. Asymmetric epoxidation of allylic alcohols catalyzed by vanadium-binaphthylbishydroxamic Acid complex.

    PubMed

    Noji, Masahiro; Kobayashi, Toshihiro; Uechi, Yuria; Kikuchi, Asami; Kondo, Hisako; Sugiyama, Shigeo; Ishii, Keitaro

    2015-03-20

    A vanadium-binaphthylbishydroxamic acid (BBHA) complex-catalyzed asymmetric epoxidation of allylic alcohols is described. The optically active binaphthyl-based ligands BBHA 2a and 2b were synthesized from (S)-1,1'-binaphthyl-2,2'-dicarboxylic acid and N-substituted-O-trimethylsilyl (TMS)-protected hydroxylamines via a one-pot, three-step procedure. The epoxidations of 2,3,3-trisubstituted allylic alcohols using the vanadium complex of 2a were easily performed in toluene with a TBHP water solution to afford (2R)-epoxy alcohols in good to excellent enantioselectivities. PMID:25714329

  20. γ-Selective Allylation of (E)-Alkenylzinc Iodides Prepared by Reductive Coupling of Arylacetylenes with Alkyl Iodides.

    PubMed

    Zhurkin, Fedor E; Hu, Xile

    2016-07-01

    The first examples of Cu-catalyzed γ-selective allylic alkenylation using organozinc reagents are reported. (E)-Alkenylzinc iodides were prepared by Fe-catalyzed reductive coupling of terminal arylalkynes with alkyl iodides. In the presence of a copper catalyst, these reagents reacted with allylic bromides derived from Morita-Baylis-Hillman alcohols to give 1,4-dienes in high yields. The reactions are highly γ-selective (generally γ/α > 49:1) and tolerate a wide range of functional groups such as ester, cyano, keto, and nitro. PMID:27285459

  1. Rhodium-catalysed asymmetric allylic arylation of racemic halides with arylboronic acids

    NASA Astrophysics Data System (ADS)

    Sidera, Mireia; Fletcher, Stephen P.

    2015-11-01

    Csp2-Csp2 cross-coupling reactions between arylboronic acid and aryl halides are widely used in both academia and industry and are strategically important in the development of new agrochemicals and pharmaceuticals. Csp2-Csp3 cross-coupling reactions have been developed, but enantioselective variations are rare and simply retaining the stereochemistry is a problem. Here we report a highly enantioselective Csp2-Csp3 bond-forming method that couples arylboronic acids to racemic allyl chlorides. Both enantiomers of a cyclic chloride are converted into a single enantiomer of product via a dynamic kinetic asymmetric transformation. This Rh-catalysed method uses readily available and inexpensive building blocks and is mild and broadly applicable. For electron-deficient, electron-rich or ortho-substituted boronic acids better results are obtained with racemic allyl bromides. Oxygen substitution in the allyl halide is tolerated and the products can be functionalized to provide diverse building blocks. The approach fills a significant gap in the methods for catalytic asymmetric synthesis.

  2. Highly regio- and enantioselective synthesis of N-substituted 2-pyridones: iridium-catalyzed intermolecular asymmetric allylic amination.

    PubMed

    Zhang, Xiao; Yang, Ze-Peng; Huang, Lin; You, Shu-Li

    2015-02-01

    The first iridium-catalyzed intermolecular asymmetric allylic amination reaction with 2-hydroxypyridines has been developed, thus providing a highly efficient synthesis of enantioenriched N-substituted 2-pyridone derivatives from readily available starting materials. This protocol features a good tolerance of functional groups in both the allylic carbonates and 2-hydroxypyridines, thereby delivering multifunctionalized heterocyclic products with up to 98% yield and 99% ee. PMID:25504907

  3. Diastereoselective Allylation of "N"-"Tert"-Butanesulfinyl Imines: An Asymmetric Synthesis Experiment for the Undergraduate Organic Laboratory

    ERIC Educational Resources Information Center

    Chen, Xiao-Yang; Sun, Li-Sen; Gao, Xiang; Sun, Xing-Wen

    2015-01-01

    An asymmetric synthetic experiment that encompasses both diastereoselectivity and enantioselectivity is described. In this experiment, Zn-mediated allylation of an ("R")-"N"-"tert"-butanesulfinyl imine is first performed to obtain either diastereomer using two different solvent systems, followed by oxidation of the…

  4. Mechanism of copper(I)-catalyzed allylic alkylation of phosphorothioate esters: influence of the leaving group on α regioselectivity.

    PubMed

    Sheng, Wenhao; Wang, Mian; Lein, Matthias; Jiang, Linbin; Wei, Wanxing; Wang, Jianyi

    2013-10-11

    The mechanism of Cu(I) -catalyzed allylic alkylation and the influence of the leaving groups (OPiv, SPiv, Cl, SPO(OiPr)2 ; Piv: pivavloyl) on the regioselectivity of the reaction have been explored by using density functional theory (DFT). A comprehensive comparison of many possible reaction pathways shows that [(iPr)2 Cu](-) prefers to bind first oxidatively to the double bond of the allylic substrate at the anti position with respect to the leaving group, and this is followed by dissociation of the leaving group. If the leaving group is not taken into account, the reaction then undergoes an isomerization and a reductive elimination process to give the α- or γ-selective product. If OPiv, SPiv, Cl, or SPO(OiPr)2 groups are present, the optimal route for the formation of both α- and γ-substituted products changes from the stepwise elimination to the direct process, in which the leaving group plays a stabilizing role for the reactant and destabilizes the transition state. The differences to the energy barrier for the α- and γ-substituted products are 2.75 kcal mol(-1) with SPO(OiPr)2 , 2.44 kcal mol(-1) with SPiv, 2.33 kcal mol(-1) with OPiv, and 1.98 kcal mol(-1) with Cl, respectively; these values show that α regioselectivity in the allylic alkylation follows a SPO(OiPr)2 >SPiv>OPiv>Cl trend, which is in satisfactory agreement with the experimental findings. This trend mainly originates in the differences between the attractive electrostatic forces and the repelling steric interactions of the SPO(OiPr)2 , SPiv, OPiv, and Cl groups on the Cu group. PMID:24038319

  5. From a Sequential to a Concurrent Reaction in Aqueous Medium: Ruthenium-Catalyzed Allylic Alcohol Isomerization and Asymmetric Bioreduction.

    PubMed

    Ríos-Lombardía, Nicolás; Vidal, Cristian; Liardo, Elisa; Morís, Francisco; García-Álvarez, Joaquín; González-Sabín, Javier

    2016-07-18

    The ruthenium-catalyzed redox isomerization of allylic alcohols was successfully coupled with the enantioselective enzymatic ketone reduction (mediated by KREDs) in a concurrent process in aqueous medium. The overall transformation, formally the asymmetric reduction of allylic alcohols, took place with excellent conversions and enantioselectivities, under mild reaction conditions, employing commercially and readily available catalytic systems, and without external coenzymes or cofactors. Optimization resulted in a multistep approach and a genuine cascade reaction where the metal catalyst and biocatalyst coexist from the beginning. PMID:27258838

  6. Domino cyclization-alkylation protocol for the synthesis of 2,3-functionalized indoles from o-alkynylanilines and allylic alcohols.

    PubMed

    Xu, Chang; Murugan, Vinod K; Pullarkat, Sumod A

    2012-05-21

    A practical and efficient protocol for the one-pot synthesis of 2,3-substituted indoles was developed via a palladacycle catalyzed domino cyclization-alkylation reaction involving 2-alkynylanilines and allylic alcohols under mild conditions without any additives. PMID:22526600

  7. Synthesis of functionalized 5-substituted thiazolidine-2-thiones via adscititious xanthate-promoted radical cyclization of allyl(alkyl/aryl)dithiocarbamates.

    PubMed

    Gao, Simiao; Zhang, Yu; Dong, Jun; Chen, Ning; Xu, Jiaxi

    2016-01-21

    Functionalized 5-substituted thiazolidine-2-thiones were synthesized efficiently from alkyl allyl(alkyl/aryl)-dithiocarbamates via radical cyclization with the corresponding S-alkyl O-ethyl xanthates as the adscititious radical precursors. The application of the adscititious radical precursors improves not only the yields, but also the efficiency in the radical cyclization reaction significantly. The current adscititious radical precursor method provides a new strategy for the achievement and improvement of some radical reactions which are hardly or difficultly realized by the traditional direct methods. PMID:26626401

  8. Asymmetric Intramolecular Alkylation of Chiral Aromatic Imines via Catalytic C-H Bond Activation

    SciTech Connect

    Watzke, Anja; Wilson, Rebecca; O'Malley, Steven; Bergman, Robert; Ellman, Jonathan

    2007-04-16

    The asymmetric intramolecular alkylation of chiral aromatic aldimines, in which differentially substituted alkenes are tethered meta to the imine, was investigated. High enantioselectivities were obtained for imines prepared from aminoindane derivatives, which function as directing groups for the rhodium-catalyzed C-H bond activation. Initial demonstration of catalytic asymmetric intramolecular alkylation also was achieved by employing a sterically hindered achiral imine substrate and catalytic amounts of a chiral amine.

  9. Dual Palladium(II)/Tertiary Amine Catalysis for Asymmetric Regioselective Rearrangements of Allylic Carbamates.

    PubMed

    Bauer, Johannes Moritz; Frey, Wolfgang; Peters, René

    2016-04-11

    The streamlined catalytic access to enantiopure allylic amines as valuable precursors towards chiral β- and γ-aminoalcohols as well as α- and β-aminoacids is desirable for industrial purposes. In this article an enantioselective method is described that transforms achiral allylic alcohols and N-tosylisocyanate in a single step into highly enantioenriched N-tosyl protected allylic amines via an allylic carbamate intermediate. The latter is likely to undergo a cyclisation-induced [3,3]-rearrangement catalysed by a planar chiral pentaphenylferrocene palladacycle in cooperation with a tertiary amine base. The otherwise often indispensable activation of palladacycle catalysts by a silver salt is not required in the present case and there is also no need for an inert gas atmosphere. To further improve the synthetic value, the rearrangement was used to form dimethylaminosulfonyl-protected allylic amines, which can be deprotected under non-reductive conditions. PMID:26990446

  10. Origin of selectivity of Tsuji-Trost allylic alkylation of lactones: highly ordered transition states with lithium-containing enolates.

    PubMed

    Patil, Mahendra; Thiel, Walter

    2012-08-13

    We report computational investigations on the mechanism and the selectivity of Pd-catalyzed allylic alkylation of γ-valerolactone. Density functional calculations using the B3LYP functional are performed on the selectivity-determining nucleophilic addition step of this reaction. The B3LYP results of commonly assumed pathways fail to reproduce the observed selectivity of the reaction. Therefore, alternative pathways are considered for the nucleophilic addition step, to explain the experimentally established role of the additives LiCl and lithium diisopropyl amide (LDA) in the Pd-catalyzed reaction. These pathways involve different approaches of the enolate toward the η(3)-allylpalladium complex that are mainly guided by stabilizing Cl(δ-)···Li(δ+)···O(enolate) interactions in the transition state. In the calculations, the experimentally observed trans-product selectivity for the prototypical reaction with (S)-BINAP ligands is found only when assuming the addition of a "mixed" Li-enolate/LiCl adduct to the η(3)-allylpalladium complex. This mechanism provides a reasonable explanation for the experimental results and sheds light on the role of LiCl in the reaction. The analysis of the different transition-state models allows us to identify steric and electronic factors that stabilize or destabilize the relevant diastereomeric transition states. Calculations for different combinations of substrates (γ-valerolactone and δ-caprolactone) and catalysts (with (R)- and (S)-BINAP ligands) reproduce the experimentally observed selectivities well and thus provide further support for the proposed mechanism. PMID:22736518

  11. Deciphering DNA-based asymmetric catalysis through intramolecular Friedel-Crafts alkylations.

    PubMed

    Park, Soyoung; Ikehata, Keiichi; Watabe, Ryo; Hidaka, Yuta; Rajendran, Arivazhagan; Sugiyama, Hiroshi

    2012-10-28

    We describe asymmetric intramolecular Friedel-Crafts alkylations with a DNA-based hybrid catalyst and propose a plausible binding model. This study shows promise for studying relationships between the helical chirality of DNA and enantioselectivity of the chemical reaction. PMID:22986468

  12. An Iridium(I) N-Heterocyclic Carbene Complex Catalyzes Asymmetric Intramolecular Allylic Amination Reactions.

    PubMed

    Ye, Ke-Yin; Cheng, Qiang; Zhuo, Chun-Xiang; Dai, Li-Xin; You, Shu-Li

    2016-07-01

    A chiral iridium(I) N-heterocyclic carbene complex was reported for the first time as the catalyst in the highly enantioselective intramolecular allylic amination reaction. The current method provides facile access to biologically important enantioenriched indolopiperazinones and piperazinones in good yields (74-91 %) and excellent enantioselectivities (92-99 % ee). Preliminary mechanistic investigations reveal that the C-H activation occurs at the position ortho to the N-aryl group of the ligand. PMID:27162135

  13. Catalytic asymmetric Claisen rearrangement of Gosteli-type allyl vinyl ethers: total synthesis of (-)-9,10-dihydroecklonialactone B.

    PubMed

    Becker, Julia; Butt, Lena; von Kiedrowski, Valeska; Mischler, Elisabeth; Quentin, Florian; Hiersemann, Martin

    2014-04-01

    The enantioselective synthesis of (-)-9,10-dihydroecklonialactone B is described. The catalytic asymmetric Claisen rearrangement of a Gosteli-type allyl vinyl ether was utilized to afford an acyclic α-keto ester building block endowed with functionality amenable to the preparation of the carbocyclic target molecule by suitable postrearrangement transformations: A highly diastereoselective Corey-Bakshi-Shibata reduction of a β-chiral α-keto ester and a reductive homologation of an α-hydroxy ester. A transprotection tactic by a chemoselective intramolecular 6-exo-trig iodoetherification enabled regioselective ring-closing alkene metatheses to afford the 5- as well as the 14-membered ring, however, with mixed success in terms of E/Z selectivity. PMID:24621347

  14. High-Throughput Screening of the Asymmetric Decarboxylative Alkylation Reaction of Enolate-Stabilized Enol Carbonates.

    PubMed

    McDougal, Nolan T; Virgil, Scott C; Stoltz, Brian M

    2010-01-01

    The use of high-throughput screening allowed for the optimization of reaction conditions for the palladium-catalyzed asymmetric decarboxylative alkylation reaction of enolate-stabilized enol carbonates. Changing to a non-polar reaction solvent and to an electron-deficient PHOX derivative as ligand from our standard reaction conditions improved the enantioselectivity for the alkylation of a ketal-protected,1,3-diketone-derived enol carbonate from 28% ee to 84% ee. Similar improvements in enantioselectivity were seen for a β-keto-ester derived- and an α-phenyl cyclohexanone-derived enol carbonate. PMID:21072327

  15. Stereochemical evaluation of bis(phosphine) copper catalysts for the asymmetric alkylation of 3-bromooxindoles with α-arylated malonate esters

    PubMed Central

    Lee, Chung Whan; Han, Seo-Jung; Virgil, Scott C.; Stoltz, Brian M.

    2014-01-01

    An improved method for the asymetric alkylation of 3-bromooxindoles with α-arylated malonate esters is described. The asymmetric alkylation demonstrated was achieved up to 70% ee utilizing a copper(II) bis(phosphine) complex. PMID:25983348

  16. Rh(III)-catalyzed dehydrogenative alkylation of (hetero)arenes with allylic alcohols, allowing aldol condensation to indenes.

    PubMed

    Shi, Zhuangzhi; Boultadakis-Arapinis, Mélissa; Glorius, Frank

    2013-07-25

    Efficient Rh(III)-catalyzed C-H activation of different classes of (hetero)arenes such as 2-phenylpyridine, indoles, aryl ketones and acetanilide and their dehydrogenative cross-coupling with allylic alcohols are described. Several important skeletons such as β-aryl aldehydes and ketones, 2-acetylindenes, 3,4-dihydro-1H-quinolin-2-one and quinoline could be produced using this protocol. PMID:23765402

  17. Dual Catalysis Using Boronic Acid and Chiral Amine: Acyclic Quaternary Carbons via Enantioselective Alkylation of Branched Aldehydes with Allylic Alcohols.

    PubMed

    Mo, Xiaobin; Hall, Dennis G

    2016-08-31

    A ferrocenium boronic acid salt activates allylic alcohols to generate transient carbocations that react with in situ-generated chiral enamines from branched aldehydes. The optimized conditions afford the desired acyclic products embedding a methyl-aryl quaternary carbon center with up to 90% yield and 97:3 enantiomeric ratio, with only water as the byproduct. This noble-metal-free method complements alternative methods that are incompatible with carbon-halogen bonds and other sensitive functional groups. PMID:27518200

  18. Lewis Acid Catalyzed Friedel-Crafts Alkylation of Alkenes with Trifluoropyruvates.

    PubMed

    Xiang, Bin; Xu, Teng-Fei; Wu, Liang; Liu, Ren-Rong; Gao, Jian-Rong; Jia, Yi-Xia

    2016-05-01

    A Friedel-Crafts alkylation reaction of styrenes with trifluoropyruvates has been developed, which delivered allylic alcohols in excellent yields (up to 98%) using the Ni(ClO4)2·6H2O/bipyridine complex as a catalyst. The asymmetric reaction was catalyzed by the chiral Cu(OTf)2/bisoxazoline complex to afford the corresponding chiral allylic alcohols bearing trifluoromethylated quaternary stereogenic centers in moderate enantioselectivities (up to 75% ee). PMID:27028539

  19. Copper-catalyzed divergent kinetic resolution of racemic allylic substrates.

    PubMed

    Pineschi, Mauro; Di Bussolo, Valeria; Crotti, Paolo

    2011-10-01

    When a racemic mixture is fully consumed the products may still be enantiomerically enriched. In particular, the regiodivergent kinetic resolution is a process in which a single chiral catalyst or reagent reacts with a racemic substrate to form regioisomers possessing an opposite configuration on the newly-formed stereogenic centers. This review reports the major advances in the field of the copper-catalyzed regiodivergent and stereodivergent kinetic resolution of allylic substrates with organometallic reagents. The chiral recognition matching phenomena found with particular allylic substrates with the absolute configuration of the chiral catalyst allows in some cases an excellent control of the regio- and stereoselectivity, sheding some light on the so-called "black-box" mechanism of a copper-catalyzed asymmetric allylic alkylation. PMID:21837639

  20. Palladium-Catalyzed Asymmetric Benzylic Alkylation of Active Methylene Compounds with α-Naphthylbenzyl Carbonates and Pivalates.

    PubMed

    Tabuchi, Sho; Hirano, Koji; Miura, Masahiro

    2016-06-01

    A Pd/(R)-H8 -BINAP-catalyzed asymmetric benzylic alkylation of active methylene compounds has been developed. The reaction proceeds without the use of an external base, and the starting racemic diarylmethyl carbonates are converted into the optically active coupling products which contain the benzylic chiral stereocenter by a dynamic kinetic asymmetric transformation (DYKAT). Additionally, with suitable carbonates bases, the same palladium catalysis allows the corresponding pivalates to be adopted in the same DYKAT process. PMID:27120184

  1. A review of new developments in the Friedel–Crafts alkylation – From green chemistry to asymmetric catalysis

    PubMed Central

    2010-01-01

    Summary The development of efficient Friedel–Crafts alkylations of arenes and heteroarenes using only catalytic amounts of a Lewis acid has gained much attention over the last decade. The new catalytic approaches described in this review are favoured over classical Friedel–Crafts conditions as benzyl-, propargyl- and allyl alcohols, or styrenes, can be used instead of toxic benzyl halides. Additionally, only low catalyst loadings are needed to provide a wide range of products. Following a short introduction about the origin and classical definition of the Friedel–Crafts reaction, the review will describe the different environmentally benign substrates which can be applied today as an approach towards greener processes. Additionally, the first diastereoselective and enantioselective Friedel–Crafts-type alkylations will be highlighted. PMID:20485588

  2. Asymmetric Synthesis of (-)-Incarvillateine Employing an Intramolecular Alkylation via Rh-Catalyzed Olefinic C-H Bond Activation

    SciTech Connect

    Tsai, Andy; Bergman, Robert; Ellman, Jonathan

    2008-02-18

    An asymmetric total synthesis of (-)-incarvillateine, a natural product having potent analgesic properties, has been achieved in 11 steps and 15.4% overall yield. The key step is a rhodium-catalyzed intramolecular alkylation of an olefinic C-H bond to set two stereocenters. Additionally, this transformation produces an exocyclic, tetrasubstituted alkene through which the bicyclic piperidine moiety can readily be accessed.

  3. Iridium-Catalyzed Diastereoselective and Enantioselective Allylic Substitutions with Acyclic α-Alkoxy Ketones.

    PubMed

    Jiang, Xingyu; Chen, Wenyong; Hartwig, John F

    2016-05-01

    The asymmetric alkylation of acyclic ketones is a longstanding challenge in organic synthesis. Reported herein are diastereoselective and enantioselective allylic substitutions with acyclic α-alkoxy ketones catalyzed by a metallacyclic iridium complex to form products with contiguous stereogenic centers derived from the nucleophile and electrophile. These reactions occur between allyl methyl carbonates and unstabilized copper(I) enolates generated in situ from acyclic α-alkoxy ketones. The resulting products can be readily converted into enantioenriched tertiary alcohols and tetrahydrofuran derivatives without erosion of enantiomeric purity. PMID:27038004

  4. Catalytic asymmetric reductive coupling of alkynes and aldehydes: enantioselective synthesis of allylic alcohols and alpha-hydroxy ketones.

    PubMed

    Miller, Karen M; Huang, Wei-Sheng; Jamison, Timothy F

    2003-03-26

    A highly enantioselective method for catalytic reductive coupling of alkynes and aldehydes is described. Allylic alcohols are afforded with complete E/Z selectivity, generally >95:5 regioselectivity, and in up to 96% ee. In conjunction with ozonolysis, this process is complementary to existing methods of enantioselective alpha-hydroxy ketone synthesis. PMID:12643701

  5. Synthesis of α-Chiral Butyrolactones by Highly Stereoselective Radical Transfer or Sequential Asymmetric Alkylations: Concise Preparation of Leupyrrin Moieties.

    PubMed

    Schrempp, Michael; Thiede, Sebastian; Herkommer, Daniel; Gansäuer, Andreas; Menche, Dirk

    2015-11-01

    Inspired by the bioactive natural metabolites leupyrrin A1 and B1 , two novel stereoselective methods for the highly concise synthesis of densely substituted α-chiral butyrolactones are reported. The first approach relies on an innovative three-step Ti(III) -catalyzed radical reaction that proceeds with excellent chemo-, regio-, and stereoselectivity. The alternative route utilizes sequential asymmetric alkylations and enables asymmetric synthesis of the authentic α-tetrasubstituted butyrolactone motif of the leupyrrins in only four steps from commercially available substrates. PMID:26354047

  6. Asymmetric 1-Alkyl-2-acyl Phosphatidylcholine: a Helper Lipid for Enhanced Non-viral Gene Delivery

    PubMed Central

    Huang, Zhaohua; Li, Weijun; Szoka, Francis C.

    2011-01-01

    Rationally designed asymmetrical alkylacyl phosphatidylcholines (APC) have been synthesized and evaluated as helper lipids for non-viral gene delivery. A long aliphatic chain (C22~C24) was introduced at the 1-position of glycerol backbone, a branched lipid chain (C18) at the 2-position, and a phosphocholine head group at the 3-position. The fusogenicity of APC depends on the length and degree of saturation of the alkyl chain. Cationic lipids were formulated with APC as either lipoplexes or nanolipoparticles, and evaluated for their stability, transfection efficiency, and cytotoxicity. APC mediated high in vitro transfection efficiency, and had low cytotoxicity. Small nanolipoparticles (less than 100 nm) can be obtained with APC by applying as low as 0.1% PEG-lipid. Our study extends the type of helper lipids that are suitable for gene transfer and points the way to improve non-viral nucleic acid delivery system other than the traditional cationic lipids optimization. This work is supported by NIH grant EB003008. PMID:21718766

  7. Synthesis of chiral biphenol-based diphosphonite ligands and their application in palladium-catalyzed intermolecular asymmetric allylic amination reactions.

    PubMed

    Shi, Ce; Chien, Chih-Wei; Ojima, Iwao

    2011-02-01

    A library of new 2,2'-bis(diphenylphosphinoyloxy)-1,1'-binaphthyl (binapo)-type chiral diphosphonite ligands was designed and synthesized based on chiral 3,3',5,5',6,6'-hexasubstituted biphenols. These bop ligands have exhibited excellent efficiency in a palladium-catalyzed intermolecular allylic amination reaction, which provides a key intermediate for the total synthesis of Strychnos indole alkaloids with enantiopurities of up to 96% ee. PMID:21254441

  8. Allyl astatide

    SciTech Connect

    Norseev, Yu.V.; Vasaros, L.; Syuch, Z.

    1988-11-01

    Allyl astatide was prepared by the interhalogen exchange method, by replacement of the bromine in allyl bromide with astatide ion. The most favorable conditions for the synthesis were found by variations of the method that uses hydrazine hydrate and sodium formaldehyde sulfoxylate as reductants. A by-product is formed by the reaction of allyl bromide with excited astatine-211 which forms by disintegration of radon-211. Allyl astatide was identified by radio gas-liquid chromatography. Its retention indexes on nonpolar and weakly polar liquid phases were found. The stability of this newly prepared astatine compound was studied. The extrapolated boiling point of allyl astatide is 129 +/- 2/sup 0/C.

  9. Selective cleavage of the two CS bonds in asymmetrically alkylated dibenzothiophenes by Rhodococcus erythropolis KA2-5-1.

    PubMed

    Onaka, T; Kobayashi, M; Ishii, Y; Konishi, J; Maruhashi, K

    2001-01-01

    The Rhodococcus erythropolis strain KA2-5-1 was characterized by its ability to cleave carbon-sulfur bonds in the dibenzothiophene (DBT) ring by asymmetrically alkyl substitution, such as C2-DBTs (e.g., dimethyl and ethyl DBTs) and C3-DBTs (e.g., trimethyl and propyl DBTs), which are known to remain in hydrodesulfurization-treated diesel fuels. After treatment by solid-phase extraction (SPE) of solvents from microbial reactions of alkylated DBTs (Cx-DBTs), we used gas chromatography (GC), GC-atomic emission detection, GC-mass spectrometry and 1H nuclear magnetic resonance spectroscopy to identify and quantitatively evaluate the Cx-DBT metabolites. Molar ratios of metabolic isomers of the desulfurization products suggested that resting-cell reactions of KA2-5-1 against these Cx-DBTs occurrs through specific carbon-sulfur-bond-targeted cleavages, yielding alkylated hydroxybiphenyls, and that the manner of the attack on the DBT skeleton is affected not only by the position but also by the number and length of the alkyl substituents. PMID:16233063

  10. Asymmetric Total Synthesis of (+)- and (−)-Clusianone and (+)- and (−)Clusianone Methyl Enol Ether via ACC Alkylation and Evaluation of their Anti-HIV Activity

    PubMed Central

    Garnsey, Michelle R.; Matous, James A.; Kwiek, Jesse J.; Coltart, Don M.

    2011-01-01

    The total asymmetric synthesis of (+)- and (−)-clusianone and (+)- and (−)-clusianone methyl enol ether is reported. Asymmetric induction is achieved through the use of ACC alkylation, providing the key intermediates with an er of 99:1. The four synthetic compounds were evaluated for their anti-HIV activity. Both (+)- and (−)-clusianone displayed significant anti-HIV activity. PMID:21414776

  11. A catalytic, asymmetric formal synthesis of (+)-hamigeran B.

    PubMed

    Mukherjee, Herschel; McDougal, Nolan T; Virgil, Scott C; Stoltz, Brian M

    2011-03-01

    A concise asymmetric, formal synthesis of (+)-hamigeran B is reported. A Pd-catalyzed, decarboxylative allylic alkylation, employing a trifluoromethylated derivative of t-BuPHOX, is utilized as the enantioselective step to form the critical quaternary carbon center in excellent yield and enantioselectivity. The product is converted in three steps to a late-stage intermediate previously used in the synthesis of hamigeran B. PMID:21271716

  12. Comparative analysis of the conformations of symmetrically and asymmetrically deca- and undecasubstituted porphyrins bearing meso-alkyl or -aryl groups

    SciTech Connect

    Senge, M.O.; Medforth, C.J.; Forsyth, T.P.

    1997-03-12

    Conformational analysis of highly substituted porphyrins, has potential implications for modeling the behavior of macrocycles in tetrapyrrole-containing protein complexes and during catalytic reactions. In order to study the influence of different substituent patterns of the conformation of the porphyrin macrocycle, a series of metal free and nickel(II) decasubstituted porphyrins bearing aryl or ethyl groups at opposite meso positions and alkyl groups at the pyrrole positions have been synthesized and characterized by X-ray crystallography. Crystal structures of the free-base porphyrins with 5,15-diaryl substituents showed negligible out-of-plane distortion but a large amount of in-plane distortion along the 5,15-axis accompanied by large bond angle changes similar to those previously seen for related porphyrins with 5,15-dialkyl substituents. Nickel(II) complexes of the 5,15-diaryl-substituted porphyrins show planar or modestly nonplanar conformations, suggesting that these complexes are not intrinsically nonplanar, whereas a complex with 5,15-diethyl substituents has a very ruffled conformation similar to those observed for related complexes with other metals. The nickel(II) complexes are also elongated along the 5,15-axis in a qualitatively similar but less dramatic fashion than are the free-base porphyrins. Spectroscopic studies ({sup 1}H NMR, optical, and resonance Raman spectroscopy) suggest that conformations similar to those determined by X-ray crystallography are present in solution for the 5,15-disubstituted porphyrins containing both aryl and alkyl mesosubstituents were also investigated. Metal-free 5,15-dialkyl- and 5,15-diaryl-substituted porphyrins. Several asymmetric nickel(II) and metal-free deca- and undecasubstituted porphyrins containing both aryl and alkyl mesosubstituents were also investigated.

  13. Allyl alcohol

    Integrated Risk Information System (IRIS)

    Allyl alcohol ; CASRN 107 - 18 - 6 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Eff

  14. Allyl chloride

    Integrated Risk Information System (IRIS)

    Allyl chloride ; CASRN 107 - 05 - 1 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Ef

  15. Synthetic applications of aqueous accelerated [3,3] sigmatropic rearrangements of allyl vinyl ethers. [1,3] sigmatropic rearrangements of allyl vinyl ethers in 3 M lithium perchlorate-diethyl ether at ambient temperature. New methods to effect the retro Diels-Alder reaction of N-alkyl-2-azanorbornenes

    SciTech Connect

    Clark, J.D.

    1992-01-01

    Claisen rearrangements employed in the synthesis of natural and unnatural products that were heretofore difficult or impossible using conventional means are realized through the agency of water. Allyl vinyl ether 35, the unprotected form of McMurry's aphidicolin intermediate 7, rearranged after 24 h in 2.5:1 water/methanol at 80[degrees]C, affording aldehyde 40 in 70--85% yield. Acetaldehyde elimination witnessed using conventional reaction conditions was suppressed when employing water. The application of a Claisen rearrangement within the molecular framework of fenestranes was realized for the first time. Fenestrene vinyl ethers 28 and 30 rearranged to form the fenestrenes 29 and 31, respectively. Noteworthy is fenestrene 29, the first fenestrane synthesized possessing a trans-ring fusion common to two five-membered rings. The medium of 3.0 M lithium perchlorate-diethyl ether has been found to induce the rarely witnessed rearrangement of allyl vinyl ethers, despite the fact that the corresponding sigmatropic rearrangement is energetically more favorable. Yields are very good; however, in some instances the sigmatropic rearrangement and elimination processes compete slightly. Results from the observed stereoselectivities, concentration effects on reaction rate, and a crossover study indicate that these shifts take place via dissociated ions followed by recombination, and that the observed stereoselectivities are a result of unequal steric effects in the transition states for recombination. Copper(II) and sulfonic acid ion exchange resins have been found to readily catalyze the heterocycloreversion of N-alkyl-2-azanorbornenes to the corresponding primary amines, eliminating the necessity of employing a reactive dienophile to trap out the released cyclopentadiene.

  16. Asymmetric allylic substitution catalyzed by C1-symmetrical complexes of molybdenum: structural requirements of the ligand and the stereochemical course of the reaction.

    PubMed

    Malkov, Andrei V; Gouriou, Laure; Lloyd-Jones, Guy C; Starý, Ivo; Langer, Vratislav; Spoor, Paul; Vinader, Victoria; Kocovský, Pavel

    2006-09-01

    Application of new chiral ligands (R)-(-)-12 a and (S)-(+)-12 c (VALDY), derived from amino acids, to the title reaction, involving cinnamyl (linear) and isocinnamyl (branched) type substrates (4 and 5 --> 6), led to excellent regio- and enantioselectivities (>30:1, < or =98 % ee), showing that ligands with a single chiral center are capable of high asymmetric induction. The structural requirements of the ligand and the mechanism are discussed. The application of single enantiomers of deuterium-labeled substrates (both linear 38 c and branched 37 c) and analysis of the products (41-43) by (2)H{(1)H} NMR spectroscopy in a chiral liquid crystal matrix allowed the stereochemical pathways of the reaction to be distinguished. With ligand (S)-(+)-12 c, the matched enantiomer of branched substrate was found to be (S)-5, which was converted into (R)-6 with very high regio- and stereoselectivity via a process that involves net retention of stereochemistry. The mismatched enantiomer of the branched substrate was found to be (R)-5, which was also converted into (R)-6, that is, with apparent net inversion, but at a lower rate and with lower overall enantioselectivity. This latter feature, which may be termed a "memory effect", reduced the global enantioselectivity in the reaction of the racemic substrate (+/-)-5. The stereochemical pathway of the mismatched manifold has been shown also to be one of net retention, the apparent inversion occurring through equilibration via an Mo-allyl intermediate prior to nucleophilic attack. Incomplete equilibration leads to the memory effect and thus to lower enantioselectivity. Analysis of the mismatched manifold over the course of the reaction revealed that the memory effect is progressively attenuated with the nascent global selectivity increasing substantially as the reaction proceeds. The origin of this effect is suggested to be the depletion of CO sources in the reaction mixture, which attenuates turnover rate and thus facilitates

  17. A Systematic Study on the Mesomorphic Behavior of Asymmetrical 1-Alkyl-3-dodecylimidazolium Bromides

    SciTech Connect

    Yang, Mei; Mallick, Bert; Mudring, Anja-Verena

    2014-04-02

    To determine the essential parameters for mesophase formation in imidazolium-based ionic liquids (ILs), a library of 1-alkyl-3-dodecylimidazolium bromides was synthesized, abbreviated as CnC12, where 0 ≤ n ≤ 13, as the general notion is that a dodecyl side chain would guarantee the formation of an ionic liquid crystal (ILC). All salts were fully characterized by NMR spectroscopy and mass spectrometry. Their thermal properties were recorded, and mesophase formation was assessed. An odd–even effect is observed for 5 ≤ n ≤ 10 in the temperatures of melting transitions. While the majority of this series, as expected, formed mesophases, surprisingly compounds C2C12 and C6C12 could not be classified as ILCs, the latter being a room temperature IL, while C2C12 is a crystalline solid with melting point at 37 °C. The single crystal structure of compound 1-ethyl-3-dodecylimidazolium bromide (C2C12) was successfully obtained. Remarkably, the arrangement of imidazolium cores in the structure is very complicated due to multiple nonclassical hydrogen bonds between bromide anions and imidazolium head groups. In this arrangement, neighboring imidazolium rings are forced by hydrogen bonds to form a “face-to-face” conformation. This seems to be responsible for the elimination of a mesophase. To conclude, the general view of a dodecyl chain being a functional group to generate a mesophase is not entirely valid.

  18. Cp2ZrMeCl: A Reagent for Asymmetric Methyl Addition.

    PubMed

    Garrec, Kilian; Fletcher, Stephen P

    2016-08-01

    The use of Cp2ZrMeCl is described as a source of nucleophilic methyl in asymmetric catalysis. This easily prepared reagent is bench stable, weighable in air, and generally useful in highly enantioselective copper-catalyzed addition reactions at room temperature. Methyl is successfully (generally >90% ee) added in 1,4-additions to cyclic and acyclic α,β-unsaturated ketones to provide tertiary and quaternary centers. Examples of catalyst controlled diastereoselective 1,6-addition and dynamic kinetic asymmetric allylic alkylation reactions are also reported. The reagent is used in the catalytic asymmetric synthesis of naturally occurring fragrance (R)-(-)-muscone (82% yield, 91% ee). PMID:27458650

  19. Pd-catalyzed asymmetric allylic etherification using chiral biphenol-based diphosphinite ligands and its application for the formal total synthesis of (-)-galanthamine.

    PubMed

    Zang, Yang; Ojima, Iwao

    2013-04-19

    A library of novel chiral biphenol-based diphosphinite (BOP) ligands was designed and created. These BOP ligands were applied to a Pd-catalyzed intermolecular allylic etherification reaction, which provided a key intermediate for the formal total synthesis of (-)-galanthamine with 97% ee in 97% yield. PMID:23472673

  20. Enantioselective synthesis of 3-fluoro-3-allyl-oxindoles via phosphine-catalyzed asymmetric γ-addition of 3-fluoro-oxindoles to 2,3-butadienoates.

    PubMed

    Wang, Tianli; Hoon, Ding Long; Lu, Yixin

    2015-06-25

    The first phosphine-catalyzed enantioselective γ-addition of 3-fluoro-oxindoles to 2,3-butadienoates has been developed. A range of 3-fluoro-substituted oxindole substrates were employed, and oxindoles containing a 3-fluoro quaternary center were constructed in high yields and with excellent enantioselectivities. The γ-addition products could be converted readily to optically enriched 3-fluoro-3-allyl oxindole derivatives. PMID:26013076

  1. Synergistic fungicidal activity of Cu(2+) and allicin, an allyl sulfur compound from garlic, and its relation to the role of alkyl hydroperoxide reductase 1 as a cell surface defense in Saccharomyces cerevisiae.

    PubMed

    Ogita, Akira; Hirooka, Kiyoo; Yamamoto, Yoshihiro; Tsutsui, Nobuo; Fujita, Ken-Ichi; Taniguchi, Makoto; Tanaka, Toshio

    2005-11-15

    Cu(2+) showed a dose-dependent fungicidal activity against Saccharomyces cerevisiae cells, and its lethal effect was extremely enhanced in the presence of allicin, an allyl sulfur compound from garlic. The fungicidal activity of Cu(2+) was unaffected or rather attenuated by other sulfur-containing compounds such as N-acetyl-cysteine, l-cysteine or dithiothreitol. Ca(2+) could absolutely protect against the lethal effect of Cu(2+) itself, but showed no protection against the fungicidal activity of Cu(2+) newly generated in combination with allicin. Cu(2+) accelerated an endogenous generation of reactive oxygen species (ROS) in S. cerevisiae cells at a lethal concentration, but such intracellular oxidative stress induction was not observed during cell death progression upon treatment with Cu(2+) and allicin. A surfactant, sodium N-lauroyl sarcosinate (SLS), enhanced the solubilization of a few proteins including alkyl hydroperoxide reductase 1 (AHP1) in intact cells, accounting for the absence of this protein in the extract from allicin-treated cells. Allicin-treated cells were rendered extremely sensitive to the subsequent Cu(2+) treatment as in the case of SLS-treated cells. Allicin-treated cells and SLS-treated cells similarly showed an increased sensitivity to exogenously added tert-butyl hydroperoxide (t-BOOH), an organic peroxide that is detoxified by the action of AHP1. Our study suggests that allicin influences the mode of cell surface localization or the related function of AHP1 as a defense against phospholipid peroxidation by the external action of Cu(2+). PMID:16102883

  2. Iridium-Catalyzed Allylic Substitution

    NASA Astrophysics Data System (ADS)

    Hartwig, John F.; Pouy, Mark J.

    Iridium-catalyzed asymmetric allylic substitution has become a valuable method to prepare products from the addition of nucleophiles at the more substituted carbon of an allyl unit. The most active and selective catalysts contain a phosphoramidite ligand possessing at least one arylethyl substituent on the nitrogen atom of the ligand. In these systems, the active catalyst is generated by a base-induced cyclometalation at the methyl group of this substituent to generate an iridium metalacycle bound by the COD ligand of the [Ir(COD)Cl]2 precursor and one additional labile dative ligand. Such complexes catalyze the reactions of linear allylic esters with alkylamines, arylamines, phenols, alcohols, imides, carbamates, ammonia, enolates and enolate equivalents, as well as typical stabilized carbon nucleophiles generated from malonates and cyanoesters. Iridium catalysts for enantioselective allylic substitution have also been generated from phosphorus ligands with substituents bound by heteroatoms, and an account of the studies of such systems, along with a description of the development of iridium catalysts is included.

  3. Synthesis of a Series of γ-Keto Allyl Phosphonates.

    PubMed

    Elleuch, Haitham; Ayadi, Marwa; Bouajila, Jalloul; Rezgui, Farhat

    2016-03-01

    Under solvent-free conditions and at 80 °C, a DMAP- or imidazole-mediated clean and rapid conversion of cyclic Morita-Baylis-Hillman (MBH) acetates into the corresponding γ-keto allyl phosphonates in 70-93% yields is described herein. This allylic nucleophilic substitution works well with primary and secondary acetates bearing, at the β'-position, linear or branched alkyl groups and aryl groups. PMID:26872500

  4. The Palladium Catalyzed Asymmetric Addition of Oxindoles and Allenes: an Atom-Economical Versatile Method for the Construction of Chiral Indole Alkaloids

    PubMed Central

    Trost, Barry M.; Xie, Jia; Sieber, Joshua D.

    2011-01-01

    The Pd-catalyzed asymmetric allylic alkylation (AAA) is one of the most useful and versatile methods for asymmetric synthesis known in organometallic chemistry. Development of this reaction over the past 30 years has typically relied on the use of an allylic electrophile bearing an appropriate leaving group to access the reactive Pd(π-allyl) intermediate that goes on to the desired coupling product after attack by the nucleophile present in the reaction. Our group has been interested in developing alternative approaches to access the reactive Pd(π-allyl) intermediate that does not require the use of an activated electrophile, which ultimately generates a stoichiometric byproduct in the reaction that is derived from the leftover leaving group. Along these lines, we have demonstrated that allenes can be used to generate the reactive Pd(π-allyl) intermediate in the presence of an acid cocatalyst, and this system is compatible with nucleophiles to allow for formation of formal AAA products by Pd-catalyzed additions to allenes. This article describes our work regarding the use of oxindoles as carbon-based nucleophiles in a Pd-catalyzed asymmetric addition of oxindoles to allenes (Pd-catalyzed hydrocarbonation of allenes). By using the chiral standard Trost ligand (L1) and 3-aryloxindoles as nucleophiles, this hydrocarbonation reaction provides products with two vicinal stereocenters, with one being quaternary, in excellent chemo-, regio-, diastereo-, and enantioselectivities in high chemical yields. PMID:22070545

  5. Copper(I)-Catalyzed Allylic Substitutions with a Hydride Nucleophile.

    PubMed

    Nguyen, T N Thanh; Thiel, Niklas O; Pape, Felix; Teichert, Johannes F

    2016-05-20

    An easily accessible copper(I)/N-heterocyclic carbene (NHC) complex enables a regioselective hydride transfer to allylic bromides, an allylic reduction. The resulting aryl- and alkyl-substituted branched α-olefins, which are valuable building blocks for synthesis, are obtained in good yields and regioselectivity. A commercially available silane, (TMSO)2Si(Me)H, is employed as hydride source. This protocol offers a unified alternative to the established metal-catalyzed allylic substitutions with carbon nucleophiles, as no adaption of the catalyst to the nature of the nucleophile is required. PMID:27151495

  6. Highly effective asymmetric hydrogenation of cyclic N-alkyl imines with chiral cationic Ru-MsDPEN catalysts.

    PubMed

    Chen, Fei; Ding, Ziyuan; Qin, Jie; Wang, Tianli; He, Yanmei; Fan, Qing-Hua

    2011-08-19

    A range of cyclic N-alkyl imines were efficiently hydrogenated by using a chiral cationic Ru(η(6)-cymene)(MsDPEN)(BArF) complex (MsDPEN = N-(methanesulfonyl)-1,2-diphenylethylenediamine) in high yields and up to 98% ee. A one-pot synthesis of chiral 2-phenylpyrrolidine via reductive amination was also developed. PMID:21766831

  7. Silver-Catalyzed Decarboxylative Allylation of Aliphatic Carboxylic Acids in Aqueous Solution.

    PubMed

    Cui, Lei; Chen, He; Liu, Chao; Li, Chaozhong

    2016-05-01

    Direct decarboxylative radical allylation of aliphatic carboxylic acids is described. With K2S2O8 as the oxidant and AgNO3 as the catalyst, the reactions of aliphatic carboxylic acids with allyl sulfones in aqueous CH3CN solution gave the corresponding alkenes in satisfactory yields under mild conditions. This site-specific allylation method is applicable to all primary, secondary, and tertiary alkyl acids and exhibits wide functional group compatibility. PMID:27065060

  8. Stereoselective Substrate-Controlled Asymmetric Syntheses of both 2,5-cis- and 2,5-trans-Tetrahydrofuranoid Oxylipids: Stereodivergent Intramolecular Amide Enolate Alkylation.

    PubMed

    Jang, Hongjun; Shin, Iljin; Lee, Dongjoo; Kim, Hyoungsu; Kim, Deukjoon

    2016-05-23

    The concise, highly stereoselective, substrate-controlled asymmetric total syntheses of both 2,5-cis- and 2,5-trans-tetrahydrofuranoid nematocidal oxylipids from the Australian brown algae Notheia anomala have been accomplished in a stereodivergent fashion. The highly stereoselective intramolecular amide enolate alkylation strategy provides access to both stereoisomers of the 3-hydroxy-2,5-disubstituted tetrahydrofuran core of these marine natural products through chelate and nonchelate control, which is driven by the C3-hydroxy protecting group. This approach offers an optional and highly stereoelective access to any of the eight possible stereoisomers of the 2,5-disubstituted-3-oxygenated tetrahydrofuran skeleton, an important structural feature which is present in many biologically active natural products. PMID:27100276

  9. α-Sulfonyl succinimides: versatile sulfinate donors in Fe-catalyzed, salt-free, neutral allylic substitution.

    PubMed

    Jegelka, Markus; Plietker, Bernd

    2011-09-01

    Allyl sulfones are versatile intermediates in organic chemistry. The presence of two distinct functional groups sets the stage for a plethora of subsequent transformations. However, despite these advantages the preparation of regioisomerically enriched sulfones is not easy. The use of sulfinate salts as nucleophiles in substitutions is frequently accompanied by side reactions such as π-bond migration, β-elimination, and so on. Herein we present a preparatively simple way to synthesize a variety of different aryl or alkyl allyl sulfones starting from readily accessible allylic carbonates. By employing aryl or alkyl α-sulfonyl succinimides as sulfinate synthons, mild and regioselective ipso substitution of diverse allylic carbonates was realized. PMID:21818793

  10. Pd-Catalyzed Synthesis of Allylic Silanes from Allylic Ethers

    PubMed Central

    Moser, Ralph; Nishikata, Takashi; Lipshutz, Bruce H.

    2009-01-01

    Allylic phenyl ethers serve as electrophiles towards Pd(0) en route to a variety of allylic silanes. The reactions can be run at room temperature in water as the only medium using micellar catalysis. PMID:19950911

  11. Amide groups switch selectivity: C-H trifluoromethylation of α,β-unsaturated amides and subsequent asymmetric transformation.

    PubMed

    Li, Lei; Guo, Jing-Yao; Liu, Xing-Guo; Chen, Su; Wang, Yong; Tan, Bin; Liu, Xin-Yuan

    2014-11-21

    The first direct C-H β-trifluoromethylation of unsubstituted or α-alkyl-substituted α,β-unsaturated carbonyl compounds under metal-free conditions was realized with excellent regio- and stereoselectivity as well as a very broad substrate scope. Both olefinic and allylic trifluoromethylation products are accessible with high selectivities by altering the substrate substitutions. The resultant olefinic products, namely (E)-β-trifluoromethyl (CF3) α,β-unsaturated hydroxamic acid derivatives, served as acceptors in organocatalytic asymmetric Michael addition reactions to give hydroxamic acid derivatives bearing a chiral CF3-substituted stereocenter with high enantioselectivities. PMID:25383919

  12. Iridium-Catalyzed Selective Isomerization of Primary Allylic Alcohols.

    PubMed

    Li, Houhua; Mazet, Clément

    2016-06-21

    This Account presents the development of the iridium-catalyzed isomerization of primary allylic alcohols in our laboratory over the past 8 years. Our initial interest was driven by the long-standing challenge associated with the development of a general catalyst even for the nonasymmetric version of this seemingly simple chemical transformation. The added value of the aldehyde products and the possibility to rapidly generate molecular complexity from readily accessible allylic alcohols upon a redox-economical isomerization reaction were additional sources of motivation. Certainly influenced by the success story of the related isomerization of allylic amines, most catalysts developed for the selective isomerization of allylic alcohols were focused on rhodium as a transition metal of choice. Our approach has been based on the commonly accepted precept that hydrogenation and isomerization are often competing processes, with the latter being usually suppressed in favor of the former. The cationic iridium complexes [(Cy3P)(pyridine)Ir(cod)]X developed by Crabtree (X = PF6) and Pfaltz (X = BArF) are usually considered as the most versatile catalysts for the hydrogenation of allylic alcohols. Using molecular hydrogen to generate controlled amounts of the active form of these complexes but performing the reaction in the absence of molecular hydrogen enabled deviation from the typical hydrogenation manifold and favored exclusively the isomerization of allylic alcohols into aldehydes. Isotopic labeling and crossover experiments revealed the intermolecular nature of the process. Systematic variation of the ligand on the iridium center allowed us to identify the structural features beneficial for catalytic activity. Subsequently, three generations of chiral catalysts have been investigated and enabled us to reach excellent levels of enantioselectivity for a wide range of 3,3-disubstituted aryl/alkyl and alkyl/alkyl primary allylic alcohols leading to β-chiral aldehydes. The

  13. Palladium-Catalyzed Allylic C-H Bond Functionalization of Olefins

    NASA Astrophysics Data System (ADS)

    Liu, Guosheng; Wu, Yichen

    Transition metal-mediated carbon-hydrogen bond cleavage and functionalization is a mechanistically interesting and synthetically attractive process. One of the important cases is the removal of a allylic hydrogen from an olefin by a PdII salt to yield a π-allylpalladium complex, followed by nucleophilic attack to efficient produce allylic derivatives. In contrast to the well-known allylic acetoxylation of cyclohexene, the reaction of open-chain olefins is fairly poor until recent several years. Some palladium catalytic systems have been reported to achieve allylic C-H functionalization, including acetoxylation, amination and alkylation of terminal alkenes. In the most of cases, ligand is crucial to the success of the transformation. This review surveys the recent development of palladium-catalyzed allylic C-H functionalziation of alkenes. These results promise a significant increase in the scope of olefin transformation.

  14. PHOTOOXIDATION OF ALLYL CHLORIDE

    EPA Science Inventory

    The photooxidation of allyl chloride was studied by irradiation either in 100-L Teflon bags or in a 22.7-cu m Teflon smog chamber in the presence of added NOx. In the absence of added hydrocarbons, the reaction involves a Cl atom chain, which leads to a highly reactive system. A ...

  15. ION EXCHANGE SUBSTANCES BY SAPONIFICATION OF ALLYL PHOSPHATE POLYMERS

    DOEpatents

    Kennedy, J.

    1959-04-14

    An ion exchange resin having a relatively high adsorption capacity tor uranyl ion as compared with many common cations is reported. The resin comprises an alphyl-allyl hydrogen phosphate polymer, the alphyl group being either allyl or a lower alkyl group having up to 5 carbon atoins. The resin is prepared by polymerizing compounds such as alkyl-diallyl phosphate and triallyl phosphate in the presence of a free radical generating substance and then partially hydrolyzing the resulting polymer to cause partial replacement of organic radicals by cations. A preferred free radical gencrating agent is dibenzoyl peroxide. The partial hydrolysis is brought about by refluxing the polymer with concentrated aqueous NaOH for three or four hours.

  16. Advanced asymmetric synthesis of (1R,2S)-1-amino-2-vinylcyclopropanecarboxylic acid by alkylation/cyclization of newly designed axially chiral Ni(II) complex of glycine Schiff base.

    PubMed

    Kawashima, Aki; Shu, Shuangjie; Takeda, Ryosuke; Kawamura, Akie; Sato, Tatsunori; Moriwaki, Hiroki; Wang, Jiang; Izawa, Kunisuke; Aceña, José Luis; Soloshonok, Vadim A; Liu, Hong

    2016-04-01

    Asymmetric synthesis of (1R,2S)-1-amino-2-vinylcyclopropanecarboxylic acid (vinyl-ACCA) is in extremely high demand due to the pharmaceutical importance of this tailor-made, sterically constrained α-amino acid. Here we report the development of an advanced procedure for preparation of the target amino acid via two-step SN2 and SN2' alkylation of novel axially chiral nucleophilic glycine equivalent. Excellent yields and diastereoselectivity coupled with reliable and easy scalability render this method of immediate use for practical synthesis of (1R,2S)-vinyl-ACCA. PMID:26661034

  17. Catalytic asymmetric alkylation of acylsilanes.

    PubMed

    Rong, Jiawei; Oost, Rik; Desmarchelier, Alaric; Minnaard, Adriaan J; Harutyunyan, Syuzanna R

    2015-03-01

    The highly enantioselective addition of Grignard reagents to acylsilanes is catalyzed by copper diphosphine complexes. This transformation affords α-silylated tertiary alcohols in up to 97% yield and 98:2 enantiomeric ratio. The competing Meerwein-Ponndorf-Verley reduction is suppressed by the use of a mixture of Lewis acid additives. The chiral catalyst can be recovered as a copper complex and used repeatedly without any loss of catalytic activity. PMID:25403641

  18. Immobilized catalysts for iridium-catalyzed allylic amination: rate enhancement by immobilization.

    PubMed

    Malakar, Chandi C; Helmchen, Günter

    2015-05-01

    The first immobilized catalyst for Ir-catalyzed asymmetric allylic aminations is described. The catalyst is a cationic (π-allyl)Ir complex bound by cation exchange to an anionic silica gel support. Preparation of the catalyst is facile, and the supported catalyst displayed considerably enhanced activity compared with the parent homogeneous catalyst. Up to 43 consecutive amination runs were possible in recycling experiments. PMID:25787122

  19. Asymmetric direct α-alkylation of 2-oxindoles with Michler's hydrol catalyzed by bis-cinchona alkaloid-Brønsted acid via an SN1-type pathway.

    PubMed

    Zhang, Tao; Qiao, Zhen; Wang, Yan; Zhong, Nengjun; Liu, Li; Wang, Dong; Chen, Yong-Jun

    2013-02-25

    An enantioselective direct α-alkylation of 2-oxindoles with Michler's hydrol via an S(N)1-type pathway in the non-covalent activation mode using the bis-cinchona alkaloid and Brønsted acid as a co-catalyst was developed and good to high yields and enantioselectivities were obtained. PMID:23340601

  20. Mild and Site-Selective Allylation of Enol Carbamates with Allylic Carbonates under Rhodium Catalysis.

    PubMed

    Sharma, Satyasheel; Han, Sang Hoon; Oh, Yongguk; Mishra, Neeraj Kumar; Han, Sangil; Kwak, Jong Hwan; Lee, Seok-Yong; Jung, Young Hoon; Kim, In Su

    2016-03-18

    The rhodium(III)-catalyzed mild and site-selective C-H allylation of enol carbamates with 4-vinyl-1,3-dioxolan-2-one and allylic carbonates affords allylic alcohols and terminal allylated products, respectively. The assistance of the carbamoyl directing group provides a straightforward preparation of biologically and synthetically important allylated enol carbamates. PMID:26906724

  1. Gold(I)-Catalyzed Intramolecular Hydroamination of N-Allylic,N'-Aryl Ureas to form Imidazolidin-2-ones.

    PubMed

    Li, Hao; Song, Feijie; Widenhoefer, Ross A

    2011-04-18

    Treatment of N-allylic,N'-aryl ureas with a catalytic 1:1 mixture of di-tert-butyl-o-biphenylphoshphine gold(I) chloride and silver hexafluorophosphate (1 mol %) in chloroform at room temperature led to 5-exo hydroamination to form the corresponding imidazolidin-2-ones in excellent yield. In the case of N-allylic ureas that possessed an allylic alkyl, benzyloxymethyl, or acetoxymethyl substituent, gold(I)-catalyzed 5-exo hydroamination leads to formation of the corresponding trans-3,4-disubstituted imidazolidin-2-ones in excellent yield with ≥50:1 diastereoselectivity. PMID:21709731

  2. Asymmetric Conjugate Addition of Benzofuran-2-ones to Alkyl 2-Phthalimidoacrylates: Modeling Structure-Stereoselectivity Relationships with Steric and Electronic Parameters.

    PubMed

    Yang, Chen; Zhang, En-Ge; Li, Xin; Cheng, Jin-Pei

    2016-05-23

    A highly predictive model to correlate the steric and electronic parameters of tertiary amine thiourea catalysts with the stereoselectivity of Michael reactions of 3-substituted benzofuranones and alkyl 2-phthalimidoacrylates is described. As predicted, new 3,5-bis(trifluoromethyl)benzyl- and methyl-substituted tertiary amine thioureas turned out to be highly suitable catalysts for this reaction and enabled the synthesis of enantioenriched α-amino acid derivatives with 1,3-nonadjacent stereogenic centers. PMID:27080558

  3. Tsuji-Trost N-allylation with allylic acetates using cellulose-Pd catalyst

    EPA Science Inventory

    Allylic amines are synthesized using heterogeneous cellulose-Pd catalyst via N-allylation of amines; aliphatic and benzyl amines undergo facile reaction with substituted and unsubstituted allyl acetates in high yields.

  4. Regioselective Transition-Metal-Free Allyl-Allyl Cross-Couplings.

    PubMed

    Ellwart, Mario; Makarov, Ilya S; Achrainer, Florian; Zipse, Hendrik; Knochel, Paul

    2016-08-22

    Readily prepared allylic zinc halides undergo SN 2-type substitutions with allylic bromides in a 1:1 mixture of THF and DMPU providing 1,5-dienes regioselectively. The allylic zinc species reacts at the most branched end (γ-position) of the allylic system furnishing exclusively γ,α'-allyl-allyl cross-coupling products. Remarkably, the double bond stereochemistry of the allylic halide is maintained during the cross-coupling process. Also several functional groups (ester, nitrile) are tolerated. This cross-coupling of allylic zinc reagents can be extended to propargylic and benzylic halides. DFT calculations show the importance of lithium chloride in this substitution. PMID:27430745

  5. Induction of unscheduled DNA synthesis in HeLa cells by allylic compounds.

    PubMed

    Schiffmann, D; Eder, E; Neudecker, T; Henschler, D

    1983-10-01

    Thirteen allylic compounds, mostly with close structural relationship, were tested for their ability to induce unscheduled DNA synthesis (UDS) in HeLa cells and mutations in the Ames test; 11 induced UDS in dose dependence. Allyl isothiocyanate was negative in UDS (borderline in the Ames test) and acrolein (positive in the Ames test) proved toxic to HeLa cells, therefore UDS measurement was excluded. In general, positive qualitative and quantitative correlation between UDS, Ames test and alkylating properties (as measured in the 4-nitrobenzyl-pyridine test, NBP) were found. Among structural analogs and typical allylic compounds with various leaving groups, the amount of induced DNA repair at equimolar concentrations decreased in the same order as the mutagenic and alkylating activities in the other 2 test systems: 1,3-dichloropropene (cis) greater than 1,3-dichloropropene (trans) greater than 2,3-dichloro-1-propene; 1-chloro-2-butene greater than 3-chloro-1-butene greater than 3-chloro-2-methyl-1-propene greater than allyl chloride; allyl-methane-sulfonate greater than -iodide greater than -bromide greater than -chloride. PMID:6627227

  6. Visible-Light-Mediated Alkenylation, Allylation, and Cyanation of Potassium Alkyltrifluoroborates with Organic Photoredox Catalysts.

    PubMed

    Heitz, Drew R; Rizwan, Komal; Molander, Gary A

    2016-08-19

    Iridium- and ruthenium-free approaches to protected allylic amines and alkyl nitriles under photoredox conditions are reported. An inexpensive organic dye, eosin Y, catalyzes coupling of Boc-protected potassium α-aminomethyltrifluoroborates with a variety of substituted alkenyl sulfones through an α-aminomethyl radical addition-elimination pathway. Allylic and homoallylic amines were formed in moderate yields with high E/Z selectivity. The mechanistic approach was extended using tosyl cyanide as a radical trap, enabling the conversion of alkyltrifluoroborates to nitriles via a Fukuzumi acridinium-catalyzed process. PMID:27336284

  7. Mechanistic Study of the Asymmetric Carbonyl-Ene Reaction between Alkyl Enol Ethers and Isatin Catalyzed by the N,N'-Dioxide-Mg(OTf)2 Complex.

    PubMed

    Wang, Junming; Su, Zhishan; Yang, Na; Hu, Changwei

    2016-08-01

    The mechanism and origin of the stereoselectivity of the asymmetric carbonyl-ene reaction between N-methyl-protected isatin and 2-methyloxypropene catalyzed by the N,N'-dioxide-Mg(OTf)2 complex were investigated by DFT and ONIOM methods. The background reaction occurred via a two-stage, one-step mechanism with a high activation barrier of 30.4 kcal mol(-1) at the B3LYP-D3(BJ)/6-311G**(SMD, CH2Cl2)//B3LYP/6-31G*(SMD, CH2Cl2) level at 303 K. Good linear correlations between the global nucleophilicity index (N) and the activation energy barrier (ΔG(⧧)) were found. The chiral N,N'-Mg(II) complex catalyst could enhance the electrophilicity of the isatin substrate by forming hexacoordinate Mg(II) reactive species. The substituent at the ortho positions of aniline combined with the aliphatic ring of the backbone in the chiral N,N'-dioxide ligand played an important role in the construction of a favorable "pocket-like" chiral environment (chiral pocket) around the Mg(II) center, directing the preferential orientation of the incoming substrate. An unfavorable steric arrangement in the re-face attack pathway translated into a more destabilizing activation strain of the ene substrate, enhancing enantiodifferentiation of two competing pathways for the desired R product. This work also suggested a new phosphine ligand (N-L1) for the formation of the Mg(II) complex catalyst for the asymmetric carbonyl-ene reaction. The chiral environment and Lewis acidity of the Mg(II) complex could be fine-tuned by introduction of P-donor units into the ligand for highly efficient asymmetric catalysis. PMID:27400326

  8. Enantioselective Allylic C-H Oxidation of Terminal Olefins to Isochromans by Palladium(II)/Chiral Sulfoxide Catalysis.

    PubMed

    Ammann, Stephen E; Liu, Wei; White, M Christina

    2016-08-01

    The enantioselective synthesis of isochroman motifs has been accomplished by palladium(II)-catalyzed allylic C-H oxidation from terminal olefin precursors. Critical to the success of this goal was the development and utilization of a novel chiral aryl sulfoxide-oxazoline (ArSOX) ligand. The allylic C-H oxidation reaction proceeds with the broadest scope and highest levels of asymmetric induction reported to date (avg. 92 % ee, 13 examples with greater than 90 % ee). PMID:27376625

  9. Branching Out: Rhodium-Catalyzed Allylation with Alkynes and Allenes.

    PubMed

    Koschker, Philipp; Breit, Bernhard

    2016-08-16

    We present a new and efficient strategy for the atom-economic transformation of both alkynes and allenes to allylic functionalized structures via a Rh-catalyzed isomerization/addition reaction which has been developed in our working group. Our methodology thus grants access to an important structural class valued in modern organic chemistry for both its versatility for further functionalization and the potential for asymmetric synthesis with the construction of a new stereogenic center. This new methodology, inspired by mechanistic investigations by Werner in the late 1980s and based on preliminary work by Yamamoto and Trost, offers an attractive alternative to other established methods for allylic functionalization such as allylic substitution or allylic oxidation. The main advantage of our methodology consists of the inherent atom economy in comparison to allylic oxidation or substitution, which both produce stoichiometric amounts of waste and, in case of the substitution reaction, require prefunctionalization of the starting material. Starting out with the discovery of a highly branched-selective coupling reaction of carboxylic acids with terminal alkynes using a Rh(I)/DPEphos complex as the catalyst system, over the past 5 years we were able to continuously expand upon this chemistry, introducing various (pro)nucleophiles for the selective C-O, C-S, C-N, and C-C functionalization of both alkynes and the double-bond isomeric allenes by choosing the appropriate rhodium/bidentate phosphine catalyst. Thus, valuable compounds such as branched allylic ethers, sulfones, amines, or γ,δ-unsaturated ketones were successfully synthesized in high yields and with a broad substrate scope. Beyond the branched selectivity inherent to rhodium, many of the presented methodologies display additional degrees of selectivity in regard to regio-, diastereo-, and enantioselective transformations, with one example even proceeding via a dynamic kinetic resolution. Many advances

  10. Regioselective hydroformylation of allylic alcohols.

    PubMed

    Lightburn, Thomas E; De Paolis, Omar A; Cheng, Ka H; Tan, Kian L

    2011-05-20

    A highly regioselective hydroformylation of allylic alcohols is reported toward the synthesis of β-hydroxy-acid and aldehyde products. The selectivity is achieved through the use of a ligand that reversibly binds to alcohols in situ, allowing for a directed hydroformylation to occur. The application to trisubstituted olefins was also demonstrated, which yields a single diastereomer product consistent with a stereospecific addition of CO and hydrogen. PMID:21504208

  11. Regioselective Hydroformylation of Allylic Alcohols

    PubMed Central

    Lightburn, Thomas E.; De Paolis, Omar A.; Cheng, Ka H.; Tan, Kian L.

    2011-01-01

    A highly regioselective hydroformylation of allylic alcohols is reported towards the synthesis of β-hydroxy-acid and aldehyde products. The selectivity is achieved through the use of a ligand that reversibly binds to alcohols in situ, allowing for a directed hydroformylation to occur. The application to trisubstituted olefins was also demonstrated, which yields a single diastereomer product consistent with a stereospecific addition of CO and hydrogen. PMID:21504208

  12. Interplay of metal-allyl and metal-metal bonding in dimolybdenum allyl complexes

    SciTech Connect

    John, Kevin D; Martin, Richard L; Obrey, Steven J; Scott, Brian L

    2008-01-01

    Addition of PMe{sub 3} to Mo{sub 2}(allyl){sub 4} afforded Mo{sub 2}(allyl){sub 4}(PMe{sub 3}){sub 2}, in which two of the allyl groups adopt an unprecedented {mu}{sub 2{sup -}}{eta}{sup 1}, {eta}{sup 3} bonding mode; theoretical studies elucidate the role sof the {sigma}- and {pi}-donor ligands in the interplay of metal-allyl and metal-metal bonding.

  13. Synthetic studies of callyspongiolide: synthesis of the macrolactone core of the molecule.

    PubMed

    Athe, Sudhakar; Sharma, Ashish; Marumudi, Kanakaraju; Ghosh, Subhash

    2016-07-12

    A concise synthetic strategy has been developed for the synthesis of the macrolactone core 2 of a unique polyketide callyspongiolide 1. The key features of the strategy included an Evan's asymmetric alkylation, diastereoselective Michael type alkylation, Brown's asymmetric allylation reaction, an allylic alkylation of an activated Z-allylic alcohol and an intramolecular Z-selective intramolecular H-W-E olefination. PMID:27337038

  14. O-Allylation of phenols with allylic acetates in aqueous media using a magnetically separable catalytic system

    EPA Science Inventory

    Allylic ethers were synthesized in water using magnetically recoverable heterogeneous Pd catalyst via O-allylation of phenols with allylic acetates under ambient conditions. Aqueous reaction medium, easy recovery of the catalyst using an external magnet, efficient recycling, and ...

  15. Tyrosine-selective protein alkylation using pi-allylpalladium complexes.

    PubMed

    Tilley, S David; Francis, Matthew B

    2006-02-01

    A new protein modification reaction has been developed based on a palladium-catalyzed allylic alkylation of tyrosine residues. This technique employs electrophilic pi-allyl intermediates derived from allylic acetate and carbamate precursors and can be used to modify proteins in aqueous solution at room temperature. To facilitate the detection of modified proteins using SDS-PAGE analysis, a fluorescent allyl acetate was synthesized and coupled to chymotrypsinogen A and bacteriophage MS2. The tyrosine selectivity of the reaction was confirmed through trypsin digest analysis. The utility of the reaction was demonstrated by using taurine-derived carbamates as water solubilizing groups that are cleaved upon protein functionalization. This solubility switching technique was used to install hydrophobic farnesyl and C(17) chains on chymotrypsinogen A in water using little or no cosolvent. Following this, the C(17) alkylated proteins were found to associate with lipid vesicles. In addition to providing a new protein modification strategy targeting an under-utilized amino acid side chain, this method provides convenient access to synthetic lipoproteins. PMID:16433516

  16. Tandem rhodium catalysis:Exploiting sulfoxides for asymmetric transition-metal catalysis

    PubMed Central

    Kou, K. G. M.

    2015-01-01

    Sulfoxides are uncommon substrates for transition-metal catalysis due to their propensity to inhibit catalyst turnover. In a collaborative effort with Ken Houk, we developed the first dynamic kinetic resolution (DKR) of allylic sulfoxides using asymmetric rhodium-catalyzed hydrogenation. Detailed mechanistic analysis of this transformation using both experimental and theoretical methods revealed rhodium to be a tandem catalyst that promoted both hydrogenation of the alkene and racemization of the allylic sulfoxide. Using a combination of deuterium labelling and DFT studies, a novel mode of allylic sulfoxide racemization via a Rh(III)-π-allyl intermediate was identified. PMID:25940066

  17. Regiodivergent Addition of Phenols to Allylic Oxides

    PubMed Central

    Vaccarello, David N.; Moschitto, Matthew J.; Lewis, Chad A.

    2015-01-01

    The regiodivergent addition of substituted phenols to allylic-oxides has been demonstrated using C2-symmetric palladium complexes. Complex phenol donors tyrosine, estradiol, and griseofulvin follow the predictive model. The Tsuji-Trost reaction is a powerful method to append both O- and C-donors to η3-allyl systems.1 The η3-allyl progenitor structures include allylic esters, carbonates, halides, and oxides. Internal allylic oxides2 remain one of the few systems that retain a marker of stereochemical induction with the newly liberated carbinol. The origin of the products can be traced to the diastereomeric η3-allyl intermediate and stereoisomer of oxide employed. We have recently identified3 a system capable of the conversion of racemic allylic oxides to distinct enantioenriched regioisomers using achiral phenol donors (Scheme 1). The allylic oxide regio-resolution (AORR) allowed the preparation of enantioenriched carbasugar natural products. We have now expanded this study to include a diverse array of achiral and chiral phenol donors. PMID:25933102

  18. Nickel-Catalyzed Asymmetric Reductive Cross-Coupling Between Vinyl and Benzyl Electrophiles

    PubMed Central

    2015-01-01

    A Ni-catalyzed asymmetric reductive cross-coupling between vinyl bromides and benzyl chlorides has been developed. This method provides direct access to enantioenriched products bearing aryl-substituted tertiary allylic stereogenic centers from simple, stable starting materials. A broad substrate scope is achieved under mild reaction conditions that preclude the pregeneration of organometallic reagents and the regioselectivity issues commonly associated with asymmetric allylic arylation. PMID:25245492

  19. Catalytic deallylation of allyl- and diallylmalonates.

    PubMed

    Necas, David; Turský, Matyás; Kotora, Martin

    2004-08-25

    Substituted allylmalonates undergo the selective C-C bond cleavage in the presence of triethylaluminum and a catalytic amount of nickel and ruthenium phosphine complexes, resulting in the loss of the allyl moiety and formation of monosubstituted malonates. Comparison of reactivity of the nickel and ruthenium complexes showed that the use of the former is general with respect to the structure of the substituted allylmalonates, and the activity of the latter depended on the substitution pattern of the double bond of the allylic moiety. The smooth deallylation may encourage the use of the allyl group as a protective group for the acidic hydrogen in malonates. PMID:15315416

  20. Crystal structure of bis­(allyl­ammonium) oxalate

    PubMed Central

    Dziuk, Błażej; Zarychta, Bartosz; Ejsmont, Krzysztof

    2014-01-01

    The title salt, 2C3H8N+·C2O4 2−, crystallized with six independent allyl­ammonium cations and three independent oxalate dianions in the asymmetric unit. One of the oxalate dianions is nearly planar [dihedral angle between CO2 planes = 1.91 (19)°], while the other two are twisted with angles of 11.3 (3) and 26.09 (13)°. One cation has a synperiplanar (cis) conformation with an N—C—C—C torsion angle of 0.9 (3)°, whereas the five remaining cations are characterized by gauche arrangements, with the N—C—C—C torsion angles ranging from 115.9 (12) to 128.8 (3)°. One of the allyl­ammonium cations is positionally disordered (fixed occupancy ratio = 0.45:0.55). In the crystal, the cations and anions are connected by a number of strong N—H⋯O and N—H⋯(O,O) hydrogen bonds, forming layers parallel to (001), with the vinyl groups protruding into the space between the layers. PMID:25553015

  1. Palladium(0)-Catalyzed Allylation of Highly Acidic and Nonnucleophilic Anilines. The Origin of Stereochemical Scrambling When Using Allylic Carbonates.

    PubMed

    Moreno-Mañas, Marcial; Morral, Lurdes; Pleixats, Roser

    1998-09-01

    Acidic anilines such as diphenylamine, phenothiazine, and nitroanilines are efficiently allylated under palladium catalysis using allyl carbonates as allylating reagents. A stereochemical study of the reactions of ethyl cis-5-methyl-2-cyclohexenylcarbonate with 4-nitro- and 2,4-dinitroaniline was performed. Bidentate phosphines as stabilizing ligands gave clean retention of configuration whereas triphenylphosphine permitted cis-trans isomerization of the allylic carbonate, the allylation reactions occurring under Curtin-Hammet preequilibrium conditions. PMID:11672246

  2. Ni-Catalyzed C-C Couplings Using Alkyl Electrophiles.

    PubMed

    Iwasaki, Takanori; Kambe, Nobuaki

    2016-10-01

    Much effort has been devoted to developing new methods using Ni catalysts for the cross-coupling reaction of alkyl electrophiles with organometallic reagents, and significant achievements in this area have emerged during the past two decades. Nickel catalysts have enabled the coupling reaction of not only primary alkyl electrophiles, but also sterically hindered secondary and tertiary alkyl electrophiles possessing β-hydrogens with various organometallic reagents to construct carbon skeletons. In addition, Ni catalysts opened a new era of asymmetric cross-coupling reaction using alkyl halides. Recent progress in nickel-catalyzed cross-coupling reaction of alkyl electrophiles with sp(3)-, sp(2)-, and sp-hybridized organometallic reagents including asymmetric variants as well as mechanistic insights of nickel catalysis are reviewed in this chapter. PMID:27580894

  3. Copper-Catalyzed Oxidative Dehydrogenative Carboxylation of Unactivated Alkanes to Allylic Esters via Alkenes

    PubMed Central

    2015-01-01

    We report copper-catalyzed oxidative dehydrogenative carboxylation (ODC) of unactivated alkanes with various substituted benzoic acids to produce the corresponding allylic esters. Spectroscopic studies (EPR, UV–vis) revealed that the resting state of the catalyst is [(BPI)Cu(O2CPh)] (1-O2CPh), formed from [(BPI)Cu(PPh3)2], oxidant, and benzoic acid. Catalytic and stoichiometric reactions of 1-O2CPh with alkyl radicals and radical probes imply that C–H bond cleavage occurs by a tert-butoxy radical. In addition, the deuterium kinetic isotope effect from reactions of cyclohexane and d12-cyclohexane in separate vessels showed that the turnover-limiting step for the ODC of cyclohexane is C–H bond cleavage. To understand the origin of the difference in products formed from copper-catalyzed amidation and copper-catalyzed ODC, reactions of an alkyl radical with a series of copper–carboxylate, copper–amidate, and copper–imidate complexes were performed. The results of competition experiments revealed that the relative rate of reaction of alkyl radicals with the copper complexes follows the trend Cu(II)–amidate > Cu(II)–imidate > Cu(II)–benzoate. Consistent with this trend, Cu(II)–amidates and Cu(II)–benzoates containing more electron-rich aryl groups on the benzamidate and benzoate react faster with the alkyl radical than do those with more electron-poor aryl groups on these ligands to produce the corresponding products. These data on the ODC of cyclohexane led to preliminary investigation of copper-catalyzed oxidative dehydrogenative amination of cyclohexane to generate a mixture of N-alkyl and N-allylic products. PMID:25389772

  4. Copper-catalyzed oxidative dehydrogenative carboxylation of unactivated alkanes to allylic esters via alkenes.

    PubMed

    Tran, Ba L; Driess, Matthias; Hartwig, John F

    2014-12-10

    We report copper-catalyzed oxidative dehydrogenative carboxylation (ODC) of unactivated alkanes with various substituted benzoic acids to produce the corresponding allylic esters. Spectroscopic studies (EPR, UV-vis) revealed that the resting state of the catalyst is [(BPI)Cu(O2CPh)] (1-O2CPh), formed from [(BPI)Cu(PPh3)2], oxidant, and benzoic acid. Catalytic and stoichiometric reactions of 1-O2CPh with alkyl radicals and radical probes imply that C-H bond cleavage occurs by a tert-butoxy radical. In addition, the deuterium kinetic isotope effect from reactions of cyclohexane and d12-cyclohexane in separate vessels showed that the turnover-limiting step for the ODC of cyclohexane is C-H bond cleavage. To understand the origin of the difference in products formed from copper-catalyzed amidation and copper-catalyzed ODC, reactions of an alkyl radical with a series of copper-carboxylate, copper-amidate, and copper-imidate complexes were performed. The results of competition experiments revealed that the relative rate of reaction of alkyl radicals with the copper complexes follows the trend Cu(II)-amidate > Cu(II)-imidate > Cu(II)-benzoate. Consistent with this trend, Cu(II)-amidates and Cu(II)-benzoates containing more electron-rich aryl groups on the benzamidate and benzoate react faster with the alkyl radical than do those with more electron-poor aryl groups on these ligands to produce the corresponding products. These data on the ODC of cyclohexane led to preliminary investigation of copper-catalyzed oxidative dehydrogenative amination of cyclohexane to generate a mixture of N-alkyl and N-allylic products. PMID:25389772

  5. Direct and Highly Regioselective and Enantioselective Allylation of β-Diketones

    PubMed Central

    Chalifoux, Wesley A.; Reznik, Samuel K.; Leighton, James L.

    2012-01-01

    The enantioselective allylation of ketones represents both a problem of fundamental importance in asymmetric reaction design and one of only a very small number of available methods to access valuable tertiary carbinols. Despite the vast amount of attention from chemists that this problem has elicited,1-8 however, success has generally been limited to just a few simple ketone types thus limiting the utility of these methods. A method for the selective allylation of functionally complex ketones would be expected to increase the utility of ketone allylation methods in the chemical synthesis of important targets. Here we describe the operationally simple, direct, regioselective, and enantioselective allylation of β-diketones. The strong tendency of β-diketones to act as nucleophilic species was overcome by the co-optation of their enol form to provide the necessary Brønsted acid activation. This unprecedented reaction thus not only significantly expands the pool of enantiomerically enriched and functionally complex tertiary carbinols that may be easily accessed, but also overturns more than a century of received wisdom regarding the reactivity of β-diketones. PMID:22763452

  6. N-Allylation of amines with allyl acetates using chitosan-immobilized palladium

    EPA Science Inventory

    A simple procedure for N-Allylation of allyl Acetates has been developed using a biodegradable and easily recyclable heterogeneous chitosan-supported palladium catalyst. The general methodology, applicable to wide range of substrates, has sustainable features that include a ligan...

  7. Hydroxamic Acids in Asymmetric Synthesis

    PubMed Central

    Li, Zhi; Yamamoto, Hisashi

    2012-01-01

    Metal-catalyzed stereoselective reactions are a central theme in organic chemistry research. In these reactions, the stereoselection is achieved predominantly by introducing chiral ligands at the metal catalyst’s center. For decades, researchers have sought better chiral ligands for asymmetric catalysis and have made great progress. Nevertheless, to achieve optimal stereoselectivity and to catalyze new reactions, new chiral ligands are needed. Due to their high metal affinity, hydroxamic acids play major roles across a broad spectrum of fields from biochemistry to metal extraction. Dr. K. Barry Sharpless first revealed their potential as chiral ligands for asymmetric synthesis in 1977: He published the chiral vanadium-hydroxamic-acid-catalyzed, enantioselective epoxidation of allylic alcohols before his discovery of Sharpless Asymmetric Epoxidation, which uses titanium-tartrate complex as the chiral reagent. However, researchers have reported few highly enantioselective reactions using metal-hydroxamic acid as catalysts since then. This Account summarizes our research on metal-catalyzed asymmetric epoxidation using hydroxamic acids as chiral ligands. We designed and synthesized a series of new hydroxamic acids, most notably the C2-symmetric bis-hydroxamic acid (BHA) family. V-BHA-catalyzed epoxidation of allylic and homoallylic alcohols achieved higher activity and stereoselectivity than Sharpless Asymmetric Epoxidation in many cases. Changing the metal species led to a series of unprecedented asymmetric epoxidation reactions, such as (i) single olefins and sulfides with Mo-BHA, (ii) homoallylic and bishomoallylic alcohols with Zr- and Hf-BHA, and (iii) N-alkenyl sulfonamides and N-sulfonyl imines with Hf-BHA. These reactions produce uniquely functionalized chiral epoxides with good yields and enantioselectivities. PMID:23157425

  8. Hydroxamic acids in asymmetric synthesis.

    PubMed

    Li, Zhi; Yamamoto, Hisashi

    2013-02-19

    Metal-catalyzed stereoselective reactions are a central theme in organic chemistry research. In these reactions, the stereoselection is achieved predominantly by introducing chiral ligands at the metal catalyst's center. For decades, researchers have sought better chiral ligands for asymmetric catalysis and have made great progress. Nevertheless, to achieve optimal stereoselectivity and to catalyze new reactions, new chiral ligands are needed. Because of their high metal affinity, hydroxamic acids play major roles across a broad spectrum of fields from biochemistry to metal extraction. Dr. K. Barry Sharpless first revealed their potential as chiral ligands for asymmetric synthesis in 1977: He published the chiral vanadium-hydroxamic-acid-catalyzed, enantioselective epoxidation of allylic alcohols before his discovery of Sharpless asymmetric epoxidation, which uses the titanium-tartrate complex as the chiral reagent. However, researchers have reported few highly enantioselective reactions using metal-hydroxamic acid as catalysts since then. This Account summarizes our research on metal-catalyzed asymmetric epoxidation using hydroxamic acids as chiral ligands. We designed and synthesized a series of new hydroxamic acids, most notably the C2-symmetric bis-hydroxamic acid (BHA) family. V-BHA-catalyzed epoxidation of allylic and homoallylic alcohols achieved higher activity and stereoselectivity than Sharpless asymmetric epoxidation in many cases. Changing the metal species led to a series of unprecedented asymmetric epoxidation reactions, such as (i) single olefins and sulfides with Mo-BHA, (ii) homoallylic and bishomoallylic alcohols with Zr- and Hf-BHA, and (iii) N-alkenyl sulfonamides and N-sulfonyl imines with Hf-BHA. These reactions produce uniquely functionalized chiral epoxides with good yields and enantioselectivities. PMID:23157425

  9. Catalytic alkylation apparatus

    SciTech Connect

    Hann, P.D.; VanPool, J.

    1989-09-05

    This patent describes an apparatus. It comprises alkylation reactor means for producing alkylate product; acid catalyst settler means having an upper portion, an intermediate portion and a lower portion; means for withdrawing alkylate product from the alkylation reactor means and for providing alkylate product from the alkylation reactor means to a point of introduction in the intermediate portion of the acid catalyst settler means; and means for establishing a temperature gradient in the upper the gas lines to the detector so that a flow rate of a sample gas passing through the detector is constant.

  10. HPLC and TLC characterisation of ecdysteroid alkyl ethers.

    PubMed

    Lapenna, Silvia; Dinan, Laurence

    2009-10-01

    Semi-synthetic ecdysteroid alkyl ethers have increased potential over natural ecdysteroids as actuators of ligand-inducible gene-expression systems based on the ecdysteroid receptor for in vivo applications. However, a scalable synthesis of these compounds has yet to be developed. We report a set of reversed-phase (RP; C(18) and C(6)) and normal-phase (NP; diol) HPLC systems which can be used to analyse and separate ecdysteroid ethers with single or multiple O-methyl substitutions at the 2alpha-, 3beta-, 14alpha-, 22- and 25-positions. The elution order of methyl ether analogues of the prototypical ecdysteroid 20-hydroxyecdysone (20E) was 3-methyl<2-methyl<14-methyl<25-methyl<22-methyl with both C(18)- and C(6)-RP-HPLC, when eluted with methanol/water mixtures. Further, the elution order of 20E 22-O-alkyl ethers was methylallylalkyl ethers can also be adequately resolved by NP-HPLC and silica HPTLC. On the latter, detection of ecdysteroid O-alkyl ethers with the p-anisaldehyde/sulphuric acid reagent distinguishes 22-O-alkyl ethers from non-22-O-alkyl ether analogues by the colour of the resulting spot. PMID:19648067

  11. N-Alkylation by Hydrogen Autotransfer Reactions.

    PubMed

    Ma, Xiantao; Su, Chenliang; Xu, Qing

    2016-06-01

    Owing to the importance of amine/amide derivatives in all fields of chemistry, and also the green and environmentally benign features of using alcohols as alkylating reagents, the relatively high atom economic dehydrative N-alkylation reactions of amines/amides with alcohols through hydrogen autotransfer processes have received much attention and have developed rapidly in recent decades. Various efficient homogeneous and heterogeneous transition metal catalysts, nano materials, electrochemical methods, biomimetic methods, asymmetric N-alkylation reactions, aerobic oxidative methods, and even certain transition metal-free, catalyst-free, or autocatalyzed methods, have also been developed in recent years. With a brief introduction to the background and developments in this area of research, this chapter focuses mainly on recent progress and technical and conceptual advances contributing to the development of this research in the last decade. In addition to mainstream research on homogeneous and heterogeneous transition metal-catalyzed reactions, possible mechanistic routes for hydrogen transfer and alcohol activation, which are key processes in N-alkylation reactions but seldom discussed in the past, the recent reports on computational mechanistic studies of the N-alkylation reactions, and the newly emerged N-alkylation methods based on novel alcohol activation protocols such as air-promoted reactions and transition metal-free methods, are also reviewed in this chapter. Problems and bottlenecks that remained to be solved in the field, and promising new research that deserves greater future attention and effort, are also reviewed and discussed. PMID:27573267

  12. One-Pot Multicomponent Coupling Methods for the Synthesis of Diastereo- and Enantioenriched (Z)-Trisubstituted Allylic Alcohols

    PubMed Central

    Kerrigan, Michael H.; Jeon, Sang-Jin; Chen, Young K.; Salvi, Luca; Carroll, Patrick J.; Walsh, Patrick J.

    2009-01-01

    (Z)-Trisubstituted allylic alcohols are widespread structural motifs in natural products and biologically active compounds but are difficult to directly prepare. Introduced herein is a general one-pot multicomponent coupling method for the synthesis of (Z)-α,α,β-trisubstituted allylic alcohols. (Z)-Trisubstituted vinylzinc reagents are formed in situ by initial hydroboration of 1-bromo-1-alkynes. Addition of dialkylzinc reagents induces a 1,2-metallate rearrangement that is followed by a boron-to-zinc transmetallation. The resulting vinylzinc reagents add to a variety of prochiral aldehydes to produce racemic (Z)-trisubstituted allylic alcohols. When enantioenriched aldehyde substrates are employed (Z)-trisubstituted allylic alcohols are isolated with high dr (>20:1 in many cases). For example, vinylation of enantioenriched benzyl protected α- and β-hydroxy propanal derivatives furnished the expected anti-Felkin addition products via chelation control. Surprisingly, silyl protected α-hydroxy aldehydes also afford anti-Felkin addition products. A protocol for the catalytic asymmetric addition of (Z)-trisubstituted vinylzinc reagents to prochiral aldehydes with a (−)-MIB-based catalyst has also been developed. Several additives were investigated as inhibitors of the Lewis acidic alkylzinc halide byproducts, which promote the background reaction to form the racemate. α-Ethyl and α-cyclohexyl (Z)-trisubstituted allylic alcohols can now be synthesized with excellent levels of enantioselectivity in the presence of diamine inhibitors. PMID:19476375

  13. From allylic alcohols to aldols through a new nickel-mediated tandem reaction: synthetic and mechanistic studies.

    PubMed

    Cuperly, David; Petrignet, Julien; Crévisy, Christophe; Grée, René

    2006-04-12

    Nickel hydride type complexes have been successfully developed as catalysts for the tandem isomerization-aldolization reaction of allylic alcohols with aldehydes. Optimization of the reaction conditions has shown that a cocatalyst, such as MgBr2, has a very positive effect on the kinetics of the reaction and in the yields of aldols. Under such optimized conditions {[NiHCl(dppe)] + MgBr(2) at 3-5 mol %)}, this reaction affords the aldols in good to excellent yields. It is a full-atom-economy-type reaction that occurs under mild conditions. Furthermore, it has a broad scope for the allylic alcohols and it is compatible with a wide range of aldehydes, including very bulky derivatives. The reaction is completely regioselective, but it exhibits a low stereoselectivity, except for allylic alcohols with a bulky substituent at the carbinol center. The use of chiral nonracemic catalysts was not successful, affording only racemic compounds. However, it was possible to use asymmetric synthesis for the preparation of optically active aldols. Various mechanistic studies have been performed using, for instance, a deuterated alcohol or a deuterated catalyst. They gave strong support to a mechanism involving first a transition-metal-mediated isomerization of the allylic alcohol into the free enol, followed by the addition of the latter intermediate onto the aldehyde in an "hydroxyl-carbonyl-ene" type reaction. These results confirm that allylic alcohols can be considered as new and useful partners in the development of the aldol reaction. PMID:16506253

  14. The stability of allyl radicals following the photodissociation of allyl iodide at 193 nm.

    SciTech Connect

    Fan, H.; Pratt, S. T.; Chemistry

    2006-01-01

    The photodissociation of allyl iodide (C{sub 3}H{sub 5}I) at 193 nm was investigated by using a combination of vacuum-ultraviolet photoionization of the allyl radical, resonant multiphoton ionization of the iodine atoms, and velocity map imaging. The data provide insight into the primary C-I bond fission process and into the dissociative ionization of the allyl radical to produce C{sub 3}H{sup 3+}. The experimental results are consistent with the earlier results of Szpunar et al. [J. Chem. Phys. 119, 5078 (2003)], in that some allyl radicals with internal energies higher than the secondary dissociation barrier are found to be stable. This stability results from the partitioning of available energy between the rotational and vibrational degrees of freedom of the radical, the effects of a centrifugal barrier along the reaction coordinate, and the effects of the kinetic shift in the secondary dissociation of the allyl radical. The present results suggest that the primary dissociation of allyl iodide to allyl radicals plus I*({sup 2}P{sub 1/2}) is more important than previously suspected.

  15. The stability of allyl radicals following the photodissociation of allyl iodide at 193 nm.

    PubMed

    Fan, H; Pratt, S T

    2006-10-14

    The photodissociation of allyl iodide (C3H5I) at 193 nm was investigated by using a combination of vacuum-ultraviolet photoionization of the allyl radical, resonant multiphoton ionization of the iodine atoms, and velocity map imaging. The data provide insight into the primary C-I bond fission process and into the dissociative ionization of the allyl radical to produce C3H3+. The experimental results are consistent with the earlier results of Szpunar et al. [J. Chem. Phys. 119, 5078 (2003)], in that some allyl radicals with internal energies higher than the secondary dissociation barrier are found to be stable. This stability results from the partitioning of available energy between the rotational and vibrational degrees of freedom of the radical, the effects of a centrifugal barrier along the reaction coordinate, and the effects of the kinetic shift in the secondary dissociation of the allyl radical. The present results suggest that the primary dissociation of allyl iodide to allyl radicals plus I*(2P(1/2)) is more important than previously suspected. PMID:17042585

  16. Transition‐Metal‐Free Borylation of Allylic and Propargylic Alcohols

    PubMed Central

    Miralles, Núria; Alam, Rauful

    2016-01-01

    Abstract The base‐catalyzed allylic borylation of tertiary allylic alcohols allows the synthesis of 1,1‐disubstituted allyl boronates, in moderate to high yield. The unexpected tandem performance of the Lewis acid–base adduct, [Hbase]+[MeO‐B2pin2]− favored the formation of 1,2,3‐triborylated species from the tertiary allylic alcohols and 1‐propargylic cyclohexanol at 90 °C. PMID:26934578

  17. Transition-Metal-Free Borylation of Allylic and Propargylic Alcohols.

    PubMed

    Miralles, Núria; Alam, Rauful; Szabó, Kálmán J; Fernández, Elena

    2016-03-18

    The base-catalyzed allylic borylation of tertiary allylic alcohols allows the synthesis of 1,1-disubstituted allyl boronates, in moderate to high yield. The unexpected tandem performance of the Lewis acid-base adduct, [Hbase](+) [MeO-B2 pin2 ](-) favored the formation of 1,2,3-triborylated species from the tertiary allylic alcohols and 1-propargylic cyclohexanol at 90 °C. PMID:26934578

  18. Enantioselective synthesis of fluorinated branched allylic compounds via Ir-catalyzed allylations of functionalized fluorinated methylene derivatives.

    PubMed

    Zhang, Hongbo; Chen, Jiteng; Zhao, Xiao-Ming

    2016-08-14

    Enantioselective introduction of the functionalized monofluorinated methylenes into the allylic fragment under Ir catalysis has been realized, which gave the fluorinated branched allyl products in good to high yields with excellent regio- and enantioselectivities. PMID:27383920

  19. Asymmetric formal synthesis of schulzeines A and C.

    PubMed

    Jang, Jaebong; Jung, Jong-Wha; Ahn, Jaeseung; Sim, Jaehoon; Chang, Dong-Jo; Kim, Dae-Duk; Suh, Young-Ger

    2012-07-21

    The asymmetric formal synthesis of schulzeines A and C is described. Key features of the synthesis include the efficient and stereoselective construction of the benzoquinolizidine skeleton via the aza-Claisen rearrangement-induced ring expansion of the 1-vinyl-N-glycyl-isoquinoline, which was prepared by the highly enantioselective asymmetric allylation of the 8-benzyloxy-substituted dihydroisoquinoline and by the acid-catalyzed transannulation of the resulting 10-membered lactam. PMID:22692049

  20. Kinetic Resolution of Racemic and Branched Monosubstituted Allylic Acetates by a Ruthenium-Catalyzed Regioselective Allylic Etherification.

    PubMed

    Shinozawa, Toru; Terasaki, Shou; Mizuno, Shota; Kawatsura, Motoi

    2016-07-01

    We demonstrated the kinetic resolution of racemic and branched monosubstituted allylic acetates by a ruthenium-catalyzed regioselective allylic etherification. The reaction was effectively catalyzed by the chiral ruthenium catalyst, which was generated by [RuCl2(p-cymene)]2 and (S,S)-iPr-pybox and a catalytic amount of TFA, and both the allylic etherification product and recovered allylic acetate were obtained as an enantiomerically enriched form with up to a 103 s value. PMID:27276556

  1. Asymmetric Synthesis of 2-Substituted Azetidin-3-ones via Metalated SAMP/RAMP Hydrazones.

    PubMed

    Pancholi, Alpa K; Geden, Joanna V; Clarkson, Guy J; Shipman, Michael

    2016-09-01

    2-Substituted azetidin-3-ones can be prepared in good yields and enantioselectivities (up to 85% ee) by a one-pot procedure involving the metalation of the SAMP/RAMP hydrazones of N-Boc-azetidin-3-one, reaction with a wide range of electrophiles, including alkyl, allyl, and benzyl halides and carbonyl compounds, followed by hydrolysis using oxalic acid. PMID:27447363

  2. Isolation and Asymmetric Total Synthesis of Perforanoid A.

    PubMed

    Lv, Chao; Yan, Xiaohui; Tu, Qian; Di, Yingtong; Yuan, Chunmao; Fang, Xin; Ben-David, Yaacove; Xia, Lei; Gong, Jianxian; Shen, Yuemao; Yang, Zhen; Hao, Xiaojiang

    2016-06-20

    A novel limonoid, perforanoid A, was isolated, and an asymmetric total synthesis was achieved in 10 steps. The key steps are chiral tertiary aminonaphthol mediated enantioselective alkenylation of an aldehyde to an allylic alcohol, Pd-catalyzed coupling of the allylic alcohol with vinyl ether to form the γ-lactone ring, and cyclopentenone ring formation through a Rh-catalyzed Pauson-Khand reaction. Preliminary studies show that perforanoid A is cytotoxic towards HEL, K562, and CB3 tumor cell lines. PMID:27167098

  3. Palladium-Catalyzed Aminocarbonylation of Allylic Alcohols.

    PubMed

    Li, Haoquan; Neumann, Helfried; Beller, Matthias

    2016-07-11

    A benign and efficient palladium-catalyzed aminocarbonylation reaction of allylic alcohols is presented. The generality of this novel process is demonstrated by the synthesis of β,γ-unsaturated amides including aliphatic, cinnamyl, and terpene derivatives. The choice of ligand is crucial for optimal carbonylation processes: Whereas in most cases the combination of PdCl2 with Xantphos (L6) gave best results, sterically hindered substrates performed better in the presence of simple triphenylphosphine (L10), and primary anilines gave the best results using cataCXium® PCy (L8). The reactivity of the respective catalyst system is significantly enhanced by addition of small amounts of water. Mechanistic studies and control experiments revealed a tandem allylic alcohol amination/C-N bond carbonylation reaction sequence. PMID:27283958

  4. 2-Allyl-7-nitro-2H-indazole

    PubMed Central

    Kouakou, Assoman; Rakib, El Mostapha; Spinelli, Domenico; Saadi, Mohamed; El Ammari, Lahcen

    2013-01-01

    The asymmetric unit of the title compound, C10H9N3O2, contains two independent mol­ecules linked by a C—H⋯N hydrogen bond. Each mol­ecule has a similar conformation, being built up from fused five- and six-membered rings, each linked to an ally and nitro group, respectively. The indazole ring system makes dihedral angles of 2.7 (2) and 2.2 (2)°, respectively, with the plane through the nitro group. The allyl group is nearly perpendicular to the indazole system, as indicated by the N—N—C—C torsion angles of −75.3 (2) and −82.2 (2)°, this being the most important difference between the conformations of the two mol­ecules. In the crystal, mol­ecules are linked by C—H⋯O and π–π [inter-centroid distance = 3.6225 (8) Å] inter­actions to form a three-dimensional network. PMID:24454056

  5. Enantioselective domino reaction of CO2, amines and allyl chlorides under iridium catalysis: formation of allyl carbamates.

    PubMed

    Zhang, Min; Zhao, Xiaoming; Zheng, Shengcai

    2014-05-01

    The enantioselective domino reaction between CO2 (1 atm), amines and linear allyl chlorides in the presence of an iridium complex, DABCO and toluene at 15 °C was realized, which gave branched allyl carbamates in acceptable to high yields with up to excellent regioselectivity (99/1) and 94% ee. This is the first example of the synthesis of chiral allyl carbamates through catalytic domino reactions using CO2. PMID:24652315

  6. Temperature-controlled redox-neutral ruthenium(ii)-catalyzed regioselective allylation of benzamides with allylic acetates.

    PubMed

    Manikandan, Rajendran; Jeganmohan, Masilamani

    2016-08-10

    Substituted aromatic amides reacted efficiently with allylic acetates in the presence of a cationic ruthenium complex in ClCH2CH2Cl at room temperature providing ortho allylated benzamides in a highly regioselective manner without any oxidant and base. The whole catalytic reaction occurred in a Ru(ii) oxidation state and thus the oxidation step is avoided. By tuning the reaction temperature, ortho allyl and vinyl benzamides were prepared exclusively. Later, ortho allyl and vinylated benzamides were converted into biologically useful six- and five-membered benzolactones in the presence of HCl. PMID:27456467

  7. Alkylating potential of oxetanes.

    PubMed

    Gómez-Bombarelli, Rafael; Palma, Bernardo Brito; Martins, Célia; Kranendonk, Michel; Rodrigues, Antonio S; Calle, Emilio; Rueff, José; Casado, Julio

    2010-07-19

    Small, highly strained heterocycles are archetypical alkylating agents (oxiranes, beta-lactones, aziridinium, and thiirinium ions). Oxetanes, which are tetragonal ethers, are higher homologues of oxiranes and reduced counterparts of beta-lactones, and would therefore be expected to be active alkylating agents. Oxetanes are widely used in the manufacture of polymers, especially in organic light-emitting diodes (OLEDs), and are present, as a substructure, in compounds such as the widely used antimitotic taxol. Whereas the results of animal tests suggest that trimethylene oxide (TMO), the parent compound, and beta,beta-dimethyloxetane (DMOX) are active carcinogens at the site of injection, no studies have explored the alkylating ability and genotoxicity of oxetanes. This work addresses the issue using a mixed methodology: a kinetic study of the alkylation reaction of 4-(p-nitrobenzyl)pyridine (NBP), a trap for alkylating agents with nucleophilicity similar to that of DNA bases, by three oxetanes (TMO, DMOX, and methyloxetanemethanol), and a mutagenicity, genotoxicity, and cell viability study (Salmonella microsome test, BTC E. coli test, alkaline comet assay, and MTT assay). The results suggest either that oxetanes lack genotoxic capacity or that their mode of action is very different from that of epoxides and beta-lactones. PMID:20550097

  8. Stereoselective Alkylation of the Vinylketene Silyl N,O-Acetal and Its Application to the Synthesis of Mycocerosic Acid.

    PubMed

    Nakamura, Tatsuya; Kubota, Kei; Ieki, Takanori; Hosokawa, Seijiro

    2016-01-01

    Stereoselective alkylation of the vinylketene silyl N,O-acetal possessing a chiral auxiliary has been achieved by using activated alkyl halides including allyl iodides, benzyl iodides, and propargyl iodide with Ag(I) ion in the presence of BF3·OEt2. The reaction proceeded to give reduced polyketides in high stereoselectivity. The synthesis of mycocerosic acid, a component of the cell envelope of Mycobacterium tuberculosis, has been accomplished by this methodology. During the synthetic studies, 2-methylbenzimidazole was found to be a bulky proton source which worked in the presence of liquid ammonia. PMID:26673532

  9. Asymmetric synthesis of Crispine A: constructing tetrahydroisoquinoline scaffolds using pummerer cyclizations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    For the first time, a concise, linear and protecting group-free stereoselective synthesis of both enantiomers of crispine A have been achieved in six steps with an overall yield of less than or equal to 20%,starting from commercially available veratraldehyde. Asymmetric Keck allylation and trifluoro...

  10. New biphenol-based, fine-tunable monodentate phosphoramidite ligands for catalytic asymmetric transformations

    PubMed Central

    Hua, Zihao; Vassar, Victor C.; Choi, Hojae; Ojima, Iwao

    2004-01-01

    Monodentate phosphoramidite ligands have been developed based on enantiopure 6,6′-dimethylbiphenols with axial chirality. These chiral ligands are easy to prepare and flexible for modifications. The fine-tuning capability of these ligands plays a significant role in achieving high enantioselectivity in the asymmetric hydroformylation of allyl cyanide and the conjugate addition of diethylzinc to cycloalkenones. PMID:15020764

  11. Development and application of versatile bis-hydroxamic acids for catalytic asymmetric oxidation

    PubMed Central

    Barlan, Allan U.; Zhang, Wei; Yamamoto, Hisashi

    2010-01-01

    In this article, we describe the development and preliminary results of our new designed C2-symmetric bis-hydroxamic acid (BHA) ligands and the application of the new ligands for vanadium-catalyzed asymmetric epoxidation of allylic alcohols as well as homoallylic alcohols. From this success we demonstrate the versatile nature of BHA in the molybdenum catalyzed asymmetric oxidation of unfunctionalized olefins and sulfides. PMID:21152351

  12. Decarboxylative Allylation of Amino Alkanoic Acids and Esters via Dual Catalysis

    PubMed Central

    2015-01-01

    A combination of photoredox and palladium catalysis has been employed to facilitate the room temperature decarboxylative allylation of recalcitrant α-amino and phenylacetic allyl esters. This operationally simple process produces CO2 as the only byproduct and provides direct access to allylated alkanes. After photochemical oxidation, the carboxylate undergoes radical decarboxylation to site-specifically generate radical intermediates which undergo allylation. A radical dual catalysis mechanism is proposed. Free phenylacetic acids were also allylated utilizing similar reactions conditions. PMID:25228064

  13. N-alkylation of exogenous haem analogues caused by drugs in isolated hepatocytes. Structural isomerism and chirality of the resulting porphyrins.

    PubMed Central

    De Matteis, F; Harvey, C; Martin, S R

    1986-01-01

    Isolated rat hepatocytes incubated with two suicide substrates of cytochrome P-450, 2-allyl-2-isopropylacetamide and 3,5-diethoxycarbonyl-4-ethyl-1,4-dihydro-2,6-dimethylpyridine(4-ethyl-DD C), convert exogenous mesohaem and deuterohaem into N-alkylated mesoporphyrins and deuteroporphyrins respectively. The N-alkylated mesoporphyrins can be separated by h.p.l.c. from the corresponding N-alkylated protoporphyrins originating from endogenous haem; in this way the contribution of both endogenous and exogenous pools of haem can be studied in the same experiment. N-Alkylated mesoporphyrin exhibits chiral properties, and its isomeric composition and/or amount are dependent on the particular cytochrome P-450 enzyme predominating in the cell. These findings provide additional and more direct evidence that exchangeable haem is taken up by cytochrome P-450 before being N-alkylated. PMID:3800937

  14. Allyl­ammonium hydrogen oxalate hemihydrate

    PubMed Central

    Dziuk, Błażej; Zarychta, Bartosz; Ejsmont, Krzysztof

    2014-01-01

    In the title hydrated mol­ecular salt, C3H8N+·C2HO4 −·0.5H2O, the water O atom lies on a crystallographic twofold axis. The C=C—C—N torsion angle in the cation is 2.8 (3)° and the dihedral angle between the CO2 and CO2H planes in the anion is 1.0 (4)°. In the crystal, the hydrogen oxalate ions are linked by O—H⋯O hydrogen bonds, generating [010] chains. The allyl­ammonium cations bond to the chains through N—H⋯O and N—H⋯(O,O) hydrogen bonds. The water mol­ecule accepts two N—H⋯O hydrogen bonds and makes two O—H⋯O hydrogen bonds. Together, the hydrogen bonds generate (100) sheets. PMID:25249903

  15. Bis[3-allyl-1-(4-cyanobenzyl)-2-methylbenzimidazolium] di-μ-bromido-bis[bromidocuprate(I)

    PubMed Central

    Xu, Guang-Hai; Wang, Wei

    2008-01-01

    The asymmetric unit of the title compound, (C19H18N3)2[Cu2Br4], contains one cation and one half-anion; there is a centre of symmetry mid-way between the two Cu atoms. In the cation, the nearly planar benzimidazole ring system is oriented at dihedral angles of 75.31 (3) and 21.39 (3)° with respect to the cyano­benzyl and allyl groups, respectively. The dihedral angle between cyano­benzyl and allyl groups is 87.94 (3)°. In the crystal structure, inter­molecular C—H⋯Br hydrogen bonds link the mol­ecules. There is a C—H⋯π contact between the cyano­benzyl ring and the anion; π—π contacts also exist between the benzimidazole ring systems as well as between the anion and the cyano­benzyl ring [centroid–centroid distances = 4.024 (1) and 4.617 (1) Å, respectively]. PMID:21201637

  16. Iron complexes of tetramine ligands catalyse allylic hydroxyamination via a nitroso–ene mechanism

    PubMed Central

    Porter, David; Poon, Belinda M-L

    2015-01-01

    Summary Iron(II) complexes of the tetradentate amines tris(2-pyridylmethyl)amine (TPA) and N,N′-bis(2-pyridylmethyl)-N,N′-dimethylethane-1,2-diamine (BPMEN) are established catalysts of C–O bond formation, oxidising hydrocarbon substrates via hydroxylation, epoxidation and dihydroxylation pathways. Herein we report the capacity of these catalysts to promote C–N bond formation, via allylic amination of alkenes. The combination of N-Boc-hydroxylamine with either FeTPA (1 mol %) or FeBPMEN (10 mol %) converts cyclohexene to the allylic hydroxylamine (tert-butyl cyclohex-2-en-1-yl(hydroxy)carbamate) in moderate yields. Spectroscopic studies and trapping experiments suggest the reaction proceeds via a nitroso–ene mechanism, with involvement of a free N-Boc-nitroso intermediate. Asymmetric induction is not observed using the chiral tetramine ligand (+)-(2R,2′R)-1,1′-bis(2-pyridylmethyl)-2,2′-bipyrrolidine ((R,R′)-PDP). PMID:26734101

  17. Thermally Reduced Graphene Oxide Electrochemically Activated by Bis-Spiro Quaternary Alkyl Ammonium for Capacitors.

    PubMed

    He, Tieshi; Meng, Xiangling; Nie, Junping; Tong, Yujin; Cai, Kedi

    2016-06-01

    Thermally reduced graphene oxide (RGO) electrochemically activated by a quaternary alkyl ammonium-based organic electrolytes/activated carbon (AC) electrode asymmetric capacitor is proposed. The electrochemical activation process includes adsorption of anions into the pores of AC in the positive electrode and the interlayer intercalation of cations into RGO in the negative electrode under high potential (4.0 V). The EA process of RGO by quaternary alkyl ammonium was investigated by X-ray diffraction and electrochemical measurements, and the effects of cation size and structure were extensively evaluated. Intercalation by quaternary alkyl ammonium demonstrates a small degree of expansion of the whole crystal lattice (d002) and a large degree of expansion of the partial crystal lattice (d002) of RGO. RGO electrochemically activated by bis-spiro quaternary alkyl ammonium in propylene carbonate/AC asymmetric capacitor exhibits good activated efficiency, high specific capacity, and stable cyclability. PMID:27180820

  18. Aryne 1,2,3-Trifunctionalization with Aryl Allyl Sulfoxides.

    PubMed

    Li, Yuanyuan; Qiu, Dachuan; Gu, Rongrong; Wang, Junli; Shi, Jiarong; Li, Yang

    2016-08-31

    An aryne 1,2,3-trisubstitution with aryl allyl sulfoxides is accomplished, featuring an incorporation of C-S, C-O, and C-C bonds on the consecutive positions of a benzene ring. The reaction condition is mild with broad substrate scope. Preliminary mechanistic study suggests a cascade formal [2 + 2] reaction of aryne with S═O bond, an allyl S → O migration, and a Claisen rearrangement. PMID:27527334

  19. Synthesis of Substituted Benzenes via Bi(OTf)3-Mediated Intramolecular Carbonyl Allylation of α-Prenyl or α-Geranyl β-Arylketosulfones.

    PubMed

    Chang, Meng-Yang; Cheng, Yu-Chieh; Lu, Yi-Ju

    2015-06-19

    Intramolecular carbonyl allylation of α-prenyl or α-geranyl β-arylketosulfones 5 in the presence of molecule sieves (MS) affords substituted benzenes 6-7 in moderate to good yields. The facile transformation proceeds by a synthetic sequence starting with the α-prenylation or α-geranylation of 1 and the Bi(OTf)3-mediated annulation of 5 followed by a sequential desulfonative aromatization or then an intramolecular Friedel-Crafts alkylation. A plausible mechanism has been studied and proposed. PMID:26068123

  20. Method of making alkyl esters

    DOEpatents

    Elliott, Brian

    2010-09-14

    Methods of making alkyl esters are described herein. The methods are capable of using raw, unprocessed, low-cost feedstocks and waste grease. Generally, the method involves converting a glyceride source to a fatty acid composition and esterifying the fatty acid composition to make alkyl esters. In an embodiment, a method of making alkyl esters comprises providing a glyceride source. The method further comprises converting the glyceride source to a fatty acid composition comprising free fatty acids and less than about 1% glyceride by mass. Moreover, the method comprises esterifying the fatty acid composition in the presence of a solid acid catalyst at a temperature ranging firm about 70.degree. C. to about 120.degree. C. to produce alkyl esters, such that at least 85% of the free fatty acids are converted to alkyl esters. The method also incorporates the use of packed bed reactors for glyceride conversion and/or fatty acid esterification to make alkyl esters.

  1. Development of Non-C2-symmetric ProPhenol Ligands. The Asymmetric Vinylation of N-Boc Imines.

    PubMed

    Trost, Barry M; Hung, Chao-I Joey; Koester, Dennis C; Miller, Yan

    2015-08-01

    The development and application of a new generation of non-C2-symmetric ProPhenol ligands is reported herein. Rational design of the ProPhenol ligand paved the way to the first catalytic and asymmetric vinylation of N-Boc imines via hydrozirconation giving rise to valuable allylic amines in excellent yields and enantioselectivities. The utility of this method was demonstrated by developing the shortest reported asymmetric synthesis of the selective serotonine reuptake inhibitor (SSRI) (-)-dapoxetine. PMID:26200769

  2. Allyl-silica Hybrid Monoliths For Chromatographic Application

    NASA Astrophysics Data System (ADS)

    Guo, Wenjuan

    Column technology continues to be the most investigated topics in the separation world, since the column is the place where the chromatographic separation happens, making it the heart of the separation system. Allyl-silica hybrid monolithic material has been exploited as support material and potential stationary phases for liquid chromatography; the stationary phase anchored to the silica surface by Si-C bond, which is more pH stable than traditional stationary phase. First, nuclear magnetic resonance spectroscopy has been used to study the sol in the synthesis of allyl-silica hybrid monoliths. Allyl-trimethoxysilane (allyl-TrMOS), dimethyldimethoxysilane (DMDMOS) and tetramethoxysilane (TMOS) have been served as co-precursors in the sol-gel synthesis of organo-silica hybrid monolithic columns for liquid chromatography (LC). 29Si nuclear magnetic resonance (NMR) and 1H NMR spectroscopy were employed to monitor reaction profiles for the acid-catalyzed hydrolysis and initial condensation reactions of the individual precursor and the hybrid system. 29Si-NMR has also been used to identify different silane species formed during the reactions. The overall hydrolysis rate has been found to follow the trend DMDMOS > allyl-TrMOS > TMOS, if each precursor is reacted individually (homo-polymerization). Precursors show different hydrolysis rate when reacted together in the hybrid system than they are reacted individually. Cross-condensation products of TMOS and DMDMOS (QD) arise about 10 minutes of initiation of the reaction. The allyl-silica monolithic columns for capillary liquid chromatography can only be prepared in capillaries with 50 im internal diameter with acceptable performance. One of the most prominent problems related to the synthesis of silica monolithic structures is the volume shrinkage. The synthesis of allylfunctionalized silica hybrid monolithic structures has been studied in an attempt to reduce the volume shrinkage during aging, drying and heat treatment

  3. The Reaction of Carbon Dioxide with Palladium Allyl Bonds

    PubMed Central

    Wu, Jianguo; Green, Jennifer C.; Hruszkewycz, Damian P.; Incarvito, Christopher D.; Schmeier, Timothy J.

    2010-01-01

    A family of palladium allyl complexes of the type bis(2-methylallyl)Pd(L) (L = PMe3 (1), PEt3 (2), PPh3 (3) or NHC (4); NHC = 1,3-Bis(2,6-diisopropylphenyl)-1,3-dihydro-2H-imidazol-2-ylidene) have been prepared through the reaction of bis(2-methylallyl)Pd with the appropriate free ligand. Compounds 1–4 contain one η1 and one η3-2-methylallyl ligand and 3 was characterized by X-ray crystallography. These complexes react rapidly with CO2 at low temperature to form well defined unidentate palladium carboxylates of the type (η3-2-methylallyl)Pd(OC(O)C4H7)(L) (L = PMe3 (6), PEt3 (7), PPh3 (8) or NHC (9). The structure of 9 was elucidated using X-ray crystallography. The mechanism of the reaction of 1–4 with CO2 was probed using a combination of experimental and theoretical (density functional theory) studies. The coordination mode of the allyl ligand is crucial and whereas nucleophilic η1-allyls react rapidly with CO2, η3-allyls do not react. We propose that the reaction of η1-palladium allyls with CO2 does not proceed via direct insertion of CO2 into the Pd-C bond but through nucleophilic attack of the terminal olefin on electrophilic CO2, followed by an associative substitution at palladium. PMID:21218132

  4. Scalable and sustainable electrochemical allylic C-H oxidation.

    PubMed

    Horn, Evan J; Rosen, Brandon R; Chen, Yong; Tang, Jiaze; Chen, Ke; Eastgate, Martin D; Baran, Phil S

    2016-05-01

    New methods and strategies for the direct functionalization of C-H bonds are beginning to reshape the field of retrosynthetic analysis, affecting the synthesis of natural products, medicines and materials. The oxidation of allylic systems has played a prominent role in this context as possibly the most widely applied C-H functionalization, owing to the utility of enones and allylic alcohols as versatile intermediates, and their prevalence in natural and unnatural materials. Allylic oxidations have featured in hundreds of syntheses, including some natural product syntheses regarded as "classics". Despite many attempts to improve the efficiency and practicality of this transformation, the majority of conditions still use highly toxic reagents (based around toxic elements such as chromium or selenium) or expensive catalysts (such as palladium or rhodium). These requirements are problematic in industrial settings; currently, no scalable and sustainable solution to allylic oxidation exists. This oxidation strategy is therefore rarely used for large-scale synthetic applications, limiting the adoption of this retrosynthetic strategy by industrial scientists. Here we describe an electrochemical C-H oxidation strategy that exhibits broad substrate scope, operational simplicity and high chemoselectivity. It uses inexpensive and readily available materials, and represents a scalable allylic C-H oxidation (demonstrated on 100 grams), enabling the adoption of this C-H oxidation strategy in large-scale industrial settings without substantial environmental impact. PMID:27096371

  5. Scalable and sustainable electrochemical allylic C–H oxidation

    NASA Astrophysics Data System (ADS)

    Horn, Evan J.; Rosen, Brandon R.; Chen, Yong; Tang, Jiaze; Chen, Ke; Eastgate, Martin D.; Baran, Phil S.

    2016-05-01

    New methods and strategies for the direct functionalization of C–H bonds are beginning to reshape the field of retrosynthetic analysis, affecting the synthesis of natural products, medicines and materials. The oxidation of allylic systems has played a prominent role in this context as possibly the most widely applied C–H functionalization, owing to the utility of enones and allylic alcohols as versatile intermediates, and their prevalence in natural and unnatural materials. Allylic oxidations have featured in hundreds of syntheses, including some natural product syntheses regarded as “classics”. Despite many attempts to improve the efficiency and practicality of this transformation, the majority of conditions still use highly toxic reagents (based around toxic elements such as chromium or selenium) or expensive catalysts (such as palladium or rhodium). These requirements are problematic in industrial settings; currently, no scalable and sustainable solution to allylic oxidation exists. This oxidation strategy is therefore rarely used for large-scale synthetic applications, limiting the adoption of this retrosynthetic strategy by industrial scientists. Here we describe an electrochemical C–H oxidation strategy that exhibits broad substrate scope, operational simplicity and high chemoselectivity. It uses inexpensive and readily available materials, and represents a scalable allylic C–H oxidation (demonstrated on 100 grams), enabling the adoption of this C–H oxidation strategy in large-scale industrial settings without substantial environmental impact.

  6. 40 CFR 721.9595 - Alkyl benzene sulfonic acids and alkyl sulfates, amine salts (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Alkyl benzene sulfonic acids and alkyl... Significant New Uses for Specific Chemical Substances § 721.9595 Alkyl benzene sulfonic acids and alkyl...) The chemical substances identified generically as alkyl benzene sulfonic acids and alkyl...

  7. 40 CFR 721.9595 - Alkyl benzene sulfonic acids and alkyl sulfates, amine salts (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alkyl benzene sulfonic acids and alkyl... Significant New Uses for Specific Chemical Substances § 721.9595 Alkyl benzene sulfonic acids and alkyl...) The chemical substances identified generically as alkyl benzene sulfonic acids and alkyl...

  8. 40 CFR 721.9595 - Alkyl benzene sulfonic acids and alkyl sulfates, amine salts (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Alkyl benzene sulfonic acids and alkyl... Significant New Uses for Specific Chemical Substances § 721.9595 Alkyl benzene sulfonic acids and alkyl...) The chemical substances identified generically as alkyl benzene sulfonic acids and alkyl...

  9. 40 CFR 721.9595 - Alkyl benzene sulfonic acids and alkyl sulfates, amine salts (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Alkyl benzene sulfonic acids and alkyl... Significant New Uses for Specific Chemical Substances § 721.9595 Alkyl benzene sulfonic acids and alkyl...) The chemical substances identified generically as alkyl benzene sulfonic acids and alkyl...

  10. 40 CFR 721.9595 - Alkyl benzene sulfonic acids and alkyl sulfates, amine salts (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Alkyl benzene sulfonic acids and alkyl... Significant New Uses for Specific Chemical Substances § 721.9595 Alkyl benzene sulfonic acids and alkyl...) The chemical substances identified generically as alkyl benzene sulfonic acids and alkyl...

  11. Enantioselective decarboxylative alkylation reactions: catalyst development, substrate scope, and mechanistic studies.

    PubMed

    Behenna, Douglas C; Mohr, Justin T; Sherden, Nathaniel H; Marinescu, Smaranda C; Harned, Andrew M; Tani, Kousuke; Seto, Masaki; Ma, Sandy; Novák, Zoltán; Krout, Michael R; McFadden, Ryan M; Roizen, Jennifer L; Enquist, John A; White, David E; Levine, Samantha R; Petrova, Krastina V; Iwashita, Akihiko; Virgil, Scott C; Stoltz, Brian M

    2011-12-01

    α-Quaternary ketones are accessed through novel enantioselective alkylations of allyl and propargyl electrophiles by unstabilized prochiral enolate nucleophiles in the presence of palladium complexes with various phosphinooxazoline (PHOX) ligands. Excellent yields and high enantiomeric excesses are obtained from three classes of enolate precursor: enol carbonates, enol silanes, and racemic β-ketoesters. Each of these substrate classes functions with nearly identical efficiency in terms of yield and enantioselectivity. Catalyst discovery and development, the optimization of reaction conditions, the exploration of reaction scope, and applications in target-directed synthesis are reported. Experimental observations suggest that these alkylation reactions occur through an unusual inner-sphere mechanism involving binding of the prochiral enolate nucleophile directly to the palladium center. PMID:22083969

  12. Enantioselective Decarboxylative Alkylation Reactions: Catalyst Development, Substrate Scope, and Mechanistic Studies

    PubMed Central

    Behenna, Douglas C.; Mohr, Justin T.; Sherden, Nathaniel H.; Marinescu, Smaranda C.; Harned, Andrew M.; Tani, Kousuke; Seto, Masaki; Ma, Sandy; Novák, Zoltán; Krout, Michael R.; McFadden, Ryan M.; Roizen, Jennifer L.; Enquist, John A.; White, David E.; Levine, Samantha R.; Petrova, Krastina V.; Iwashita, Akihiko; Virgil, Scott C.; Stoltz, Brian M.

    2012-01-01

    α-Quaternary ketones are accessed through novel enantioselective alkylations of allyl and propargyl electrophiles by unstabilized prochiral enolate nucleophiles in the presence of palladium complexes with various phosphinooxazoline (PHOX) ligands. Excellent yields and high enantiomeric excesses are obtained from three classes of enolate precursors: enol carbonates, enol silanes, and racemic β-ketoesters. Each of these substrate classes functions with nearly identical efficiency in terms of yield and enantioselectivity. Catalyst discovery and development, the optimization of reaction conditions, the exploration of reaction scope, and applications in target-directed synthesis are reported. Experimental observations suggest that these alkylation reactions occur through an unusual inner-sphere mechanism involving binding of the prochiral enolate nucleophile directly to the palladium center. PMID:22083969

  13. The adsorption stability & inhibition by allyl-thiourea of bulk nanocrystalline ingot iron in dilute HCl solution

    NASA Astrophysics Data System (ADS)

    Shen, C. B.; Wang, S. G.; Yang, H. Y.; Long, K.; Wang, F. H.

    2006-12-01

    The inhibitive effect of thiourea's (TU) alkyl derivative—allyl-thiourea (ATU) on the corrosion behaviors of bulk nanocrystalline and conventional polycrystalline ingot iron (BNII & CPII) was tested. Results indicate that BNII is less prone to get corrosive than its coarse grain counterpart in blank 1 mol L -1 HCl at room temperature. When CPII and BNII were immersed for a very short time in the corrosive solution inhibited by ATU, namely, 5 min, no inductive loop appears at different concentrations. When time became prolonged, for BNII, a Warburg impedance appeared. Inhibited by ATU, the electrodes composed of the samples are polarized anodically during the potentiodynamic polarization tests, the phenomena of desorption happens at the concentration of 100 mg L -1, but the variation between potential Edes is obvious. The inhibition effect of ATU for BNII is very limited by comparison with CPII in dilute HCl.

  14. A recyclable heavy fluorous tag carrying an allyl alcohol pendant group: design and evaluation toward applications in synthetic carbohydrate chemistry.

    PubMed

    Fukuda, Kazuo; Tojino, Mami; Goto, Kohtaro; Dohi, Hirofumi; Nishida, Yoshihiro; Mizuno, Mamoru

    2015-04-30

    Toward applications in synthetic carbohydrate chemistry, we converted our previous acid-resistant heavy fluorous tag [(Rf)3C-CH2-OH, 1] to allyl alcohol derivatives [(Rf)3C-CH2-O-(CH2)n-CH=CH-CH2-OH, 3 (n=1) or 4 (n=3)] by means of olefin cross metathesis. They were then subjected to β-glycosylation reactions by using a series of glycosyl donors, including glycosyl bromide and trichloroacetimidates. The terminal OH group in 3 and 4 was found to be β-glycosylated in moderate yield when 2,3,4,6-tetra-O-benzoyl-D-galactosyl trichloroacetimidate was used as the glycosyl donor. Upon a detachment reaction using Pd(PPh3)4, the initial heavy fluorous tag 1 was recovered in high yield (>90%) together with 1-hydroxy sugar, indicating that not only the allyl ether linkage in the glycosides but also the internal di-alkyl ether linkage in 4 be cleaved by the action of the Pd-catalyst enabling long-range olefin transmigration. Potential utility was demonstrated by using the tetra-O-benzoyl-β-D-galactosylated derivative of 3 in a series of deprotection, protection and glycosylation reactions, which were conductible in high yields without using chromatographic purification process. These findings prompt us to propose a general scheme in which the acid-resistant heavy fluorous compound 1 is applied as a recyclable tag in synthetic carbohydrate chemistry. PMID:25753904

  15. Asymmetric fluorocyclizations of alkenes.

    PubMed

    Wolstenhulme, Jamie R; Gouverneur, Véronique

    2014-12-16

    .g., TRIP and derivatives) brings into solution the resulting chiral Selectfluor reagent, now capable of asymmetric fluorocyclization. This strategy is best applied to a subset of substrates bearing a nucleophilic pendent group (benzamide is best) capable of hydrogen bonding for association with the chiral phosphate catalyst. These contributions focused on fluoroheterocyclization involving either O- or N-nucleophiles. As for other halocyclizations, alkenes armed with π C-nucleophiles represent the most demanding class of substrates for asymmetric F(+)-induced electrophilic fluorination-cyclization. Successful implementation required the design of new chiral Selectfluor reagents featuring stereogenicity on the DABCO core. These reagents, accessible from chiral vicinal diamines, allowed the synthesis of unusual chiral fluorine-containing tetracyclic compounds, some composed of carbon, hydrogen, and fluorine exclusively. The challenges associated with F(+)-induced fluorocarbocyclizations prompted methodologists to consider chemistry where the Csp(3)-F bond formation event follows a catalyst-controlled cyclization. An exciting development built on in the area of transition metal π-cyclization of polyenes leading to cationic metal-alkyl intermediates. When intercepted by oxidative fluorodemetalation with a F(+) source, the resulting products are complex polycyclic structures emerging from an overall catalytic cascade fluorocarbocyclization. Complementing F(+)-based reactions, examples of fluorocyclizations with fluoride in the presence of an oxidant were reported. Despite some exciting developments, the field of asymmetric fluorocyclizations is in its infancy and undoubtedly requires new activation modes, catalysts, as well as F(+) and F(-) reagents to progress into general retrosynthetic approach toward enantioenriched fluorocycles. Numerous opportunities emerge, not least the use of a latent fluorine source as a means to minimize background fluorination. PMID:25379791

  16. 40 CFR 721.9952 - Alkoxylated aliphatic diisocyanate allyl ether (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... allyl ether (generic). 721.9952 Section 721.9952 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.9952 Alkoxylated aliphatic diisocyanate allyl ether... identified generically as alkoxylated aliphatic diisocyanate allyl ether (PMN P-00-0353) is subject...

  17. 40 CFR 721.9952 - Alkoxylated aliphatic diisocyanate allyl ether (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... allyl ether (generic). 721.9952 Section 721.9952 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.9952 Alkoxylated aliphatic diisocyanate allyl ether... identified generically as alkoxylated aliphatic diisocyanate allyl ether (PMN P-00-0353) is subject...

  18. Pyridine-NHC: effective ligand in Pd-catalyzed cyclopropanation of esters with substituted allyl carbonates.

    PubMed

    Huang, Jian-Qiang; Ding, Chang-Hua; Hou, Xue-Long

    2014-12-19

    By consideration of the mechanism of Pd-catalyzed cyclopropanation and allylation, NHC-pyridine compounds were adopted as the ligand in Pd-catalyzed cyclopropanation of esters and monosubstituted allylic reagents. The corresponding cyclopropanes were afforded as major products in moderate to good yields with high cyclopropane/allylation selectivity. PMID:25284365

  19. 40 CFR 721.7000 - Polymer of disodium maleate, allyl ether, and ethylene oxide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Polymer of disodium maleate, allyl... New Uses for Specific Chemical Substances § 721.7000 Polymer of disodium maleate, allyl ether, and... substance identified generically as a polymer of disodium maleate, allyl ether, and ethylene oxide...

  20. 40 CFR 721.7000 - Polymer of disodium maleate, allyl ether, and ethylene oxide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Polymer of disodium maleate, allyl... New Uses for Specific Chemical Substances § 721.7000 Polymer of disodium maleate, allyl ether, and... substance identified generically as a polymer of disodium maleate, allyl ether, and ethylene oxide...

  1. 40 CFR 721.7000 - Polymer of disodium maleate, allyl ether, and ethylene oxide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Polymer of disodium maleate, allyl... New Uses for Specific Chemical Substances § 721.7000 Polymer of disodium maleate, allyl ether, and... substance identified generically as a polymer of disodium maleate, allyl ether, and ethylene oxide...

  2. 40 CFR 721.7000 - Polymer of disodium maleate, allyl ether, and ethylene oxide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Polymer of disodium maleate, allyl... New Uses for Specific Chemical Substances § 721.7000 Polymer of disodium maleate, allyl ether, and... substance identified generically as a polymer of disodium maleate, allyl ether, and ethylene oxide...

  3. 40 CFR 721.7000 - Polymer of disodium maleate, allyl ether, and ethylene oxide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Polymer of disodium maleate, allyl... New Uses for Specific Chemical Substances § 721.7000 Polymer of disodium maleate, allyl ether, and... substance identified generically as a polymer of disodium maleate, allyl ether, and ethylene oxide...

  4. Polyimides with pendant alkyl groups

    NASA Technical Reports Server (NTRS)

    Jensen, B. J.; Young, P. R.

    1982-01-01

    The effect on selected polyimide properties when pendant alkyl groups were attached to the polymer backbone was investigated. A series of polymers were prepared using benzophenone tetracarboxylic acid dianhydride (BTDA) and seven different p-alkyl-m,p'-diaminobenzophenone monomers. The alkyl groups varied in length from C(1) (methyl) to C(9) (nonyl). The polyimide prepared from BTDA and m,p'-diaminobenzophenone was included as a control. All polymers were characterized by various chromatographic, spectroscopic, thermal, and mechanical techniques. Increasing the length of the pendant alkyl group resulted in a systematic decrease in glass transition temperature (Tg) for vacuum cured films. A 70 C decrease in Tg to 193 C was observed for the nonyl polymer compared to the Tg for the control. A corresponding systematic increase in Tg indicative of crosslinking, was observed for air cured films. Thermogravimetric analysis revealed a slight sacrifice in thermal stability with increasing alkyl length. No improvement in film toughness was observed.

  5. Preparation of anti-Vicinal Amino Alcohols: Asymmetric Synthesis of d-erythro-Sphinganine, (+)-Spisulosine, and d-ribo-Phytosphingosine

    PubMed Central

    2013-01-01

    Two variations of the Overman rearrangement have been developed for the highly selective synthesis of anti-vicinal amino alcohol natural products. A MOM ether-directed palladium(II)-catalyzed rearrangement of an allylic trichloroacetimidate was used as the key step for the preparation of the protein kinase C inhibitor d-erythro-sphinganine and the antitumor agent (+)-spisulosine, whereas the Overman rearrangement of chiral allylic trichloroacetimidates generated by the asymmetric reduction of an α,β-unsaturated methyl ketone allowed rapid access both to d-ribo-phytosphingosine and l-arabino-phytosphingosine. PMID:23795558

  6. [Cu(NHC)]-Catalyzed C-H Allylation and Alkenylation of both Electron-Deficient and Electron-Rich (Hetero)arenes with Allyl Halides.

    PubMed

    Xie, Weilong; Chang, Sukbok

    2016-01-26

    New reactivity of a [Cu(NHC)] (NHC=N-heterocyclic carbene) catalyst is disclosed for the efficient C-H allylation of polyfluoroarenes using allyl halides in benzene at room temperature. The same catalyst system also promotes an isomerization-induced alkenylation of initially the generated allyl arenes when the reaction is run in tetrahydrofuran. Significantly, not only electron-deficient but also electron-rich (hetero)arenes undergo this double-bond migration process, thus leading to alkenylated products. The present system features mild reaction conditions, broad scope with respect to the arene substrates and allyl halide reactants, good functional-group tolerance, and high stereoselectivity. PMID:26695120

  7. Health and environmental effects profile for allyl chloride

    SciTech Connect

    Not Available

    1986-07-01

    The Health and Environmental Effects Profile for allyl chloride was prepared to support listings of hazardous constituents of a wide range of waste streams under Section 3001 of the Resource Conservation and Recovery Act (RCRA) and to provide health-related limits for emergency actions under Section 101 of the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA). Both published literature and information obtained from Agency program office files were evaluated as they pertained to potential human health, aquatic life, and environmental effects of hazardous-waste constituents. Quantitative estimates are presented provided sufficient data are available. Allyl chloride has been evaluated as a carcinogen. The human carcinogen potency factor (q1*) for allyl chloride is 0.0206 for oral exposure. The Reportable Quantity (RQ) value of 1, 10, 100, 1000 or 5000 pounds is used to determine the quantity of a hazardous substance for which notification is required in the event of a release as specified by CERCLA based on chronic toxicity. The RQ value for allyl chloride is 100.

  8. Sulfonium-based Ionic Liquids Incorporating the Allyl Functionality

    PubMed Central

    Zhao, Dongbin; Fei, Zhaofu; Ang, Wee Han; Dyson, Paul J.

    2007-01-01

    A series of sulfonium halides bearing allyl groups have been prepared and characterized. Anion metathesis with Li[Tf2N] and Ag[N(CN)2] resulted in sulfonium-based ionic liquids which exhibit low viscosities at room temperature. The solid state structure of one of the halide salts was determined by single crystal X-ray diffraction.

  9. Carbonylation reactions of alkyl iodides through the interplay of carbon radicals and Pd catalysts.

    PubMed

    Sumino, Shuhei; Fusano, Akira; Fukuyama, Takahide; Ryu, Ilhyong

    2014-05-20

    Numerous methods for transition metal catalyzed carbonylation reactions have been established. Examples that start from aryl, vinyl, allyl, and benzyl halides to give the corresponding carboxylic acid derivatives have all been well documented. In contrast, the corresponding alkyl halides often encounter difficulty. This is inherent to the relatively slow oxidative addition step onto the metal center and subsequent β-hydride elimination which causes isomerization of the alkyl metal species. Radical carbonylation reactions can override such problems of reactivity; however, carbonylation coupled to iodine atom transfer (atom transfer carbonylation), though useful, often suffers from a slow iodine atom transfer step that affects the outcome of the reaction. We found that atom transfer carbonylation of primary, secondary, and tertiary alkyl iodides was efficiently accelerated by the addition of a palladium catalyst under light irradiation. Stereochemical studies support a mechanistic pathway based on the synergic interplay of radical and Pd-catalyzed reaction steps which ultimately lead to an acylpalladium species. The radical/Pd-combined reaction system has a wide range of applications, including the synthesis of carboxylic acid esters, lactones, amides, lactams, and unsymmetrical ketones such as alkyl alkynyl and alkyl aryl ketones. The design of unique multicomponent carbonylation reactions involving vicinal C-functionalization of alkenes, double and triple carbonylation reactions, in tandem with radical cyclization reactions, has also been achieved. Thus, the radical/Pd-combined strategy provides a solution to a longstanding problem of reactivity involving the carbonylation of alkyl halides. This novel methodology expands the breadth and utility of carbonylation chemistry over either the original radical carbonylation reactions or metal-catalyzed carbonylation reactions. PMID:24712759

  10. 40 CFR 721.1875 - Boric acid, alkyl and substituted alkyl esters (generic name).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Boric acid, alkyl and substituted... Significant New Uses for Specific Chemical Substances § 721.1875 Boric acid, alkyl and substituted alkyl... chemical substance boric acid, alkyl and substituted alkyl esters (PMN P-86-1252) is subject to...

  11. 40 CFR 721.1875 - Boric acid, alkyl and substituted alkyl esters (generic name).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Boric acid, alkyl and substituted... Significant New Uses for Specific Chemical Substances § 721.1875 Boric acid, alkyl and substituted alkyl... chemical substance boric acid, alkyl and substituted alkyl esters (PMN P-86-1252) is subject to...

  12. 40 CFR 721.1875 - Boric acid, alkyl and substituted alkyl esters (generic name).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Boric acid, alkyl and substituted... Significant New Uses for Specific Chemical Substances § 721.1875 Boric acid, alkyl and substituted alkyl... chemical substance boric acid, alkyl and substituted alkyl esters (PMN P-86-1252) is subject to...

  13. 40 CFR 721.1875 - Boric acid, alkyl and substituted alkyl esters (generic name).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Boric acid, alkyl and substituted... Significant New Uses for Specific Chemical Substances § 721.1875 Boric acid, alkyl and substituted alkyl... chemical substance boric acid, alkyl and substituted alkyl esters (PMN P-86-1252) is subject to...

  14. 40 CFR 721.1875 - Boric acid, alkyl and substituted alkyl esters (generic name).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Boric acid, alkyl and substituted... Significant New Uses for Specific Chemical Substances § 721.1875 Boric acid, alkyl and substituted alkyl... chemical substance boric acid, alkyl and substituted alkyl esters (PMN P-86-1252) is subject to...

  15. C2-Symmetric diamines and their derivatives as promising organocatalysts for asymmetric synthesis

    NASA Astrophysics Data System (ADS)

    Zlotin, S. G.; Kochetkov, S. V.

    2015-11-01

    The review is devoted to the application of C2-symmetric diamines and their derivatives as organocatalysts for asymmetric reactions (aldol, Michael, Mannich, Diels-Alder reactions, desymmetrization, allylation, etc.). Amino acid derivatives, di- and polyamides (sulfamides), bisureas, bisthioureas, bisamidines and bisguanidines are considered. Significant attention is given to the effect of the catalyst structure on the mechanism of catalytic action. Successful applications of such catalysts in enantioselective synthesis of chiral biologically active compounds are summarized. The bibliography includes 181 references.

  16. Alkylation and acylation of cyclotriphosphazenes.

    PubMed

    Benson, Mark A; Zacchini, Stefano; Boomishankar, Ramamoorthy; Chan, Yuri; Steiner, Alexander

    2007-08-20

    Phosphazenes (RNH)6P3N3 (R = n-propyl, isobutyl, isopropyl, cyclohexyl, tert-butyl, benzyl) are readily alkylated at ring N sites by alkyl halides forming N-alkyl phosphazenium cations. Alkylation of two ring N sites occurred after prolonged heating in the presence of methyl iodide or immediately at room temperature with methyl triflate yielding N,N'-dimethyl phosphazenium dications. Geminal dichloro derivatives Cl2(RNH)4P3N3 are methylated by methyl iodide at the ring N site adjacent to both P centers carrying four RNH groups. X-ray crystal structures showed that the alkylation of ring N sites leads to substantial elongation of the associated P-N bonds. Both N-alkyl and N,N'-dialkyl phosphazenium salts form complex supramolecular networks in the solid state via NH...X interactions. Systems carrying less-bulky RNH groups show additional NH...N bonds between N-alkyl phosphazenium ions. N-Alkyl phosphazenium halides form complexes with silver ions upon treatment with silver nitrate. Depending on the steric demand of RNH substituents, either one or both of the vacant ring N sites engage in coordination to silver ions. Treatment of (RNH)6P3N3 (R = isopropyl) with acetyl chloride and benzoyl chloride, respectively, yielded N-acyl phosphazenium ions. X-ray crystal structures revealed that elongation of P-N bonds adjacent to the acylated ring N site is more pronounced than it is in the case of N-alkylated species. Salts containing N-alkyl phosphazenium ions are stable toward water and other mild nucleophiles, while N,N'-dialkyl and N-acyl phosphazenium salts are readily hydrolyzed. The reaction of (RNH)6P3N3 with bromoacetic acid led to N-alkylation at one ring N site in addition to formation of an amide via condensation of an adjacent RNH substituent with the carboxylic acid group. The resulting bromide salt contains mono cations of composition (RNH)5P3N3CH2CONR in which a CH2-C(O) unit is embedded between a ring N and an exocyclic N site of the phosphazene. PMID

  17. Mild Catalytic methods for Alkyl-Alkyl Bond Formation

    SciTech Connect

    Vicic, David A

    2009-08-10

    Overview of Research Goals and Accomplishments for the Period 07/01/06 – 06/30/07: Our overall research goal is to transform the rapidly emerging synthetic chemistry involving alkyl-alkyl cross-couplings into more of a mechanism-based field so that that new, rationally-designed catalysts can be performed under energy efficient conditions. Our specific objectives for the previous year were 1) to obtain a proper electronic description of an active catalyst for alkyl-alkyl cross-coupling reactions and 2) to determine the effect of ligand structure on the rate, scope, selectivity, and functional group compatibility of C(sp3)-C(sp3) cross-coupling catalysis. We have completed both of these initial objectives and established a firm base for further studies. The specific significant achievements of the current grant period include: 1) we have performed magnetic and computational studies on (terpyridine)NiMe, an active catalyst for alkyl-alkyl cross couplings, and have discovered that the unpaired electron resides heavily on the terpyridine ligand and that the proper electronic description of this nickel complex is a Ni(II)-methyl cation bound to a reduced terpyridine ligand; 2) we have for the first time shown that alkyl halide reduction by terpyridyl nickel catalysts is substantially ligand based; 3) we have shown by isotopic labeling studies that the active catalyst (terpyridine)NiMe is not produced via a mechanism that involves the formation of methyl radicals when (TMEDA)NiMe2 is used as the catalyst precursor; 4) we have performed an extensive ligand survey for the alkyl-alkyl cross-coupling reactions and have found that electronic factors only moderately influence reactivity in the terpyridine-based catalysis and that the most dramatic effects arise from steric and solubility factors; 5) we have found that the use of bis(dialkylphosphino)methanes as ligands for nickel does not produce active catalysts for cross-coupling but rather leads to bridging hydride

  18. Competing sigmatropic shift rearrangements in excited allyl radicals

    SciTech Connect

    Stranges, D.; O'Keeffe, P.; Scotti, G.; Di Santo, R.; Houston, P. L.

    2008-04-21

    The competition between rearrangement of the excited allyl radical via a 1,3 sigmatropic shift versus sequential 1,2 shifts has been observed and characterized using isotopic substitution, laser excitation, and molecular beam techniques. Both rearrangements produce a 1-propenyl radical that subsequently dissociates to methyl plus acetylene. The 1,3 shift and 1,2 shift mechanisms are equally probable for CH{sub 2}CHCH{sub 2}, whereas the 1,3 shift is favored by a factor of 1.6 in CH{sub 2}CDCH{sub 2}. The translational energy distributions for the methyl and acetylene products of these two mechanisms are substantially different. Both of these allyl dissociation channels are minor pathways compared to hydrogen atom loss.

  19. Copper-catalyzed trifluoromethylation of trisubstituted allylic and homoallylic alcohols.

    PubMed

    Lei, Jian; Liu, Xiaowu; Zhang, Shaolin; Jiang, Shuang; Huang, Minhao; Wu, Xiaoxing; Zhu, Qiang

    2015-04-27

    An efficient copper-catalyzed trifluoromethylation of trisubstituted allylic and homoallylic alcohols with Togni's reagent has been developed. This strategy, accompanied by a double-bond migration, leads to various branched CF3-substituted alcohols by using readily available trisubstituted cyclic/acyclic alcohols as substrates. Moreover, for alcohols in which β-H elimination is prohibited, CF3-containing oxetanes are isolated as the sole product. PMID:25810003

  20. Rotational Spectroscopy of Isocyanic Molecules: Allyl Isocyanide and Diisocyanomethane

    NASA Astrophysics Data System (ADS)

    Motiyenko, R. A.; Margules, L.; Haykal, I.; Huet, T. R.; Cocinero, E. J.; Ecija, P.; Fernandez, J. A.; Castano, F.; Lesarri, A.; Guillemin, J.-C.

    2012-06-01

    Isocyanides are less stable isomers of nitriles and some of them have already been observed in the interstellar medium (HNC, CH_3NC, HCCNC). But still there exists a lack of experimental spectroscopic data on simple isocyanic molecules that can represent potential astrophysical interest. In this view we have performed high resolution studies of rotational spectra of allyl isocyanide (CH_2=CH--CH_2--NC) and diisocyanomethane (CN--CH_2--NC). The rotational spectra of allyl isocyanide have been measured in the frequency range 6 -- 18 GHz by means of FTMW spectrometer in Bilbao and in the frequency range 150 -- 945 GHz by means of classic absorption spectroscopy in Lille. Two stable confomers of allyl isocyanide have been observed in both series of measurements. In addition, all 13C-monosubstituted isotopologues and 15N isotopologues were detected in natural abundance. Due to much lower kinetic stability the rotational spectrum of diisocyanomethane has been measured only in absorption using the Lille spectrometer. The spectral assignments have been supported by high-level quantum chemical calculations. For both molecules accurate sets of rotational and centrifugal distortion constants (up to the octics) have been produced. As a result, reliable predictions of transitions frequencies suitable for astrophysical detection have been obtained for both molecules. Finally, the effective and substitution structures were determined for the two conformers of allyl isocyanide, comparing the result with ab initio data. This work is supported by Centre Nationale d'Etudes Spatiales (CNES), Action sur Projet Physico-Chimie du Milieu Interstellaire (PCMI-CNRS) and by the contract ANR-08-BLAN-0054. Spanish part acknowledges funding from the MICINN and the MINECO.

  1. Stereoselective terminal functionalization of small peptides for catalytic asymmetric synthesis of unnatural peptides

    PubMed Central

    Maruoka, Keiji; Tayama, Eiji; Ooi, Takashi

    2004-01-01

    The asymmetric phase-transfer catalytic alkylation of peptides has been achieved by the use of designed C2-symmetric chiral quaternary ammonium bromide 1 as catalyst. Excellent stereoselectivities were uniformly observed in the alkylation with a variety of alkyl halides and the efficiency of the transmission of stereochemical information was not affected by the side-chain structure of the preexisting amino acid residues. This method also enables an asymmetric construction of noncoded α,α-dialkyl-α-amino acid residues at the peptide terminal. Since this chirality can be efficiently transferred to the adjacent amino acid moiety, our approach provides a general procedure not only for the highly stereoselective terminal functionalization of peptides but also for the sequential asymmetric construction of unnatural oligopeptides, which should play a vital role in the peptide-based drug discovery process. PMID:15079083

  2. Crystal structure of allyl­ammonium hydrogen succinate at 100 K

    PubMed Central

    Dziuk, Błażej; Zarychta, Bartosz; Ejsmont, Krzysztof

    2014-01-01

    The asymmetric unit of the title compound, C2H8N+·C4H5O4 −, consists of two allyl­ammonium cations and two hydrogen succinate anions (Z′ = 2). One of the cations has a near-perfect syn-periplanar (cis) conformation with an N—C—C—C torsion angle of 0.4 (3)°, while the other is characterized by a gauche conformation and a torsion angle of 102.5 (3)°. Regarding the anions, three out of four carboxilic groups are twisted with respect to the central C–CH2–CH2–C group [dihedral angles = 24.4 (2), 31.2 (2) and 40.4 (2)°], the remaining one being instead almost coplanar, with a dihedral angle of 4.0 (2)°. In the crystal, there are two very short, near linear O—H⋯O hydrogen bonds between anions, with the H atoms shifted notably from the donor O towards the O⋯O midpoint. These O—H⋯O hydrogen bonds form helical chains along the [011] which are further linked to each other through N—H⋯O hydrogen bonds (involving all the available NH groups), forming layers lying parallel to (100). PMID:25309251

  3. Alkylation of toluene with ethanol

    SciTech Connect

    Walendziewski, J.; Trawczynski, J.

    1996-10-01

    A series of Y and ZSM-5 zeolite based catalysts was prepared. Zeolites were cation exchanged and formed with 50% of aluminum hydroxide as a binder, and the obtained catalysts were finally thermally treated. Activity tests in alkylation of toluene with ethanol were carried out in the temperature range of 325--400 C, in nitrogen or hydrogen stream, and a pressure up to 3 MPa. The feed consisted of toluene and ethanol mixed in a mole ratio 1/1 or 2/1. The obtained results showed that among the studied catalysts the highest activity in the alkylation reaction was attained by ZSM-5 zeolite based catalyst with a moderate acidity and medium silica to alumina ratio, i.e., {approximately}50. Activity and selectivity of the most active catalyst as well as conversion of the feed components were similar to those reported in other papers. The content of p-ethyltoluene in alkylation products attained ca. 60%.

  4. Asymmetric Ashes

    NASA Astrophysics Data System (ADS)

    2006-11-01

    that oscillate in certain directions. Reflection or scattering of light favours certain orientations of the electric and magnetic fields over others. This is why polarising sunglasses can filter out the glint of sunlight reflected off a pond. When light scatters through the expanding debris of a supernova, it retains information about the orientation of the scattering layers. If the supernova is spherically symmetric, all orientations will be present equally and will average out, so there will be no net polarisation. If, however, the gas shell is not round, a slight net polarisation will be imprinted on the light. This is what broad-band polarimetry can accomplish. If additional spectral information is available ('spectro-polarimetry'), one can determine whether the asymmetry is in the continuum light or in some spectral lines. In the case of the Type Ia supernovae, the astronomers found that the continuum polarisation is very small so that the overall shape of the explosion is crudely spherical. But the much larger polarization in strongly blue-shifted spectral lines evidences the presence, in the outer regions, of fast moving clumps with peculiar chemical composition. "Our study reveals that explosions of Type Ia supernovae are really three-dimensional phenomena," says Dietrich Baade. "The outer regions of the blast cloud is asymmetric, with different materials found in 'clumps', while the inner regions are smooth." "This study was possible because polarimetry could unfold its full strength thanks to the light-collecting power of the Very Large Telescope and the very precise calibration of the FORS instrument," he adds. The research team first spotted this asymmetry in 2003, as part of the same observational campaign (ESO PR 23/03 and ESO PR Photo 26/05). The new, more extensive results show that the degree of polarisation and, hence, the asphericity, correlates with the intrinsic brightness of the explosion. The brighter the supernova, the smoother, or less clumpy

  5. A biological source of oceanic alkyl nitrates

    NASA Astrophysics Data System (ADS)

    Dahl, E. E.; Lewis, C. B.; Velasco, F. L.; Escobar, C.; Kellogg, D.; Velcamp, M.

    2013-12-01

    Alkyl nitrates are an important component of reactive nitrogen in the troposphere. The oceans are a source of alkyl nitrates to the atmosphere, however the source of alkyl nitrates in the oceans is unknown. It has been demonstrated that the reaction of alkyl peroxy radicals (ROO) with nitric oxide (NO) produces alkyl nitrates in the aqueous phase. We hypothesize that alkyl nitrates may be formed by organisms through the same reaction and therefore biological production could be a source of alkyl nitrates to the troposphere. This work focuses on the production of alkyl nitrates by the diatoms Chaetoceros muelleri and Thalassiosira weisfloggi. Using chemostats, we measure alkyl nitrates formed under nitrate limited conditions. We also use triggers and inhibitors of nitric oxide formation to determine if alkyl nitrate formation is affected by changes in NO production. To date, the rates of production of alkyl nitrates in our cultures, lead us to estimate a production rate on the order of femtomolar/day for C1-C3 alkyl nitrates by diatom species in the equatorial Pacific Ocean. This suggests that diatoms may contribute to the overall ocean source of alkyl nitrates; however, it is possible that other types of phytoplankton, such as cyanobacteria, that are more abundant in the open ocean, may contribute to a greater extent.

  6. Phosphine-alkene ligand-mediated alkyl-alkyl and alkyl-halide elimination processes from palladium(II).

    PubMed

    Tuxworth, Luke; Baiget, Lise; Phanopoulos, Andreas; Metters, Owen J; Batsanov, Andrei S; Fox, Mark A; Howard, Judith A K; Dyer, Philip W

    2012-10-28

    N-Diphenylphosphino-7-aza-benzobicyclo[2.2.1]hept-2-ene (2) behaves as a chelating phosphine-alkene ligand for Pd(0) and Pd(II), promoting direct alkyl-alkyl and indirect alkyl-halide reductive elimination reactions due to the stabilisation of the resulting bis(phosphine-alkene)Pd(0) complex. PMID:22986447

  7. Asymmetric dark matter

    SciTech Connect

    Kumar, Jason

    2014-06-24

    We review the theoretical framework underlying models of asymmetric dark matter, describe astrophysical constraints which arise from observations of neutron stars, and discuss the prospects for detecting asymmetric dark matter.

  8. 40 CFR 721.9892 - Alkylated urea.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alkylated urea. 721.9892 Section 721... Alkylated urea. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as an alkylated urea (PMN P-93-1649) is subject to reporting under...

  9. 40 CFR 721.9892 - Alkylated urea.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Alkylated urea. 721.9892 Section 721... Alkylated urea. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as an alkylated urea (PMN P-93-1649) is subject to reporting under...

  10. 40 CFR 721.9892 - Alkylated urea.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Alkylated urea. 721.9892 Section 721... Alkylated urea. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as an alkylated urea (PMN P-93-1649) is subject to reporting under...

  11. 40 CFR 721.9892 - Alkylated urea.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Alkylated urea. 721.9892 Section 721... Alkylated urea. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as an alkylated urea (PMN P-93-1649) is subject to reporting under...

  12. 40 CFR 721.9892 - Alkylated urea.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Alkylated urea. 721.9892 Section 721... Alkylated urea. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as an alkylated urea (PMN P-93-1649) is subject to reporting under...

  13. Trajectory study of energy transfer and unimolecular dissociation of highly excited allyl with argon.

    PubMed

    Conte, Riccardo; Houston, Paul L; Bowman, Joel M

    2014-09-11

    The influence of rotational excitation on energy transfer in single collisions of allyl with argon and on allyl dissociation is investigated. About 90,000 classical scattering simulations are performed in order to determine collision-induced changes in internal energy and in allyl rotational angular momentum. Dissociation is studied by means of about 50,000 additional trajectories evolved for the isolated allyl under three different conditions: allyl with no angular momentum (J = 0); allyl with the same microcanonically sampled initial conditions used for the collisions (J*); allyl evolving from the corresponding exit conditions after the collision. The potential energy surface is the sum of an intramolecular potential and an interaction one, and it has already been used in a previous work on allyl-argon scattering (Conte, R.; Houston, P. L.; Bowman, J. M. J. Phys. Chem. A 2013, 117, 14028-14041). Energy transfer data show that increased initial rotation favors, on average, increased relaxation of the excited molecule. The availability of a high-level intramolecular potential energy surface permits us to study the dependence of energy transfer on the type of starting allyl isomer. A turning point analysis is presented, and highly efficient collisions are detected. Collision-induced variations in the allyl rotational angular momentum may be quite large and are found to be distributed according to three regimes. The roles of rotational angular momentum, collision, and type of isomer on allyl unimolecular dissociation are considered by looking at dissociations times, kinetic energies of the fragments, and branching ratios. Generally, rotational angular momentum has a strong influence on the dissociation dynamics, while the single collision and the type of starting isomer are less influential. PMID:25116695

  14. 10 Step Asymmetric Total Synthesis and Stereochemistry of (+)-Dragmacidin D

    PubMed Central

    Jackson, Jeffrey J.; Kobayashi, Hiroyuki; Steffens, Sophia D.

    2015-01-01

    The asymmetric synthesis of dragmacidin D (1) has been completed in 10 steps. Its sole stereocenter was set using direct asymmetric alkylation enabled by a C2-symmetric tetramine and lithium N-(trimethylsilyl)-tert-butylamide as the enolization reagent. A central Larock indole synthesis was employed in a convergent assembly of heterocyclic subunits. The stereochemical evidence from this work strongly supports the predicted S configuration at 6′″ position consistent with other members of the dragmacidin family of natural products. PMID:26130270

  15. Recent advances in copper-catalyzed asymmetric coupling reactions.

    PubMed

    Zhou, Fengtao; Cai, Qian

    2015-01-01

    Copper-catalyzed (or -mediated) asymmetric coupling reactions have received significant attention over the past few years. Especially the coupling reactions of aryl or alkyl halides with nucleophiles became a very powerful tool for the formation of C-C, C-N, C-O and other carbon-heteroatom bonds as well as for the construction of heteroatom-containing ring systems. This review summarizes the recent progress in copper-catalyzed asymmetric coupling reactions for the formation of C-C and carbon-heteroatom bonds. PMID:26734106

  16. Recent advances in copper-catalyzed asymmetric coupling reactions

    PubMed Central

    2015-01-01

    Summary Copper-catalyzed (or -mediated) asymmetric coupling reactions have received significant attention over the past few years. Especially the coupling reactions of aryl or alkyl halides with nucleophiles became a very powerful tool for the formation of C–C, C–N, C–O and other carbon–heteroatom bonds as well as for the construction of heteroatom-containing ring systems. This review summarizes the recent progress in copper-catalyzed asymmetric coupling reactions for the formation of C–C and carbon–heteroatom bonds. PMID:26734106

  17. Oil compositions containing alkyl amine or alkyl mercaptan derivatives of copolymers of an alpha olefin or an alkyl vinyl ether

    SciTech Connect

    Le, H.T.

    1990-02-13

    This patent describes an oil composition. It comprises a major amount of an oil selected from a crude oil or fuel oil and a minor amount of an alkyl amine or alkyl mercaptan derivative of an alpha olefin or alkyl vinyl ether and an unsaturated alpha, beta-dicarboxylic compound copolymer having pour point depressant ;properties. The copolymer comprising the reaction product of an alpha olefin having from about 2 to about 30 carbon atoms or mixtures of alpha olefins having from about 2 to about 30 carbon atoms or an alkyl vinyl ether or mixture of alkyl vinyl ethers.

  18. Palladium(0)-Catalyzed Intermolecular Allylic Dearomatization of Indoles by a Formal [4+2] Cycloaddition Reaction.

    PubMed

    Gao, Run-Duo; Xu, Qing-Long; Zhang, Bo; Gu, Yiting; Dai, Li-Xin; You, Shu-Li

    2016-08-01

    Bridged indoline derivatives were synthesized by an intermolecular Pd-catalyzed allylic dearomatization reaction of substituted indoles. The reaction between indoles and allyl carbonates bearing a nucleophilic alcohol side-chain proceeds in a cascade fashion, providing bridged indolines in excellent enantioselectivity. PMID:27321285

  19. Magnetic silica supported palladium catalyst: synthesis of allyl aryl ethers in water

    EPA Science Inventory

    A simple and benign procedure for the synthesis of aryl allyl ethers has been developed using phenols, allyl acetates and magnetically recyclable silica supported palladium catalyst in water; performance of reaction in air and easy separation of the catalyst using an external mag...

  20. Trifluoromethylallylation of Heterocyclic C-H Bonds with Allylic Carbonates under Rhodium Catalysis.

    PubMed

    Choi, Miji; Park, Jihye; Sharma, Satyasheel; Jo, Hyeim; Han, Sangil; Jeon, Mijin; Mishra, Neeraj Kumar; Han, Sang Hoon; Lee, Jong Suk; Kim, In Su

    2016-06-01

    The rhodium(III)-catalyzed γ-trifluoromethylallylation of various heterocyclic C-H bonds with CF3-substituted allylic carbonates is described. These reactions provide direct access to linear CF3-containing allyl frameworks with complete trans-selectivity via C-H bond activation followed by a formal SN-type reaction pathway. PMID:27187625

  1. 1-Allyl-3-chloro-5-nitro-1H-indazole

    PubMed Central

    Chicha, Hakima; Rakib, El Mostapha; Spinelli, Domenico; Saadi, Mohamed; El Ammari, Lahcen

    2013-01-01

    In the title compound, C10H8ClN3O2, the indazole ring system makes a dihedral angle of 7.9 (3)° with the plane through the nitro group. The allyl group is rotated out of the plane of the indazole ring system [N—N—C—C torsion angle = 104.28 (19)°]. In the crystal, mol­ecules are linked by C—H⋯O hydrogen bonds, forming zigzag chains propagating along the b-axis direction. PMID:24427047

  2. Practical Stannylation of Allyl Acetates Catalyzed by Nickel with Bu3 SnOMe.

    PubMed

    Komeyama, Kimihiro; Itai, Yuuhei; Takaki, Ken

    2016-06-27

    A practical and scalable nickel-catalyzed allylic stannylation of allyl acetates with Bu3 SnOMe is described. A variety of acyclic and cyclic allyl acetates, even with base-sensitive moieties, undergoes the stannylation by using NiBr2 /4,4'-di-tert-butylbipyridine (dtbpy)/Mn catalyst system to afford highly functionalized allyl stannanes with excellent regioselectivity and yields. Furthermore, the scope of protocol is also extended by the reaction of propargyl acetates, giving rise to propargyl or allenyl stannanes. Additionally, a unique diastereoselectivity using the nickel catalyst different from the palladium was demonstrated for the stannylation of cyclic allyl acetates. In the reaction, inexpensive and stable nickel complexes, abundant reductant (Mn), and atom-economical stannyl source were used. PMID:27124370

  3. Allyl alcohol activation of protein kinase C delta leads to cytotoxicity of rat hepatocytes.

    PubMed

    Maddox, Jane F; Roth, Robert A; Ganey, Patricia E

    2003-05-01

    Hepatotoxicity of allyl alcohol involves its bioactivation to acrolein and subsequent protein sulfhydryl loss and lipid peroxidation. However, the links between these events and hepatocellular death are not known. The purpose of these studies was to examine whether specific signal transduction pathways are associated with allyl alcohol toxicity in hepatocytes. Inhibition or augmentation of cyclic AMP and/or protein kinase A (PKA) by Rp-Ado-3N,5N-cyclic monophosphorothioate triethylamine salt or 3-isobutyl-1-methylxanthine had no effect on allyl alcohol-induced cell death. H-7, an inhibitor of PKA, PKC, and PKG, partially inhibited cell killing by allyl alcohol, whereas chelerythrine chloride, a nonselective PKC inhibitor, almost completely abolished allyl alcohol cytotoxicity. Neither 2,2N,3,3N,4,4N-hexahydroxy-1,1N,-biphenyl-6,6N-dimethanol-dimethyl ether, a selective PKC alpha and beta inhibitor, nor bisindolylmaleimide I, an inhibitor of PKC alpha, beta, and epsilon, had any effect on allyl alcohol cytotoxicity. In contrast, rottlerin, a selective PKCdelta inhibitor, blocked hepatocellular killing by allyl alcohol. Cytoprotection by chelerythrine chloride and rottlerin was not the result of inhibition of bioactivation of allyl alcohol because each inhibitor also prevented cell death from acrolein. Western blotting and immunohistochemical techniques revealed that allyl alcohol stimulated phosphorylation and translocation of PKCdelta to hepatocyte membranes (i.e., activation), and this activity was inhibited by rottlerin. Cell death appeared to occur via oncotic necrosis rather than apoptosis based on single-stranded DNA ELISA and propidium iodide staining. Together, these results indicate that activation of PKCdelta is a critical, early event in initiating hepatocyte injury and death from allyl alcohol. PMID:12755590

  4. Oxidative addition of allylic halides to ruthenium(II) compounds. Preparation, reactions, and X-ray crystallographic structure of ruthenium(IV)-allyl complexes

    SciTech Connect

    Nagashima, Hideo; Mukai, Katsunori; Shiota, Yusuke; Yamaguchi, Keitaro; Ara, Kenichi; Fukahori, Takahiko; Itoh, Kenji ); Suzuki, Hiroharu; Akita, Munetaka; Moro-oka, Yoshihiko )

    1990-03-01

    The oxidative addition of allylic halides to (C{sub 5}R{sub 5})RuL{sub 2}X (R = H, Me; L = CO, PPh{sub 3}) gave new Ru(IV)-{eta}{sup 3}-allyl complexes, (C{sub 5}R{sub 5})RuX{sub 2}({eta}{sup 3}-allyl). An X-ray structure determination was carried out on (C{sub 5}Me{sub 5})RuBr{sub 2}({eta}{sup 3}-C{sub 3}H{sub 5}), indicating a pseudo-piano-stool structure having two Br atoms and two terminal carbons of the endo-{eta}{sup 3}-allyl ligand located at the basal positions. There is a crystal mirror plane bisecting the pentamethylcyclopentadienyl and the {pi}-allyl ligands. Crystal data: orthorhombic, space group P2{sub 1}2{sub 1}2{sub 1}, a = 22.738 (1) {angstrom}, b = 13.367 (7) {angstrom}, c = 9.383 (1) {angstrom}, Z = 4., data refined to R = 0.0695. Its {sup 1}H and {sup 13}C NMR spectra showed symmetric allyl signals, supporting that the above-described piano-stool structure is maintained even in solution.

  5. Methods of making alkyl esters

    DOEpatents

    Elliott, Brian

    2010-08-03

    A method comprising contacting an alcohol, a feed comprising one or more glycerides and equal to or greater than 2 wt % of one or more free fatty acids, and a solid acid catalyst, a nanostructured polymer catalyst, or a sulfated zirconia catalyst in one or more reactors, and recovering from the one or more reactors an effluent comprising equal to or greater than about 75 wt % alkyl ester and equal to or less than about 5 wt % glyceride.

  6. PREPARATION OF ALKYL PYROPHOSPHATE EXTRACTANTS

    DOEpatents

    Levine, C.A.; Skiens, W.E.; Moore, G.R.

    1960-08-01

    A process for providing superior solvent extractants for metal recovery processes is given wherein the extractant comprises an alkyl pyrophosphoric acid ester dissolved in an organic solvent diluent. Finely divided solid P/sub 2/O/ sub 5/ is slurried in an organic solvent-diluent selected from organic solvents such as kerosene, benzene, chlorobenzene, toluene, etc. An alcohol selected from the higher alcohols having 4 to 17 carbon atoms. e.g.. hexanol-1. heptanol-3, octanol-1. 2.6-dimethyl-heptanol-4, and decanol-1, is rapidly added to the P/sub 2/O/sub 5/ slurry in the amount of about 2 moles of alcohol to 1 mole of P/sub 2/ O/sub 5/. The temperature is maintained below about 110 deg C during the course of the P/sub 2/O/sub 5/-alcohol reaction. An alkyl pyrophosphate extractant compound is formed as a consequence of the reaction process. The alkyl pyrophosphate solvent-diluent extractant phase is useful in solvent extraction metal recovery processes.

  7. Cross-Coupling of Aromatic Bromides with Allylic Silanolate Salts

    PubMed Central

    Denmark, Scott E; Werner, Nathan S.

    2009-01-01

    The sodium salts of allyldimethylsilanol and 2-butenyldimethylsilanol undergo palladium-catalyzed cross-coupling with a wide variety of aryl bromides to afford allylated and crotylated arenes. The coupling of both silanolates required extensive optimization to deliver the expected products in high yields. The reaction of the allyldimethylsilanolate takes place at 85 °C in DME with allylpalladium chloride dimer (2.5 mol %) to afford 7–95% yields of the allylation products. Both electron-rich and sterically-hindered bromides reacted smoothly, whereas electron-poor bromides cross-coupled in poor yield because of a secondary isomerization to the 1-propenyl isomer (and subsequent polymerization). The 2-butenyldimethylsilanolate (E/Z, 80:20) required additional optimization to maximize the formation of the branched (γ-substitution product). A remarkable influence of added alkenes (dibenzylideneacetone and norbornadiene) led to good selectivities for electron-rich and electron-poor bromides in 4–83% yields. However, bromides containing coordinating groups (particularly in the ortho position) gave lower, and in one case even reversed, selectivity. Configurationally homogeneous E-silanolates gave slightly higher γ-selectivity than the pure Z-silanolates. A unified mechanistic picture involving initial γ-transmetalation followed by direct reductive elimination or σ–π isomerization can rationalize all of the observed trends. PMID:18998687

  8. Development of a strategy for the asymmetric synthesis of polycyclic polyprenylated acylphloroglucinols via N-amino cyclic carbamate hydrazones: application to the total synthesis of (+)-clusianone.

    PubMed

    Garnsey, Michelle R; Lim, Daniel; Yost, Julianne M; Coltart, Don M

    2010-11-19

    A broadly applicable asymmetric synthetic strategy utilizing N-amino cyclic carbamate alkylation that provides access to the various stereochemical permutations of a common structural motif found in many polycyclic polyprenylated acylphloroglucinols is described. The utility of this methodology is demonstrated through the first asymmetric total synthesis of the antiviral agent (+)-clusianone. PMID:20977254

  9. O–H hydrogen bonding promotes H-atom transfer from a C–H bonds for C-alkylation of alcohols

    PubMed Central

    Jeffrey, Jenna L.; Terrett, Jack A.; MacMillan, David W. C.

    2015-01-01

    The efficiency and selectivity of hydrogen atom transfer from organic molecules are often difficult to control in the presence of multiple potential hydrogen atom donors and acceptors. Here, we describe the mechanistic evaluation of a mode of catalytic activation that accomplishes the highly selective photoredox α-alkylation/lactonization of alcohols with methyl acrylate via a hydrogen atom transfer mechanism. Our studies indicate a particular role of tetra-n-butylammonium phosphate in enhancing the selectivity for α C–H bonds in alcohols in the presence of allylic, benzylic, α-C=O, and α-ether C–H bonds. PMID:26316601

  10. Enantioselective Functionalization of Allylic C-H Bonds Following a Strategy of Functionalization and Diversification

    PubMed Central

    Sharma, Ankit; Hartwig, John F.

    2013-01-01

    We report the enantioselective functionalization of allylic C-H bonds in terminal alkenes by a strategy involving the installation of a temporary functional group at the terminal carbon atom by C-H bond functionalization, followed by diversification of this intermediate with a broad scope of reagents. The method consists of a one-pot sequence of palladium-catalyzed allylic C-H bond oxidation under neutral conditions to form linear allyl benzoates, followed by iridium-catalyzed allylic substitution. This overall transformation forms a variety of chiral products containing a new C-N, C-O, C-S or C-C bond at the allylic position in good yield with high branched-to-linear selectivity and excellent enantioselectivity (ee ≤ 97%). The broad scope of the overall process results from separating the oxidation and functionalization steps; by doing so, the scope of nucleophile encompasses those sensitive to direct oxidative functionalization. The high enantioselectivity of the overall process is achieved by developing an allylic oxidation that occurs without acid to form the linear isomer with high selectivity. These allylic functionalization processes are amenable to an iterative sequence leading to (1,n)-functionalized products with catalyst-controlled diastereo- and enantioselectivity. The utility of the method in the synthesis of biologically active molecules has been demonstrated. PMID:24156776

  11. Asymmetric synthesis of trifluoromethylated amines via catalytic enantioselective isomerization of imines.

    PubMed

    Wu, Yongwei; Deng, Li

    2012-09-01

    A new approach toward the asymmetric synthesis of optically active trifluoromethylated amines was enabled by an unprecedented, highly enantioselective catalytic isomerization of trifluoromethyl imines with a new chiral organic catalyst. Not only aryl but also alkyl trifluoromethylated amines could be obtained in high enantioselectivities. PMID:22906148

  12. Triazolium based ionic liquid crystals: Effect of asymmetric substitution

    SciTech Connect

    Stappert, K.; Mudring, A. -V.

    2015-01-27

    A new series of ten different asymmetrical 1-dodecyl-3-alkyl-triazolium bromides, [C12CnTr][Br], has been synthesized and their mesomorphic behavior studied by DSC (differential scanning calorimetry), POM (polarizing optical microscopy) and SAXS (small angle X-ray scattering). The influence of the chain length of the triazolium salts is investigated to explore the effect of asymmetric substitution on the phase behaviour of these compounds. For that reason, the length of one alkyl chain was varied from 14 to 1 carbon atoms (n = 14, 12, 10, 8–4, 2, 1) while the other alkyl chain was kept at 12 carbon. Single crystal X-ray structure analysis of compounds [C12C12Tr][Br] and [C12C5Tr][Br] reveal that the cations adopt a U-shaped conformation with head-to-head arranged triazolium cores. In contrast, for [C12C1Tr][Br], a rod like shape of the cation with interdigitated alkyl chains is found. All investigated compounds are thermotropic liquid crystals. Higher ordered smectic phases, smectic C as well as smectic A phases were found depending on the chain length of the cation. Moreover, the clearing point temperature decreases with decreasing chain length with exception for the n-dodecyl-3-alkyltrizoliumbromides with the two shortest alkyl chains, [C12C2Tr][Br] and [C12C1Tr][Br], which present higher clearing temperatures (86 and 156 °C) and are structurally distinctly different.

  13. Triazolium based ionic liquid crystals: Effect of asymmetric substitution

    DOE PAGESBeta

    Stappert, K.; Mudring, A. -V.

    2015-01-27

    A new series of ten different asymmetrical 1-dodecyl-3-alkyl-triazolium bromides, [C12CnTr][Br], has been synthesized and their mesomorphic behavior studied by DSC (differential scanning calorimetry), POM (polarizing optical microscopy) and SAXS (small angle X-ray scattering). The influence of the chain length of the triazolium salts is investigated to explore the effect of asymmetric substitution on the phase behaviour of these compounds. For that reason, the length of one alkyl chain was varied from 14 to 1 carbon atoms (n = 14, 12, 10, 8–4, 2, 1) while the other alkyl chain was kept at 12 carbon. Single crystal X-ray structure analysis ofmore » compounds [C12C12Tr][Br] and [C12C5Tr][Br] reveal that the cations adopt a U-shaped conformation with head-to-head arranged triazolium cores. In contrast, for [C12C1Tr][Br], a rod like shape of the cation with interdigitated alkyl chains is found. All investigated compounds are thermotropic liquid crystals. Higher ordered smectic phases, smectic C as well as smectic A phases were found depending on the chain length of the cation. Moreover, the clearing point temperature decreases with decreasing chain length with exception for the n-dodecyl-3-alkyltrizoliumbromides with the two shortest alkyl chains, [C12C2Tr][Br] and [C12C1Tr][Br], which present higher clearing temperatures (86 and 156 °C) and are structurally distinctly different.« less

  14. Conformations of allylic fluorides and stereoselectivities of their diels-alder cycloadditions.

    PubMed

    Grée, D; Vallerie, L; Grée, R; Toupet, L; Washington, I; Pelicier, J P; Villacampa, M; Pérez, J M; Houk, K N

    2001-04-01

    The preparations of new allylic fluorides from the corresponding alcohols are reported. Conformational analysis is achieved by comparison of experimental NMR measurements with theoretical (B3LYP) calculations of relative energies of conformers and J(H,H) and J(H,F) coupling constants. The Diels-Alder reactions of allylic fluorides are investigated experimentally and theoretically. The stereoselectivities of the reactions were determined by NMR analysis and, in one case, by X-ray crystallography. Theoretical predictions of stereoselectivity based upon transition state modeling provided good agreement with experiment. Theoretical models for allylic fluorides and transition state conformations are reported. PMID:11281778

  15. Sequence-defined polymers via orthogonal allyl acrylamide building blocks.

    PubMed

    Porel, Mintu; Alabi, Christopher A

    2014-09-24

    Biological systems have long recognized the importance of macromolecular diversity and have evolved efficient processes for the rapid synthesis of sequence-defined biopolymers. However, achieving sequence control via synthetic methods has proven to be a difficult challenge. Herein we describe efforts to circumvent this difficulty via the use of orthogonal allyl acrylamide building blocks and a liquid-phase fluorous support for the de novo design and synthesis of sequence-specific polymers. We demonstrate proof-of-concept via synthesis and characterization of two sequence-isomeric 10-mer polymers. (1)H NMR and LCMS were used to confirm their chemical structure while tandem MS was used to confirm sequence identity. Further validation of this methodology was provided via the successful synthesis of a sequence-specific 16-mer polymer incorporating nine different monomers. This strategy thus shows promise as an efficient approach for the assembly of sequence-specific functional polymers. PMID:25204618

  16. Rhodium-Catalyzed Regiodivergent Hydrothiolation of Allyl Amines and Imines.

    PubMed

    Kennemur, Jennifer L; Kortman, Gregory D; Hull, Kami L

    2016-09-14

    The regiodivergent Rh-catalyzed hydrothiolation of allyl amines and imines is presented. Bidentate phosphine ligands with larger natural bite angles (βn ≥ 99°), for example, DPEphos, dpph, or L1, promote a Markovnikov-selective hydrothiolation in up to 88% yield and >20:1 regioselectivity. Conversely, when smaller bite angle ligands (βn ≤ 86°), for example, dppbz or dppp, are employed, the anti-Markovnikov product is formed in up to 74% yield and >20:1 regioselectivity. Initial mechanistic investigations are performed and are consistent with an oxidative addition/olefin insertion/reductive elimination mechanism for each regioisomeric pathway. We hypothesize that the change in regioselectivity is an effect of diverging coordination spheres to favor either Rh-S or Rh-H insertion to form the branched or linear isomer, respectively. PMID:27547858

  17. Aerobic Linear Allylic C-H Amination: Overcoming Benzoquinone Inhibition.

    PubMed

    Pattillo, Christopher C; Strambeanu, Iulia I; Calleja, Pilar; Vermeulen, Nicolaas A; Mizuno, Tomokazu; White, M Christina

    2016-02-01

    An efficient aerobic linear allylic C-H amination reaction is reported under palladium(II)/bis-sulfoxide/Brønsted base catalysis. The reaction operates under preparative, operationally simple conditions (1 equiv of olefin, 1 atm O2 or air) with reduced Pd(II)/bis-sulfoxide catalyst loadings while providing higher turnovers and product yields than systems employing stoichiometric benzoquinone (BQ) as the terminal oxidant. Pd(II)/BQ π-acidic interactions have been invoked in various catalytic processes and are often considered beneficial in promoting reductive functionalizations. When such electrophilic activation for functionalization is not needed, however, BQ at high concentrations may compete with crucial ligand (bis-sulfoxide) binding and inhibit catalysis. Kinetic studies reveal an inverse relationship between the reaction rate and the concentration of BQ, suggesting that BQ is acting as a ligand for Pd(II) which results in an inhibitory effect on catalysis. PMID:26730458

  18. 40 CFR 721.8673 - [(Disubstituted phenyl)]azo dihydro hydroxy alkyl oxo alkyl-substituted-pyridines (generic name).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false azo dihydro hydroxy alkyl oxo alkyl... Significant New Uses for Specific Chemical Substances § 721.8673 azo dihydro hydroxy alkyl oxo alkyl...) The chemical substances identified generically as azo dihydro hydroxy alkyl oxo...

  19. 40 CFR 721.8673 - [(Disubstituted phenyl)]azo dihydro hydroxy alkyl oxo alkyl-substituted-pyridines (generic name).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false azo dihydro hydroxy alkyl oxo alkyl... Significant New Uses for Specific Chemical Substances § 721.8673 azo dihydro hydroxy alkyl oxo alkyl...) The chemical substances identified generically as azo dihydro hydroxy alkyl oxo...

  20. 40 CFR 721.8673 - [(Disubstituted phenyl)]azo dihydro hydroxy alkyl oxo alkyl-substituted-pyridines (generic name).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false azo dihydro hydroxy alkyl oxo alkyl... Significant New Uses for Specific Chemical Substances § 721.8673 azo dihydro hydroxy alkyl oxo alkyl...) The chemical substances identified generically as azo dihydro hydroxy alkyl oxo...

  1. Theoretical study on the mechanism of iron carbonyls mediated isomerization of allylic alcohols to saturated carbonyls.

    PubMed

    Branchadell, Vicenç; Crévisy, Christophe; Grée, René

    2003-05-01

    The conversion of allylic alcohols to enols mediated by Fe(CO)(3) has been studied through density functional theoretical calculations. From the results obtained a complete catalytic cycle has been proposed in which the first intermediate is the [(allyl alcohol)Fe(CO)(3)] complex. This intermediate evolves to the [(enol)Fe(CO)(3)] complex through two consecutive 1,3-hydrogen shifts involving a pi-allyl hydride intermediate. The highest Gibbs energy transition state corresponds to the partial decoordination ot the enol ligand prior to the coordination of a new allyl alcohol molecule that regenerates the first intermediate. Alternative processes for the [(enol)Fe(CO)(3)] complex such as [Fe(CO)(3)]-mediated enol-aldehyde transformation and enol isomerization have also been considered. The results obtained show that the former process is unfavourable, whereas the enol isomerization may compete with the enol decoordination step of the catalytic cycle. PMID:12740854

  2. Total Synthesis of Clavosolide A via Tandem Allylic Oxidation/Oxa-Conjugate Addition Reaction

    PubMed Central

    Baker, Joseph B.; Kim, Hyoungsu; Hong, Jiyong

    2015-01-01

    The tandem allylic oxidation/oxa-conjugate addition reaction promoted by the gem-disubstituent effect in conjunction with the NHC-mediated oxidative esterification was explored for the facile synthesis of clavosolide A. PMID:26236051

  3. Cross coupling of dialkylmagnesium derivatives with allylic compounds catalyzed by copper salts

    SciTech Connect

    Ibragimov, A.G.; Dzhemilev, U.M.; Saraev, R.A.

    1985-07-20

    The reaction of allylic compounds with Grignard reagents catalyzed by salts of copper, nickel, iron and cobalt, titanium and palladium is a simple and efficient method for the preparation of unsaturated hydrocarbons. However, information concerning the use of dialkylmagnesium derivatives, which are more reactive than Grignard reagents, is extremely limited in these reactions. To continue a study of the cross-coupling of allylic compounds with dialkylmagnesium derivatives in an effort to expand the scope of this reaction and to elucidate the effect of the R/sub 2/Mg reagent structure on its reactivity, the authors investigated the reaction of dialkylmagnesium and diarlmagnesium reagents with allylic ethers and esters, thioethers, and amines, by the action of transition metal salts. This work demonstrates the feasibility of the preparation of unsaturated hydrocarbons of given structure by the cross-coupling of dialkylmagnesium derivatives with functional allylic compounds by the action of catalytic amounts of copper complexes.

  4. Effect of Allyl Isothiocyanate on developmental toxicity in exposed Xenopus laevis embryos

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The pungent natural compound allyl isothiocyanate isolated from the seeds of Cruciferous (Brassica) plants such as mustard is reported to exhibit numerous beneficial health-promoting antimicrobial, antifungal, anticarcinogenic, cardioprotective, and neuroprotective properties. Because it is also re...

  5. Occupational asthma due to alkyl cyanoacrylate

    SciTech Connect

    Nakazawa, T. )

    1990-08-01

    A case of bronchial asthma induced by occupational exposure to alkyl cyanoacrylate, an adhesive, occurred in an assembly operation. Provocative exposure testing induced immediate and delayed asthmatic responses. Alkyl cyanoacrylate seemed to act as an allergen or as an irritant, resulting in the development of asthma.

  6. Stabilized dialkyl aluminum complexes as alkylating agents

    SciTech Connect

    Blum, J.; Baidossi, W.; Rosenfeld, A.

    1995-12-31

    Although trialkylaluminum derivatives are widely used as Ziegler-Natta polymerization co-catalysts, their application as routine alkylating agents is limited owing to their pyrophoric nature. The authors have now found that substitution of one of the alkyl moieties by a chelating group reduces the sensitivity of the organoaluminum compounds to air, and enables one to utilize them under normal laboratory conditions.

  7. Control of Diastereoselectivity for Iridium-catalyzed Allylation of a Prochiral Nucleophile with a Phosphate Counterion

    PubMed Central

    Chen, Wenyong; Hartwig, John F.

    2013-01-01

    We report a highly diastereo- and enantioselective allylation of azlactones catalyzed by the combination of a metallayclic iridium complex and an optically inactive phosphate anion. The process demonstrates an approach to conduct diastereoselective reactions with prochiral nucleophiles in the presence of metallacyclic allyliridium complexes. The reaction provides access to an array of enantioenriched allylated azlactones containing adjacent tertiary and quaternary carbon centers. Preliminary mechanistic studies suggest that the phosphate and methyl carbonate anions together induce the unusually high diastereoselectivity. PMID:23286279

  8. A Concomitant Allylic Azide Rearrangement/Intramolecular Azide–Alkyne Cycloaddition Sequence

    PubMed Central

    2015-01-01

    An intramolecular Huisgen cycloaddition of an interconverting set of isomeric allylic azides with alkynes affords substituted triazoles in high yield. The stereoisomeric vinyl-substituted triazoloxazines formed depend on the rate of cycloaddition of the different allylic azide precursors when the reaction is carried out under thermal conditions. In contrast, dimerized macrocyclic products were obtained when the reaction was done using copper(I)-catalyzed conditions, demonstrating the ability to control the reaction products through changing conditions. PMID:24635056

  9. Enantiomerization of Allylic Trifluoromethyl Sulfoxides Studied by HPLC Analysis and DFT Calculations.

    PubMed

    Bailly, Laetitia; Petit, Emilie; Maeno, Mayaka; Shibata, Norio; Trapp, Oliver; Cardinael, Pascal; Chataigner, Isabelle; Cahard, Dominique

    2016-02-01

    Enantiomerization of allylic trifluoromethyl sulfoxides occurs spontaneously at room temperature through the corresponding allylic trifluoromethanesulfenates via a [2,3]-sigmatropic rearrangement. Dynamic enantioselective high-performance liquid chromatography (HPLC) analysis revealed the stereodynamics of these sulfoxides ranging from chromatographic resolution to peak coalescence at temperatures between 5 and 53 °C. The rate constant of enantiomerization and activation parameters were determined and compared with Density Functional Theory (DFT) calculations. PMID:26689286

  10. Stereospecific Synthesis of α-Amino Allylsilane Derivatives through a [3,3]-Allyl Cyanate Rearrangement. Mild Formation of Functionalized Disiloxanes.

    PubMed

    Henrion, Sylvain; Carboni, Bertrand; Cossío, Fernando P; Roisnel, Thierry; Villalgordo, Jose M; Carreaux, François

    2016-06-01

    An efficient asymmetric synthesis of α-amino allylsilane derivatives is reported. The strategy is based on a [3,3]-allyl cyanate sigmatropic rearrangement from enantioenriched γ-hydroxy alkenylsilyl compounds. The isocyanate intermediate can be trapped by several nucleophiles, opening the way for the preparation of unknown chiral functionalized compounds such as the α-ureido allylsilanes as well as carbamate derivatives. A computational study was conducted to rationalize the complete 1,3-chirality transfer of this kind of rearrangement. Moreover, starting from products bearing a phenyldimethyl silyl substituent, the α-amino silane derivatives or the corresponding disiloxanes can be obtained under hydrogenation conditions in an exclusive way according to the used catalyst. PMID:27163288