The Experts below are selected from a list of 1398 Experts worldwide ranked by ideXlab platform
Barry M Trost - One of the best experts on this subject based on the ideXlab platform.
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palladium catalyzed asymmetric allylic alkylation of electron deficient pyrroles with meso electrophiles
Organic Letters, 2012Co-Authors: Barry M Trost, Maksim Osipov, Guangbin DongAbstract:Pyrroles can serve as competent nucleophiles with meso electrophiles in the Pd-catalyzed asymmetric allylic alkylation. The products from this transformation were obtained as a single regio- and diastereomer in high yield and Enantiopurity. A nitropyrrole-containing nucleoside analogue was synthesized in seven steps to demonstrate the synthetic utility of this transformation.
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palladium catalyzed allylic alkylation of carboxylic acid derivatives n acyloxazolinones as ester enolate equivalents
Angewandte Chemie, 2012Co-Authors: Barry M Trost, David J Michaelis, Julie CharpentierAbstract:A general asymmetric allylic alkylation of ester enolate equivalents at the carboxylic acid oxidation state is reported. N-Acylbenzoxazolinone-derived enol carbonates are synthesized in good yield and employed in the palladium-catalyzed alkylation reaction. Good yields (up to 99%) and enantioselectivities (up to 99% ee) are obtained and the imide products are readily converted to a series of carboxylic acid derivatives without loss of Enantiopurity. High enantioselectivity in the reaction is achieved by a new strategy for ligand design involving variation of the steric properties of the diarylphosphine moiety.
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ligand accelerated enantioselective propargylation of aldehydes via allenylzinc reagents
Organic Letters, 2011Co-Authors: Barry M Trost, Mingyu Ngai, Guangbin DongAbstract:An enantioselective propargylation of aldehydes using an allenylzinc reagent generated in situ via a zinc−iodine exchange reaction is described. The enantioselectivity is controlled by addition of a catalytic amount of readily accessible and highly tunable amino alcohol ligand L13. A wide range of aldehydes can be propargylated to afford valuable and versatile homopropargyl alcohols in good to excellent yields with high levels of Enantiopurity.
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palladium catalyzed asymmetric allylic alkylation of 2 acylimidazoles as ester enolate equivalents
Journal of the American Chemical Society, 2010Co-Authors: Barry M Trost, Konrad Lehr, David J Michaelis, Andreas K BucklAbstract:A broad range of highly enantioenriched 2-acylimidazoles are synthesized by palladium-catalyzed decarboxylative asymmetric allylic alkylation (DAAA) of 2-imidazolo-substituted enol carbonates. The enantioenriched 2-acylimidazole products can easily be converted to the corresponding carboxylic acid, ester, amide, and ketone derivatives with complete retention of the Enantiopurity. The synthetic utility of this new method is demonstrated in the short, efficient synthesis of cetiedil.
James M Bobbitt - One of the best experts on this subject based on the ideXlab platform.
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asymmetric electrochemical lactonization of diols on a chiral 1 azaspiro 5 5 undecane n oxyl radical mediator modified graphite felt electrode
Chemical Communications, 2003Co-Authors: Yoshitomo Kashiwagi, Futoshi Kurashima, Shinya Chiba, Junichi Anzai, Tetsuo Osa, James M BobbittAbstract:A graphite felt electrode modified with (6S,7R,10R)-4-amino-2,2,7-trimethyl-10-isopropyl-1-azaspiro[5.5]undecane N-oxyl was prepared for electrocatalytic oxidation of diols; electrolysis of diols on the modified electrode yielded optically active lactones (92.0–96.4%), with an Enantiopurity of 82–99% ee.
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enantioselective electrocatalytic oxidation of racemic sec alcohols using a chiral 1 azaspiro 5 5 undecane n oxyl radical
Tetrahedron Letters, 1999Co-Authors: Yoshitomo Kashiwagi, Futoshi Kurashima, Junichi Anzai, Tetsuo Osa, James M Bobbitt, Chikara KikuchiAbstract:Abstract Nitroxyl radical (6S,7R,10R)-4-acetylamino-2,2,7-trimethyl-10-isopropyl-1-azaspiro[5.5]-undecane-N-oxyl reveals a reversible redox peak in cyclic voltammetry at + 0.62 V vs. Ag/AgCl. A preparative electrocatalytic oxidation of racemic sec-alcohols on the nitroxyl radical yielded mixtures of 51.4 – 63.9 % ketones and 36.1 – 48.6 % alcohols by 10 h of electrolysis. The current efficiency and turnover number of the reactions were 85.6 – 87.9 % and 20.6 – 25.6, respectively. The Enantiopurity of the remaining (R)-isomers was 50 – 70 % and the S values as a selective factor was 4.1 – 4.6.
Kwunmin Chen - One of the best experts on this subject based on the ideXlab platform.
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Three-Component Organocascade Kinetic Resolution of Racemic Nitroallylic Acetates via Sequential Iminium/Enamine Asymmetric Catalysis
2016Co-Authors: Suparna Roy, Kwunmin ChenAbstract:Nitroallylic acetates 1a–f have been kinetically resolved via an asymmetric three-component coupling that involves indoles, acrolein, and nitroolefin allylic acetates and is mediated by the chiral catalyst 2 (5 mol %). The reactions proceed via iminium/enamine cascade catalysis. Both recovered starting substrates and reaction products are typically obtained in high chemical yield and in good to excellent Enantiopurity (79–95% ee for 1a–f and 83–99% ee for 3a–n). For the first time, a highly efficient three-component, organocascade kinetic resolution has been demonstrated
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three component organocascade kinetic resolution of racemic nitroallylic acetates via sequential iminium enamine asymmetric catalysis
Organic Letters, 2012Co-Authors: Suparna Roy, Kwunmin ChenAbstract:Nitroallylic acetates 1a–f have been kinetically resolved via an asymmetric three-component coupling that involves indoles, acrolein, and nitroolefin allylic acetates and is mediated by the chiral catalyst 2 (5 mol %). The reactions proceed via iminium/enamine cascade catalysis. Both recovered starting substrates and reaction products are typically obtained in high chemical yield and in good to excellent Enantiopurity (79–95% ee for 1a–f and 83–99% ee for 3a–n). For the first time, a highly efficient three-component, organocascade kinetic resolution has been demonstrated.
Lanny S Liebeskind - One of the best experts on this subject based on the ideXlab platform.
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organometallic enantiomeric scaffolding a molybdenum mediated intramolecular nucleophilic ketalization demetalation cascade total synthesis of 1r 2s 5s 7r 2 hydroxy exo brevicomin
Organic Letters, 2009Co-Authors: Bo Cheng, Lanny S LiebeskindAbstract:TpMo(CO)2(5-oxo-η3-pyranyl) scaffolds bearing an internal alkoxide undergo a novel intramolecular nucleophilic ketalization reaction. The anionic intermediate is easily demetalated, rapidly providing the 6,8-dioxabicyclo[3.2.1]oct-3-en-2-one framework in moderate to good yields with high Enantiopurity. An enantiocontrolled total synthesis of (+)-(1R,2S,5S,7R)-2-hydroxy-exo-brevicomin was accomplished utilizing the reaction sequence.
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practical scalable high throughput approaches to η3 pyranyl and η3 pyridinyl organometallic enantiomeric scaffolds using the achmatowicz reaction
Journal of Organic Chemistry, 2008Co-Authors: Thomas C Coombs, Maurice D Lee, Heilam Wong, Matthew Armstrong, Bo Cheng, Wenyong Chen, And Alessandro F Moretto, Lanny S LiebeskindAbstract:A unified strategy for the high-throughput synthesis of multigram quantities of the η3-oxopyranyl- and η3-oxopyridinylmolybdenum complexes TpMo(CO)2(η3-oxopyranyl) and TpMo(CO)2(η3-oxopyridinyl) is described (Tp = hydridotrispyrazolylborato). The strategy uses the oxa- and aza-Achmatowicz reaction for the preparation of these organometallic enantiomeric scaffolds, in both racemic and high Enantiopurity versions.
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Ambient temperature synthesis of high Enantiopurity N-protected peptidyl ketones by peptidyl thiol ester-boronic acid cross-coupling
Journal of the American Chemical Society, 2007Co-Authors: Hao Yang, Ruediger Wittenberg, Wenwei Huang, Hao Li, Lanny S LiebeskindAbstract:α-Amino acid thiol esters derived from N-protected mono-, di-, and tripeptides couple with aryl, π-electron-rich heteroaryl, or alkenyl boronic acids in the presence of stoichiometric Cu(I) thiophene-2-carboxylate and catalytic Pd2(dba)3/triethylphosphite to generate the corresponding N-protected peptidyl ketones in good-to-excellent yields and in high Enantiopurity. Triethylphosphite plays a key role as a supporting ligand by mitigating an undesired palladium-catalyzed decarbonylation−β-elimination of the α-amino thiol esters. The peptidyl ketone synthesis proceeds at room temperature under nonbasic conditions and demonstrates a high tolerance to functionality.
Guangwu Zhang - One of the best experts on this subject based on the ideXlab platform.
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catalytic asymmetric mukaiyama mannich reaction of cyclic c acylimines with difluoroenoxysilanes access to difluoroalkylated indolin 3 ones
Organic Letters, 2017Co-Authors: Yongjie Liu, Guangwu ZhangAbstract:A catalytic enantioselective Mukaiyama–Mannich reaction of cyclic C-acylimines with difluoroenoxysilanes is reported. (S)-TRIP enables the enantioselective synthesis of a series of novel difluoroalkylated indolin-3-ones bearing a quaternary stereocenter in up to 97% yield and 98% ee. The synthetic utility of this protocol is highlighted by efficient conversion of the products to the corresponding indolin-3-one derivatives without any erosion of the Enantiopurity.
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Catalytic Asymmetric Mukaiyama–Mannich Reaction of Cyclic C‑Acylimines with Difluoroenoxysilanes: Access to Difluoroalkylated Indolin-3-ones
2017Co-Authors: Yongjie Liu, Guangwu ZhangAbstract:A catalytic enantioselective Mukaiyama–Mannich reaction of cyclic C-acylimines with difluoroenoxysilanes is reported. (S)-TRIP enables the enantioselective synthesis of a series of novel difluoroalkylated indolin-3-ones bearing a quaternary stereocenter in up to 97% yield and 98% ee. The synthetic utility of this protocol is highlighted by efficient conversion of the products to the corresponding indolin-3-one derivatives without any erosion of the Enantiopurity