Abstractmagnified imageA new class of primary amine‐thioureas based on tert‐butyl esters of (S)‐α‐amino acids and (1S,2S)‐diphenylethylenediamine was synthesized and their activity as catalysts in Michael additions was evaluated. Derivatives based on di‐tert‐butyl aspartate and tert‐butyl O‐tert‐butyl threoninate provided the product of the reaction between trans‐β‐nitrostyrene and acetone in quantitative yield and high enantioselectivity (87–91% ee). All the thioureas based on tert‐butyl esters of amino acids catalyzed the reaction of nitroolefins with acetophenone with high enantioselectivity (92–98% ee). Thus, low‐cost, commercially available tert‐butyl esters of natural amino acids are very important chiral building blocks for the construction of novel chiral thioureas able to catalyze asymmetric Michael additions with high enantioselectivity.
Enantioselective Conjugate Addition of Nitro Compounds to α,β-Unsaturated Ketones: An Experimental and Computational Study
作者:Rubén Manzano、José M. Andrés、Rosana Álvarez、María D. Muruzábal、Ángel R. de Lera、Rafael Pedrosa
DOI:10.1002/chem.201100241
日期:2011.5.16
thioureas derived from easily available diamines, prepared from α‐amino acids, have been tested as catalysts in the enantioselective Michael additions of nitroalkanes to α,β‐unsaturated ketones. The best results are obtained with the bifunctional catalyst prepared from L‐valine. This thiourea promotes the reaction with high enantioselectivities and chemical yields for aryl/vinyl ketones, but the enantiomeric
Organocatalyzed highly stereoselective Michael addition of ketones to alkylidene malonates and nitroolefins using chiral primary-secondary diamine catalysts based on bispidine
based on bispidine have been developed to catalyze the asymmetric Michaeladdition of ketones to alkylidenemalonates and nitroalkenes. The corresponding products were obtained in high yields (up to 99%) with high diastereoselectivities (up to 99:1) and high enantioselectivities (up to 97% ee) under mild conditions using either environmentally benign water as the solvent or no solvent.
Enantiomerically pure carbamate-monoprotected trans-cyclohexane-1,2-diamines are used as chiral organocatalysts for the addition of aryl ketones and acetone to nitroalkenes to give enantioenriched beta-substituted gamma-nitroketones. The reaction was performed in the presence of 3,4-dimethoxybenzoic acid as an additive, in chloroform as the solvent at room temperature, achieving enantioselectivities up to 96%. Theoretical calculations are used to justify the observed sense of the stereoinduction. (C) 2015 Elsevier Ltd. All rights reserved.
Primary Amine-Thioureas based on<i>tert</i>-Butyl Esters of Natural Amino Acids as Organocatalysts for the Michael Reaction
作者:Christoforos G. Kokotos、George Kokotos
DOI:10.1002/adsc.200800812
日期:2009.6
Abstractmagnified imageA new class of primary amine‐thioureas based on tert‐butyl esters of (S)‐α‐amino acids and (1S,2S)‐diphenylethylenediamine was synthesized and their activity as catalysts in Michael additions was evaluated. Derivatives based on di‐tert‐butyl aspartate and tert‐butyl O‐tert‐butyl threoninate provided the product of the reaction between trans‐β‐nitrostyrene and acetone in quantitative yield and high enantioselectivity (87–91% ee). All the thioureas based on tert‐butyl esters of amino acids catalyzed the reaction of nitroolefins with acetophenone with high enantioselectivity (92–98% ee). Thus, low‐cost, commercially available tert‐butyl esters of natural amino acids are very important chiral building blocks for the construction of novel chiral thioureas able to catalyze asymmetric Michael additions with high enantioselectivity.