Primary Amine-Thioureas with Improved Catalytic Properties for “Difficult” Michael Reactions: Efficient Organocatalytic Syntheses of (S)-Baclofen, (R)-Baclofen and (S)-Phenibut
作者:Michail Tsakos、Christoforos G. Kokotos、George Kokotos
DOI:10.1002/adsc.201100636
日期:2012.3
Among the class of primary amine‐thioureas based on tert‐butyl esters of α‐amino acids, the most efficient organocatalyst for “difficult” Michaelreactions was identified. The derivative based on (S)‐di‐tert‐butyl aspartate and (1R,2R)‐diphenylethylenediamine provided the products of the reaction between aryl methyl ketones and nitroolefins in excellent yields and enantioselectivities. In addition
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.