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.