Polystyrene supported benzoylthiourea-pyrrolidine organocatalyst for the enantioselective Michael addition

Herein the preparation of a swellable pearl-like copolymer of styrene with anchored (S)-1-benzoyl-3-(pyrrolidine-2-ylmethyl)thiourea (20-600 mu m) and its application as a recyclable organocatalyst for the Michael addition of ketones to functionalized beta-nitrostyrenes is described. The rate of the reaction taking place in the matrix of the swellable polymeric catalyst was comparable with the reaction rate in homogeneous medium. The corresponding functionalized 4-nitroketones were formed quantitatively with the enantiomeric excesses up to 98% ee. After a fivefold recycling of the catalyst, no decrease in the yield was detected, but the enantioselectivity was slightly lowered (95 -> 88% ee). (C) 2016 Elsevier Ltd. All rights reserved.