Polymer-supported thioamide-derived cinchona alkaloids as efficient organocatalysts for the enantioselective decarboxylative protonation

A new family of copolymers based on styrene and a polymerizable cinchonidine thioamide derivative was synthesized by conventional radical polymerization. The copolymers were tested as homogeneous supported organocatalysts in the enantioselective decarboxylative protonation (EDP) of alpha-aminomalonate hemiesters giving access to alpha-amino acids under very mild conditions. These macromolecular catalysts could be prepared on a large scale and outperformed their unsupported analogues providing the desired products in high yield and enantioselectivity. Furthermore, recycling experiments were conducted which showed good enantioselectivities.