Thiourea-catalysed conjugate additions of amines to vinyl phosphonates and phosphinates

Abstract

Thiourea catalysts activated a,ß-unsaturated phosphonates and phosphinates toward conjugate addition by amines to give ß-aminophosphonates and ß-aminophosphinates. The organocatalytic methodology was used to synthesise 15 ß-aminophosphonates and -phosphinates in yields up to 99%. A gram-scale example furnished the corresponding ß-aminophosphonate in an isolated yield of 99% with 97% catalyst recovery. Based on mechanistic experiments, hydrogen bonding between the phosphoryl oxygen and thiourea are proposed to play a crucial role in substrate activation.