Bottom-up Synthesis of Novel Supported Thioureas and Their Use in Enantioselective Solvent-free Aza-Henry and Michael Additions

Abstract

Two sets of supported chiral thioureas, which differ in the length of the tether connecting the chiral appendage to the polymer structure and the effective functionalization, have been prepared by co-polymerization of styrene, novel styryl thioureas derived from (L)-valine, and divinylbenzene. The efficiency of these polymeric thioureas has been tested in two different enantioselective transformations such as aza-Henry and nitro-Michael reactions in neat reaction conditions. The obtained results show that it is possible to recycle, and they are able to promote the reactions with good enantioselectivity in low catalyst loading.