Enantioselective Decarboxylative Protonation

Abstract

A base-mediated enantioselective decarboxylative protonation of acyclic, cyclic, and bicyclic α-aminomalonate hemiesters is described. Presumably, the tertiary amine moiety of the thiourea-containing cinchona alkaloid acts as a base, promoting the formation of an enolate via decarboxylation. While binding the enolate through urea-mediated hydrogen bonds, the chiral catalyst may enantioselectively protonate this intermediate. Enantioenriched aminoesters were obtained in high yields and enantioselectivities. Both enan­tiomeric forms could be produced by using either base A or pseudoenantiomeric base B. Interestingly, a wide range of polar as well as apolar aprotic solvents afforded high selectivities.