A p-toluenesulfinic acid-catalyzed three-component Ugi-type reaction and its application for the synthesis of α-amino amides and amidines

A mild, cost-effective, and simple three-component Ugi-type reaction using p-toluenesulfinic acid (pTSIA) as the acid catalyst has been developed to synthesize α-amino amides and α-amino amidines. Employing 1 equiv of amine used in the reaction generated α-amino amides exclusively, while 2 equiv of amines, especially with more nucleophilic aniline such as p-anisidine, yielded the α-amino amidines as the major product. This methodology would be suitable for the synthesis of natural or unnatural amino acids and drug-like amidine analogues.