α-Imino acids, prepared from α-ketoacids and primary amines, undergo facile decarboxylation to the corresponding imines on heating at ⩽,80°C in benzene or methylene chloride. Decarboxylation proceeds via a 1,2-ylide which can be trapped by sulphur to give the corresponding secondary thioamides in good yield. 1,2-Ylides from secondary amines and ∞-keto acids can be generated in situ and trapped with