Synthesis of α-Keto Thioamides by Metal-Free C=C Bond Cleavage in Enaminones Using Elemental Sulfur

An unprecedented method for cleaving the C=C bond in N,N-disubstituted enaminones in the presence of elemental sulfur and N,N-dimethyl-4-aminopyridine is disclosed. Without using any metal catalyst or additive, the cascade functionalization of both C=C and C-H bonds takes place to enable the formation of new C=S and C-N bonds, thus providing a facile and practical method for the synthesis of N,N-disubstituted alpha-keto thioamides.