Addition of dithio esters and trithiocarbonates to 1-(diethylamino)propyne. Formation of α, β-unsaturated thioamides and vinylogous thioamides

α,β-Unsaturated thioamides and vinylogous thioamides have been prepared by thermal addition of trithiocarbonates RS-C(S)SR1 to 1-(diethylamino)propyne. Aromatic dithio esters Ar-C(S)SR only gave the α,β-unsaturated thioamides. The dithio ester Me2CH-C(S)SMe adds as acidic enethiol tautomer Me2CC(SH)SMe to 1-(diethylamino)propyne. Reaction mechanisms and the stereochemistry of the adducts are discussed.