Catalytic Ynamide Oxidation Strategy for the Preparation of α-Functionalized Amides

A Lewis acid-catalyzed alkyne oxidation strategy has been developed to produce diverse α-functionalized amides from readily and generally available ynamides. An efficient zinc(II)-catalyzed oxidative azidation and thiocyanation has been achieved, providing facile access to synthetically useful α-azido amides and α-thiocyanate amides, respectively. This chemistry can also be extended to oxidative halogenations by employing the 2-halopyridine N-oxide as both the oxidant and the halogen source, and its mechanistic rationale is also supported by density functional theory calculations. Moreover, NaBARF has been demonstrated to catalyze such an alkyne oxidation effectively, thus further excluding the metal carbene pathway in this cascade reaction.