Annulation of 1,2,3‐Thiadiazoles and Alkynes to Construct Thiophene Derivatives Enabled by Visible‐Light Photocatalysis

Although the transition‐metal‐catalyzed denitrogenative annulation of 1,2,3‐thiadiazoles has been greatly advanced over the past decade, visible‐light‐mediated conversion of 1,2,3‐thiadiazoles remains rarely explored. Herein, a mild and efficient strategy for the synthesis of thiophene derivatives via visible‐light photocatalytic denitrogenative annulation of 1,2,3‐thiadiazoles with alkynes is achieved. This protocol shows broad substrate scope with good selectivity. Combined experimental and computational mechanistic studies reveal a feasible reaction pathway initiated by photocatalyst‐mediated energy transfer to the 1,2,3‐thiadiazole, followed by sequential denitrogenation to generate a key 1,3‐diradical intermediate. This intermediate could undergo regioselective addition to the alkyne and subsequent ring closure to afford the desired products. This work expands the synthetic utility of visible‐light photocatalysis in the denitrogenative functionalization of 1,2,3‐thiadiazoles.