Visible Light-Induced Difunctionalization of Alkynes: The Synthesis of Thiazoles and 1,1-Dibromo-1-en-3-ynes

A visible light-induced cascade cyclization of thioamides with alkynes was developed to synthesize 1,3-thiozoles. The sulfur radical generated from thioamide via the single-electron transfer (SET) pathway was promoted by photocatalysis as a key intermediate in this reaction. When bromoalkynes were used as the substrate, the self-coupling products 1,1-dibromo-1-en-3-ynes were obtained in moderate yields, and an energy transfer pathway for this transformation promoted by visible-light photocatalysis was proposed.