Selenium Radical Mediated Cascade Cyclization: Concise Synthesis of Selenated Benzofurans (Benzothiophenes)

Presented in this work is a novel methodology for the synthesis of selenated benzofurans (or benzothiophenes) via AgNO₂-catalyzed radical cyclization of 2-alkynylanisoles (or 2-alkynylthioanisoles), Se powder, and arylboronic acids. This method enables the construction of a benzofuran (benzothiophene) ring, two C-Se bonds, and a C-O(S) bond as well as the cleavage of a C-O(S) bond in a single step. Preliminary mechanistic studies imply that the AgNO₂-catalyzed cyclization proceeds via an aryl selenium radical intermediate.