Palladium-Catalyzed Direct Cross-Dehydrogenative Alkynylation of Selenophenes

Abstract

A palladium-catalyzed (Pd(PPh3)4/Ag2O/PivOH) C2-regioselective direct dehydrogenative alkynylation of unsubstituted selenophene was achieved. The selenophenes substituted with R1 groups at 2-position can be C5-alkynylated with a variety of 4-substituted phenylacetylenes (R2 groups). The R1 and R2 can be either electron-withdrawing or electron-donating groups, demonstrating a wide range of substrate scope with various functional group tolerance. The mono/C2-alkynylated selenophenes can subsequently undergo the second direct alkynylation at C5-position to afford symmetrical or unsymmetrical donor-π-acceptor 2,5-dialkynylated selenophenes. (Figure presented.).