Studies on pyridinium salts as bifunctional reagents for photochemical difunctionalizations

Abstract

A powerful strategy for visible-light-enabled site-selective trifluoromethylative pyridylation of unactivated alkenes has been developed using N-triflylpyridinium salts, which are synthesized in pyridines and triflic anhydrides ($Tf_{2}O$). Interestingly, the N-triflylpyridnium salts serve as bifunctional reagents which afford both $CF_{3}$ and pyridyl groups, installing both groups to various olefins. We found that C4-selectivity to the pyridine core was achieved in this protocol. This novel synthetic tool tolerates a broad range of substrate scope under metal-free and mild reaction conditions, and provides convenient and effective synthetic route for access to valuable C4-alkylated pyridines and quinolines without requiring prefunctionalization of the reaction sites.