Studies on site-selective C–H functionalization of pyridines utilizing in-situ generated pyridinium salts

Abstract

An efficient visible-light-induced site-selective trifluoromethylative pyridylation of unactivated alkenes has been developed. It is well known that pyridines and triflic anhydride generate electrophilic N-triflylpyridinium salts. In this work, N-triflylpyridinium salts were introduced under visible-light-mediated photocatalytic condition and it serves as bifunctional reagents to install both CF$_3$ and pyridyl group to various alkenes. Interestingly, C4-selective alkylation to the pyridine core was achieved without prefunctionalization. CF$_3$ and N-heteroarenes were successfully installed into broad alkene scope under metal-free and mild photocatalytic conditions. This synthetic method is atom economic and has high efficiency using in situ generated pyridinium salt without purification.