Photoinduced Divergent Alkylation/Acylation of Pyridine N-Oxides with Alkynes under Anaerobic and Aerobic Conditions.

Ortho-alkylated and ortho-acylated pyridines have been conveniently synthesized from pyridine N-oxides and alkynes under visible-light-mediation in a metal-free manner. The alkynes served as both alkylating and acylating agents via switching between anaerobic and aerobic conditions. The overall strategy accommodates a broad scope of substituted pyridine N-oxides and alkynes, with excellent regioselectivity in a number of cases.