Photocatalyst-controlled and visible light-enabled selective oxidation of pyridinium salts

This study proposes two different methods of photocatalytic-controlled and visible light-induced selective oxidation of pyridiniums with air as the terminal oxidant. The key to these transformations is to choose the appropriate light source and photocatalyst. Pyridiniums are successfully converted into pyrroles through oxygen-mediated cycloaddition, proton-coupled electron transfer (PCET), pyridine ring opening, and recyclization. The other route is that pyridiniums selectively form 4-carbonyl pyridines through free radical rearrangement/aerobic oxidation under the catalysis of cobalt (II).

Automated summary

This study presents two methods for the selective oxidation of pyridiniums, one utilizing photocatalysis and the other visible light induction. The transformations involve oxygen-mediated cycloaddition, PCET, pyridine ring opening, and recyclization to convert pyridiniums to pyrroles, and free radical rearrangement/aerobic oxidation catalyzed by cobalt (II) for the selective formation of 4-carbonyl pyridines.