ortho‐Alkylation of Pyridine N‐Oxides with Alkynes by Photocatalysis: Pyridine N‐Oxide as a Redox Auxiliary

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A photocatalyzed ortho-alkylation of pyridine N-oxide with ynamides and arylacetylenes has been developed, which yields a series of α-(2-pyridinyl) benzyl amides/ketones. Mechanistic studies, including electrochemical studies, radical-trapping experiments, and Stern-Volmer fluorescence quenching studies demonstrate that pyridine N-oxide serves as both a redox auxiliary and radical acceptor to achieve the mild photocatalytic single-electron oxidation of carbon-carbon triple bonds with the generation of a cationic vinyl radical intermediate.