Visible Light Photocatalysis of Carbon–Carbon σ‑Bond Anaerobic Oxidation of Ketones with Water by Cobalt(II) Porphyrins

Co^II(por) (por = porphyrinato dianion) reacted selectively with isopropyl ketones at the carbon (CO)–carbon (α) bond at room temperature to give high yields of Co^III(por) acyls and the corresponding oxidized carbonyl compounds in up to 89% yields. Co^III(por)­OH is proposed to be the C–C bond activation (CCA) intermediate. The stoichiometric reaction is further developed into the photocatalytic CCA using both UV and visible light sources (λ 405 nm). Under ambient conditions, the photocatalytic C–C oxidation of 2,6-dimethylcyclohexanone gives 2-heptanone in up to 24 turnovers in the presence of isopropyl alcohol as the H atom donor and H₂O as the oxidant. Various isopropyl ketones successfully undergo photocatalysis.