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Visible Light Photocatalytic Aerobic Oxygenation of Indoles and pH as a Chemoselective Switch

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journal contribution
posted on 02.09.2016, 00:00 authored by Chenhao Zhang, Sanliang Li, Filip Bureš, Richmond Lee, Xinyi Ye, Zhiyong Jiang
An efficient chemodivergent strategy for visible light photocatalysis is developed. In the presence of a dicyanopyrazine-derived chromophore (DPZ) photocatalyst, aerobic photooxygenation of indoles could produce either isatins or formylformanilides in satisfactory yields by judiciously selecting inorganic salts or modulating the reaction pH. The current chemodivergent method is also effective with 2-substituted indoles, opening straightforward synthetic routes to valuable 2,2-disubstituted 3-oxindoles, formylformanilide derivatives, and benzoxazinones. Mechanistic investigations involving cyclic voltammetry studies further confirm that reaction pH influences the electrochemical properties of DPZ, thus affecting the oxidative pathway by which indoles are being transformed.