Intermolecular Photocatalytic C-H Functionalization of Electron-Rich Heterocycles with Tertiary Alkyl Halides

The coupling of tertiary alkyl halides with electron-rich arenes is promoted by visible-light photoredox catalysis. Tris[2-phenylpyridinato-C-2,N]iridium(III) [Ir(ppy)(3)] was the optimal catalyst, enabling direct reduction of the halide from the excited state, and thereby eliminating the requirement for a stoichiometric electron donor. High yields were obtained when the aromatic component was used in excess, although equimolar amounts afforded only slightly diminished yields. The reaction tolerates a number of functional groups, including allyl, ester, amide, or carbamate. The efficiency of this reaction has been improved through demonstration of scale-up in flow, and a new substituted Ir(ppy)(3) derivative was isolated and characterized.