Trifluoromethylative Bifunctionalization of Alkenes via a Bibenzothiazole-Derived Photocatalyst under Both Visible- and Near-Infrared-Light Irradiation
Bidyut Kumar Kundu, Chuang Han, Prasenjit Srivastava, Siddhant Nagar, Katie E. White, Jeanette A. Krause, Christopher G. Elles, Yujie Sun
Abstract
The incorporation of trifluoromethyl groups into organic molecules such as agrochemicals and pharmaceuticals has attracted a significant amount of interest because they will impact the binding ability, lipophilicity, metabolic stability, and chemical stability of the resulting molecules. Over the past few years, photocatalytic trifluoromethylation of aryl alkenes has been reported, which typically requires precious Ru/Ir-containing photocatalytic systems. Herein, we report a metal-free organic photocatalyst composed of a bibenzothiazole core and two imine-bridged methoxyphenyl substituents ( dBIP–OMe ), which is able to drive trifluoromethylative bifunctionalization of alkenes photocatalytically without the use of any sacrificial reagents. Mechanistic studies reveal two consecutive single-electron-transfer steps between the excited dBIP–OMe *, the CF 3 precursor (Umemoto’s reagent), and the alkene substrate. Substrate scope studies demonstrated that our trifluoromethylative bifunctionalization strategy using dBIP–OMe is applicable for both aryl and aliphatic alkenes. Furthermore, a variety of nucleophiles, such as H 2 O, acetate, cyanide, azide, etc., can be readily incorporated into the carbocation intermediate once the foremost trifluoromethylation step is accomplished, substantially broadening the application scope of this photocatalytic method. Finally, taking advantage of the two-photon absorption capability of dBIP–OMe in the near-infrared region, we demonstrated that the hydroxytrifluoromethylation of styrene could be achieved using an inexpensive 740 nm LED as the sole light source.