Synergistic Lewis Acid and Photoredox-Catalyzed Trifluoromethylative Difunctionalization of Alkenes with Selenium Ylide-Based Trifluoromethylating Reagent
Hangming Ge, Botao Wu, Yafei Liu, Haoyang Wang, Qilong Shen
Abstract
Trifluoromethylative difunctionalization of alkenes with a variety of nucleophiles including amine, azide, alcohol, water, and electron-rich arenes using reagent 1 as trifluoromethyl radical source in the presence of a synergistic catalyst including a Lewis acid scandium(III) trifluoromethanesulfonate (Sc(OTf)3) and a photoredox catalyst [fac-Ir(ppy)3] was described. Mechanistic studies showed that the role of Sc(OTf)3 in the reaction is to activate reagent 1 via Lewis acid–Lewis base interaction to form complex [Sc(OTf)3•3(1)], which was fully characterized by nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry, and elemental analysis. Cyclic voltammetry (CV) experiments and density functional theory (DFT) calculation showed that the reduction potential of complex [Sc(OTf)3•3(1)] is much higher than that of reagent 1, thus suggesting complex [Sc(OTf)3•3(1)] is much easier to accept electron through single-electron-transfer (SET) process, and consequently, much easier to generate trifluoromethyl radical.