Synergistic Lewis Acid and Photoredox-Catalyzed Trifluoromethylative Difunctionalization of Alkenes with Selenium Ylide-Based Trifluoromethylating Reagent

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.