A Mechanistic Investigation of the Visible-Light Photocatalytic Trifluoromethylation of Heterocycles Using CF3I in Flow

Photocatalytic radical trifluoromethylation strategies have impacted the synthesis of trifluoromethyl-containing molecules. However, mechanistic aspects concerning such transformations remain poorly understood. Here, we describe in detail the mechanism of the visible-light photocatalytic trifluoromethylation of N-methylpyrrole with gaseous CF3I in flow. The use of continuous-flow microreactor technology allowed for the determination of different important parameters with high precision (e.g., photon flux, quantum yield, reaction rate constants) and for the handling of CF3I in a convenient manner. Our data indicates that the reaction occurs through a reductive quenching mechanism and that there is no radical chain process present.