A complementary oxidative photocatalytic strategy is presented. In the presence of 4‐nitroanisole, hexafluoroisopropanol (HFIP) as a proton source is activated and the proton photoreduction is enhanced, enabling a range of cyclizative aryltrifluoromethylations of alkenes and CF3SO2Na (Langlois’ reagent) with hydrogen evolution. Such a protocol is general, for both activated and unactivated olefins could be used as the substrates, affording a variety of CF3‐containing heterocycles such as indolines, indolin‐2‐ones, 3,4‐dihydroisoquinolin‐1‐ones, 5,6‐dihydrobenzoimidazo[2,1‐a]isoquinolines, benzoimidazo[2,1‐a]isoquinolin‐6(5H)‐ones and 1,2,3,4‐tetrahydroisoquinolines, under mild and metal‐ and oxidant‐free conditions with a good functional‐group tolerance. Extensive mechanistic investigations revealed that p‐nitroanisole (p‐NA) does not react with the photocatalyst directly as an oxidant, but rather activates HFIP via proton‐coupled electron transfer (PCET) and scavenges some of the reduced protons to improve proton photoreduction.
A visible light‐induced perfluoroalkylative cyclization of 3‐aza‐1,5‐dienes leading to pentasubstituted 1,3‐dihydropyrrole‐2‐ones is presented. The reaction is regiospecific, for the radical adds across the acrylamido moiety, whereas the enaminic double bond functions as a built‐in radical trap. It could be carried out on a 2‐gram scale, and the sunlight is a usable light source. Other virtues of the protocol include a short reaction time, a low catalyst loading, mild conditions and a broad substrate scope.
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