Benzoyl cyanide, a general radical acylating reagent for photoredox-catalyzed benzylic site-selective acylation reactions

Based on rational design, benzoyl cyanide, a well-known ionic acylating reagent, has been developed as a general radical acylating reagent for benzylic site-selective acylation reactions for the first time. Using visible-light photoredox-catalyzed single electron transfer (SET) and hydrogen atom transfer (HAT) strategies, two different direct benzylic C-H acylation reactions with high atom economy have been developed. This newly developed radical acylating reagent could also be used to achieve three component acyltrifluoromethylation of styrenes, which is usually challenging to achieve by other means. All of these reactions proceed under mild nickel-free and NHC-free conditions with high functional group tolerance. In addition, based on our detailed mechanistic experiments, the process of radical-radical cross-coupling mechanism was suggested for these transformations.