Generation and cross-coupling of benzyl and phthalimide-N-oxyl radicals in a cerium(IV) ammonium nitrate/N-hydroxyphthalimide/ArCH2R system

A method was developed for the cross-dehydrogenative coupling of alkylarenes and related compounds with N-hydroxyphthalimide (NHPI) using cerium(IV) ammonium nitrate (CAN) to prepare O-substituted NHPI derivatives. The characteristic feature of the reaction is that NHPI plays a dual role. Thus, in the presence of CAN, NHPI generates the phthalimide-N-oxyl (PINO) radical, which abstracts a hydrogen atom from the benzyl position to form a C-centered radical. The target oxidative cross-coupling product is formed mainly through the recombination of PINO with the C-centered radical. Therefore, NHPI serves as a mediator for the radical process and a reagent for the radical cross-coupling. The target products were obtained in yields from 35 to 80%.