α-Diimine-mediated C–H functionalization of arenes for aryl–aryl cross-coupling reactions

Abstract

Easily accessible methods for direct C–H arylation of arenes have been explored in the presence of transition metal catalysts to facilitate C–C bond formation; however, the absence of transition-metal impurities is a significant concern in the preparation of active pharmaceutical ingredients (APIs). Herein, we examine the use of bis(imino)acenaphthene (BIAN) as a potential single-electron transfer initiator in transition metal-free C–C bond-forming reactions. Using this approach, arenes are coupled to several aryl and heteroaryl halides. Based upon preliminary mechanistic evidence and crystallographic probation of an active initiator species, we tentatively propose a potassium-stabilized ‘metal-free’ radical pathway is in operation.