Selective Functionalization of Benzene Ring via Carbene-Initiated [4,5]-Rearrangement.

The extreme similarity in electronic and steric reactivity among the C─H bonds present on alkyl-substituted aromatic rings presents a formidable challenge when it comes to achieving high selectivity during the para-selective functionalization of these bonds. This article presents a unique study that delves into the para-selective functionalization or dearomatization functionalization of benzene rings, achieved through the reaction of carbenes with allyl sulfoxides. Mechanistic investigations suggest that the transformation likely proceeds via an uncommon carbene-mediated [4,5]-rearrangement process.