Room Temperature Ring Opening of Benzene by Four-Electron Reduction and Carbonylation

Cleaving a benzene ring under mild conditions requires disrupting its aromaticity, which is a significant challenge in modern chemistry. Although the generation of cyclic products from cleaving benzene has been reported in a few cases, the formation of acyclic products remains exceedingly rare. Inspired by the transition metal-mediated cleavage of inert bonds through multielectron reduction and functionalization, we have discovered an unprecedented ring-opening protocol for benzene and toluene. This is achieved by the reactions of their four-electron-reduced scandium arene complexes with metal hexacarbonyls M(CO)₆ (M = Cr, Mo, and W), resulting in the formation of linear hexadiene products. Further mechanistic studies indicate that the transformation involves the dearomatization of benzene into a dianionic 1,3-cyclohexadiene moiety, followed by the cleavage of the carbon-carbon bond to form the linear hexadiene unit. This work demonstrates a new strategy for the ring opening of benzene through a multielectron-reduction/functionalization approach.