Mechanism Reevaluation and Reaction Development in Rhodium‐Catalyzed Cycloaddition of <i>gem</i> ‐Difluorinated Cyclopropanes

Abstract

ABSTRACT Transition‐metal‐catalyzed cycloadditions of strained carbocycles have emerged as a powerful strategy for constructing complex molecular architectures through C–C bond reorganization. We previously reported a Rh‐catalyzed (3 + 2) cycloaddition of gem ‐difluorinated cyclopropanes ( gem ‐DFCPs) with internal olefins, which was initially interpreted to proceed via a conventional cycloaddition mechanism. Mechanistic interrogation, through control experiments and DFT calculations, now reveals that this transformation proceeds through a previously unrecognized pathway involving dual C–C/C–F bond activation. The unusual cyclization mechanism involves fluoroallylic substitution, carbocation‐mediated intramolecular cyclization, and fluoride transfer. This revised mechanistic framework not only redefines the understanding of such cycloadditions but also directly inspires the development of new reactions.