Catalyst-Controlled Chemodivergent Carbene Transfer Reactions With Bicyclo[1.1.0]butane-Derived Acceptor Metallocarbenes.

Transition-metal-catalyzed carbene transfer reactions are powerful tools in organic synthesis, yet they traditionally rely on diazo compounds, which raise stability and safety concerns. While alternative precursors have emerged, a general, redox-neutral, and atom-economical platform for metallocarbenes generation remains a persistent challenge. Herein, we introduce carboxamide-functionalized BCBs as versatile carbene precursors that undergo catalyst-controlled chemodivergent reactions. Under nickel catalysis, cyclopropanation of multisubstituted alkenes proceeds via an acceptor-type Ni-carbene, affording azabicyclo[n.1.0] architectures bearing up to three contiguous stereocenters with excellent diastereocontrol. In contrast, copper catalysis promotes efficient and chemoselective formal C(sp2)─H insertion to access allyl oxindoles. Both protocols exhibit broad substrate scope, high functional group tolerance, and exceptional atom economy, and their synthetic utility is highlighted through the preparation of core structures of bioactive compounds. Computational and experimental studies reveal that Ni-carbene generation proceeds via a stepwise dual C─C cleavage, contrasting with the concerted dual cleavage and subsequent electrophilic aromatic substitution manifold established for the copper system.