ScholarWorks@중앙대학교

초록

Precise activation of otherwise inert σ-bonds such as C(sp3)–C(sp3) and C(sp3)–OH remains a formidable challenge in homogeneous catalysis. While recent advances have harnessed cyclopropyl alcohol as a masked homoenolate or employed directing-group-assisted C–C bond insertion, these strategies exclusively follow conventional β-scission pathways. Herein, we report a noncanonical deoxygenative γ-C–C bond activation of cyclopropyl alcohols, enabling cross-coupling without the formation of homoenolate. Key to the transformation is tris(3,5-di-tert-butylphenyl)phosphine that creates a tris-ligated, pentacoordinate nickel transition state. The large cone angle directs oxidative addition to the distal C–C bond, while a low buried volume (% Vbur) preserves coordination sites. Competing homoenolate chemistry through β-scission is effectively suppressed by boronate masking under biphasic conditions. A series of mechanistic studies support a rate-determining γ-oxidative addition via a pentacoordinate transition state. The resulting π-allyl nickel intermediate undergoes intramolecular transmetalation in a highly regioselective C–C bond-forming event, forging a wide array of 1,1-dialkylethenes. This work establishes a distinct mechanistic framework for C–C bond activation, expanding the synthetic utility of cyclopropanol-based cross-coupling.

키워드