Geminal hyperconjugation as a driving force for C-C bond shortening in heavy-atom tunnelling.

ABSTRACT: Quantum mechanical tunnelling significantly influences the reactivity of strained ring systems, yet strategies for controlling such reactivity remain largely unexplored. Here, we identify geminal hyperconjugation, i.e., electron delocalization between σ-bonds attached to a common atom, as a decisive electronic factor in governing heavy-atom tunnelling reactions involving three-membered rings. We illustrate this through a case study of the oxepin (1') ⇌ benzene oxide (1) equilibrium, recently shown to undergo solvent-controlled tunnelling at 3 K (Angew. Chem. Int. Ed., 2020, 59, 20318). Natural bond orbital analyses reveal that coordination of ICF₃, H₂O, or H⁺ to the oxygen atom of 1 enhances geminal C-O σ → O-C σ* delocalization in the

SUBMITTER: Laconsay CJ 

PROVIDER: S-EPMC12409669 | biostudies-literature | 2025 Aug

REPOSITORIES: biostudies-literature