The thermal conversions of 6,6-difluorobicyclo[3.1.0]hex-2-enes to fluorobenzenes. An interesting dichotomy of mechanisms

Article abstract of DOI:10.1016/S0040-4020(01)81182-0

A kinetic study of the thermal, dehydrofluorinative aromatization reactions of two ostensibly-similar 6,6-difluorobicyclo[3.1.0]hex-2-ene systems led to the conclusion that drastically different mechanisms operate for the two reactions. Activation parameters, solvent effects, kinetic isotope effects, isotope labelling experiments and observation of reactive intermediates all contributed to the conclusion that the reaction of 6,6-difluorobicyclo[3.1.0]hex-2-ene, 1, proceeds via a homolytic hydrogen-shift rearrangement, while the reaction of 2,3-benzo-6,6-difluorobicyclo[3.1.0]hex-2-ene, 6, proceeds via a solvolytic mechanism involving rate-determining carbocation formation.