Cyclopropyl–Allyl Rearrangement of gem-Dibromoycyclopropanes under the Action of Aluminum Carbenoids

It was found for the first time that 2,3-dialkyl-substituted gem-dibromocyclopropanes react with a solution of the aluminum carbenoid Me₂AlCH₂I in CH₂Cl₂ to form substituted bromoalkenes in a good yield. The reaction is sensitive both to the nature of the organoaluminum Lewis acid and to the substitution in gem-dibromocyclopropane. A mechanism of the cyclopropyl–allyl rearrangement was proposed. The free activation energies of the cyclopropyl–allyl rearrangement were calculated by the B3LYP/6-31G(d) method for a number of gem-dibromocyclopropanes and aluminum-containing Lewis acids.