Radical Cations of Tetraalkylcyclopropanes. The Cyclopropane Moiety as an Electron Donor

The radical cations of simple tri- and tetraalkylcyclopropanes have been generated by light-induced electron transfer to chloranil and fluoranil. Nuclear spin polarization effects observed during these reactions are compatible with radical cations in which the most highly substituted cyclopropane bond is broken or weakened. In all these reactions the intermediate radical ion pairs recombine to regenerate the reactant hydrocarbons. In the case of tricyclo[4.4.1.0’ 6]undeca-3,8-diene (If) and of l,6-dimethylbicyclo[4.1,0]hept-3-ene (1g), the photoreaction also results in the dehydrogenation of the reactants to yield 1,6-dimethylcycloheptatnene (6) and bicyclo[4.4.1]undeca-1,3,5,8-tetraene, respectively. The polarization of the dehydrogenation products identifies the radical cations, 3f,g, as primary intermediates in the dehydrogenation reaction.