Investigations on selective bromination of tertiary hydrogen atoms in alicyclic compounds

Investigations are described on selective bromination of tertiary hydrogen atoms in alicyclic compounds by radical halogenation with molecular bromine. Isopropylcyclopentane, isopropylcyclohexane, bicyclopentyl and bicyclohexyl have been chosen as simple model systems. From the first two compounds the corresponding di-tertiary 1,6-dibromoisopropylcyclopentane and 1,7-dibromoisopropylcyclohexane, respectively, were obtained in good yields. The structure of both these substances has been elucidated by degradation reactions as well as by independent syntheses; N.M.R.-spectra also provide confirmatory evidence for the structures assigned to the di-tertiary dibromo compounds. The tertiary hydrogen atoms in bicyclopentyl and bicyclohexyl cannot be brominated selectively; in both cases higher brominated compounds are obtained as the main products.