Epoxidation and oxygen insertion into alkane CH bonds by dioxirane do not involve detectable radical pathways

The dimethyldioxirane oxidation of alpha-methylstyrene, trans-cycleoctene, and 1-vinyl-2,2-diphenylcyclopropane gave, under all reaction conditions employed, the corresponding epoxides in high yields. No radical products from allylic oxidation, from trans/cis isomerization, or from cyclopropylcarbinyl rearrangement (radical clock) were observed. Even for these alkenes, which are prone to radical reactions, the previously established electrophilic concerted mechanism applies, rather than the recently proposed radical mechanism. The selective hydroxylation of (-)-2-phenylbutane by dimethyldioxirane gave only (-)-2-phenylbutan-2-o1 with complete retention of configuration and no loss of optical purity. Thus, a radical-chain oxidation is also discounted in the oxygen insertion into hydrocarbon C-H bonds for dioxiranes.