Transition states for alkane oxidations by dioxiranes

The mechanism of the oxygen insertion by dioxiranes into alkane C-H bonds has been investigated theoretically. Becke3LYP hybrid DFT calculations with the 6-31G* basis set on the reactions of dioxirane and cyanodioxirane with methane and on the reactions of cyanodioxirane with ethane, propane, and isobutane predict that the reactions are concerted with highly asynchronous transition states. The transition states have considerable diradical character, but are polarized as well. Substituent effects, stereoselectivity, and the possibility of the formation of radical pairs are discussed.