"Dirnethyldioxirane (DMDO) is a mild reagent for epoxidation under neutral conditions of electron-rich as well as of electron-deficient alkenes. Moreover, dimethyldioxirane is often the oxidant of choice for the preparation of labile epoxides. … Methyl(trifluoromethyl)dioxirane (TFDO), … is more reactive than DMDO by a factor of ~600. … TFDO can be used to regioselectively oxidize tertiary over secondary C-H bonds via an “oxenoid” (butterfly) mechanism."