Epoxidation and Oxygen Insertion Into Alkane Ch Bonds by Dioxirane Do Not Involve Detectable Radical Pathways

Abstract

Abstract:The dimethyldioxirane oxida-served. Even for these alkenes, which are proposed radical mechanism. The selection of a-methylstyrene, rruns-cyclo-prone to radical reactions, the previously tive hydroxylation of ( -)-2-phenylbutane octene, and 1 -vinyl-2,2-diphenylcycloestablished electrophilic concerted mech-by dimethyldioxirane gave only ( -)-2-propane gave, under all reaction condi-anism applies, rather than the recently phenylbutan-2-01 with complete retention tions employed, the corresponding epoxof configuration and no loss of optical ides in high yields. No radical products purity. Thus, a radical-chain oxidation is also discounted in the oxygen insertion infrom allylic oxidation, from translcis isoto hydrocarbon C-H bonds for dioximerization, or from cyclopropylcarbinyl ranes. rearrangement (radical clock) were ob-

Mechanisms of the aerobic oxidations catalyzed by N-hydroxyderivatives

“…Few years ago we have explained the oxidation of a variety of organic compounds (hydrocarbons, alcohols, ethers, aldehydes, etc.) by peracids [25] and dioxiranes [59], in contrast with the generally accepted mechanism of "concerted oxenoid oxygen insertion" [60,61], which postulates butterfly type transition states (Eqs. (86) and (87)), similar to the one originally suggested by Bartlett [62] for alkene epoxidation by peroxides:…”

The kinetic regularities, products, and mechanism of the thermal decomposition of dimethyldioxirane. The contribution of molecular and radical reaction channels

“…The oxidation of (R)-2-phenylbutane by D MDO proceeds with complete maintenance of the configuration, although the radical H atom abstraction from the chiral center should be accompanied by racemization. 16 The data on the oxidation of (trans-2-phenylcyclopropyl)ethane by dioxirane la can serve as additional argument in favor of the "oxenoid" mechanismfl 7 This reaction virtually proceeds without opening the three-membered cycle of the hydrocarbon (Scheme 3).…”

Metal‐Free, Selective Alkane Functionalizations

“…The mechanistic interpretations and the origins of the selectivities are not clear yet, [74] however, the concerted mechanism of the C À H insertion of the peracid through a highly polarized transition structures is likely. [74] The mechanistic dichotomy in the reactions of alkanes with peracids, i.e., concerted asc.wiley-vch.de insertion vs. molecule induced homolysis [75] is somewhat reminiscent of dioxirane chemistry, where clear evidence for concerted [76] paths was identified recently. [42] The selectivities for radical oxyfunctionalizations may also be substantially increased with the less reactive and bulky t-BuO radical.…”