Oxygen Transfer fom Oxaziridines: A Chemical Model for Flavin-Dependent Monooxygenases

Article abstract of DOI:10.1021/ja00317a049

The ability of several aryloxaziridines to transfer an oxygen atom to phenolates was examined. 2-(p-Nitrophenyl)-3-tert-butyloxaziridine (1) was found to oxidize potassium 2,6-dialkylphenolates to the corresponding p-benzoquinones.Product studies and an observed ESR signal suggest an electron-transfer mechanism for these oxidations. 18O-labeled oxaziridine 30 was prepared.Oxidations of phenolates with 30 rigorously establish the oxaziridine ring oxygen as the atom that is transferred to substrate.Kinetic studies with oxaziridine 1 and the isomeric nitrone 15 rule out the nitrone as an obligate intermediate in the oxygen-transfer reaction.In the oxidation of substrate, a single electron transfer from phenolate to oxaziridine is thought to generate a phenoxy/nitroxyl radical pair, which upon coupling and fragmentation achieves the oxygen transfer.These oxygen-transfer reactions serve as models for the proposed flavin-based oxaziridine 34 in enzyme-mediated monooxygenations.