Biomimetic oxidation studies. 10. Cyclohexane oxidation reactions with active site methane monooxygenase enzyme models and t-butyl hydroperoxide in aqueous micelles: Mechanistic insights and the role of t-butoxy radicals in the CH functionalization reaction

Abstract

The oxidation of cyclohexane (CyH) in an aqueous micelle system with t-butyl hydroperoxide (TBHP) in the presence of biomimetic methane monooxygenase enzyme complexes, [Fe 2O( η 1-H 2O)( η 1-OAc)(TPA) 2] 3+, 1, [Fe 2O( η 1-H 2O)( η 1-OAc)(BPIA) 2] 3+, 2, and O 2, was studied and found to provide cyclohexanol (CyOH), cyclohexanone (CyONE), and cyclohexyl- t-butyl peroxide (CyOO t-Bu). The mechanistic aspects of this oxidation reaction in aqueous micelles were studied and included the effects of the surfactant concentration, cetyltrimethylammonium hydrosulfate; concentration of CyH and TBHP; and a trapping reagent, CCl 4. Several factors allowed us to conclude that a t-butoxy radical ( t-BuO) was generated from the favorable redox chemistry of the biomimetic complexes with TBHP, and was responsible for the free radical initiation process with CyH in the aqueous micelle system.