It is shown that an electron-deficient manganese (III) porphyrin complex of meso-pentafluorophenylporphyrin associated with iodobenzene diacetate (PhI(OAc)2) is an potent catalytic system for the oxidation of alkenes and activated hydrocarbons. When the reactions were carried out in the presence of a small amount of water at 50 oC, quantitative conversions, rapid turnovers(TONs) and high selevtivities were observed for most alkenes. In the case of cyclohexene, for example, 100% conversion with a 93% selectivity for epoxide was achieved within 10 mins, exhibiting a 40 TON/min. Competitive catalytic oxidation of ethylbenzene and ethlybenzene-d10 revealed a kinetic isotope effect (KIE) of kH/kD = 2.8±0.1 at 298 K, similar to the KIE reported for the reaction of ethylbenzene with an electron-deficient manganese(V)-oxo porphyrin species. On the basis of Hammett correlation (ρ+ =-0.33, R = 0.99) and competitive product analysis, a highly reactive porphyrin-manganese(V)-oxo intermediate is favored.

Synthetic and mechanistic studies of catalytic oxidations by manganeses(III) porphyrins and iodobenzene diacetate

249th National Meeting (2015)

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