Allylic oxidation of cyclohexene catalyzed by manganese porphyrins: DFT studies

The present paper summarizes density functional theory studies on hydroxylation of cyclohexene catalyzed by manganese oxo porphyrin. The reaction is preceded by the physisorption of the substrate over the catalyst molecule at the distance of 2.18 angstrom. Next, a hydrogen atom form the C-H bond is abstracted by the catalyst oxo group and the cyclohexene radical is readily bound to the OH group formed at a catalyst active site. Formation of alcohol requires spin crossing on the reaction pathway. Present studies show that alcohol is formed on the catalyst active site via oxygen rebound mechanism without the cyclohexene radical dissociation. Results are compared with the data obtained earlier for epoxidation. The intermediate structures, found for both pathways, clearly indicate that each may lead to only one reaction product. (C) 2010 Elsevier B.V. All rights reserved.