Homogeneous catalysis by transition metal complexes. Selective oxidation of cyclohexene by mixed-catalysts containing rhodium(II) complexes

The oxidation of cyclohexene catalyzed by mixtures of rhodium(II) carboxylates and epoxidation catalysts (V, Mo) has been studies at 55°C under 1 atm of oxygen. The main product of oxidation is 1,2-epoxycyclohexene-3-ol (II), the yield of which depends strongly on the catalytic system used. The best yields (ca 70% at 15% conversion) are attained with mixtures of electron-deficient rhodium carboxylates and a vanadium cocatalyst. The proposed mechanistic scheme involves two distinct steps: initially autooxidation of the olefin occurs to yield cyclohexenly hydroperoxide, which is used to epoxidize preferentially 2-cyclohexen-1-ol. © 1979.