Epoxidation of alkenes catalysed by Mn III (Schiff base) complexes

Abstract

The epoxidation of cyclohexene using various Mn"' (Schiff base) NCS complexes as catalyst and PhlO as oxidant give cyclohexeneoxide, cyclohexenol and cyclohexenone as the products. The effect of catalyst concentration shows that, on increasing the concentration of catalyst the yield of the epoxide decreases. The relative rate of reaction of cyclic alkenes follows the order; norbornene > cyclo-octene > cycloheptene > cyclohexene > cyclopentene. This shows that rigid co-ordination of alkene t o oxomanganese(v) catalyst does not take place in the rate-determining step. The effect of various additives viz., pyridine, imidazole, NaHCO,, NaH,PO,, sodium lauryl sulphate, cetyl trimethyl ammonium bromide, and Triton X-100 shows that axial ligation due t o pyridine, imidazole etc. increases the yield of epoxide. The surfactants Triton X-100 and sodium lauryl sulphate show that micellar catalysis plays a positive role.

Chromium− and Manganese−salen Promoted Epoxidation of Alkenes

“…Agarwal et al reported evidence to suggest that substrate precoordination was not important in the epoxidation mechanism . In 1989 Breslow et al reported attempts to precoordinate substrates to Mn(salen) complexes modified with pyridyl groups in the presence of Cu 2+ ions .…”

Enantioselective Epoxidation of Styrene by Manganese Chiral Schiff Base Complexes Immobilized on MCM‐41

“…[8,9] Since then chiral Mn Schiff base complexes have been used for the epoxidation of various alkenes and for ring-opening reactions. [10][11][12] Although homogeneous chiral Mn Schiff base complexes have been found to be effective for asymmetrice poxidation still they have certain limitations. Homogeneous catalysts fail in terms of reusability and recovery,w hich prevents their commercial application.…”

Synthesis, characterization and catalytic properties of heterogeneous iron(III) tetradentate Schiff base complexes for the aerobic epoxidation of styrene

“…In this field, polystyrene (PS), zeolite-Y, M41S and mesoporous carbon-anchored Cu(II), VO(II), Mn(III), Cr(III), Bi(III), Mo(VI) and Co(II) complexes have been widely used for the oxidation of cyclohexanol [2], selective epoxidation of olefins [3][4][5][6][7] or decomposition of H 2 O 2 [8]. The use of dioxygen or air as the oxidant for such processes is particularly attractive from both economic and environmental standpoints.…”