SELECTIVE EPOXIDATION OF UNFUNCTIONALIZED OLEFINS CATALYZED BY UNSYMMETRIC MN(III)-SCHIFF-BASE COMPLEXES

The selective epoxidation of unfunctionalized olefins (styrene, cycloh exene, cr-methylstyrene) catalyzed by unsymmetric Schiff base-Mn(III) complexes Mn(CBP-phen-XSal)Cl [X = H, Cl, Br, NO2, CH3, OCH3] 1 and th e symmetric analogs Mn(III)(CBP-R-CBP)Y [R = CH2CH2, CH(CH3)CH2, C6H4, Y = Cl, OAc] 2 was investigated under mild conditions with iodosylben zene as the terminal oxidant. The results showed that: the unsymmetric complexes Mn(III)(CBP-phen-XSal)Cl are effective catalysts in catalyt ically selective olefin epoxidation, superior to the symmetric analogs ; with X = Cl, Br, the catalytic effectiveness was higher, X = strong electron-withdrawing group (NO2) or electron-releasing (OCH3) lowered the catalytic effectiveness; the highest percent yields of the three o lefins were 73%, 98% and 92%, respectively. (C) 1997 Elsevier Science B.V.