POLYMERIC CATALYSTS FOR CHEMOSELECTIVE AND ENANTIOSELECTIVE EPOXIDATION OF OLEFINS - NEW CROSS-LINKED CHIRAL TRANSITION-METAL COMPLEXING POLYMERS

Polymeric analogs of well-known chiral Mn(III)-salen complexes were sy nthesized and were used as recyclable catalysts for asymmetric epoxida tion of olefins. For this purpose two different monomers, 2 and 3, bea ring chiral Mn(III)-salen moieties were synthesized. The monomer 3 car ries a bulky substituent closer to the Schiff base moiety, while monom er 2 lacks such a substituent. These metal complexed chiral monomers w ere subsequently copolymerized with ethylene glycol dimethacrylate pro ducing insoluble crosslinked functional matrices that possess macropor ous morphology. Chemo- and enantioselective catalytic activities of th ese two polymers were evaluated for epoxidation of olefins. Both polym ers catalysed the epoxidation of a variety of olefins at room temperat ure in the presence of iodosylbenzene (PhIO) as the terminal oxidant w ith yields comparable to the homogenous system. In terms of their enan tioselective catalytic activity, polymer P-2 (obtained from 3) perform ed better than polymer P-1 (obtained from 2). Unfortunately, while the homogeneous systems are reported to offer over 80% enantioselectivity , with the present polymeric catalysts, enantioselectivity to a maximu m of 30% were observed. Unlike the homogeneous system, use of an exter nal nitrogenous donor played a very insignificant role in influencing enantioselectivity. (C) 1997 John Wiley & Sons, Inc.