Enantioselective epoxidation of olefins catalyzed by two novel chiral poly-salen-Mn(III) complexes

Two novel chiral poly-salen-Mn(III) complexes 1 and 2, derived from (R,R)-1 ,2-diaminocyclohexane and the disalicylaldehydes 5 and 6 were synthesized a nd employed in the enantioselective epoxidation of olefins. A range of 30-9 2% ee and 75-97% yield was achieved in NaClO/4-PPNO and m-CPBA/NMO oxidant systems when substituted styrenes and substituted 2,2-dimethylchromenes wer e used as substrates. Furthermore, the poly-salen-Mn(III) complexes could b e recovered easily and recycled efficiently several times by a simple catal ysis/separation method. After five reactions, an 82% ee and 78% yield of ep oxide were obtained using 2,2-dimethylchromene as substrate. (C) 2000 Elsev ier Science Ltd. All rights reserved.