Influence of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymers on stereoselective catalysis in water

The first application of (EO)(n)-(PO)(m)-(EO)(n) triblock copolymers as sur factants in asymmetric hydrogenation is described. We observed a dependence of the activity and enantioselectivity on the asymmetric hydrogenation of methyl (Z)-a-acetamidocinnamate on the length of the (PO)(m) domain of the copolymer. The activity and enantioselectivity were observed to be independ ent of the hydrophilic-lipophilic-balance (HLB) or the critical micelle con centration (cmc) of the copolymer. The size of the (EO)(n) unit does not pl ay an important role, however the addition of a small amount of SDS enhance s the enantioselectivities significantly. The triblock copolymers were also successfully used as phase transfer reagent in two-phase Suzuki carbon-car bon coupling reactions. The use of polymeric reagents in micellar and phase -transfer systems has the advantage that these reagents can be easily separ ated from the reaction mixture by means of a membrane.