INFLUENCE OF A SPACER ON THE KINETICS OF REDUCTION OF CARBONYL-COMPOUNDS WITH POROUS BOROHYDRIDE EXCHANGE RESIN

The influence of the introduction of a spacer on the kinetics of reduction of carbonyl compounds with porous borohydride exchange resin is examined. The porous polymer supports were obtained by a four-step reaction sequence starting from styrene-divinylbenzene crosslinked polymer. We have shown that for porous polymers introduction of a spacer arm does not improve the rate and the yield of the reaction, and that the kinetics are approximatively independent of the texture of the polymeric support. These results are explained by the extension of the spacer with swelling of the polymers, this extension (shown in comparison with the pore size distribution in the dry and swollen state) reduces the site accessibility and so decreases the rate and the yield of the reduction.