Studies on asymmetric synthesis with catalysts on mesoporous polymer materials

Abstract

Since Merrifield’s pioneering work in the area of polypeptide synthesis delineated many of the benefits of polymer supported strategies such as easy workup and easy isolation of product, polymer-supported synthesis is a major tool for the development of new synthetic strategies in organic chemistry. Moreover, as the importance of the environment has been increased, green chemistry becomes one of the major research areas in organic chemistry. To preserve the environment, many strategies have been developed. One example is to use polymer support. When a reactive species or toxic reagents are attached to a polymer support, side product or pollutant formation may often be minimized. Our research was to develop more advanced heterogeneous polymer supported system. Recently, Ryu reported CMK materials which are uniform mesoporous materials made by nanocasting method. We first tested Mannich reaction and cyanation using CMK supported catalyst. After the efficiency of these kinds of materials in heterogeneous reaction was confirmed, we planed to use mesoporous polymer support prepared by nanocasting method. Enantioseletive reduction, CBS reduction was chosen as a model organic reaction. We found the higher efficiency when using mesoporous polymer supported chiral sulfonamide catalyst. To extent our scope, masking agents was introduced for site –isolated catalyst on the support. Not only some reasonable data but also unexpected data were obtained. Chiral sulfonamide and salt-formed oxazaborolidien on the support were confirmed by elementary analysis and XRF data. From the results we found that the higher enantioselectivity in the salt-formed oxazaborolidien than that in the oxazaborolidien. We made a polymer with (S)-diphenylprolinol. After polymerization, enantioselective reduction and diethylzinc addition was tested. Asymmetric diethylzinc addition was tested to find out the tangible mechanism. However, detailed investigation is required because of other factors...