Asymmetric Heterogeneous Catalysts Implemented in Industry

Strategies to induce chirality in a prochiral substrate included modification of existing heterogeneous catalysts by addition of naturally occurring chiral molecules, such as tartaric acid, natural amino acids, or alkaloids, and the implementation of chiral supports, that include quartz or natural fibers, for metallic catalysts. Both strategies have been successful on a limited basis. 

Despite the convenience of handling and separation in heterogeneous catalysis, many other parameters have a strong influence on the stereochemical outcome pressure, temperature, modifier, purity of substrates, high substrate specificity, catalyst preparation (which includes type, texture, and porosity of the support), dispersion, impregnation, reduction, and pretreatment of the metal [18]. 

Reproducibility of catalyst activities and enantioselectivities can often be a problem attributed to variations in catalyst preparations, and purity of the substrate [5,18]. 

The transformations that use asymmetric heterogeneous catalysis will be highlighted P-keto esters and diketone reductions by Raney nickel catalyst modified with R,R-tartaric acid and NaBr, and a-keto acid reductions with cinchona modified Pt catalysts. 

The stereoselective reduction of a-keto acid derivatives at a preparative scale are performed with cinchona-modified Pt catalyst. Enantioselectivities range from 57-95% for the reduction of a-keto acid derivatives [5] and are dependent on the preparation of the Pt catalyst [5,18.79.80] 

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