Development of New icroencapsulated Polymer-Supported Catalysts

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The utility of polymer catalysts is now well-recognized because of their ease of workup and of separation of products and catalysts, from the economical point of view, and in application to industrial processes, etc. However, in general, polymer catalysts have some disadvantages such as difficult preparation, instability, and low activity. To address these issues, we have already developed new types polymer catalysts, named 'microencapsulated catalysts,' which are readily prepared, have high activity, and are recoverable and reusable.Catalytic asymmetric dihydroxylation of olefins using microencapsulated osmium tetroxide was developed. The catalyst was readily prepared from osmium tetroxide and an ABS polymer based on a microencapsulation technique. In most cases, the desired diols were obtained in high yields with high enantiomeric excesses.We have also developed a phenoxyethoxymethylpolystyrene (PEM)-based novel polymer-supported osmium catalyst. The catalyst system does not require a slow addition of olefins, which has been a tedious procedure. The catalyst was recovered quantitatively by simple filtration and reused without loss of activity.While palladium catalysts find wide-spread utility in a variety of transformations in organic synthesis, they are expensive, air-sensitive, and cannot be recovered in many cases. We have developed triphenylphosphine palladium, which has been successfully used in several palladium-catalyzed reactions.