New Approaches for Reusable Chiral Heterogeneous Catalysts for Epoxide Ring Opening Reaction

The heterogenization of chiral homogeneous catalysts, which endows homogeneous systems with attractive features such as easy product separation and catalyst recovery by simple filtration, constitutes a rapidly expanding research area in asymmetric catalysis. Among various organic transformations, chiral transition-metal complexes catalyzed asymmetric ring opening reaction is one of the most fascinating areas because the enantiopure end-products have wider application in pharmaceuticals, fine chemicals and as chiral auxillaries. In this direction attempts were made to develop highly active and enantioselective catalysts based on chiral ligands viz. BINOLs, SALENs etc., with various transition metals. As chiral catalysts are expensive, focuses on low catalyst loading and/ or their recovery and re-use are important aspects. Since various homogeneous catalysts have been found to be efficient in asymmetric catalysis their immobilization on solid supports is of great interest. This led researches to make these systems recyclable by way of supporting the catalyst on organic and inorganic polymeric materials or making use of ionic liquids or manipulating solubility of the catalyst by increasing the molecular weight of catalyst with simultaneous increase in active sites so that the catalyst is easily recovered by simple precipitation method in a post catalytic workup process. Therefore, this chapter will give an in-sight of epoxide asymmetric ring opening reaction based on chiral recyclable catalysts and would bring about the latest trends in this area of research. Introduction The growing demand for enantiopure compounds in pharmaceuticals, food & agrochemicals, fragrance & flavors, biochemicals and fine chemicals industries has