The Study Of New Types Chiral Catalysts For Asymmetric Ring Opening And Ring Closing Terminal Epoxides Reaction

New dinuclear chiral Co (salen) complexes bearing group 13 metals have been synthesized and characterized. The easily prepared complexes exhibited very high catalytic reactivity and enantioselectivity for the asymmetric ring opening of epoxides with H2O, chloride ions, carboxylic acids and sulfonic acids.First the asymmetric hydrolytic kinetic resolution (HKR) of racemic terminal epoxides by new easily synthesized dimeric chiral (salen) Co bearing Al group provides a practical and straightforward method for the synthesis of enantiomerically enriched terminal epoxides (>99%ee) and diols. Chiral epoxides are widely used as intermediates in pharmaceutical and other chemical synthesis fields. The advantage of this reaction is enantiopure products can be got in one step and after reaction the catalysts can be collected easily and reused multiple times without loss of activity and selectivity. An inorganic acid, HC1 is applied first time for the asymmetric ring opening reaction of terminal epoxides. Reactions are conveniently carried out at an air atmosphere and ice bath condition.Second the binuclear chiral (Salen) Co complexes bearing Lewis acids of Al group catalyze regio- and enantioselective ring opening of terminal epoxides with carboxylic acids. The ring opening product of epichlorohydrin with carboxylic acids followed by cyclization step in the presence of catalyst and base represent straightforward. Although the ring opened products of epoxides with carboxylic acid are not high (maximum is around 75%ee) the ring closed product Enantiomeric excess can reach to 98%. Strong synergistic effects of different Lewis acid of Co-Al and Co-Ga were exhibited in the catalytic process. A very efficient and highly enantioselective ring-opening reaction of epoxides with sulfonic acids in the presence of tetrabutylammonium chloride (TBAC) in solvent of tert-butyl methyl ether (TBME) has been developed. This method is useful and effective for the preparation of chiral sulfonates as precursor in pharmaceutical and other synthetic purposes. High enantioselectivity (>99%ee) and yield (>45%) were achieved in this method.