Synthesis Of Zirconium Poly(Styrene-phenyl-vinylphosphonate)-phosphate Immobilized Schiff Base Mo(Ⅵ)Complexes And Chiral Salen Co(Ⅲ)as Heterogeneous Catalysts For Epoxidation Of Unfunctionalized Olefins And HKR Of Epoxides

Epoxidation of unfunctionalized olefins in organic synthesis has always attracted the interest of chemists in catalytic field. Many Schiff base metal complexes have been applied in this process so far. While the Schiff base dioxomolybdenum(Ⅵ) complexes are the most promising candidates for the epoxidation of unfunctionalized olefins by organic hydroperoxides in homogeneous systems. In the catalytic hydrolysis of racemic epoxide reaction kinetic resolution, chiral Salen Co (Ⅲ) catalysts have also been recognized to be the most promising catalyst. These catalysts usually display higher catalytic activity, selectivity and mild reaction conditions for the catalytic reactions. However, the separation and recycling of the expensive catalysts, as well as leaching of the active metal into the solvent and the insufficient stability of the catalysts are still problematic in homogeneous phase. Another disadvantage in homogeneous system is that the formation ofμ-oxo dimmers and other polymeric species will lead to irreversible catalyst deactivation. To solve this problem, active homogeneous catalysts were immobilized onto organic polymer and inorganic materials to attain immobilized catalyst. Therefore, in recent years, many groups have devoted to utilizing solid support in the heterogenization of some transition metal catalysts in an attempt to tailor-made catalysts for desired performance. Thus, the synthesis of various organic-inorganic hybrid mesoporous materials emerges as a potential tool to anchor various homogenous metal salts/complexes and it is interesting to probe the stability of such materials during various modification processes.Four new kinds of heterogeneous catalysts for olefins epoxidation were obtained by grafting diamines on organic polymer-inorganic hybrid material:zirconium poly (styrene-phenylvinylphosp-honate)-phosphate (ZPS-PVPA) and subsequently coordinating with Schiff base Mo(Ⅵ) complexes. The catalysts were characterized by IR, XPS, SEM and TEM. All catalysts were evaluated through the epoxidation of olefins using teit-BuOOH as oxidant. The heterogeneous catalysts possess the advantageous of high conversion, selectivity and excellent reusability. The catalysts were easily separated from the reaction systems and could be reused for thirteen times without significant loss of catalytic activity.Here it was described an unprecedented synthetic approach to chiral salen Co(Ⅲ) immobilized onto amino acid grafting modified zirconium poly(styrene-phenylvinyl- phosphonate)-phosphate (ZPS-PVPA) with different length of linkers. Excellent enantioselec- tivities (>99%) and isolated yields have been achieved for the hydrolytic kinetic resolution (HKR) of epoxides. using the anchored chiral salen Co(Ⅲ) catalysts. It is deduced that the proper chain length of linkers for the HKR of racemic terminal epoxide that follows a bimetallic cooperative pathway. In addition, recovery of the immobilized catalyst was accomplished by simple filtration, catalyst reoxidation and repeated recycling for ten times were possible with no loss of reactivity or enantioselectivity.