The Preparation Of Catalytic Properties Of Polymer-Immobilized Chiral Salen-Mn(Ⅲ) And The Studies On Complex In Catalytic Asymmetric Epoxidation Of Olefins

The chiral epoxides compounds is a kind of important intermediates in fineorganic synthesis, and the asymmetric epoxidation reaction is an important way forsynthesis of chiral epoxides. In recent years, induced by the chiral metal compoundsas catalyst of olefin, much attention has been paid to the asymmetric epoxidation,thereinto the reaction of chiral Salen-Mn (Ⅲ) is the most effective catalyst, thepreparation of different structure solid immobilized chiral Salen-Mn (Ⅲ) compoundsis an important research topic in the field. This study through molecular design, usethe crosslinked polystyrene as the carrier, through the multi-step macromolecularreaction, research and make a novel structure of immobilized Salen-Mn (Ⅲ)compound catalyst, and in the asymmetric epoxidation of styrene and alpha-methylstyrene showed higher catalytic activity, in addition found some valuable regularities.The results of this paper is to promote the development of asymmetric catalyticepoxidation has obvious theory reference significance and potential application value.Firstlly, in this work, with chloromethylated crosslinked polysltyrene (CMCPS)microshpheres as starting microshpheres, Chiral Mn(Ⅲ)-Salen Complex immobilizedon CPS microshpheres was prepared via two polymer reactions and acoordination-chelating reaction. Firstly, the Friedel-Crafts alkylation between thechloromethyl group CMCPS microshpheres and2-Hydroxy-4-methoxybenzaldehyde(HMBA) was allowed to be carried out, obtaining the modified microspheresHMBA-CPS. Subsequently, the Schiff base reaction between HMBA-CPS ando-phenylenediamine was performed, and the microspheres Salen-CPS, on whichSalen ligands were bonded, were obtained. Finally, the coordination-chelatingreaction of Salen-CPS with Mn salt was conducted, resulting solid catalystMn(Ⅲ)Salen-CPS, on which Chiral Mn(Ⅲ)-Salen Complex was immobilized. The microspheres Salen-CPS and Mn(Ⅲ) Salen-CPS were fully characterized by usingseveral methods, such as FTIR, UV/Vis and SEM. The Friedel-Crafts alkylationbetween CMCPS microshpheres and HMBA was mainly investigated because it was akey reaction. The experimental results show that the Friedel-Crafts alkylation cansmoothly be carried out as AlCl3was used as Lewis catalyst and a mixture ofdichloromethane and nitrobenzene was used as solvent.Secondly, this solid catalyst was used in the asymmetric epoxidation of styrenewith m-chloroperoxybenzoic acid (m-CPBA) as oxidant and N-methyl morpholine-N-oxi-de (NMO) as axial base, ands its catalytic properties were examined indepth. The effects of main factors on the asymmetric epoxidation reaction ofstyrene were researched detailedly, and the relevant rules were analysed and discussedfrom the view of micro-mechanism. The experimental results show that in theasymmetric epoxidation reaction of styrene, Mn(Ⅲ)Salen-CPS microspheres havehigh catalytic activity and excellent enantioselectivity of the epoxide. At thetemperature of20℃in8h, the conversion of styrene is closed to85%, and at thetemperature of0℃in2h, the ee value of the epoxide of styrene can reach58%. All ofthe asymmetric environment of the diamine, the addition of the axial base, thereaction time and temperature, and the polarity of the solvent effect theasymmetric epoxidation reaction of styrene greatly. The addition of the axial base willmake both styrene conversion and enantioselectivity of the epoxide to increase. Thelower temperature is beneficial to the enhancement of enantioselectivity of theepoxide, and for this present system, the suitable temperature of the asymmetricepoxidation of styrene is zero centigrade. Using the solvent with weak polarity isadvantageous to the enantioselectivity of the epoxide. The ee value of the epoxide willexhibit a maximum value as the reaction is carried out to a certain degree, and thenthe ee value will decrease with the increase of the reaction time. Furthermore, the timeat which the ee value exhibit a maximum value is different under the differentreaction conditions.Finally, in the same way, this solid catalyst was used in the asymmetricepoxidation of alpha-methyl styrene with m-chloroperoxybenzoic acid (m-CPBA) as oxidant and N-methyl morpholine-N-oxi-de (NMO) as axial base, ands itscatalytic properties were examined in depth, the effects of main factors on theasymmetric epoxidation reaction of alpha-methyl styrene were researched detailedly.The experimental results show that in the asymmetric epoxidation reaction of styrene,Mn(Ⅲ)Salen-CPS microspheres have high catalytic activity and excellentenantioselectivity of the epoxide. At the temperature of20℃in8h, the conversion ofalpha-methyl styrene is closed to46%, and at the temperature of0℃in2h, the eevalue of the epoxide of alpha-methyl styrene can reach81%.The new route to prepare immobilized Chiral metal-Salen complex found in thiswork is simple, convenient, direct and efficient, and it will be valuable in the filed ofthe asymmetric epoxidation of olefins. Use the CPS microsphere immobilized chiralSalen-Mn (Ⅲ) asymmetric catalyst in olefin epoxidation were found in a number oflaws, for the development of asymmetric catalytic epoxidation, has potentialapplication value and theoretical reference value.