Design, Synthesis And Application Of Hydrolytic Kinetic Resolution Catalysts

A simple and reasonable method to design the hydrolytic kinetic resolution (HKR) catalysts with high efficiency was developed.Guided by this method,the structure-reactivity relation of HKR catalysts was found and heteronuclear bimetallic catalysts were proposed to enhance the catalytic activity of traditional catalysts.Based on this,a new kind of cheap and high effective HKR catalysts were designed and synthesized,which could overcome the poor activity of traditional catalysts, furthermore,chitosan supported heteronuclear bimetallic catalysts were designed, which were easy to recover.The purpose of this thesis was not limited to prepare and apply the new catalysts. How to construct a reasonable model and develop a feasible method to design the catalysts accurately and effectively was also studied.Several questions were proposed in this thesis:Why does the Jacobsen's Co-salen catalyst deactivate in HKR? What will affect the activity of catalyst? What's the relationship between the structure and performance of the catalysts? Is there any catalyst with more activity? Can the catalyst be loaded homogeneously?All of above questions were concluded step by step in four research sections, which are listed as follows:(1) the mechanism of deactivation of Jacobsen's Co-salen catalyst during the HKR;(2) relationship between the structure and performance of the catalysts; (3)synthesis and apply the new heteronuclear bimetallic catalysts;(4) synthesis and apply new loading heteronuclear bimetallic catalysts.The first part of the thesis concerned the mechanism of deactivation of Jacobsen's catalysts.Possible mechanisms of deactivation of Jacobsen's Co-salen catalyst during the HKR of epichlorohydrin were explored by UV-vis spectroscopy, IR spectroscopy and GC-MS.It indicated that the main reason was the addition of the Co-salen counterions to epoxide the formation of Co-OH during the reaction correlated with deactivation.(salen)Co(â…¢)OAc+H₂O→(salen)Co(â…¢)(OH)+HOAc. The deactivation also could be attributed to the destroy of complexation structure.The second part of the thesis concerned the relationship between the structure and performance of the catalysts.Some fundamental research were put forward to the (salen)Co containing different anionic axial ligands.The geometric structures,E_HOMO, E_LUMO,electron densities of cobalt and energy are calculated at PM3 level.Compared to the results reported in literature,the structure-reactivity relation of HKR catalysts was found and a method to enhance the catalytic ability of HKR catalysts was proposed.A new kind of high effective catalysts were designed.The factors affect catalytic activity directly were not the HOMO and the LUMO.The center cobalt atom of (salen)Co(â…¢) activated the epoxy compounds and epoxy compounds broke at the same time.ΔE_L-H(Energy level difference of E_LUMO and E_HOMO) determined the activity of catalyst.This could be owned to the adsorption and desorption on the active center-cobalt.The relationship of theΔE_L-H and speed constant was K^*10³=27.8-3.12ΔE_L-H,and the related coefficient R for regression was 0.97.At the same time,some catalysts containing different axial direction anionic ligands were applied in HKR of racemic terminal epoxides.Reliability of the catalyst design was verified.At 20℃,with the water equivalent of 0.55,and the catalyst concentration of 0.5mol%,the e.e.of the(S)-epichlorohydrin would reach 99%in 8 hr catalyzed by the new or the reused(salen)Co(â…¢)(OOCF₃).The third part of the thesis concerned the synthesis and application of heteronuclear bimetallic catalysts.The synthesized heteronuclear bimetallic catalysts were expected to improve the reactivity.This kind of new catalysts was explored by UV-vis spectroscopy,IR spectroscopy,elementary analysis and ICP.Validity of the catalysts were inspected and verified by the application in HKR of racemic terminal epoxides.At 20℃,with the water equivalent of 0.55,and the catalyst concentration of 0.25mol%,the activity of(salen)Co(â…¡)(ZnCl₂),(salen)Co(â…¡)(FeCl₃), (salen)Co(â…¡)(SnCl₄),and(salen)Co(â…¡)(AlCl₃)was better than that of (salen)Co(â…¢)OAc,and the e.e.of the(S)-epichlorohydrin could reach 99.5%in 10 hr.The activity of heteronuclear bimetallic catalysts were higher than that of the (salen)Co(â…¢)OAc.The reason could be that the cobalt activated epoxy compounds in one salen unit and other active center may active the water,and the reaction may take place in one unit or two,and then the activity of catalyst may be improved.The water connected on the other metals could attack the activatory epoxy compounds to form a transient formation,which could react with water quickly to form water and diol.Nonlinear effects of the heteronuclear bimetallic catalysts were discovered in the experiments,and the mathematical model of(+NLE) proposed by Kagan were used to fit the results.The fourth part of the thesis concerned the preparation of chitosan-supported chiral salen Co(â…¡) catalyst and its application in HKR of epichlorohydrine.Chitosan supported(salen)Co(â…¡) with different anionic ligand were synthesized.The ligand and catalyst were characterized by NMR,IR spectroscopy,elemental analysis and ICP.The catalystes were then used for HKR of ECH.The results showed that in respect of catalytic effect,the ZnCl₂,AlCl₃,FeCl₃,and SnCl₄ as anionic ligand was better,and the e.e.of the(S)-epichlorohydrin could reach 99%in 10 hr.This project comes from the industry and the obtained results are preponderant, compared to some of the previous methods.It provides more choices for the industry. This thesis deals with both the experiments and theories.Especially,it concerns how to build reasonable models to enhance the accuracy and efficiency of the design process.The methods used in this thesis are universal.It provides some feasible methods and ideas for the catalyst designing process.