Synthesis Of Chiral Salen Ligands And Their Applications In Two Types Of Asymmetric Catalytic Reactions

Objective:Chiral salen ligands and chiral salen complexes were synthesized.Salen and metal salen were applied to several kinds of asymmetric reactions to develop several types of reactions with high enantioselectivity.Methods:1.Synthesis of chiral salen and metal salen complexesChiral salen were ligands synthesized from 2-ethylphenol and 2-sec-butylph enol via carboxylation or formylation,followed by condensation with（1R,2R）-1,2-diphenylethylenediamine,（1R,2R）-1,2-cyclohexanediamine and（R）-1,1’-bi naphthyl-2,2’-diamine,respectively.Chiral salen ligands coordinated with metal ions to form chiral metal salen complexes.2.Optimization of asymmetric reaction conditions and substrates expansionSeveral kinds of asymmetric reactions were optimized by changing the amount of catalyst,the kinds of ligands,different solvents,reaction temperature and time.Then the universality of reaction substrates was investigated.The structures of the aimed products were characterized by ¹H NMR,¹³C NMR and HPLC.Results:1.Nine novel salen ligands and five Mn（III）-salen complexes were synthesized successfully.2.All above compounds were applied to two kinds of asymmetric catalytic reactions.The results are as follows:（1）The asymmetric cyanation of aromatic aldehydes with ethyl cyanoate was successfully catalyzed by in-situ assembly of ligand and tetraisopropyl titanate in chloroform and isopropanol.The highest yield was 95%and ee value was 74%.（2）Mn（III）-salen complexes were used as catalysts,dichloromethane and water as solvent,in the presence of hypobromic acid and potassium acetate,The oxidation kinetic resolution of secondary benzylic alcohols was successfully performed.The highest yield was 42%and ee value was 99%.Conclusion:In this study,several novel chiral salen ligands and metal salen complexes were synthesized,which expanded the number of asymmetric catalysts.Two kinds of asymmetric reactions were successfully catalyzed under mild conditions with good conversion and enantioselectivity.