The Synthesis Of Chiral S,N-Ligands With Imidazoline And Their Application In Asymmetric Allylic Alkylation Reaction

In this thesis, the synthesis, characterization of six chiral S,N-ligands withimidazoline and their application in asymmetric allylic alkylation of1,3-diphenylallylacetate and methyl malonate were studied. The main research contents are as follows:1. Synthesis and characterization of S,N-ligands with imidazolineFirst, a series of chiral imidazoline compounds3a-c and7a-c have beensynthesized from commercially available2-bromobenzoic acid or1-bromo-2-naphthoic acid and amion alcohols in three steps. Then the compounds3a-c and7a-c were treated with n-BuLi, followed by reaction with diphenyldisulfide.After purification by preparative TLC on silica gel plates, the chiral S,N-ligands withimidazoline4a-c and8a-c were obtained in10%-72%(total yield)(Scheme1). Allthe compounds were characterized by IR, HRMS and NMR spectra. 2. Application in asymmetric allylic alkylationThe Pd-catalyzed asymmetric allylic alkylation of1,3-diphenylallyl acetate andmethyl malonate was used as a model reaction to examine the catalytic efficiencies ofthese chiral S,N-ligands with imidazoline. The enantioselectivity of these ligands wasevaluated with various base, palladium source and solvents at different reactiontemperatures. And10mol%ligand4c and2.5mol%[Pd(η3-C3H5)Cl]2afforded theyield of up to94%and the enantioselectivity of up to86%ee with BSA-KOAc indichloromethane at room temperature.(Scheme2).