The Synthesis,Characterization And Catalytic Properties Of Chiral(6-Methylpyridine)-(Imidazoline)Pincer Pd Complexes

In this dissertation,the synthesis and characterization of chiral(6-methylpyridine)-(imidazoline)NCN' pincer palladium complexes were studied.And the applications of these complexes in the asymmetric aza-Morita-Baylis-Hillman reaction between imine and acrylonitrile were preliminarily carried out.The main results are as follows:1.Synthesis and characterization of chiral(6-methylpyridine)-(imidazoline)NCN' pincer Palladium complexes(1)Firstly,3-(6-methylpyridine)-2-benzoic acid 1 was synthesized via coupling reaction of commercially available 3-boronobenzoic acid and 2-bromo-6-methylpyridine under palladium catalysis,then 1 reacted with dichlorosulfoxide to afford acyl chloride,and then reacted different chiral amino alcohols to obtain the corresponding amido alcohols.Next,The different amido alcohols were reacted with dichlorsulfoxide and p-toluidine in sequence without separation and purification,and then alkali treated to obtain chiral 1-(imidazoline)-3-(6-methylpyridine)benzene ligands 2a-f.Then the reaction of ligands 2a-f and palladium chloride afforded the corresponding chiral(6-methylpyridine)-(imidazoline)NCN ' pincer Palladium complexes 3a-f via C-H bond activation(Scheme 1).The new complexes 2a-f and 3a-f were characterized by 1H NMR,13C NMR and elemental analysis(HR-MS for the ligands 2a-f).In addition,the formation of the complex 3a is confirmed by single crystal X-ray diffraction.(2)3-(6-methylpyridine)-2-benzaldehyde was synthesized via coupling reaction of commercially available 3-formylphenylboronic acid and 2-bromo-6-methylpyridine in the presence of palladium acetate,then 3-(6-methylpyridine)-2-benzaldehyde,different chiral ethanediamine and acetyl chloride afforded chiral 1-(imidazoline)-3-(6-methylpyridine)benzene ligand 2g.Ligand 2g and palladium acetate were refluxed in acetic acid,and then stirred at room temperature by adding acetone/aqueous solution of lithium chloride to afford the corresponding chiral(6-methylpyridine)-(imidazoline)NCN ' pincer Palladium complex 3g via C-H bond activation(Scheme 2).The new complexes 2g and 3g were characterized by 1H NMR,13C NMR(HR-MS for the ligand 2g).2.Application of chiral pincer palladium complexes in the asymmetric aza-Morita-Baylis-Hillman reaction between imine and acrylonitrileThe catalytic properties of chiral(6-methylpyridine)-(imidazoline)NCN' pincer Palladium complexes 3a-g in the asymmetric aza-Morita-Baylis-Hillman reaction between imine and acrylonitrile were preliminarily studied.The template reaction was the reaction of(E)-N-benzylidene-4-methylbenzenesulfonamide with acrylonitrile.With the aid of silver acetate and DABCO,complex 3b can catalyze this reaction to get the target product in 71%yield and 30%ee(Scheme 3).