Study On Syntheses, Characterization And Application As A Catalyst Of Chiral Diam Inocyclohexane Schiffbases Complexes

Recently, The extensive application and syntheses of Schiff bases and their complexes have received much attention, becase of their easy synthesis and Diversity, Flexibility in the choice of a variety of amines with carbonyl compounds such as aldehydes or ketones to respond. Thereby changing the functional groups attached to derivatization, Thus become an important class of organic ligands. In recent years, Schiff base and its complexes in medicine, biology, materials science, analytical chemistry and catalysis fields, especially in the field of asymmetric catalysis and so on has made great progress.In this article, we use the L-tartaric acid to split with the Racemic trans-diaminocyclohexane, and obtained (-)-(R, R)-1, 2-diaminocyclohexane L-tartrate. Four types of Schiffbase ligands were obtained by condensing Salicylaldehyde, 2-hydroxy-1-naphthaldehyde, 3, 5-di-tert-butyl-Salicylaldehyde, 3, 5-di-(1-meth- yl-1-phenyl-ethyl)-Salicylaldehyde with (1R, 2R)-cyclohexane-diamine and the Chiral copper(II), nickel(II), and cobalt(II) complexes of the Schiff bases were prepared, A total of 12 kinds(of which 6 species were no literature reported new compounds). Their structures were characterized by IR, MS, NMR and Elemental analysis. This article also prepared two complexes of the single crystal, and their structures was identificationed on the X-ray diffraction.The results showed that the ratio of ligand and metal ion is 1:1. The single crystal of the complex 26b was obtained by solvent crystallization, the appearance is dark red diamond-shaped, Crystal system is Monoclinic, space group is P21. Unit cell dimensions is: a = 10.959(2) (?), b = 12.703(2) (?), c = 12.322(2) (?), alpha = 90 deg, beta = 95.279(3) deg, gamma = 90 deg.The crystal 26d is dark brown, The section is a triangle, The results of Single crystal X-diffraction show that, The crystal is composed of two molecules of ligand, four acetate, two Co3+ ions and a Co²⁺ ion. Through a Co²⁺ as the central bridge to connecting the two Co(II) complexes, Unit cell dimensions is a = 13.953(4) (?), b = 13.953(4) (?), c = 27.405(16) (?), alpha = 90 deg, beta = 90 deg, gamma = 120 deg.The 12 kinds of chiral Schiff-base complexes were used to catalyze the 1, 3-dipolar cycloaddition of nitrone 3a and electron-deficient alkenes 3-((E)-2-Buteneacyl)-1, 3-Oxazolidine-2-Ketone 4a, 3-(2-Acryloyl)-1, 3-Oxazolidine-2-Ketone 4b.The results showed that the complexes of schiff bases have an important effect Concentrated expression in the Conversion, diastereo- and enantioselectivi -ty of the 1, 3-dipolar cycloaddition reaction. With 26b as the catalyst, the reaction conversion rate is improved from 70% to 96%. the ratio of endo/exo improved from 68: 32 to 73: 27. the isomer of ee is up to 36%. Ligand structure has a great impact on the regioselectivity: the greater of ligand steric, the better of the reaction regioselectivity. By comparing the ligand substituents on the same location, hydrogen atoms, tert-butyl, 1-methyl-1-phenyl-ethyl, found 1-methyl-1-phenyl-ethyl-substitued catalyst 28c received only 4-substituted isoxazole. Ligand in the presence of naphthalene relative to the benzen, the conjugation system is increased, the regioselectivity increased. the catalytic 29c catalysted the reaction and get the ratio of 4-substituted isoxazole and 5-substituted isoxazole is 5:2. The coordination of metal ions have an impact on enantioselectivity: when the coordination metal ion is cobalt, that showed good enantioselectivity.