Structural characterization of copper complexes with chiral 1,2,4-triazine-oxazoline ligands

[摘要] The crystal structure determination of oxazoline-1,2,4-triazine ligand 1f and pyridine-oxazoline ligand 2g was used to analyze their conformational preferences when forming complexes with metals. Proton nuclear magnetic resonance ( 1 H NMR), electrospray ionization mass spectrometry and UV-vis spectroscopy as well as theoretical calculation using molecular mechanics (MM) were adopted to study the composition and geometry of oxazoline-1,2,4-triazine ligands 1 complexes with copper(II) acetate monohydrate. The study revealed that during the complexation, (i) Cu(II) ion is reduced to Cu(I) upon the ligand-to-metal charge transfer transition and (ii) the ligands form with copper(I) 2:1 (L:Cu) complexes of tetrahedral geometry. On the basis of the findings, the catalytic cycle and the active transition state for the enantioselective nitroaldol reaction (the Henry reaction) catalyzed by 1 –Cu are proposed.

[学科分类] 内科医学

[关键词] asymmetric catalysis;chiral 1;2;4-triazine-oxazoline ligands;enantioselective nitroaldol reaction;X-ray diffraction analysis