342898-24-2Relevant academic research and scientific papers
Chiral bis(oxazoline) and pyridyl alcoholate dioxo-molybdenum(VI) complexes: Synthesis, characterization and catalytic examinations
Kühn, Fritz E.,Santos, Ana M.,Lopes, André D.,Gon?alves, Isabel S.,Rodríguez-Borges, José E.,Pillinger, Martyn,Rom?o, Carlos C.
, p. 207 - 217 (2001)
A group of chiral molybdenum(VI) complexes comprising MoO2Cl2L**, MoO2Cl(THF)L* and MoO2L*2 [L** = chiral bis(oxazoline) and L* = chiral 2′-pyridyl alcoholate] have been prepared in good yields by reaction of the solvent substituted complex MoO2Cl2(THF)2 with one or two equivalents of chiral ligand. Optically active aminoalcohols (L*) were obtained by reaction of the appropriate organolithium compound with (-)-menthone, (+)-8-phenylisomenthone, (-)-8-phenylmenthone, (+)-camphor and (-)-thujone. The molybdenum complexes were characterized by multinuclear NMR (1H, 13C, 17O, 95Mo) spectroscopy, IR spectroscopy and elemental analysis. 95Mo-NMR data reflected the donor capability of the organic ligands, whereas 1H-NMR and IR data were comparatively indifferent to the changes in the Lewis base ligand. The complexes were evaluated as catalysts for the asymmetric epoxidation of trans-β-methylstyrene by tert-butylhydroperoxide. The bis(oxazoline) complexes showed good catalytic activity but had low optical yields. Complexes of the type MoO2Cl(THF)L* (L* = chiral 2′-pyridyl alcoholate) also exhibited high catalytic activity and enantiomeric excesses of up to 23%. The corresponding MoO2L*2 alcoholate complexes were considerably less active with comparable optical yields.
