'Div exchanged K10-montmorillonite: characterisation and catalyticproperties in liquid-phase sulfide oxidation

摘要

Titanium-containing K10 has been synthesised and characterised by X-ray diffraction, UV-visible reflectance, solidstate NMR spectroscopy, N2 nitrogen adsorption at 77K and chemical analysis. Two different titanium species haveidentified with a high dispersion in K10. The first is in an isolated penta- and hexa-coordinated state and the secondis in the form of polymerised hexacoordinated species, which contains Ti-O-–Ti bonds. These titanium species werefound to be the catalytic sites that readily interact with oxidant to offer an active and selective catalytic system forthe oxidation of sulfides. This catalytic system was studied in the asymmetric oxidation of methyl phenyl sulfide,using different types of chiral modifier, and gives excellent conversion and sulfoxide selectivity, together with asignificant enantioselectivity in the range of 16-18% ee with (R)-binol.