Mixed oxides titania-silica catalysts (3 wt.% TiO2) were prepared using the sol-gel technique. The catalysts were characterized using adsorption-desorption isotherms of N-2 at 77 K, XRD, SAXS, UV-Vis, FTIR and XPS. They were tested in sulfoxidation of 2-thiomethyl-4,6-dimethyl-pyrimidine and 2-thiobenzyl-4,6-dimethyl-pyrimidine in presence of H2O2. The catalysts were used as such or after modification with L(+)-tartaric or R(-)-alpha-metoxyphenylacetic acid at 373 K. The chemoselectivity was found to be influenced by the solvent, properties of catalyst and nature of the substrate. The enantiomeric excess (e.e.) obtained using modified catalysts was lower than 30%.