Activation of hexamethyldisilazane (HMDS) by TiO 2 nanoparticles for protection of alcohols and phenols: the effect of the catalyst phase on catalytic activity

Anatase TiO 2 nanoparticles (TiO 2 NPs) were synthesized by the sol–gel method using titanium tetra-isopropoxide (TTIP), isopropyl alcohol, and distilled water and then calcined at 400 °C for 3 h. X-ray diffraction and scanning electron microscopy methods, and Fourier transform infrared spectroscopy were used for characterization of the obtained TiO 2 NPs. The obtained anatase TiO 2 NPs were used as heterogeneous catalyst for trimethylsilation of various alcohols or phenols with hexamethyldisilazane (HMDS) in CH 3 CN at room temperature. High to quantitative yields of the products were obtained within short reaction times at room temperature using a very low loading of pure TiO 2 NPs without any post-modification with Bronsted or Lewis acid species such as ClSO 3 H or HClO 4 . The catalyst can be recycled at least three times without significant loss of its activity. The results of this study provide evidence that the pure anatase phase of TiO 2 exhibits higher catalytic activity in terms of catalyst loading and required reaction time compared to a mixture of anatase and rutile phases found in the commercial samples for trimethylsilation of various alcohols or phenols with HMDS.