Oxidative, photo-activated TiO2 nanoparticles in the catalytic acetylation of primary alcohols

A series of TiO2 particles of varying particle sizes from nano to micro scales was treated with three different oxidants (O-2, TBHP, and aqueous H2O2) under irradiation conditions to form activated TiO2 particles bearing surface peroxo Ti(O-2) species. The resultant, heterogeneous catalysts were tested for photo-catalytic acetylation of 2-phenylethanol by acetic anhydride in 8 different solvents. The best scenario involves the use of 32 nm grade of TiO2 nanoparticles and aqueous H2O2 for pre-activation and the use of CH2Cl2 as the reaction solvent. The 2-phenethyl acetate product can be completely formed in 10 h and isolated in essential quantitative yield. It was also found that catalysts derived from TiO2 nanoparticles are superior to those from ZrO2, Y2O3 and WO3 nanoparticles by using the oxidative, photo-activation protocol. The newly developed heterogeneous catalytic system can be smoothly applied to photocatalytic acetylation of several representative primary aliphatic and aromatic alcohols. The intermediacy of Ti-OH or Ti=O surface groups was proposed in the photo-catalytic acetylation conditions.