Catalytic oxidation of Benzyl Alcohol and its derivatives by Palladium Oxides supported on Ceria Nanorods

The selective oxidation of benzyl alcohol (BnOH) to benzaldehyde (PhCHO) is a crucial organic reaction either for the importance of PhCHO as a fine chemical and for the environmental implications (toxic oxidants, pollutant solvents, etc.).1 Using supported noble metals, the catalytic activity shows dependence not only on the properties of metal particles but also on the nature and characteristics of the support. In particular, the nature of the support can affect the electronic structure of the metal and/or, modify the catalytic reaction by itself.2 Palladium oxide (PdOx) supported on ceria nanorods (CeO2-NR) was used for aerobic selective oxidation of BnOH to PhCHO. The use of oxygen or air as oxidants and the study of the reaction in protic solvent or without solvent (solvent free procedure) have permitted to obtain eco-friendly procedures. In these conditions, benzyl alcohols containing various EDGs were oxidized with good conversions and high selectivity towards the corresponding aldehydes. On the contrary, the presence of EWG on the aromatic ring leads to no reactivity. Some mechanistic hypotheses will be presented as a function of the different oxidation state of the metal, the support and the reaction solvent. In particular, in solvent free catalysis the support ease a partial reduction of the metal producing a Pd(0)/PdOx/CeO2-NR redox couple stable in the reaction condition, more reactive and recyclable. References [1] C.E. Chan-Thaw, A. Savara, A.Villa, Catalysts 2018, 8, 431-452 [2] P. Xin, J. Li, Y. Xiong, X. Wu, et al. Angew. Chem. 2018, 130, 4732–4736.