Allylic oxidation of α-pinene over supported SeO2-based catalysts

Abstract

SeO2-based samples were tested for the oxidation of α-pinene and of benzil alcohol using ethanol as solvent. Commercial SeO2 was tested both at reflux and at 6 atm. of O2. At conversion level of approximately 40%, the yield of myrtenal was much higher in the latter case (34.4%) than under reflux (18.0%). A palladium-promoted selenium dioxidesupported catalyst (Pd/SeO2/SiO2) was prepared. Characterization results indicated that selenium dioxide (14.4%) strongly interacts with silica support. The introduction of palladium (0.98%) modifies the reducibility of SeO2, originating a selenium species activation towards allylic oxidation. A conversion level of 23% is attained over Pd/SeO2/SiO2 after 15 h of reaction time, using ethanol as solvent at 134°C the main product being myrtenal, obtained with a selectivity of 76%. Pd/SeO2/SiO2 allows to carry out a catalytic allylic oxidation of α-pinene, being the catalyst easy to handle and being possible its recovery and reuse after the reaction in liquid phase.