Palladium-catalyzed benzylic acetoxylation of toluene

Abstract

The acetoxylation of toluene to benzyl acetate was found to be a purely heterogeneous catalyzed reaction which occurred on supported metallic palladium particles or on suspended palladium particles in the absence of a carrier material. An optimized catalytic system prepared in situ was found to be composed of [Pd(OAc) 2, Sn(octoate) 2, KOAc and Norit PKDA 1–3 charcoal] where the Pd/Sn/K mole ratio was 1/5/10. High toluene conversion (100%) and benzyl acetate selectivity (77%) were obtained after 180 minutes at 100°C. The addition of Sn 2+, K + and charcoal all led to an increased rate of Pd(OAc) 2 decomposition to metallic palladium. The addition of tin(II) lowered the activation energy of the reaction by over 25%. Tin(II) may also serve as a reducing agent in the initial stages of Pd(0) particle formation. The addition of several potential co-catalysts other than tin, some of which possessed accessible redox potentials, had no effect or a negative effect on catalytic activity. The addition of various acetate counter ions had little effect on catalytic activity with the exceptions of K + and Rb +.