CeO₂-Supported Pd(II)-on-Au Nanoparticle Catalyst for Aerobic Selective α,β-Desaturation of Carbonyl Compounds Applicable to Cyclohexanones

Abstract

Direct selective desaturation of carbonyl compounds to synthesize α,β-unsaturated carbonyl compounds represents an environmentally benign alternative to classical stepwise procedures. In this study, we designed an ideal CeO2-supported Pd(II)-on-Au nanoparticle catalyst (Pd/Au/CeO2) and successfully achieved heterogeneously catalyzed selective desaturation of cyclohexanones to cyclohexenones using O2 in air as the oxidant. Besides cyclohexenones, various bioactive enones can also be synthesized from the corresponding saturated ketones under open air conditions in the presence of Pd/Au/CeO2. Preliminary mechanistic studies revealed that α-C–H bond cleavage in the substrates is the turnover-limiting step of this desaturation reaction.