Effective Heterogeneous MoO_x-Modified CeO₂ Catalyst for Michael Addition of Dimethyl Malonate to 2-Cyclohexen-1-one

Molybdenum oxide-modified cerium oxide (MoO_x−CeO₂) with 1 wt % Mo acted as an effective and reusable heterogeneous catalyst for Michael addition of dimethyl malonate to 2-cyclohexen-1-one, providing high yield of the target product (99 %). The catalyst showed higher activity with high selectivity (>99 %) than simple metal oxides and the other combination of metal oxides and CeO₂. Based on the catalyst characterization and experimental studies, MoO_x species in the MoO_x−CeO₂ catalyst are isolated Mo⁶⁺, and the interface between the isolated MoO_x and CeO₂ is the active site. The activity based on the active site was about 74-fold and 1800-fold higher than that of CeO₂ surface and the typical strong organic base of DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), respectively.