A Supported Rhodium Hydroxide Catalyst: Preparation, Characterization, and Scope of the Synthesis of Primary Amides from Aldoximes or Aldehydes

A supported rhodium hydroxide catalyst, Rh(OH)x/Al2O3 (x=3), is prepared by the reaction of Al2O3 with RhCl3 in an aqueous medium followed by treatment with NaOH. The RhIII hydroxide species is monomerically (or highly) dispersed on the Al2O3 support. Rh(OH)x/Al2O3 acts as a reusable heterogeneous catalyst in water, rather than in an explosive, hazardous, and carcinogenic organic solvent, for the synthesis of primary amides from aldoximes or aldehydes by an efficient sequential process of dehydration and rehydration. The dehydrative condensation of aldehydes and hydroxylamine is also promoted by the Rh(OH)x/Al2O3 catalyst. All roads lead to amides: A supported rhodium hydroxide, Rh(OH)x/Al2O3, acts as a reusable heterogeneous catalyst for the synthesis of primary amides from aldoximes or aldehydes by an efficient sequential process of dehydration and rehydration.