Highly efficient homogeneous and heterogenized ruthenium catalysts for transfer hydrogenation of carbonyl compounds†
[Ru(acac)2(CH3CN)2] was synthesized from [Ru(acac)3] by refluxing it with zinc powder in ethanol–acetonitrile mixture. The prepared catalyst was characterized by FT-IR, 1H and 13C NMR techniques. The silica supported catalyst (‘SiO2’–NH2–RuII) was prepared by stirring [Ru(acac)2(CH3CN)2] with ‘SiO2’–NH2 in a 1 : 1 mixture of CH2Cl2–toluene for 3 days at room temperature. It was characterized by FT-IR, SEM, solid state NMR, ICP and BET surface area methods. The transfer hydrogenation reaction of carbonyl compounds was carried out separately using [Ru(acac)2(CH3CN)2] and ‘SiO2’–NH2–RuII as catalysts. The reaction conditions were optimized with different solvents, bases, catalyst amounts and temperatures using acetophenone as a model system. The scope of the reaction was extended to various substituted aryl ketones including heteroaryl ketones.