Catalytic Reductive Transformations of Carboxylic and Carbonic Acid Derivatives Using Molecular Hydrogen

A comprehensive overview on homogeneous catalytic hydrogenation of carboxylic acids and its derivatives as well as carbonic acid derivatives with transition metal-based molecular catalysts is described. Despite the tremendous potential in the hydrogenation of these less electrophilic carbonyl compounds using molecular hydrogen in synthetic organic chemistry, their reduction still relies mostly on the stoichiometric use of metal hydride reagents, such as LiAlH4, NaBH4, and their derivatives. For the past decade, a significant and rapid progress in particularly ester hydrogenation has been achieved by utilization of conceptually new bifunctional molecular catalysts originating from the metal-ligand cooperation effects. The bifunctional-catalyst-promoted hydrogenation using molecular hydrogen is now realized to be a practical tool in synthetic organic chemistry in both academia and industry. The industrial outlook for the present hydrogenation is bright because of its operational simplicity, scope, economic viability, and growing awareness of the need for green chemistry.