Hydrogenation of carboxylic acid derivatives catalyzed by 3d transition metals

The reduction of carboxylic acid derivatives to alcohols and amines ranks among the most fundamental transformations in synthetic chemistry, with molecular hydrogen offering an atom-economical and sustainable approach to access these valuable products. While these reactions have traditionally relied on noble metal catalysts, the past decade has witnessed remarkable progress in the development of earth-abundant 3d transition metal alternatives. This review surveys recent advances in homogeneous manganese, iron, and cobalt catalysis for the hydrogenation of esters, amides, and nitriles. Special emphasis is placed on ligand design strategies, ranging from classical pincer architectures featuring metal-ligand cooperation to emerging N-heterocyclic carbene and non-pincer frameworks. For each metal, we discuss the evolution of catalytic systems, their substrate scope, and operational characteristics. Mechanistic aspects are examined in detail, revealing diverse activation modes including outer-sphere and inner-sphere pathways, aromatization-dearomatization processes, and Lewis acid-base cooperativity. The review highlights how increasing electron density at the metal center through ligand modification enhances hydride donor ability and catalytic activity. Recent breakthroughs in polyester depolymerization and challenging substrate classes demonstrate the potential of these base metal catalysts for circular economy applications. This comprehensive overview provides a foundation for future catalyst development and mechanistic investigation in this rapidly evolving field. • Comprehensive review on manganese, iron and cobalt catalysts for hydrogenation of esters, amides and nitriles • Mechanistic analysis reveals diverse pathways beyond classical MLC cooperativity • Recent advances enable polyester depolymerization for circular economy applications