Recent Advances in Iridium-Catalysed Transfer Hydrogenation Reactions

This review focuses on the contributions of the last 5 years to the application of iridium complexes as homogeneous catalysts in transfer hydrogenation (TH) reactions. The reduction of carbonyls, imines, alkenes and alkynes is considered. The TH of unsaturated alkene-carbonyl substrates and heterocycles is particularly studied. Recent results on the reduction of CO2 are also included. Special attention is paid to THs performed in aqueous medium as well as to the development of TH in biological media. The employ of biomass-derived products as reagents or solvents in TH transformations is also reviewed. Finally, the proposed mechanisms for TH reactions are revised.