Abstract: The present invention relates to processes for the reduction by hydrogenation, using molecular H2, of a substrate containing one or two esters, or lactones, functional groups into the corresponding alcohol, or diol, with the process being carried out in the presence of a base and at least one catalyst or pre-catalyst in the form of a ruthenium complex, wherein the ruthenium is coordinated by a diphosphine bidentate ligand (PP ligand) and a diamino bidentate ligand (NN ligand) that includes at least one substituted ?-carbon and one primary amine as one of the coordinating atoms.