Hydrogenation of imines with RU complexes

A process for the reduction by hydrogenation, using molecular H2, of a C5-C20 substrate of formula

• wherein Ra and Rc represent, independently from each other, a hydrogen atom or a C1-C15 hydrocarbon group optionally comprising one to three oxygen atoms and/or one to two nitrogen atoms and/or one sulphur or halogen atom;
• Rb represent a C1-C15 hydrocarbon group optionally comprising one to three oxygen atoms and/or one to two nitrogen atoms and/or one sulphur or halogen atom, a hydrogen atom, a SO2Rb′, a ORb″, or a PORb′2 group, wherein Rb′ represents a C1-C6 alkyl group or a phenyl or tolyl group and Rb″ represents a hydrogen atom, a C1-C6 alkyl group, or a phenyl or tolyl group;
• or Ra and Rc represent, when taken together, a C1-C10 alkanediyl or alkenediyl group;
• provided than at least one Ra, Rb, or Rc is not a hydrogen atom;
• into the corresponding amine, characterized in that said process is carried out in the absence of base and in the presence of at least one catalyst or pre-catalyst of formula absence of base and in the presence of at least one catalyst or pre-catalyst of formula
• [Ru(PP)(P)m(NN)n(Y)2] (1) or
• [Ru(P)2(P)m(NN)n(Y)2] (1′)
• wherein m is 0 when n is 0 or 1 or m is 1 when n is 0;
• PP represents a C5-C50 bidentate ligand wherein the coordinating groups are two phosphino groups;
• each P, simultaneously or independently, represents a C3-C30 monodentate ligand;
• NN represents a C2-C20 bidentate ligand wherein the coordinating atoms are two nitrogen atoms;
• and
• each Y represents, simultaneously or independently, a hydrogen or halogen atom.