A process for the reduction by hydrogenation, using molecular H 2, of a C 5 -C 20 substrate of formula wherein R a and R c represent, independently from each other, a hydrogen atom or a C 1 -C 15 hydrocarbon group optionally comprising one to three oxygen atoms and/or one to two nitrogen atoms and/or one sulphur or halogen atom; R b represent a C 1 -C 15 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 SO 2 R b',a OR b" or a POR b' 2 group wherein R b' represents a C 1 -C 6 alkyl group or a phenyl or tolyl group and R b" represents a hydrogen atom, a C 1 -C 6 alkyl group or a phenyl or tolyl group; or R a and R c represent, when taken together, a C 1 -C 10 alkanediyl or alkenediyl group; provided than at least one R a, R b or R c 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 [Ru m n 2] or [Ru 2 m n 2] wherein m is 0 when n is 0 or 1 or m is 1 when n is 0; PP represents a C 5 -C 50 bidentate ligand wherein the coordinating groups are two phosphino groups; each P, simultaneously or independently, represents a C 3 -C 30 monodentate ligand; NN represents a C 2 -C 20 bidentate ligand wherein the coordinating atoms are two nitrogen atoms; and each Y represents, simultaneously or independently, a hydrogen or halogen atom. wherein R a and R c represent, independently from each other, a hydrogen atom or a C 1 -C 15 hydrocarbon group optionally comprising one to three oxygen atoms and/or one to two nitrogen atoms and/or one sulphur or halogen atom; R b represent a C 1 -C 15 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 SO 2 R b',a OR b" or a POR b' 2 group wherein R b' represents a C 1 -C 6 alkyl group or a phenyl or tolyl group and R b" represents a hydrogen atom, a C 1 -C 6 alkyl group or a phenyl or tolyl group; or R a and R c represent, when taken together, a C 1 -C 10 alkanediyl or alkenediyl group; provided than at least one R a, R b or R c 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 [Ru m n 2] or [Ru 2 m n 2] wherein m is 0 when n is 0 or 1 or m is 1 when n is 0; PP represents a C 5 -C 50 bidentate ligand wherein the coordinating groups are two phosphino groups; each P, simultaneously or independently, represents a C 3 -C 30 monodentate ligand; NN represents a C 2 -C 20 bidentate ligand wherein the coordinating atoms are two nitrogen atoms; and each Y represents, simultaneously or independently, a hydrogen or halogen atom. wherein m is 0 when n is 0 or 1 or m is 1 when n is 0; PP represents a C 5 -C 50 bidentate ligand wherein the coordinating groups are two phosphino groups; each P, simultaneously or independently, represents a C 3 -C 30 monodentate ligand; NN represents a C 2 -C 20 bidentate ligand wherein the coordinating atoms are two nitrogen atoms; and each Y represents, simultaneously or independently, a hydrogen or halogen atom.