Hydrogenation of imines using RU complexes

Abstract

The present invention relates to the field of catalytic hydrogenation and to the use of ruthenium complexes in base-free hydrogenation processes for the reduction of imines to the corresponding amines.

Description

[Technical field]

[0001] The present invention relates to the field of catalytic hydrogenation, and more particularly to the base-free hydrogenation of imines to the corresponding amines in the presence of catalytic amounts of ruthenium complexes.

[0002] Background technology The reduction of imines to the corresponding amines is one of the fundamental reactions in organic chemistry and is used in numerous chemical processes. In general, two main types of processes are known to achieve such a transformation. These types of processes are: a) the hydride process using silyl or metal hydride salts, e.g. NaBH4; b) Hydrogenation processes using molecular hydrogen.

[0003] From a practical point of view, hydrogenation processes are more attractive because they can be operated using small amounts of catalyst (typically 10-1000 ppm relative to the substrate) and in the presence of small amounts of solvent or even in the absence of solvent. Furthermore, hydrogenation processes do not require the use of highly reactive and expensive hydrides and do not generate large amounts of aqueous waste.

[0004] One of the essential and defining elements of a hydrogenation process is the catalyst or catalytic system used to activate molecular hydrogen for reduction.

[0005] Catalytic hydrogenation of imines using homogeneous or heterogeneous catalysts has been widely described in the literature, for example in WO 02 / 08169, WO 03 / 097571 or EP 2 623 509, where hydrogenation of imines in the presence of base and ruthenium complexes with diamine and phosphine ligands is disclosed. However, some substrates, such as imines with at least one heteroaromatic ring or even two heteroaromatic rings, are difficult reactions that have only been reported in a few cases. In fact, the presence of additional heteroatoms in the substrate may be detrimental to the reaction as the substrate and the resulting product may chelate to the metal center, causing inhibition of the action of the catalytic system or competition with the hydrogenation of the heteroaromatic ring. In particular, the examples of hydrogenation of thiophene-substituted imines reported in WO 2008125833, WO 2006063178, and Zh. Org. Khim. 1965, 1, 1104-1108, which use the following heterogeneous catalysts, Adams' catalyst, Pd / C, and rhenium heptasulfide, respectively, demonstrate the challenges for this type of substrate.

[0006] The development of useful homogeneous catalysts or catalytic systems for the hydrogenation of imine groups that are effective for a wide range of imine-type substrates continues to represent an important need in chemistry.

[0007] The present invention provides a solution to said problem by carrying out said hydrogenation in the presence of a homogeneous ruthenium catalyst that makes it possible to reduce even the most difficult imine substrates, a method that, to our knowledge, has never been reported before.

[0008] Summary of the Invention It has surprisingly been found that imines containing heterocyclic groups can be readily reduced under hydrogenation conditions using homogeneous catalysts and in the absence of any additives, particularly in the absence of a base.

[0009] Therefore, the first object of the present invention is to provide a method for the preparation of a compound of formula [ka] [In the formula, R a and R c are each independently a hydrogen atom, or a C1-C alkyl group optionally containing 1 to 3 oxygen atoms and / or 1 to 2 nitrogen atoms and / or 1 sulfur or halogen atom. 15 represents a hydrocarbon group, R b is a C1-C alkyl group optionally containing 1 to 3 oxygen atoms and / or 1 to 2 nitrogen atoms and / or 1 sulfur or halogen atom; 15 Hydrocarbon group, hydrogen atom, SO2R b’ Group, OR b’’ Group, or POR b’ 2 groups, where R b’ represents a C1-C6 alkyl group, a phenyl group, or a tolyl group, and R b’’ represents a hydrogen atom, a C1-C6 alkyl group, a phenyl group, or a tolyl group, or R a and R c When used together, C1~C 10 represents an alkanediyl group or an alkenediyl group, provided that at least one R a , R b or R c is not a hydrogen atom] C5~C 20 to the corresponding amine, comprising the steps of: In the absence of a base, and of the formula [ka] [In the formula, when n is 0 or 1, m is 0, and when n is 0, m is 1; PP is C5~C 50 The coordinating groups are two phosphino groups, Each P may be, simultaneously or independently, C3 to C 30 represents a monodentate ligand of the formula NN is C2~C 20 The ligands are two nitrogen atoms, and each Y simultaneously or independently represents a hydrogen atom or a halogen atom. The process is characterized in that it is carried out in the presence of at least one catalyst or pre-catalyst.

[0010] Description of the Invention The present invention provides a method for producing C5-C aryl amines containing imine functional groups by hydrogenating them with the molecule H2. 20 The present invention relates to a process for reducing a substrate to the corresponding amine, characterized in that it is carried out in the presence of at least one catalyst or precatalyst in the form of a ruthenium complex having a bidentate diphosphine ligand or at least two monodentate phosphine ligands.

[0011] The process is capable of reducing even the most difficult thiophene-substituted imines using homogeneous ruthenium catalysis. Moreover, the process is carried out in the absence of acidic or basic additives, making it particularly interesting for sensitive substrates.

[0012] As is well understood by one of ordinary skill in the art, by "bidentate" it is understood that the ligand coordinates to the Ru metal at two atoms (eg, two P).

[0013] Therefore, the first object of the present invention is to provide a method for the preparation of a compound of formula [ka] [In the formula, R a and R c are each independently a hydrogen atom, or a C1-C alkyl group optionally containing 1 to 3 oxygen atoms and / or 1 to 2 nitrogen atoms and / or 1 sulfur or halogen atom. 15 represents a hydrocarbon group, R b is a C1-C alkyl group optionally containing 1 to 3 oxygen atoms and / or 1 to 2 nitrogen atoms and / or 1 sulfur or halogen atom; 15 Hydrocarbon group, hydrogen atom, SO2R b’ Group, OR b’’ Group, or POR b’ 2 groups, where Rb’ represents a C1-C6 alkyl group, a phenyl group, or a tolyl group, and R b’’ represents a hydrogen atom, a C1-C6 alkyl group, a phenyl group, or a tolyl group, or R a and R c When used together, C1~C 10 represents an alkanediyl group or an alkenediyl group, provided that at least one R a , R b or R c is not a hydrogen atom] C5~C 20 to the corresponding amine, comprising the steps of: In the absence of a base, and of the formula [ka] [In the formula, when n is 0 or 1, m is 0, and when n is 0, m is 1; PP is C5~C 50 The coordinating groups are two phosphino groups, Each P may be, simultaneously or independently, C3 to C 30 represents a monodentate ligand of the formula NN is C2~C 20 The ligands are two nitrogen atoms, and each Y simultaneously or independently represents a hydrogen atom or a halogen atom. The process is characterized in that it is carried out in the presence of at least one catalyst or pre-catalyst.

[0014] With regard to "...hydrocarbon groups...", it is understood to mean that the group consists of hydrogen and carbon atoms and may be in the form of an aliphatic hydrocarbon, i.e. a linear or branched, saturated hydrocarbon (e.g. an alkyl group), a linear or branched, unsaturated hydrocarbon (e.g. an alkenyl or alkynyl group), a saturated cyclic hydrocarbon (e.g. a cycloalkyl) or an unsaturated cyclic hydrocarbon (e.g. a cycloalkenyl or cycloalkynyl), or in the form of an aromatic hydrocarbon, i.e. an aryl group, or in the form of a mixture of said types of groups, e.g. a particular group may contain linear alkyl, branched alkenyl (e.g. a branched alkenyl having one or more carbon-carbon double bonds), (poly)cycloalkyl and aryl moieties, unless a specific restriction to only one type is mentioned. Similarly, in all embodiments of the present invention, when it is mentioned that a group may be in the form of more than one type of topology (e.g. linear, cyclic or branched) and / or saturated or unsaturated (e.g. alkyl, aromatic or alkenyl), it is also meant that the group may have any one of the topologies or may contain moieties that are saturated or unsaturated as explained above. Similarly, in all embodiments of the present invention, when a group is in the form of one type of saturated or unsaturated (e.g. alkyl), it is meant that said group may have several moieties that are any type of topology (e.g. linear, cyclic or branched) or have different topologies. In all embodiments of the present invention, when it is mentioned that a hydrocarbon group may optionally contain heteroatoms, such as oxygen, nitrogen or sulfur atoms, at least one hydrogen atom of the hydrocarbon group may be replaced by a heteroatom and / or a carbon atom of the hydrocarbon chain may be replaced / replaced by a heteroatom, i.e. the hydrocarbon may contain functional groups, such as ethers, thiols, amines, esters, amides, as substituents or as part of the chain.

[0015] The process herein, i.e. hydrogenation of the imine of formula (I), provides the corresponding amine (Ia), [ka] [In the formula, R a , R b and R c has the same meaning as defined in formula (I).

[0016] According to any one of the above embodiments of the present invention, the compound of formula (I) may be in the form of any one of its stereoisomers or as a mixture thereof. For reasons of clarity, with regard to the expression "any one of its stereoisomers or a mixture thereof" or similar expressions, the usual meaning understood by a person skilled in the art is meant, i.e. that the compound of formula (I) may be pure or in the form of a mixture of enantiomers or diastereomers.

[0017] According to any one of the above embodiments of the invention, said compound of formula (I) may be in the form of its E or Z isomer, or a mixture thereof, for example the invention includes a composition of matter consisting of one or more compounds of formula (I) having the same chemical structure but differing by the configuration of the imine double bond. In particular, compound (I) may be in the form of a mixture consisting of isomers E and Z, wherein said isomer E represents at least 0.5% of the total mixture, or even at least 50% of the total mixture, or even at least 75% of the total mixture (i.e. mixtures E / Z composed of 75 / 25 and 100 / 0).

[0018] According to any one of the above embodiments of the invention, the compound of formula (I) has the formula (R a )(R c )C(=O) carbonyl compounds with formula R b This can occur in situ by condensation between NH2 and an amine.

[0019] According to any one of the above embodiments of the present invention, R a , R b and R c are each independently a hydrogen atom, a C1-C 10It may represent an alkyl group, an alkenyl group, an alkanedienyl group, an aryl group, a heterocyclic group, a heteroarylalkyl group or an arylalkyl group.

[0020] According to any one of the above embodiments of the present invention, R a , R b and R c are each independently a hydrogen atom, a C1-C6 alkyl group, or a C1-C6 alkoxy group, each of which is optionally substituted with a hydroxyl group, a C1-C6 alkyl group, or a C1-C6 alkoxy group. 10 It may represent an alkyl group, an alkenyl group, an alkanedienyl group, an aryl group, a heterocyclic group, or an arylalkyl group.

[0021] According to any one of the above embodiments of the present invention, R a , R b and R c are each independently a hydrogen atom, a C1-C alkyl group, each of which is optionally substituted by a hydroxyl group, a C1-C6 alkyl group, or a C1-C6 alkoxy group. 10 Straight chain alkyl groups, C2-C 10 Straight chain alkenyl group, C3-C 10 Linear, branched or cyclic alkyl or alkenyl groups, C4-C 10 A linear, branched or cyclic alkadienyl group, a C3-C8 aryl group, a C2-C8 heterocyclic group or a C6-C 12 may represent an arylalkyl group, or R a and R c When used together, C1~C 10 An alkanediyl group or an alkenediyl group, provided that at least one R a , R b or R c is not a hydrogen atom. The expression "linear, branched or cyclic alkyl, alkenyl or alkadienyl group" or similar expressions refer to any of the R groups unless a specific restriction to one type is mentioned. a , R b and R c may be in the form of, for example, a straight chain alkyl group or may be in the form of a mixture of said types of groups, for example a particular Ra It is indicated that may include branched alkenyl moieties, (poly)cyclic alkyl moieties and linear alkyl moieties. Similarly, in all the following embodiments of the present invention, when a group is mentioned as alkenyl or alkadienyl, it means that the group contains one or two carbon-carbon double bonds, conjugated or not conjugated with an imine group, or in the case of alkadienyl, conjugated or not between the two double bonds. Similarly, in all the following embodiments of the present invention, when a group is mentioned as being in the form of more than one type of topology (e.g. linear, cyclic or branched) and / or in the form of unsaturation (e.g. alkyl or alkenyl), it also means that the group may have any one of the topologies or may contain unsaturated moieties, as explained above. Similarly, in all the following embodiments of the present invention, when a group is in the form of one type of unsaturation (e.g. alkyl), it means that the group may have several moieties, either in the form of any type of topology (e.g. linear, cyclic or branched) or with different topologies.

[0022] The term "heterocycle" or similar terms have their usual meaning in the art, i.e., a ring containing at least one heteroatom, such as an oxygen atom, a nitrogen atom, or an ionic atom, such as an aromatic ring.Typical examples of heterocyclic groups include, but are not limited to, groups derived from acridine, β-carboline, chromane, chromene, cinnoline, furan, imidazole, indazole, indole, indoline, indolizine, isobenzofuran, isochromene, isoindole, isoindoline, isoquinoline, isothiazole, isoxazole, naphthyridine, oxadiazole, oxazole, perimidine, phenanthridine, phenanthroline, phenazine, phthalazine, pteridine, purine, pyran, pyrazine, pyrazole, pyridazine, pyridine, pyrimidine, pyrrole, pyrrolidine, quinazoline, quinoline, quinolizine, quinoxaline, tetrazole, thiadiazole, thiazole, thiophene, triazole, or xanthene.

[0023] The term "arylalkyl" has its usual meaning in the art, i.e., a non-cyclic alkyl group in which one hydrogen atom is replaced by an aryl group.

[0024] The term "heteroarylalkyl" has its normal meaning in the art, i.e., a non-cyclic alkyl group in which one hydrogen atom is replaced with a heterocyclic group.

[0025] According to any one of the embodiments of the present invention, the substrate is an imine that provides an amine that is useful as an end product or intermediate in the pharmaceutical, agrochemical, flavor or fragrance industry. Particularly preferred substrates are imines that provide an amine that is useful as an end product or intermediate in the flavor and fragrance industry.

[0026] According to any one of the embodiments of the present invention, the substrate is a C5-C 15 It is a compound.

[0027] According to any one of the embodiments of the present invention, the substrate has the formula [ka] [In the formula, R a and R b has the same meaning as above.

[0028] According to any one of the embodiments of the present invention, R a and R b may each independently represent a C1-C8 straight-chain alkyl group, a C2-C8 straight-chain alkenyl group, a C3-C8 straight-chain, branched or cyclic alkyl or alkenyl group, a C4-C8 straight-chain, branched or cyclic alkadienyl group, or a C3-C6 aryl group, a C2-C6 heterocyclic group, a C6-C8 heteroarylalkyl group or a C6-C8 arylalkyl group, each of which is optionally substituted with a hydroxyl group, a halogen atom, a C1-C3 alkyl group or a C1-C3 alkoxy group. a and R bmay each independently represent a C1-C8 linear alkyl group, a C2-C8 linear alkenyl group, a C3-C8 linear, branched or cyclic alkyl or alkenyl group, a C4-C8 linear, branched or cyclic alkadienyl group, or a C3-C6 aryl group, a C2-C6 heterocyclic group, or a C6-C8 arylalkyl group, each of which is optionally substituted with a hydroxyl group, a C1-C3 alkyl group, or a C1-C3 alkoxy group. a and R b may each independently represent a C3-C8 linear, branched or cyclic alkyl group, or a C3-C6 aryl group, a C2-C6 heterocyclic group, or a C6-C8 arylalkyl group, each of which is optionally substituted with a hydroxyl group, a C1-C3 alkyl group, or a C1-C3 alkoxy group. a and R b may each independently represent a C3-C6 aryl group, a C2-C6 heterocyclic group, or a C6-C8 arylalkyl group, each of which is optionally substituted with a hydroxyl group, a C1-C3 alkyl group, or a C1-C3 alkoxy group. a or R b may each represent a C2-C6 heterocyclic group optionally substituted with a hydroxyl group, a C1-C3 alkyl group or a C1-C3 alkoxy group, and the other may represent a C1-C8 linear alkyl group, a C2-C8 linear alkenyl group, a C3-C8 linear, branched or cyclic alkyl or alkenyl group, a C4-C8 linear, branched or cyclic alkadienyl group, or a C3-C6 aryl group, a C2-C6 heterocyclic group, or a C6-C8 arylalkyl group, each optionally substituted with a hydroxyl group, a C1-C3 alkyl group or a C1-C3 alkoxy group. Even more preferably, R a and R b may each independently represent a C2-C6 heterocyclic group optionally substituted with a hydroxyl group, a C1-C3 alkyl group or a C1-C3 alkoxy group. a and R bare each independently a C2-C6 heterocyclic group containing 1 to 3 heteroatoms selected from a nitrogen atom, an oxygen atom, and a sulfur atom, which are optionally substituted with one or two C1-C3 alkyl groups. a and R b are each independently a C3-C6 heterocyclic group containing 1 to 3 heteroatoms selected from nitrogen, oxygen and sulfur. Even more preferably, R a and R b are each independently a C3-C5 heterocyclic group containing 1 to 3 heteroatoms selected from nitrogen, oxygen and sulfur. Even more preferably, R a and R b are each independently a C3 to C5 heterocyclic group containing 1 to 3 heteroatoms selected from nitrogen and sulfur.

[0029] According to any one of the preceding embodiments, R b represents a C3-C6 aryl group, a C6-C8 arylalkyl group, or a C3-C5 heterocyclic group containing one or two nitrogen atoms, one oxygen atom, and one sulfur atom, or one nitrogen atom and one oxygen atom. b represents a phenyl group or a benzyl group, or a C3-C5 heterocyclic group containing one or two nitrogen atoms, one nitrogen atom and one sulfur atom, or one nitrogen atom and one oxygen atom. b is a pyrazolyl group.

[0030] According to any one of the preceding embodiments, R a represents a phenyl group or a C3-C5 heterocyclic group containing one or two sulfur atoms, one oxygen atom, one nitrogen atom, or one nitrogen atom and one sulfur atom. a is a thiophenyl group.

[0031] Non-limiting examples of substrates of formula (I) include N-phenyl-1-(thiophen-2-yl)methanimine, N-(1H-pyrazol-5-yl)-1-(thiophen-2-yl)methanimine, N-(4-methoxyphenethyl)-1-(thiophen-2-yl)methanimine, N-benzyl-1-(thiophen-2-yl)methanimine, N-benzyl-1-(p-tolyl)methanimine, N-benzyl-1-(2-methoxyphenyl)methanimine or N-(1H-pyrazol-5-yl)-1-(p-tolyl)methanimine, N-phenyl-1-(thiophen-2-yl)methanimine, N-benzyl -1-(thiophen-2-yl)methanimine, N-phenyl-1-(p-tolyl)methanimine, N-(4-methoxyphenyl)-1-phenylmethanimine, N-cyclohexyl-1-(p-tolyl)methanimine, N-(4-fluorophenyl)-1-(p-tolyl)methanimine, N-(4-methoxyphenyl)-1-(p-tolyl)methanimine, N-(2,4-dimethylphenyl)-1-(p-tolyl)methanimine, N-(pyridin-4-ylmethyl)-1-(p-tolyl)methanimine, 1-(thiophen-2-yl)-N-(thiophen-2-ylmethyl)methanimine.

[0032] In the present invention, the presence of acidic or basic additives is avoided. This is an advantage, since it can significantly increase the yield of amine production from acid- and / or base-sensitive imines. Thus, according to any one of the embodiments of the present invention, the substrate is an acid- and / or base-sensitive compound.

[0033] According to any embodiment of the present invention, the process of the present invention is carried out in the absence of a base.

[0034] According to any one of the embodiments of the present invention, the ruthenium complex has the general formula [ka] [In the formula, when n is 0 or 1, m is 0, and when n is 0, m is 1; PP is a C5-C phosphino group with two coordinating groups. 50 represents a bidentate ligand, P is C3~C 30 represents a monodentate ligand, NN is a C2-C amine with two amino groups as the coordinating groups. 20 represents a bidentate ligand, and Each Y represents, simultaneously or independently, a hydrogen atom or a halogen atom. It may be.

[0035] According to any one of the embodiments of the present invention, m is 0 and n is 0 or 1. Preferably, m is 0 and n is 1.

[0036] According to any one of the embodiments of the present invention, in formula (1), each Y may simultaneously or independently represent a hydrogen atom, a chlorine atom, a bromine atom, or an iodine atom.Preferably, each Y may simultaneously or independently represent a hydrogen atom or a chlorine atom.Even more preferably, each Y may represent a chlorine atom.

[0037] In any one of the embodiments of the present invention, P has the formula PR d 3, wherein R d is C1~C 12 R may represent a group, for example an optionally substituted linear, branched or cyclic alkyl, alkoxy or aryloxy group, a substituted or unsubstituted phenyl, diphenyl, naphthyl or dinaphthyl group. d may represent a substituted or unsubstituted phenyl, diphenyl, naphthyl or dinaphthyl group. Possible substituents are the various groups R 1 ~R 12 is described below. Preferably, P is triphenylphosphine.

[0038] According to any one of the embodiments of the present invention, the bidentate N-N ligand has the formula [ka] In the formula, a and a' simultaneously or independently represent 0 or 1 (when a' is 0, the nitrogen atom is part of an aromatic heterocycle), R 1 separately, simultaneously or independently, represent a hydrogen atom, an optionally substituted C1-C6 linear, branched or cyclic alkyl group, or an optionally substituted phenyl group or benzyl group, and two R 1 together contain 3 to 7 atoms, and 1 may form a saturated heterocyclic ring containing the atom to which is attached, said heterocyclic ring being optionally substituted; R 2 and R 3 are each independently, simultaneously or separately, a hydrogen atom, an optionally substituted C1-C6 straight or branched chain alkyl group, or an optionally substituted C6-C 10 R represents an aromatic group. 1 and adjacent R 2 together contain 5 to 8 atoms, and the group R 1 and R 2 may form a saturated or unsaturated heterocyclic ring containing the atom to which R is attached, and optionally containing an additional nitrogen atom or oxygen atom; 2 R 2 may form a saturated or unsaturated ring containing the carbon atom to which the group is attached, said ring optionally containing one additional nitrogen atom and / or oxygen atom, and Q is the formula [ka] [In the formula, p is 1 or 2, and R 5 and R 6 are simultaneously or independently a hydrogen atom, an optionally substituted C1-C6 linear, branched or cyclic alkyl group, or an optionally substituted C6-C 10 It represents an aromatic group and has two different R 6 Group and / or R 5 The radicals, taken together, form R 6 Group and / or R 5The compound is a compound of the formula: which represents a group having the formula:

[0039] According to one embodiment, "aromatic group or ring" means a phenyl group or a naphthyl group.

[0040] As described above, in the ligand (B), the atoms that may be coordinated to the Ru atom are R 1 The R 1 , R 2 , R 3 , R 5 , R 6 Or, if any other group contains a heteroatom, such as N or O, it is also understood that the heteroatom is not coordinated.

[0041] R 1 , R 2 , R 3 , R 5 , R 6 The possible optional substituents of are 1, 2, 3 or 4 groups selected from among i) halogen (especially when said substituents are on an aromatic moiety), ii) C1-C6 alkoxy, alkyl, alkenyl, or iii) benzyl groups, or phenyl groups, fused or unfused, optionally substituted with 1, 2 or 3 halogen, C1-C8 alkyl, alkoxy, amino, nitro, ester, sulfonate, halohydrocarbon or perhalohydrocarbon groups.

[0042] For reasons of clarity, and as stated above, in any one of the embodiments of the present invention, when two groups of formula (B) together form a ring, said ring may be a monocyclic or bicyclic group.

[0043] According to any one of the embodiments of the invention of the bidentate N-N ligand, each R 1 simultaneously or independently represent a hydrogen atom or a C1-C4 linear or branched alkyl group.1 simultaneously or independently represent a hydrogen atom, a methyl group, or an ethyl group.

[0044] According to any one of the embodiments of the present invention of the bidentate NN ligand, at least one R 1 represents a hydrogen atom, or further represents at least two R 1 represents a hydrogen atom, or further four R 1 indicates a hydrogen atom.

[0045] According to any one of the embodiments of the invention of the bidentate N-N ligand, R 2 and R 3 separately, simultaneously or independently, represent a hydrogen atom, an optionally substituted C1-C4 linear or branched alkyl group, or an optionally substituted phenyl group; R 1 and adjacent R 2 together contain 5 or 6 atoms, and R 1 and R 2 may form a saturated or unsaturated heterocyclic ring containing the atom to which R is attached and optionally containing one additional oxygen atom, 2 together contain 5 or 6 atoms, and R 2 Group or R 3 The groups may form a saturated or unsaturated ring containing the atom to which they are attached, which ring is optionally substituted and optionally contains one additional oxygen atom.

[0046] According to any one of the embodiments of the invention of the bidentate N-N ligand, R 2 and R 3 R 1 and adjacent R 2 together contain 6 atoms and R 1 and R 2 may form a saturated or aromatic heterocyclic ring containing the atom to which R is attached, 2 together contain 5 or 6 atoms and two R 2The groups may form a saturated or unsaturated ring with the atom to which they are attached.

[0047] According to any one of the embodiments of the invention of the bidentate NN ligand, Q has the formula [ka] [In the formula, p is 1 or 2, and R 5 and R 6 represent simultaneously or independently a hydrogen atom, a C1-C4 linear or branched alkyl group, or an optionally substituted phenyl group.

[0048] According to any one of the embodiments of the invention of the bidentate N-N ligand, R 5 and R 6 simultaneously or independently represent a hydrogen atom or a C1 to C4 linear alkyl group.

[0049] According to a particular embodiment of the invention, Q is a group of formula (i) in which p is 1 or 2 and R 5 is a hydrogen atom, and R 6 is defined above.

[0050] According to any one of the embodiments of the invention of the bidentate NN ligand, the ligand NN has the formula [ka] [In the formula, a represents 0 or 1, Each R 1 represent simultaneously or independently a hydrogen atom, a C1-C4 linear or branched alkyl group, or an optionally substituted benzyl group, R 2 and R 3 R 1 and adjacent R 2 together contain 6 atoms and R1 and R 2 and may form an optionally substituted saturated heterocycle, 2 together have 5 to 6 atoms, R 2 may form a saturated ring containing the carbon atom to which the group is attached; and Q is the formula [ka] [In the formula, p is 1 or 2, and R 5 and R 6 represents a group consisting of, simultaneously or independently, a hydrogen atom, a C1-C4 linear or branched alkyl group, or an optionally substituted phenyl group.

[0051] According to a particular aspect of said embodiment, said ligand NN of formula (B') is: Each R 1 simultaneously or independently represent a hydrogen atom or a C1-C4 alkyl group, R 2 and R 3 are taken separately, simultaneously or independently, a hydrogen atom, have 5 to 6 atoms, and R 2 may form a saturated ring containing the carbon atom attached to the group, Q is the formula [ka] [In the formula, p is 1 or 2, and R 5 and R 6 represent, simultaneously or independently, a hydrogen atom or a C1-C4 linear alkyl group.

[0052] According to any one of the embodiments of the present invention, the ligand NN has the formula [ka] [In the formula, R 1 represents a hydrogen atom or a C1-C4 linear or branched alkyl group, R 2 and R 3 represent, separately, simultaneously or independently, a hydrogen atom or a C1-C4 linear or branched alkyl group; HET represents a 2-pyridinyl group optionally substituted by one, two or three C1-C4 linear or branched alkyl groups or by a benzyl group, or a fused or non-fused phenyl or indanyl group, which is optionally substituted by one, two or three halogen, C1-C4 alkyl group, alkoxy group, amino group, nitro group, ester group or sulfonate group, e.g., 2-pyridyl, 2-quinolinyl or methyl-2-pyridinyl.

[0053] According to a particular embodiment of formula (B″), R 1 indicates a hydrogen atom.

[0054] According to a particular embodiment of formula (B″), R 2 and R 3 taken separately, together or independently, represent a hydrogen atom.

[0055] According to a particular embodiment of formula (B″), HET represents a 2-pyridinyl group optionally substituted with one, two or three C1-C4 linear or branched alkyl groups, or a fused or non-fused phenyl group, such as 2-pyridyl, 2-quinolinyl or methyl-2-pyridinyl.

[0056] According to any one of the embodiments of the invention of the bidentate NN ligand, R of formula (B), (B') or (B'') 1 , R 2 , R 3 , R 5 or R 6 The possible substituents are one or two i) halogens, ii) C1-C5 alkyl or alkoxy groups, or iii) a fused or non-fused phenyl group, which is optionally substituted with one, two or three halogens, C1-C4 alkyl or alkoxy groups.

[0057] Non-limiting examples of N-N ligands include those of the following formula (A): [ka] wherein said compounds are, where appropriate, in optically active or racemic form.

[0058] Preferably, the ligand (NN) may be selected from the group consisting of ethane-1,2-diamine, N,N-dimethylethane-1,2-diamine, N,N,N',N'-tetramethylethane-1,2-diamine, 1,2-diphenylethane-1,2-diamine, (1R,2R)-1,2-diphenylethane-1,2-diamine, cyclohexane-1,2-diamine, (1R,2R)-cyclohexane-1,2-diamine, propane-1,3-diamine and pyridin-2-ylmethanamine. Even more preferably, the ligand (NN) may be selected from the group consisting of ethane-1,2-diamine and pyridin-2-ylmethanamine.

[0059] According to any one of the embodiments of the present invention, the bidentate ligand (PP) has the formula [ka] [In the formula, R 11 and R 12 may be, in separate cases, simultaneously or independently, an optionally substituted C1-C6 linear alkyl group, an optionally substituted C3-C6 branched or cyclic alkyl group, or an optionally substituted C6-C 10 represents an aromatic group, and Q' is - expression [ka] [In the formula, p' is 1, 2, 3 or 4, and R 5’ and R 6’ are simultaneously or independently a hydrogen atom, an optionally substituted C1-C6 linear or branched alkyl group, or an optionally substituted C6-C 10 Represents an aromatic group and has two separate R6’ and / or R 5’ Together, R 6’ and / or R 5’ and optionally forming an optionally substituted C3-C8 saturated or unsaturated ring containing an atom bonded to - each optionally substituted, C 10 ~C 16 Metallocene diyl, 2,2'-diphenyl, 1,1'-binaphthalene-2,2'-diyl, benzenediyl, naphthalenediyl, 2,3-bicyclo[2:2:1]hept-5-enediyl, 4,6-phenoxazinediyl, 4,5-(9,9-dimethyl)-xanthenediyl, 4,6-10H-phenoxazinediyl, 2,2'-(oxybis(2,1-phenylene)) or bis(phen-2-yl) ether group The compound may be of the formula:

[0060] As mentioned above, according to a particular embodiment of the invention, with respect to "aromatic group or ring" for (PP) we also mean phenyl or naphthyl derivatives.

[0061] As described above, in the ligand (C), the atom that may be coordinated to the Ru atom is PR 11 R 12 The P atom of the R 5’ , R 6’ , R 11 , R 12 It is also understood that when Q', or any other group contains a heteroatom, such as N or O, the heteroatom is not coordinated.

[0062] R 5’ , R 6’ , R 11 and R 12 The possible optional substituents of are 1 to 5 halogens (especially when said substituents are on an aromatic moiety) or 1, 2 or 3 i) C1 to C6 linear or branched alkyl groups, alkoxy groups, halohydrocarbon groups, perhalohydrocarbon groups, or amino groups; ii) COORh [In the formula, R h is a C1-C6 straight, branched or cyclic alkyl group, iii) a NO2 group, or iv) a benzyl group, or a fused or unfused phenyl group, which is optionally substituted with one, two or three halogens, a C1-C8 alkyl group, an alkoxy group, an amino group, a nitro group, an ester group, a sulfonate group, a halohydrocarbon or a perhalohydrocarbon group. By "halohydrocarbon or perhalohydrocarbon" we mean groups such as CF3 or CClH2, for example.

[0063] For reasons of clarity, and as stated above, in any one of the embodiments of the present invention, when two groups of formula (C) together form a ring, said ring may be a monocyclic or bicyclic group.

[0064] According to any one of the embodiments of the present invention of the bidentate PP ligand, R 11 and R 12 are, separately, simultaneously or independently, a C3 to C6 branched or cyclic alkyl group, or a C6 to C 10 It denotes an aromatic group, or preferably a phenyl group, which may be optionally substituted.

[0065] According to any one of the embodiments of the present invention of the bidentate PP ligand, R 11 and R 12 each simultaneously or independently represents a C3-C6 branched or cyclic alkyl group, or an optionally substituted phenyl group. 11 and R 12 each simultaneously or independently represents an isopropyl, cyclohexyl or phenyl group.

[0066] According to any one of the embodiments of the present invention of the bidentate PP ligand, Q′ is - expression [ka] [In the formula, p' is 1, 2, 3 or 4, and R 5’ and R6’ are simultaneously or independently a hydrogen atom, a C1-C4 linear or branched alkyl group, or a C6-C 10 represents an aromatic group, or preferably an optionally substituted phenyl group, and two separate R 6’ and / or R 5’ The radicals, taken together, form R 6’ and / or R 5’ a group of the formula: - each optionally substituted, C 10 ~C 16 Metallocene diyl, 2,2'-diphenyl, benzenediyl, naphthalenediyl, 1,1'-binaphthalene-2,2'-diyl, 2,3-bicyclo[2:2:1]hept-5-enediyl, 4,6-phenoxazinediyl, 4,5-(9,9-dimethyl)-xanthenediyl, 4,6-10H-phenoxazinediyl, 2,2'-(oxybis(2,1-phenylene)) or bis(phen-2-yl) ether group Shows.

[0067] According to any one of the embodiments of the invention of the bidentate PP ligand, Q' is a linear C1-C4 alkanediyl group, 1,2- or 1,1'-C 10 ~C 12 Metallocene diyl, 2,2'-diphenyl, 1,2-benzenediyl, 1,1'-binaphthalene-2,2'-diyl, or 1,8- or 1,2-naphthalenediyl, 4,6-10H-phenoxazinediyl, or 2,2'-(oxybis(2,1-phenylene)) group. Preferably, Q' is a linear C1-C4 alkanediyl group, 1,2- or 1,1'-C 10 ~C 12 This represents a metallocene diyl group.

[0068] According to a particular embodiment of the invention, the PP ligand is a compound of formula (C), in which R 11 and R 12 represents, simultaneously or independently, an optionally substituted C3-C6 branched or cyclic alkyl group or a phenyl group, Q' is an optionally substituted C1-C4 alkanediyl group, C 10 ~C 12 It represents a ferrocenediyl, 2,2'-diphenyl, 1,1'-binaphthalene-2,2'-diyl, 1,2-benzenediyl or naphthalenediyl group.

[0069] According to any one of the embodiments of the present invention of the bidentate PP ligand, the ligand comprises Q′, R 11 and R 12 One, two or three of the groups are saturated groups (i.e. alkyl or alkanediyl groups). In particular, Q′ represents an optionally substituted C1-C4 alkanediyl group, and / or R 11 and R 12 represents a branched or cyclic alkyl group.

[0070] R 11 and R 12 Possible substituents for are R 1 ~R 6 The possible substituents for Q' are as described above for Q.

[0071] A non-limiting example of a PP ligand is the following formula (B): [ka] [ka] where the compound is in optically active or racemic form, as appropriate, and Ph represents a phenyl group, Cy represents a C5-C6 cycloalkyl group, and i-Pr represents an isopropyl group. It is also understood that in said diphosphines, the Cy group may be replaced by a Ph group, or vice versa.

[0072] Preferred ligands (PP) are bis(dicyclohexylphosphanyl)methane, 1,2-bis(dicyclohexylphosphanyl)ethane, 1,2-bis(diphenylphosphanyl)ethane, 1,2-bis(diphenylphosphanyl)ethane, 1,3-bis(diisopropylphosphanyl)propane, 1,3-bis(dicyclohexylphosphanyl)propane, 1,3-bis(diphenylphosphanyl)propane, (2,3-butane-2,3-diyl)bisdiphenylphosphane, 1,4-bis(diphenylphosphanyl)butane, and 4,6-bis(diphenylphosphanyl)-10H-phenoxazine. Preferably, the ligand (PP) may be 1,2-bis(diphenylphosphanyl)ethane, 1,3-bis(diisopropylphosphanyl)propane, 1,3-bis(dicyclohexylphosphanyl)propane, 1,3-bis(diphenylphosphanyl)propane, (2,3-butane-2,3-diyl)bisdiphenylphosphane, 1,4-bis(diphenylphosphanyl)butane, (oxybis(2,1-phenylene))bis(diphenylphosphane), 4,6-bis(diphenylphosphanyl)-10H-phenoxazine or 1,1′-bis(diphenylphosphanyl)ferrocene. Preferably, the ligand (PP) may be 1,2-bis(diphenylphosphanyl)ethane, 1,3-bis(dicyclohexylphosphanyl)propane, 1,3-bis(diphenylphosphanyl)propane, (2,3-butane-2,3-diyl)bisdiphenylphosphane, (oxybis(2,1-phenylene))bis(diphenylphosphane), or 4,6-bis(diphenylphosphanyl)-10H-phenoxazine. Even more preferably, the ligand (PP) may be 1,2-bis(diphenylphosphanyl)ethane.

[0073] Said ligands are obtained by applying standard common methods well known in the art and by those skilled in the art. Many of said ligands NN or PP are even commercially available.

[0074] Complexes of formula (1) are generally prepared and isolated prior to their use in processes starting from [Ru(Cl)2(PPh3)3] or [(arene)RuCl2]2, as reported in the literature (see Lindner, E. & al. J. Organometallics Chemistry 2003, 665, 176-185 and Lemmon, IC Acc. Chem. Res. 2007, 40, 1291-1299).

[0075] As stated above, the process of the present invention consists in the hydrogenation of a substrate using a ruthenium complex in the absence of acid or base. A typical method involves mixing the substrate with a ruthenium complex, and optionally a solvent, and treating such mixture with molecular hydrogen at a selected pressure and temperature.

[0076] The complexes of the invention, which are essential parameters of the process, can be added to the reaction medium in a wide range of concentrations. As non-limiting examples, concentration values ​​of the complexes can be mentioned ranging from 1 ppm to 10000 ppm relative to the amount of substrate. Preferably, the concentration of said complexes is between 10 and 5000 ppm. Even more preferably, the concentration of said complexes is between 100 ppm and 2500 ppm. It goes without saying that the optimum concentration of the complex depends, as known to the skilled person, on the nature of the latter, on the nature and quality of the substrate, on the nature of the solvent used, if any, on the reaction temperature and on the pressure of H2 used during the process, as well as on the desired reaction time.

[0077] The hydrogenation may be carried out in the presence or absence of a solvent. Any solvent currently used in hydrogenation reactions may be used for the purposes of the present invention, where a solvent is required or used for practical reasons. Non-limiting examples include C6-C 10Aromatic solvents, such as toluene or xylene; C5-C 12 Hydrocarbon solvents, such as hexane or cyclohexane; C4-C8 ethers, such as tetrahydrofuran or MTBE; C4-C 10 Examples of suitable solvents include esters, such as ethyl acetate; C1-C2 chlorinated hydrocarbons, such as dichloromethane; C1-C6 primary or secondary alcohols, such as methanol, isopropanol or ethanol; C2-C6 polar solvents, such as acetone; or mixtures thereof. In particular, the solvent may be a protic solvent, such as methanol, isopropanol or ethanol. The choice of solvent is a function of the nature of the complex and the substrate, and the skilled person is well able to choose the most convenient solvent in each case to optimize the hydrogenation reaction.

[0078] In the hydrogenation process of the present invention, the reaction is 5 Pa to 80 x 10 5 The reaction may be carried out at H2 pressures between 1 and 100 bar or more if desired. Furthermore, the skilled person can adjust the pressure as a function of the amount of catalyst and the dilution of the substrate in the solvent. For example, 5 to 50 x 10 5 Typical pressures range from 5 to 50 bar.

[0079] The temperatures at which the hydrogenation can be carried out range from 0° C. to 200° C., more preferably from 50° C. to 150° C. Of course, the person skilled in the art can also select the preferred temperature as a function of the melting and boiling points of the starting and final products, as well as the desired time of the reaction or conversion.

[0080] Working Example The invention is further described in detail by the following examples, in which temperatures are given in degrees Celsius and abbreviations have their usual meaning in the art.

[0081] All procedures described below were carried out under an inert atmosphere unless otherwise noted. Hydrogenation reactions were carried out in a stainless steel autoclave. H2 gas (99.99990%) was used neat. NMR spectra were recorded on a Bruker AM-400 (400.1 MHz) unless otherwise noted. 1 H, 100.6MHz 13 C{ 1 H}, and 161.9MHz 31 P) spectrometer and were typically measured in CD2Cl2 at 300 K. Chemical shifts are listed in ppm.

[0082] Example 1 Catalytic hydrogenation of imines using the complex [Ru(Cl)2(PP)(N1)]: General procedure for the catalytic hydrogenation of (E)-N-phenyl-1-(thiophen-2-yl)methanimine as substrate: Under argon, a 75 ml stainless steel autoclave equipped with a magnetic stir bar was successively charged with [Ru(Cl)2(L1)(N1) (14.4 mg, 0.023 mmol, 0.2 mol%), imine (1.8956 g, 10.02 mmol) and MeOH (10 ml). The autoclave was sealed, purged with hydrogen (5 x 20 bar) and placed under hydrogen (50 bar). The autoclave was then heated at 100 °C and the reaction mixture was stirred. After 24 h, the autoclave was cooled to RT and vented. An aliquot (0.1 ml) was then taken, diluted with MTBE (1 ml) and analyzed by GC (Chirasil Dex CB).

[0083] Results for the various diphosphines in Table 3 are shown in Table 1.

[0084] [Table 1] a) The diphosphines used were those shown in Table 3. The diamines used were those shown in Table 4. b) Molar ratio of complex to substrate in ppm. c) Conversion calculated according to the amount of remaining starting material determined by GC (Chirasil Dex CB). d) Amount of desired amine determined by GC (Chirasil Dex CB).

[0085] Example 2 Catalytic hydrogenation of imines using the complex [Ru(Cl)2(PP)(N2)]: General procedure for the catalytic hydrogenation of (E)-N-phenyl-1-(thiophen-2-yl)methanimine as substrate: Under argon, a 75 ml stainless steel autoclave equipped with a magnetic stir bar was successively charged with [Ru(Cl)2(L1)(N2) (19.0 mg, 0.028 mmol, 0.2 mol%), imine (1.8756 g, 10.02 mmol) and MeOH (10 ml). The autoclave was sealed, purged with hydrogen (5 x 20 bar) and placed under hydrogen (50 bar). The autoclave was heated at 100 °C and the reaction mixture was stirred. After 24 h, the autoclave was cooled to RT and vented. An aliquot (0.1 ml) was then taken, diluted with MTBE (1 ml) and analyzed by GC (Chirasil Dex CB).

[0086] Results for the various diphosphines in Table 3 are shown in Table 2.

[0087] [Table 2] a) The diphosphines used were those shown in Table 3. The diamines used were those shown in Table 4. b) Molar ratio of complex to substrate in ppm. c) Conversion calculated according to the amount of remaining starting material determined by GC (Chirasil Dex CB). d) Amount of desired amine determined by GC (Chirasil Dex CB).

[0088] [Table 3]

[0089] [Table 4]

[0090] Example 3 Catalytic hydrogenation of imines using the complex [Ru(Cl)2(PP)(PPh3)]: General procedure for the catalytic hydrogenation of (E)-N-phenyl-1-(thiophen-2-yl)methanimine as substrate: Under argon, a 75 ml stainless steel autoclave equipped with a magnetic stir bar was successively charged with [Ru(Cl)2(L3)(PPh3) (19.7 mg, 0.020 mmol, 0.2 mol%), imine (1.8868 g, 10.12 mmol) and MeOH (10 ml). The autoclave was sealed, purged with hydrogen (5 x 20 bar) and placed under hydrogen (50 bar). The autoclave was heated at 100 °C and the reaction mixture was stirred. After 24 h, the autoclave was cooled to RT and vented. An aliquot (0.1 ml) was then taken, diluted with MTBE (1 ml) and analyzed by GC (Chirasil Dex CB).

[0091] Results for the various diphosphines in Table 3 are shown in Table 5.

[0092] [Table 5] a) The diphosphines used were those listed in Table 3. b) Molar ratio of complex to substrate in ppm. c) Conversion calculated according to the amount of remaining starting material determined by GC (Chirasil Dex CB). d) Amount of desired amine determined by GC (Chirasil Dex CB).

Claims

1. Molecule H ２ Using the formula 【Chemistry 1】 [In the formula, R ａ and R ｃ are each independently a hydrogen atom or a C group optionally containing 1 to 3 oxygen atoms and / or 1 to 2 nitrogen atoms and / or 1 sulfur atom or a halogen atom. １ ~C １５ represents a hydrocarbon group, R ｂ is a C group optionally containing 1 to 3 oxygen atoms and / or 1 to 2 nitrogen atoms and / or 1 sulfur or halogen atom １ ~C １５ Hydrocarbon group, hydrogen atom, SO ２ R ｂ’ Group, OR ｂ’’ group, or POR ｂ’ ２ represents a group, where R ｂ’ is C １ ~C ６ represents an alkyl group, a phenyl group, or a tolyl group, and R ｂ’’ is a hydrogen atom, C １ ~C ６ represents an alkyl group, a phenyl group, or a tolyl group, or R ａ and R ｃ When they are together, C １ ~C １０ represents an alkanediyl group or an alkenediyl group, provided that at least one R ａ , R ｂ Or R ｃ is not a hydrogen atom] ５ ~C ２０ to the corresponding amine, comprising the steps of: In the absence of a base, and of the formula 【Chemistry 2】 [In the formula, when n is 1, m is 0, and when n is 0, m is 1; PP is bis(dicyclohexylphosphanyl)methane, 1,2-bis(dicyclohexylphosphanyl)ethane, 1,2-bis(diphenylphosphanyl)ethane, 1,3-bis(diisopropylphosphanyl)propane, 1,3-bis(dicyclohexylphosphanyl)propane, 1,3-bis(diphenylphosphanyl)propane, (2,3-butane-2,3-diyl)bisdiphenylphosphane, 1,4-bis(diphenylphosphanyl)butane, 1,1'-bis(diphenylphosphanyl)methane, 1,2-bis(diphenylphosphanyl)ethane, 1,3-bis(diisopropylphosphanyl)propane, 1,3-bis(dicyclohexylphosphanyl)propane, 1,3-bis(diphenylphosphanyl)propane, (2,3-butane-2,3-diyl)bisdiphenylphosphane, 1,4-bis(diphenylphosphanyl)butane, 1,1' ... bis(dicyclohexylphosphanyl)ferrocene, 1,1'-bis(diisopropylphosphanyl)ferrocene, 1,1'-bis(dicyclohexylphosphanyl)ferrocene, 2,2'-bis(diphenylphosphanyl)-1,1'-biphenyl, 2,2'-bis(dicyclohexylphosphanyl)-1,1'-biphenyl, (oxybis(2,1-phenylene))bis(diphenylphosphane) and 4,6-bis(diphenylphosphanyl)-10H-phenoxazine; each P simultaneously or independently represents triphenylphosphine; N is selected from the group consisting of ethane-1,2-diamine, N,N-dimethylethane-1,2-diamine, N,N,N',N'-tetramethylethane-1,2-diamine, 1,2-diphenylethane-1,2-diamine, (1R,2R)-1,2-diphenylethane-1,2-diamine, cyclohexane-1,2-diamine, (1R,2R)-cyclohexane-1,2-diamine, propane-1,3-diamine and pyridin-2-ylmethanamine; and Each Y simultaneously or independently represents a hydrogen atom or a halogen atom. The process is characterized in that it is carried out in the presence of at least one catalyst or pre-catalyst of

2. R ａ , R ｂ and R ｃ are each independently a hydrogen atom, optionally a hydroxyl group, C １ ~C ６ Alkyl group or C １ ~C ６ C substituted with an alkoxy group １ ~C １０ Straight chain alkyl group, C ２ ~C １０ Straight chain alkenyl group, C ３ ~C １０ Linear, branched or cyclic alkyl or alkenyl groups, C ４ ~C １０ A linear, branched or cyclic alkadienyl group, C ３ ~C ８ Aryl group, C ２ ~C ８ Heterocyclic group or C ６ ~C １２ represents an arylalkyl group, or R ａ and R ｃ When they are together, C １ ~C １０ An alkanediyl group or an alkenediyl group, provided that at least one R ａ , R ｂ Or R ｃ The method of claim 1 , wherein is not a hydrogen atom.

3. R ｃ The method according to claim 1 or 2, wherein is a hydrogen atom.

4. R ａ Or R ｂ is a hydroxyl group, C １ ~C ３ Alkyl group or C １ ~C ３ C optionally substituted with an alkoxy group ２ ~C ６ A heterocyclic group, and the other is a hydroxyl group, C １ ~C ３ Alkyl group or C １ ~C ３ C optionally substituted with an alkoxy group １ ~C ８ Straight chain alkyl group, C ２ ~C ８ Straight chain alkenyl group, C ３ ~C ８ A linear, branched or cyclic alkyl or alkenyl group, C ４ ~C ８ A linear, branched or cyclic alkadienyl group, C ３ ~C ６ Aryl group, C ２ ~C ６ Heterocyclic group or C ６ ~C ８ 4. The method of claim 1, wherein the arylalkyl group is an arylalkyl group.

5. R ａ and R ｂ C, each independently containing 1 to 3 heteroatoms selected from nitrogen, oxygen and sulfur ３－６ 5. The method of claim 1, wherein the heterocyclic group is a heterocyclic group.

6. The catalyst or pre-catalyst has the formula 【Chemistry 3】 6. The method according to any one of claims 1 to 5, wherein PP, NN, Y and n have the same meanings as defined in claim 1.

7. 7. The process according to claim 1, wherein Y simultaneously or independently represents a hydrogen atom or a chlorine atom.

8. 8. The method according to claim 1, wherein the complex of formula (1) is generated directly in situ.

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