Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C209/00—Preparation of compounds containing amino groups bound to a carbon skeleton
  • C07C209/44—Preparation of compounds containing amino groups bound to a carbon skeleton by reduction of carboxylic acids or esters thereof in presence of ammonia or amines, or by reduction of nitriles, carboxylic acid amides, imines or imino-ethers
  • C07C209/52—Preparation of compounds containing amino groups bound to a carbon skeleton by reduction of carboxylic acids or esters thereof in presence of ammonia or amines, or by reduction of nitriles, carboxylic acid amides, imines or imino-ethers by reduction of imines or imino-ethers
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07B—GENERAL METHODS OF ORGANIC CHEMISTRY; APPARATUS THEREFOR
  • C07B2200/00—Indexing scheme relating to specific properties of organic compounds
  • C07B2200/09—Geometrical isomers
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2602/00—Systems containing two condensed rings
  • C07C2602/02—Systems containing two condensed rings the rings having only two atoms in common
  • C07C2602/04—One of the condensed rings being a six-membered aromatic ring
  • C07C2602/10—One of the condensed rings being a six-membered aromatic ring the other ring being six-membered, e.g. tetraline

Definitions

• the present invention relates to a novel, inventive process for the cis-selective catalytic hydrogenation of cyclohexylidenamines and their precursors.
• Cyclohexylamines can be used, inter alia, as antioxidants and as pharmaceutical active substances.
• An important cyclohexylamine is sertraline:
• sertaline has the 1 S-, 4S-configuration.
• Cyclohexylamine is obtained, for example, by the following method: Reacting the ketone
• the resultant imine is then catalytically hydrogenated to the amine. These reactions proceed without, or only with minor, stereoselectivity. In the case of sertraline, four enantiomers are obtained.
• This invention has for its object to prepare cyclohexylamines having as high as possible a cis-isomer proportion.
• R 2 3,4-dichlorophenyl using palladium and carbon as substrates. This affords 70 % of cis- and 30 % of trans- racemate.
• WO 93/01161 proposes to replace palladium and carbon as substrate by Raney nickel when hydrogenating the imine. This results in a cis/trans ratio of 8:1. Surprisingly, it has now been found that an even better cis/trans ratio is obtained if the - 3 -
• imine is catalytically hydrogenated in the presence of a copper.
• the preparation of secondary amines from ketones and intermediate imines by hydrogenation in the presence of copper chromite catalysts is known from ft B. C. Pillai J. Mol. Catalysis 84 (1993), 125 - 129.
• copper chromite catalysts is known from ft B. C. Pillai J. Mol. Catalysis 84 (1993), 125 - 129.
• This invention relates to a process for the preparation of cis-compounds of formula: y
• R, and R 2 are each independently of the other hydrocarbon radicals and A is sub- stituents, and m is an integer from 0 to 4 and defines the number of the substituents A, which process comprises a) hydrogenating a cyclohexylidenamine of formula:
• a (m)" is used. If in a compound (I) m is 1 to 4 (m > 0) and the cyclohexyl ring is unsymmetrically substituted, then a cis-enantiomer pair is selectively obtained during hydrogenation which can be separated into the optically pure antipodes by customary methods of racemate resolution, for example by crystallisation of the mandelic acid salt by the method of W.M.Welch et al in J. Med. Chem. 1984, 27, 1508-1515. The relationship between the two cis- and trans- enantiomer pairs and the 4 optically pure antipodes is illustrated by the following formula scheme of sertraline:
• the unbroken bonding dashes to the substituent R 2 signify that in the case of R 2 ⁇ H and of different substitution at the cyclohexyl ring, these starting materials can be used in the process in the form of racemic mixtures having identical or different antipode proportions or in the form of an optically pure antipode.
• the process is distinguished by a high yield of the desired cis-compounds.
• a ratio of the cis- to the trans-enantiomer pair is obtained which is higher than 95:5.
• the even better ratio of higher than 99:1 is obtained.
• This high cis-compound yield obviates the separation of the cis- from the trans-enantiomer pair which is otherwise necessary when different substi- tuents A (m > 0) are present.
• a hydrocarbon radical R ⁇ , or R 2 is preferably selected from the group consisting of C C 2 o- alkyl, C 4 -C 12 cycloalkyl, C 2 -Cnheterocycloalkyl, carbocyclic C 5 -C 16 aryl, C 2 -C 15 heteroaryl, car- bocyclic C 7 -C 16 aralkyl and C 2 -C ⁇ sheteroarylalkyl and can in addition be substituted by suitable functional groups, for example by the functional groups or derivatised functional groups consisting of amino, CrC ⁇ lkyiamino, CrC ⁇ dialkylamino, hydroxy, carboxy and halogen.
• the cyclohexyl ring can be substituted by 1 to 4, preferably by 2, substituents from the group A containing the substituents R 3 , R 4 , R 5 and R 6 .
• Suitable substituents are listed in the List of Radical Names, valid according to IUPAC Rules, and remain unchanged under the conditions of the catalytic hydrogenation reaction. Any of the substituents may be chosen.
• Suitable substituents A from the group R 3 , R 4 , R 5 and R 6 are selected, for example, from the group of the functional groups or derivatised functional groups consisting of amino, CrC 4 - alkylamino, d-Cdialkylamino, hydroxy, carboxy and halogen, or are saturated or unsatura- ted aliphatic, cycloaiiphatic or heterocycloaliphatic radicals, carbocyclic or heterocyclic aryl radicals, condensed carbocyclic, heterocyclic or carbocyclic-heterocyclic radicals, which can in turn be combined with any others of these radicals and which can be substituted by the cited functional groups or derivatised functional groups.
• two substituents A from the group R 3 , R 4 , R 5 and R 6 are bivalent, bridge-like C 2 -C 6 alkylene, C 4 -C 8 alkyldiylidene or C 4 -C 8 alkenyldiylidene groups, preferably butanediyiidene, more preferably 2-butenediylidene, which is bound with the cyclohexyl ring to two adjacent carbon atoms and which forms together with these car- - 6 -
• Suitable substituents A from the group R 3 , R 4 , R 5 and R 6 are also substituents from the group CrC 20 alkyl, C 4 -C 12 cycloalkyl, C 7 -C 12 bicycloalkyl, C 2 -Cnheterocycloalkyl, carbocyclic C 6 -C 16 aryl, C 2 -C ⁇ 5 heteroaryl, carbocyclic C 7 -C 16 aralkyl and C 2 -C 15 heteroarylalkyl, which can in turn be substituted by the cited functional groups and interrupted by bivalent radicals.
• C C 20 Alkyl is, for example, methyl, ethyl, n- or isopropyl or n-, sec- or tert-butyl and straight- chain or branched pentyl, hexyl, heptyl, octyl, isooctyl, nonyl, tert-nonyl, decyl, undecyl or dodecyl.
• Cycloalkyl is, for example, cyclopropyl, dimethylcyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl.
• C 7 -C 12 Bicycloalkyl is, for example, bornyl or norbornyl.
• C 2 -CnHeterocycloalkyl preferably contains 4 or 5 carbon atoms and one or two heteroatoms from the group O, S and N.
• Examples are the substituents derived from oxirane, azirine, 1 ,2- oxathiolane, pyrazoline, pyrrolidine, piperidine, piperazine, morpholine, tetrahydrofuran or tetrahydrothiophene.
• Carbocyclic C 6 -C 16 aryl is, for example, mono-, bi- or tricyclic, typically phenyl, naphthyl, in- denyl, azulenyl or anthryl.
• Heteroaryl is preferably monocyclic or is condensed with a further heterocycle or with an aryl radical, for example phenyl, and preferably contains one or two, in the case of nitrogen up to four, heteroatoms from the group O, S and N.
• Suitable substituents are derived from furan, thiophene, pyrrole, pyridine, bipyridine, picoline, ⁇ -pyran, ⁇ -thiopyran, phenan- throline, pyrimidine, bipyrimidine, pyrazine, indole, coumarone, thionaphthene, carbazole, di- benzofuran, dibenzothiophene, pyrazole, imidazole, benzimidazole, oxazole, thiazole, dithi- azole, isoxazole, isothiazole, quinoline, isoquinoline, acridine, chromene, phenazine, phen- oxazine, phenothiazine, triazine, thianthrene, purine or tetrazole.
• Carbocyclic CrC ⁇ aralkyl preferably contains 7 to 12 carbon atoms, e.g. benzyl, 1- or 2- phenethyl or cinnamyl.
• Heteroarylalkyl preferably consists of the cited heterocycles, which substitute e.g. C C 4 alkyl radicals, depending on the length of the carbon chain where possible terminally, or else also in adjacent position (1 -position) or in ⁇ -position (2-position).
• R ⁇ is C C 4 alkyl and R is aryl.
• R ⁇ and R 2 have the cited meanings, which imine or ketone may be in syn- or anti- form, is hydrogenated in the presence of a copper-containing catalyst.
• ketone (III) preferably a ketone of formula
• R 2 has the cited meanings, is reacted with a compound introducing the R r N-)(0) n group, in particular with a primary amine, preferably methylamine, or with a R substituted hydroxylamine, preferably N-methylhydroxylamine, and the imine (II) which is obtainable as intermediate is hydrogenated in situ in the presence of a copper-containing catalyst. It is also possible to replace the racemic compound (IT) or (III') with an optically pure compound (IT) or (III') and to react it to a cis-compound (I').
• This invention preferably relates to a process for the preparation of the cis-compound (I'), wherein R, is methyl and R 2 is 3,4-dichiorophenyl, which process comprises - 8 -
• Suitable catalysts for the hydrogenation reaction according to variants a) and b) are copper- containing catalysts, for example copper skeleton, copper substrate, copper chromite, copper zinc oxide, copper boride or copper urushibara catalysts.
• other elements are present in the catalyst besides copper.
• elements are aluminium, chromium, zinc, barium, manganese, zirconium, vanadium, molybdenum, titanium, tantalum, niobium, tungsten, nickel, cobalt, bismuth, tin, antimonium, hafnium, rhenium, iron, cadmium, lead or germanium and mixtures thereof.
• the amount in which the element is added can vary within wide limits and may be from 10 ppm to 200% in relation to the amount of copper used.
• Particularly suitable elements are aluminium, zinc, chromium, barium and manganese.
• the elements can be, for example, in the form of oxides or salts, such as chromates.
• Raney copper is an example of a suitable copper skeleton catalyst.
• substrates are carbon, aluminium oxide, silicium dioxide, Cr 2 0 3 , zirconium dioxide, zinc oxide, calcium oxide, magnesium oxide, barium sulfate, calcium carbonate or aluminium phosphate.
• the copper can be bound on the substrate in an amount of about 1.0 - 20.0 % by weight.
• a suitable copper chromite catalyst is represented by the empirical formula CuO*CuCr 2 0 4 .
• CuCr 2 0 4 is known, see C.A.R.N. 12018-10-9 and Gmelins Handbuch der Anorganischen Chemie, 8 th ed., Vol. Kupfer, part B, instalment 3, system number 60, page 60.
• a common name is also copper(ll)chromate(lll).
• Copper chromite catalysts having changing proportions of CuO and CuCr 2 0 4 , Raney copper catalysts and copper-zinc-aluminium-oxide catalysts are commercially available in pure form or in a form doped with the cited elements.
• the copper-containing catalysts used are copper chromite catalysts or catalysts containing copper, zinc and aluminium in the form of oxides.
• the cited catalysts are present in the reaction mixture in an amount of about 0.1 to 100 % by weight, preferably of 1 -20 % by weight, based on the amount of educt used.
• the copper-containing catalysts can be used in different ways in the process:
• catalysts prepared in situ from suitable precursors, such as copper salts or oxides, and from other compounds.
• prehydrogenation it is possible to treat e.g. a suspension of the catalyst in a suitable solvent under 5 to 150 bar hydrogen at 80-250°C for half an hour to 5 hours, or hydrogen is introduced under normal pressure up to 50 bar at 100 to 500°C over the dry catalyst.
• the catalyst used is activated by hydrogenation in the solvent which is used for hydrogenating the imine or nitrone ("prehydrogenation").
• the catalyst can be separated after the hydrogenation e.g. by filtration if the process is carried out batchwise.
• Imines (II) can be prepared by reacting ketones (II) with a compound introducing the R N group, in particular with a primary amine, preferably methylamine.
• the preparation of imines (II) is carried out in analogy to the method which is described in U.S. patent specification No. 4,536,518.
• Nitrones (II) can be prepared by reacting ketones (II) with a compound introducing the R r N ⁇ 0 group, for example , -substituted hydroxylamine, preferably N-methylhydroxylamine.
• the preparation of nitrones (II) is carried out in analogy to the method described in WO 98/27050.
• Hydrogenation is carried out in the presence of an organic solvent. It is preferred to use non- polar or polar aprotic solvents or mixtures thereof.
• non-polar solvents examples include hydrocarbons, for example aliphatic hydrocarbons, such as hexane, heptane or petroleum ether, cycloaliphatic hydrocarbons, such as cyclohexane or methylcyclohexane, aromatic hydrocarbons, such as benzene, toluene or xylene.
• hydrocarbons for example aliphatic hydrocarbons, such as hexane, heptane or petroleum ether, cycloaliphatic hydrocarbons, such as cyclohexane or methylcyclohexane, aromatic hydrocarbons, such as benzene, toluene or xylene.
• Suitable polar aprotic solvents are ethers, such as aliphatic ethers, e.g. 1 ,2- diethoxyethane or tert-butylmethyl ether, cyclic ethers, e.g. tetrahydrofuran or dioxan, amides, e.g. dimethylformamide or N-methylpyrrolidone. Ethers are particularly suitable, especially tetrahydrofuran.
• acid assistants are added where required, for example organic mono- or polyvalent acids containing more than two carbon atoms, for example acetic acid, propionic acid or malonic acid, mineral acids such as sulfuric acid, so-called Lewis acids, such as boron trifluoride, or so-called solid acids, such as zeolites or National® and/or dehydrating agent, such as sodium sulfate.
• organic mono- or polyvalent acids containing more than two carbon atoms for example acetic acid, propionic acid or malonic acid, mineral acids such as sulfuric acid, so-called Lewis acids, such as boron trifluoride, or so-called solid acids, such as zeolites or National® and/or dehydrating agent, such as sodium sulfate.
• organic mono- or polyvalent acids containing more than two carbon atoms for example acetic acid, propionic acid or malonic acid, mineral acids such as sulfuric acid, so-called Lewis acids, such as boron trifluoride, or so-called solid
• the process can be carried out in both variants preferably in the liquid phase batchwise or continuously, preferably with a catalyst suspension as liquid-phase hydrogenation or in a bubble column or with a formated catalyst in a trickle bed.
• the reaction can also be carried out in the gas phase with a powdered catalyst in a fluidised bed or with a formulated catalyst in a fixed bed.
• the hydrogenation can be carried out in a wide range of temperatures. Temperatures in the range from 60° to about 250 °C, preferably from 90° to 150°C, have been found to be advantageous.
• the hydrogen pressure can vary within a wide range during hydrogenation, for example from 1 - 100, preferably from 5 - 50, more preferably from 10 - 20 bar. Which hydrogen pressure is used depends essentially on the hydrogenation plant available. At higher temperatures of about 100°C, molecular hydrogen can also be replaced by a hydrogen-donor, such as iso- propanol.
• the reaction time can vary within wide limits. It depends on the catalyst used, on the hydrogen pressure, on the reaction temperature and on the plant used and can be, for example, from half an hour to 24 hours. Advantageous reaction times are those from about half an hour to 2 hours.
• the isolation of the reaction products is carried out by known methods and is illustrated in the Examples. After separation of the catalyst and removal of the solvent, the conventional separation processes may follow, for example preparative thin-layer chromatography, preparative HPLC, preparative gas chromatography etc..
• the cis-racemate obtained starting from racemic cyclohexylidenamine can be separated into the optically pure antipodes without any further purification using the known processes for enantiomer separation, for example by means of preparative chromatography on chiral substrates (HPLC) or by precipitation or crystallisation using optically pure precipitants, for example D -(-) or L -(-)-mandelic acid or (+) or (-)-IO-camphorsulfonic acid.
• the enantiomer-pure 4-substituted cyclohexylamine is obtained directly by the hydrogenation process of this invention.
• This invention also relates to the use of copper-containing catalysts for the diastereoselec- tive hydrogenation of cyclohexylidenamines.
• copper chromite catalysts or CuZnAI-oxide catalysts for the diastereoselective hydrogenation of cyclohexylidenamines.
• 0.1 g of barium-doped copper chromite catalyst (commercial product of S ⁇ dchemie, Girdler G 13, comprising 29% of Cu, 26% of Cr and 13.6% of Ba) and 40 ml of THF are placed in a 100 ml autoclave (stainless steel 316SS).
• the catalyst suspension is prehydrogenated for 1 hour at 12 bar initial pressure H 2 at 130°C.
• the suspension is then cooled and 0.5 g of 4-(3,4-dichlorophenyl)-1-methylimino-1 ,2,3,4-tetrahydronaphthalene is added.
• hydrogenation is carried out for 18 hours at 100°C and 12 bar initial pressure H 2 (maximum pressure: 15 bar).
• the catalyst is removed by filtration and the product is concentrated by evaporation under vacuum and dried under high vacuum.
• the cis/trans ratio of the resulting 4-(3,4-dichlorophenyl)-1 ,2,3,4-tetrahydro-N-methyl-1 -naph- thylamine is > 95 : 5.
• the crude product is purified via FLASH chromatography over silica gel at a solvent gradient of CH 2 CI 2 to CH 2 CI 2 /MeOH (9 : 1 ). This gives 83 % of the theoretical yield of pure cis-racemate.
• the cis/trans ratio of the resultant 4-(3,4-dichlorophenyl)-1 ,2,3,4-tetrahydro-N-methyl-1-napthylamine is > 9 : 1.
• the crude product is purified via FLASH chromatography over silica gel at a solvent gradient of CH 2 CI 2 to CH 2 CI 2 /MeOH (9 : 1 ). This gives 50 % of the theoretical yield of pure cis-racemate.
• the resultant 4-(3,4-dichlorophenyl)-1 ,2,3,4-tetrahydro-N-methyl-1 -napthylamine is determined via HPLC: 97.3 to 2J. 20ml of a HCI-saturated THF solution are then added dropwise at 0°C to the solution of crude product. The corresponding crystalline hydrochloride precipitates and is collected by filtration over a glass suction filter and dried under vacuum. This gives 85% of the theoretical yield of pure cis-racemate. The melting point is 292-293°C after recrystallisation from absolute methanol.
• catalyst commercial product of Engelhard Cu-0890 P, comprising 35% of CuO, 42% of ZnO and 21% of Al 2 0 3
• 30 ml of THF and 3 g of 4-(3,4-dichlorophenyl)-1-methyl- imino-1 ,2,3,4-tetrahydronaphthalene are placed in a 100 ml autoclave (stainless steel 316SS). Hydrogenation is then carried out for 1 1 / 2 hours at 150°C and at 10 bar initial pressure H 2 (maximum pressure: 15 bar).
• the catalyst is removed by filtration over Hyflo® and 0.1 ml of the solution is concentrated by evaporation under vacuum.
• the sample is taken up in isopropanol and the cis/trans ratio of the resultant 4-(3,4-dichlorophenyl)-1 ,2,3,4-tetra- hydro-N-methyl-1-napthylamine is determined via HPLC: 99.0 : 1.0.
• 1.5 g of D-(-)-mandelic acid are added to the solution of crude product and the solvent is stripped off, with heating, in a rotary evaporator. After drying for 12 hours under high vacuum, 100 ml of ethanol are added and the corresponding crystalline mandelate is dissolved under reflux conditions. After heating for 20 minutes the solution is cooled and stored overnight at room temperature.
• the colourless crystals are filtered over a glass suction filter and the mother liquor is concentrated to half its volume and, after brief heating, cooled to the second crystallisation. This gives a further product fraction.
• the total yield is 82% of theory.
• the melting points are 191 °C and 190°C for the first and second fraction, respectively.

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