METHOD FOR PRODUCING AMINO-FUNCTIONAL AROMATIC COMPOUNDS

Abstract

The invention relates to a method for producing an amino-functional aromatic compound which has a benzyl CH function. The production takes place on a boron-doped diamond electrode (BDD) in the presence of a pyridine-based aminating reagent. The invention further relates to a compound of the formula (IV) according to the invention, to a composition containing amino-functional aromatic compounds, to a method for producing a compound containing isocyanate groups, and to the compounds thus obtained.

Claims

1.-15. (canceled)

16. A process for preparing a compound of the general formula (I)
NH.sub.2Ar(CHR.sub.1R.sub.2).sub.q(I), comprising the step of oxidatively electrochemically aminating the compound of the general formula (II)
Ar(CHR.sub.1R.sub.2).sub.q(II) using at least one boron-doped diamond anode, where Ar is an aromatic hydrocarbyl group which is optionally polycyclic, with the proviso that, when Ar represents a polycyclic aromatic hydrocarbyl group, the NH.sub.2 and (CHR.sub.1R.sub.2).sub.q substituents in the general formula (I) are simultaneously at least on one ring and all other aromatic rings may optionally each be substituted independently of one another; R.sub.1 are independently selected from the group consisting of hydrogen, a linear, branched or cyclic hydrocarbyl group and an aromatic, optionally polycyclic hydrocarbyl group, each of which may optionally be substituted and/or may optionally be interrupted by a heteroatom, R.sub.2 are independently selected from the group consisting of hydrogen, a linear, branched or cyclic hydrocarbyl group and an aromatic, optionally polycyclic hydrocarbyl group, each of which may optionally be substituted and/or may optionally be interrupted by a heteroatom, and q represents an integer of at least 1, wherein the aminating reagent used is at least one compound selected from the group consisting of pyridine, one or more pyridine isomers having mixed alkyl substitution, one or more picoline isomers, one or more lutidine isomers, one or more collidine isomers, quinoline, isoquinoline and any desired mixtures of these compounds.

17. The process as claimed in claim 16, where Ar is an aromatic hydrocarbyl group which is optionally polycyclic, with the proviso that, when Ar represents a polycyclic aromatic hydrocarbyl group, the NH.sub.2 and (CHR.sub.1R.sub.2) substituents in the general formula (I) are simultaneously at least on one ring and all other aromatic rings have either no substituents or at least one substituent selected from the group consisting of NH.sub.2 and CHR.sub.1R.sub.2 where R.sub.1 and R.sub.2 have the definitions given above.

18. The process as claimed in claim 16, wherein the general formula (I) encompasses at least the structural unit of the general formula (IIIa) ##STR00012## and the general formula (II) encompasses at least the structural unit of the general formula (IIIb) ##STR00013## where the structural unit of the general formulae (IIIa) and (IIIb) is optionally part of a polycyclic aromatic hydrocarbyl group.

19. The process as claimed in claim 16, wherein the general formula (I) is represented by the general formula (IIIa) ##STR00014## and the general formula (II) is represented by the general formula (IIIb) ##STR00015##

20. The process as claimed in claim 16, wherein each R.sub.1 and/or R.sub.2 is independently selected from the group consisting of hydrogen, a linear or branched alkyl group and an aryl group, where the aryl group may optionally be substituted and where this aryl group in formula (II) is optionally likewise aminated by the step of oxidative electrochemical amination according to claim 16, such that this aryl group in formula (I) has a NH.sub.2 substituent.

21. The process as claimed in claim 16, wherein each R.sub.1 and/or R.sub.2 is independently selected from the group consisting of hydrogen, a linear or branched alkyl group having 1 to 10 carbon atoms and a phenyl group, where the phenyl group may optionally be substituted and where this phenyl group in formula (II) is optionally likewise aminated by the step of oxidative electrochemical amination according to claim 16, such that this phenyl group in formula (I) has a NH.sub.2 substituent.

22. The process as claimed in claim 16, wherein each R.sub.1 and/or R.sub.2 is independently selected from the group consisting of hydrogen and a phenyl group, where the phenyl group in formula (II) is optionally likewise aminated by the step of oxidative electrochemical amination according to claim 16, such that this phenyl group in formula (I) has a NH.sub.2 substituent.

23. The process as claimed in claim 16, wherein the step of oxidative chemical amination comprises the following steps in the sequence specified: (i) forming a primary amination product (IV) and (ii) releasing amine from the primary amination product to form the reaction product of the general formula (I).

24. The process as claimed in claim 23, wherein at least one compound selected from the group consisting of hydroxide, ammonia, hydrazine, hydroxylamine, piperidine and any desired mixtures of these compounds is used for the amine release in step (ii).

25. A compound of the general formula (IV) ##STR00016## where Ar is an aromatic hydrocarbyl group which is optionally polycyclic, with the proviso that, when Ar represents a polycyclic aromatic hydrocarbyl group, the R.sub.4(R.sub.3)N.sup.+ and (CHR.sub.1R.sub.2).sub.q substituents in the general formula (IV) are simultaneously at least on one ring and all other aromatic rings may optionally each be substituted independently of one another; R.sub.1 are independently selected from the group consisting of hydrogen, a linear, branched or cyclic hydrocarbyl group and an aromatic, optionally polycyclic hydrocarbyl group, each of which may optionally be substituted and/or may optionally be interrupted by a heteroatom, R.sub.2 are independently selected from the group consisting of hydrogen, a linear, branched or cyclic hydrocarbyl group and an aromatic, optionally polycyclic hydrocarbyl group, each of which may optionally be substituted and/or may optionally be interrupted by a heteroatom, q represents an integer of at least 1, R.sub.3 and R.sub.4 together form an aromatic ring which may optionally be substituted by at least one alkyl group and/or which may optionally be part of a polycyclic aromatic hydrocarbyl group.

26. A compound as claimed in claim 25, wherein the R.sub.4(R.sub.3)N.sup.+ substituent in the general formula (IV) is selected from the group of the following general formulae (Va) to (Vf): ##STR00017## in which R.sub.5 to R.sub.7 are each independently a linear or branched alkyl group having 1 to 6 carbon atoms.

27. A composition obtained by the process as claimed in claim 16, wherein, in the formula (II), the R.sub.1 substituent represents an aromatic, optionally polycyclic hydrocarbyl group which may optionally be substituted and/or interrupted by a heteroatom.

28. A process for preparing a compound of the general formula (VIII) ##STR00018## where R.sub.10 is selected from the group consisting of hydrogen and a phenyl group which may optionally be substituted by an NCO group, comprising steps (iii) and (iv) once each in any sequence: (iii) converting the amino groups in the composition as claimed in claim 27 or the composition of the product obtained from step (iv) to form an isocyanate group and (iv) working up the composition as claimed in claim 27 or working up the product obtained from step (iii).

29. A mixture of isomers of the general formula (VIII) ##STR00019## where R.sub.10 is selected from the group consisting of hydrogen and a phenyl group which may optionally be substituted by an NCO group, obtained by the process as claimed in claim 28.

30. A mixture of isomers comprising isomers of the general formula (IX) ##STR00020## where R.sub.11 is an NCO group or an NH.sub.2 group and R.sub.12 is selected from the group consisting of hydrogen and a phenyl group which may optionally be substituted by an NCO group or an NH.sub.2 group, wherein the ratio of the sum total of the 4,4, 2,4 and 2,2 isomers to the isomers having at least one R.sub.11 substituent in the 3 or 3 position is 1:0.25 to 1:1.5.

Description

BRIEF DESCRIPTION OF THE FIGURE

[0081] FIG. 1: Diagram of the electrolysis cell used in the examples: divided Teflon cells in the screening block; size of the electrodes: each 1070 mm; anode space and cathode space separated by means of a porous separator of sintered glass of porosity 4 having a diameter of 10 mm; solvent volume: 6 mL in each case; electrode separation: 250 mm.

EXAMPLES

Analysis Methods:

Chromatography

[0082] The preparative liquid chromatography separations via flash chromatography were conducted with a maximum pressure of 1.6 bar on 60 M silica gel (0.040-0.063 mm) from Macherey-Nagel GmbH & Co, Dren. The unpressurized separations were conducted on Geduran Si 60 silica gel (0.063-0.200 mm) from Merck KGaA, Darmstadt. The solvents used as eluents (ethyl acetate (technical grade), cyclohexane (technical grade)) were purified by distillation on a rotary evaporator beforehand.

[0083] Thin-layer chromatography (TLC) was effected using ready-made PSC silica gel 60 F254 plates from Merck KGaA, Darmstadt. The Rf values are reported together with the eluent mixture used. The TLC plates were stained using a cerium-molybdophosphoric acid solution as dipping reagent. Cerium-molybdophosphoric acid reagent: 5.6 g of molybdophosphoric acid, 2.2 g of cerium(IV) sulfate tetrahydrate and 13.3 g of concentrated sulfuric acid to 200 mL of water.

Gas Chromatography (GC/GCMS)

[0084] The gas chromatography (GC) analyses of product mixtures and pure substances were effected with the aid of the GC-2010 gas chromatograph from Shimadzu, Japan. Analysis was effected with an HP-5 quartz capillary column from Agilent Technologies, USA (length: 30 m; internal diameter: 0.25 mm; film thickness of the covalently bound stationary phase: 0.25 m; carrier gas: hydrogen; injector temperature: 250 C.; detector temperature: 310 C.; program: hard method: start temperature 50 C. for 1 min, heating rate: 15 C./min, 290 C., end temperature for 8 min). Gas chromatography mass spectra (GCMS) of product mixtures and pure substances were recorded with the aid of the GC-2010 gas chromatograph combined with the GCMS-QP2010 mass detector from Shimadzu, Japan. Analysis was effected with an HP-1 quartz capillary column from Agilent Technologies, USA (length: 30 m; internal diameter: 0.25 mm; film thickness of the covalently bound stationary phase: 0.25 m; carrier gas: hydrogen; injector temperature: 250 C.; detector temperature: 310 C.; program: hard method: start temperature 50 C. for 1 min, heating rate: 15 C./min, 290 C., end temperature for 8 min; GCMS: temperature of the ion source: 200 C.).

Mass Spectrometry

[0085] All electrospray ionization measurements (ESI+) were conducted on a QTof Ultima 3 from Waters Micromasses, Milford, Mass.

NMR Spectroscopy

[0086] The NMR spectroscopy studies were conducted on multinuclear resonance spectrometers of the Avance III HD 300 or Avance II 400 type from Bruker, Analytische Messtechnik, Karlsruhe. The solvent used was d.sub.6-DMSO. The .sup.1H and .sup.13C spectra were calibrated according to the residual content of non-deuterated solvent using the NMR Solvent Data Chart from Cambridge Isotopes Laboratories, USA. Some of the .sup.1H and .sup.13C signals were assigned with the aid of H,H-COSY, H,C-HSQC and H,C-HMBC spectra. The chemical shifts are reported as values in ppm. The following abbreviations were used for the multiplicities of the NMR signals: s (singlet), bs (broad singlet), d (doublet), t (triplet), q (quartet), m (multiplet), dd (doublet of doublets), dt (doublet of triplets), tq (triplet of quartets). All coupling constants J were reported with the number of bonds involved in hertz (Hz).

High-Pressure Liquid Chromatography (HPLC)

[0087] The semi-preparative HPLC separations were conducted on a modular LC-20A Prominence system from Shimadzu, Japan, using a UV detector (SPD-20A/AV). The stationary phase used for the separations was a Chromolithm SemiPrep RP-18 phase (internal diameter: 10 mm, length: 100 mm) from Merck KGaA, Darmstadt. The mobile phase used was acetonitrile+0.1% triethylamine/water+0.1% triethylamine. The total flow rate under isocratic conditions was 3.6 mL/min.

General Procedures

GP 1: Procedure for Electrochemical Amination

[0088] The electrochemical reduction was conducted in a divided Teflon cell. The anode material used was boron-doped diamond (BDD). The cathode material used was platinum. The anode space was charged with a solution consisting of the particular aromatic compound (0.2 mol L.sup.1) and pyridine (2.4 mol L.sup.1, dry) in 0.2 M Bu.sub.4NBF.sub.4/acetonitrile (5 mL, dry). The cathode space was charged with a solution of trifluoromethanesulfonic acid (0.4 mL) in 0.2 M Bu.sub.4NBF.sub.4/acetonitrile (5 mL, dry). The electrolyses were conducted under galvanostatic conditions at 60 C. Once the respective amounts of charge had been attained, the reaction solution was transferred into a pressure tube, and 1 mL of piperidine was added. This was followed by heating at 80 C. for 12 h. The reaction mixture was analyzed for the amination products by means of GC, TLC and GC/MS.

Example 1: Preparation of 2,4-diisopropylaniline

[0089] According to GP 1, 0.17 g (1.06 mmol, 0.085 equiv.) of 1,3-diisopropylbenzene, 0.33 g (1.00 mmol) of tetrabutylammonium tetrafluoroborate, 1 mL (0.98 g, 12.41 mmol, 1 equiv.) of pyridine were dissolved in 5 mL of dry acetonitrile and introduced into the anode space. The cathode space was charged with a solution of 0.40 g (1.21 mmol) of tetrabutylammonium tetrafluoroborate and 0.4 mL of trifluoromethanesulfonic acid in 6 mL of acetonitrile. The electrolysis was conducted in a divided Teflon cell.

[0090] Anode: BDD; electrode area: 2.2 cm.sup.2.

[0091] Cathode: platinum; electrode area: 2.2 cm.sup.2.

[0092] Amount of charge: 255.7 C.

[0093] Current density: j=10 mA cm.sup.2.

[0094] Temperature: 60 C.

[0095] After the electrolysis time had elapsed, the anode and cathode space was introduced into a pressure tube, 1 mL (0.86 g, 10.00 mmol, 0.81 equiv.) of piperidine was added and the mixture was heated at 80 C. for 12 h. After the reaction time had ended, the solvent was removed under reduced pressure and the residue was dissolved in ethyl acetate and passed through a filtration column (60 M silica gel; eluent: ethyl acetate; width: 5 cm; length: 9.5 cm) in order to remove the conductive salt. Subsequently, the crude product was dissolved in dichloromethane and adsorbed onto 60 M silica gel. The crude product was separated by column chromatography (column width: 3 cm, length: 30 cm) on 60 M silica gel in the cyclohexane/ethyl acetate 9:1 eluent mixture (R.sub.f=0.2). The product obtained was purified further by Kugelrohr distillation at 40 C. and 10.sup.3 mbar. 93.1 mg (0.5 mmol, 50%) of a colorless liquid were obtained.

[0096] .sup.1H-NMR (300 MHz, CDCl.sub.3): (ppm)=1.22 (d, .sup.3J=6.9 Hz, 6H), 1.28 (d, .sup.3J=6.8 Hz, 6H), 2.83 (hept, J=6.9 Hz, 1H), 2.98 (hept, .sup.3J=6.8 Hz, 1H), 4.35 (bs, 2H, NH.sub.2), 6.72 (d, .sup.3J=8.1 Hz, 1H), 6.92 (dd, .sup.3J=8.1 Hz, .sup.4J=2.1 Hz, 1H), 7.02 (d, .sup.4J=2.1 Hz, 1H).

[0097] .sup.13C-NMR (75 MHz, CDCl.sub.3): (ppm)=22.49, 24.30, 27.84, 33.59, 116.65, 123.70, 124.16, 133.52, 139.62, 140.52.

[0098] GC (hard method, HP-5): t.sub.R=8.14 min.

[0099] HRMS calculated for C.sub.12H.sub.20N.sup.+: 178.1596; found: 178.1592.

[0100] R.sub.f=0.2 (9:1 cyclohexane/ethyl acetate)

Example 2: Preparation of 2,4-dimethylaniline

[0101] According to GP 1, 0.12 g (1.09 mmol, 0.088 equiv.) of m-xylene, 0.33 g (1.00 mmol) of tetrabutylammonium tetrafluoroborate, 1 mL (0.98 g, 12.41 mmol, 1 equiv.) of pyridine were dissolved in 5 mL of dry acetonitrile and introduced into the anode space. The cathode space was charged with a solution of 0.40 g (1.21 mmol) of tetrabutylammonium tetrafluoroborate and 0.4 mL of trifluoromethanesulfonic acid in 6 mL of acetonitrile. The electrolysis was conducted in a divided Teflon cell.

[0102] Anode: BDD; electrode area: 2.5 cm.sup.2.

[0103] Cathode: platinum; electrode area: 2.5 cm.sup.2.

[0104] Amount of charge: 264 C.

[0105] Current density: j=10 mA cm.sup.2.

[0106] Temperature: 60 C.

[0107] After the electrolysis time had elapsed, the anode and cathode space was introduced into a pressure tube, 1 mL (0.86 g, 10.00 mmol, 0.81 equiv.) of piperidine was added and the mixture was heated at 80 C. for 12 h. Subsequently, the solvent was removed under reduced pressure and the residue was dissolved in ethyl acetate and passed through a filtration column (60 M silica gel; eluent: ethyl acetate; width: 5 cm; length: 9.5 cm) in order to remove the conductive salt. The crude product obtained was dissolved in dichloromethane and adsorbed onto 60 M silica gel. The crude product is separated by column chromatography (column width: 3 cm, length: 30 cm) on 60 M silica gel in the cyclohexane/ethyl acetate 9:1 eluent mixture (R.sub.f=0.19). The product obtained was purified further by Kugelrohr distillation at 40 C. and 10.sup.3 mbar. 49.5 mg (0.4 mmol, 37%) of a colorless liquid were obtained.

[0108] .sup.1H-NMR (300 MHz, CDCl.sub.3): (ppm)=2.17 (s, 3H), 2.24 (s, 3H), 3.64 (bs, 2H, NH.sub.2), 6.64 (d, J=7.8 Hz, 1H), 6.87 (d, .sup.3J=7.9 Hz, 1H), 6.89 (s, 1H).

[0109] .sup.13C-NMR (75 MHz, CDCl.sub.3): (ppm)=17.37, 20.45, 115.41, 122.81, 127.34, 128.29, 131.16, 141.37.

[0110] GC (hard method, HP-5): t.sub.R=5.75 min.

[0111] HRMS calculated for C.sub.8H.sub.12N.sup.+: 122.0970; found: 122.0992.

[0112] MS (EI, 70 eV): m/z (%): 121 (100) [M].sup.+

[0113] R.sub.f=0.19 (9:1 cyclohexane/ethyl acetate)

Example 3: Amination of m-tert-butyltoluene

[0114] According to GP 1, 0.16 g (1.12 mmol, 0.09 equiv.) of 1-tert-butyl-3-methylbenzene, 0.33 g (1.00 mmol) of tetrabutylammonium tetrafluoroborate, 1 mL (0.98 g, 12.41 mmol, 1 equiv.) of pyridine were dissolved in 5 mL of dry acetonitrile and introduced into the anode space. The cathode space was charged with a solution of 0.40 g (1.21 mmol) of tetrabutylammonium tetrafluoroborate and 0.3 mL of trifluoromethanesulfonic acid in 6 mL of acetonitrile. The electrolysis was conducted in a divided Teflon cell.

[0115] Anode: BDD; electrode area: 2.5 cm.sup.2.

[0116] Cathode: platinum; electrode area: 2.5 cm.sup.2.

[0117] Amount of charge: 270 C.

[0118] Current density: j=10 mA cm.sup.2.

[0119] Temperature: 60 C.

[0120] After the electrolysis time had elapsed, the anode and cathode space was introduced into a pressure tube, 1 mL (0.86 g, 10.00 mmol, 0.81 equiv.) of piperidine was added and the mixture was heated at 80 C. for 12 h. Finally, the solvent was removed under reduced pressure and the residue was dissolved in ethyl acetate and passed through a filtration column (60 M silica gel; eluent: ethyl acetate; width: 5 cm; length: 10 cm) in order to remove the conductive salt. Subsequently, the crude product obtained was dissolved in dichloromethane and adsorbed onto 60 M silica gel. The crude product was separated by column chromatography (column width: 3 cm, length: 30 cm) on 60 M silica gel in the cyclohexane/ethyl acetate 9:1 eluent mixture. The products obtained were purified further by Kugelrohr distillation at 40 C. and 10.sup.3 mbar. The following two regioisomers were obtained:

2-Methyl-4-tert-butylaniline

[0121] .sup.1H-NMR (300 MHz, CDCl.sub.3): (ppm)=1.43 (s, 9H), 2.26 (s, 3H), 4.57 (bs, 2H, NH.sub.2), 6.70 (d, .sup.3J=7.9 Hz, 1H), 6.87 (dd, .sup.3J=7.9 Hz, .sup.4J=1.3 Hz, 1H), 7.07 (d, .sup.4J=1.3 Hz, 1H).

[0122] .sup.13C-NMR (75 MHz, CDCl.sub.3): (ppm)=20.98, 29.97, 34.39, 118.96, 127.51, 127.57, 128.95, 134.95, 140.56.

[0123] GC (hard method, HP-5): t.sub.R=7.61 min

[0124] HRMS calculated for C.sub.11H.sub.18N.sup.+: 164.1439; found: 164.1439.

[0125] R.sub.f=0.34 (9:1 cyclohexane/ethyl acetate)

[0126] Yield: 20% (colorless liquid)

4-Methyl-2-tert-butylaniline

[0127] .sup.1H-NMR (300 MHz, CDCl.sub.3): (ppm)=1.28 (s, 9H), 2.21 (s, 3H), 3.83 (bs, 2H, NH.sub.2), 6.69 (d, .sup.3J=8.8 Hz, 1H), 7.06-7.11 (m, 2H).

[0128] .sup.13C-NMR (75 MHz, CDCl.sub.3): (ppm)=17.87, 31.71, 34.03, 115.42, 122.61, 123.28, 127.60, 141.25, 142.28.

[0129] GC (hard method, HP-5): t.sub.R=7.81 min

[0130] HRMS calculated for C.sub.11H.sub.18N.sup.+: 164.1439; found: 164.1436.

[0131] R.sub.f=0.13 (9:1 cyclohexane/ethyl acetate)

[0132] Yield: 35% (colorless liquid)

Example 4: Preparation of 2,4-diethylaniline

[0133] According to GP 1, 0.12 g (0.93 mmol, 0.07 equiv.) of 1,3-diethylbenzene, 0.33 g (1.00 mmol) of tetrabutylammonium tetrafluoroborate, 1 mL (0.98 g, 12.41 mmol, 1 equiv.) of pyridine were dissolved in 5 mL of dry acetonitrile and introduced into the anode space. The cathode space was charged with a solution of 0.40 g (1.21 mmol) of tetrabutylammonium tetrafluoroborate and 0.4 mL of trifluoromethanesulfonic acid in 6 mL of acetonitrile. The electrolysis was conducted in a divided Teflon cell.

[0134] Anode: BDD; electrode area: 2.5 cm.sup.2.

[0135] Cathode: platinum; electrode area: 2.5 cm.sup.2.

[0136] Amount of charge: 224.6 C.

[0137] Current density: j=5 mA cm.sup.2.

[0138] Temperature: 60 C.

[0139] After the electrolysis time had elapsed, the anode and cathode space was introduced into a pressure tube, 1 mL (0.86 g, 10.00 mmol, 0.81 equiv.) of piperidine was added and the mixture was heated at 80 C. for 12 h. Subsequently, the solvent was removed under reduced pressure and the residue was dissolved in ethyl acetate and passed through a filtration column (60 M silica gel; eluent: ethyl acetate; width: 5 cm; length: 9 cm) in order to remove the conductive salt. The crude product obtained was dissolved in dichloromethane and adsorbed onto 60 M silica gel. The crude product was separated by column chromatography (column width: 3 cm, length: 30 cm) on 60 M silica gel in the cyclohexane/ethyl acetate 9:1 eluent mixture. The product obtained was purified further by Kugelrohr distillation at 40 C. and 10.sup.3 mbar. 70.0 mg (0.4 mmol, 50%) of a colorless liquid were obtained.

[0140] .sup.1H-NMR (300 MHz, CDCl.sub.3): (ppm)=1.11-1.27 (m, 6H), 2.41-2.60 (m, 4H), 3.53 (bs, 2H, NH.sub.2), 6.61 (d, .sup.3J=7.9 Hz, 1H), 6.80-6.92 (m, 2H).

[0141] .sup.13C-NMR (75 MHz, CDCl.sub.3): (ppm)=13.31, 16.15, 24.25, 28.24, 115.87, 128.07, 128.54, 135.07, 141.39.

[0142] GC (hard method, HP-5): t.sub.R=7.36 min

[0143] HRMS calculated for C.sub.11H.sup.15N.sup.+: 150.1283; found: 150.1269.

[0144] R.sub.f=0.18 (9:1 cyclohexane/ethyl acetate)

Example 5: Amination of Diphenylmethane

[0145] According to GP 1, 0.50 mmol (0.08 g, 0.04 equiv.) of diphenylmethane, 0.33 g (1.00 mmol) of tetrabutylammonium tetrafluoroborate, 1 mL (0.98 g, 12.41 mmol, 1 equiv.) of pyridine were dissolved in 5 mL of dry acetonitrile and introduced into the anode space of each of five divided Teflon cells. The cathode space of each was charged with a solution of 0.40 g (1.21 mmol) of tetrabutylammonium tetrafluoroborate and 0.4 mL of trifluoromethanesulfonic acid in 6 mL of acetonitrile.

[0146] Anode: BDD; electrode area: 2.5 cm.sup.2.

[0147] Cathode: platinum; electrode area: 2.5 cm.sup.2.

[0148] Amount of charge: 6 F in each case

[0149] Current density: j=20 mA cm.sup.2.

[0150] Temperature: 60 C.

[0151] After the electrolysis time had elapsed, the anode and cathode space of each cell was introduced into a respective pressure tube, and 1 mL (0.86 g, 10.00 mmol, 0.81 equiv.) of piperidine was added and the mixture was heated at 80 C. for 12 h. Subsequently, the five reaction mixtures were combined and the solvent was removed under reduced pressure. The residue was dissolved in ethyl acetate and passed through a filtration column (60 M silica gel; eluent: ethyl acetate; width: 5 cm; length: 12 cm) in order to remove the conductive salt.

[0152] The crude product obtained was dissolved in dichloromethane and adsorbed onto 60 M silica gel. The crude product was separated by column chromatography (column width: 4 cm, length: 55 cm) on 60 M silica gel in the cyclohexane/ethyl acetate eluent mixture. An additional 1% triethylamine was added to the eluent mixture. The following solvent gradient was used: 600 mL of cyclohexane/ethyl acetate 4:1, 1000 mL of cyclohexane/ethyl acetate 2:1, 2000 mL of cyclohexane/ethyl acetate 1:1. The mixed fractions obtained were also separated semi-preparatively by means of HPLC, in order thus to isolate the various regioisomeric diamines. The mobile phase used was acetonitrile+0.1% triethylamine/water+0.1% triethylamine in a ratio of 15:85. The fractions obtained were extracted five times with 50 mL each time of dichloromethane. The combined organic extracts were dried over sodium sulfate and then the solvent was removed under reduced pressure. The solids obtained were dried under high vacuum (10-mbar) at 40 C.

[0153] The following amination products were obtained:

2-Benzylaniline

[0154] .sup.1H-NMR (400 MHz, DMSO): (ppm)=3.79 (s, 2H), 4.83 (bs, 2H, NH.sub.2), 6.50 (ddd, .sup.3J=7.3 Hz, .sup.4J=1.3 Hz 1H), 6.64 (dd, .sup.3J=7.9 Hz, .sup.4J=1.3 Hz, 1H), 6.85 (dd, .sup.3J=7.5 Hz, .sup.4J=1.6 Hz, 1H), 6.92 (ddd, .sup.3J=7.6 Hz, .sup.4J=1.6 Hz, 1H), 7.14-7.31 (m, 5H).

[0155] .sup.13C-NMR (101 MHz, DMSO): (ppm)=36.49, 114.74, 116.24, 124.27, 125.83, 126.90, 128.25, 128.78, 129.86, 140.35, 146.12.

[0156] GC (hard method, HP-5): t.sub.R=10.50 min

[0157] HRMS calculated for C.sub.13H.sub.14N.sup.+: 184.1126; found: 184.1134.

[0158] R.sub.f=0.48 (4:1 cyclohexane/ethyl acetate)

[0159] Yield: 10% (yellowish solid)

4-Benzylaniline

[0160] .sup.1H-NMR (400 MHz, DMSO): (ppm)=3.75 (s, 2H), 4.87 (bs, 2H, NH.sub.2), 6.50 (d, .sup.3J=8.4 Hz, 2H), 6.87 (d, .sup.3J=8.4 Hz, 2H), 7.10-7.30 (m, 5H).

[0161] .sup.13C-NMR (101 MHz, DMSO): (ppm)=40.47, 114.02, 125.61, 128.21, 128.24, 128.48, 129.14, 142.41, 146.68.

[0162] GC (hard method, HP-5): t.sub.R=11.01 min

[0163] HRMS calculated for C.sub.13H.sub.14N.sup.+: 184.1126; found: 184.1114.

[0164] R.sub.f=0.48 (4:1 cyclohexane/ethyl acetate)

[0165] Yield: 11% (yellowish solid)

4,4-Diaminodiphenylmethane

[0166] .sup.1H-NMR (300 MHz, DMSO): (ppm)=3.56 (s, 2H), 4.80 (bs, 4H, NH.sub.2), 6.47 (d, .sup.3J 8.3 Hz, 4H), 6.81 (d, .sup.3J=8.3 Hz, 4H).

[0167] .sup.13C-NMR (75 MHz, DMSO): (ppm)=39.75, 113.95, 128.93, 129.43, 146.37.

[0168] GC (hard method, HP-5): t.sub.R=13.42 min

[0169] HRMS calculated for C.sub.13H.sub.15N.sub.2.sup.+: 199.1235; found: 199.1245.

[0170] Yield: 4% (colorless solid)

3,4-Diaminodiphenylmethane

[0171] .sup.1H-NMR (300 MHz, DMSO): (ppm)=3.57 (s, 2H), 4.83 (bs, 2H, NH.sub.2), 4.91 (bs, 2H, NH.sub.2), 6.29-6.28 (m, 3H), 6.43-6.51 (m, 2H), 6.79-6.93 (m, 3H).

[0172] .sup.13C-NMR (75 MHz, DMSO): (ppm)=40.74, 111.46, 113.93, 114.12, 116.22, 128.52, 128.66, 129.11, 142.83, 146.53, 148.53.

[0173] GC (hard method, HP-5): t.sub.R=13.42 min

[0174] HRMS calculated for C.sub.13H.sub.15N.sub.2.sup.+: 199.1235; found: 199.1238.

[0175] Yield: 4% (colorless solid)

2,4-Diaminodiphenylmethane

[0176] .sup.1H-NMR (400 MHz, DMSO): (ppm)=3.63 (s, 2H), 5.75 (bs, 4H, NH.sub.2), 6.45-6.50 (m, 1H), 6.63-6.68 (m, 3H), 6.79 (dd, .sup.3J=7.5 Hz, .sup.4J=1.6 Hz, 1H), 6.87 (dd, .sup.3J=7.6 Hz, .sup.4J=1.6 Hz, 1H), 6.92 (d, .sup.3J=8.4 Hz, 2H).

[0177] .sup.13C-NMR (100 MHz, DMSO): (ppm)=35.81, 114.87, 115.61, 116.37, 125.43, 126.52, 129.07, 129.25, 129.48, 143.72, 145.58.

[0178] GC (hard method, HP-5): t.sub.R=13.02 min

[0179] HRMS calculated for C.sub.13H.sub.15N.sub.2.sup.+: 199.1235; found: 199.1242

[0180] Yield: 6% (colorless solid)

3,2-Diaminodiphenylmethane

[0181] .sup.1H-NMR (400 MHz, DMSO): (ppm)=3.65 (s, 2H), 562 (bs, 4H, NH.sub.2), 6.46-6.54 (m, 4H), 6.66 (dd, .sup.3J=7.9 Hz, .sup.4J=1.3 Hz, 1H), 6.83 (dd, .sup.3J=7.6 Hz, .sup.4J=1.6 Hz, 1H), 6.88-6.94 (m, 1H), 6.93-7.02 (m, 1H).

[0182] .sup.13C-NMR (100 MHz, DMSO): (ppm)=36.72, 113.04, 115.05, 115.53, 116.67, 118.16, 124.90, 126.73, 128.81, 129.80, 140.79, 145.43, 146.30.

[0183] GC (hard method, HP-5): t.sub.R=12.93 min

[0184] HRMS calculated for C.sub.13H.sub.15N.sub.2.sup.+: 199.1235; found: 199.1237.

[0185] Yield: 3% (yellow solid)

Example 6: Amination of Triphenylmethane

[0186] According to GP 1, 0.50 mmol (0.12 g, 0.04 equiv.) of triphenylmethane, 0.33 g (1.00 mmol) of tetrabutylammonium tetrafluoroborate, 1 mL (0.98 g, 12.41 mmol, 1 equiv.) of pyridine were dissolved in 5 mL of dry acetonitrile and introduced into the anode space of each of five divided Teflon cells. The cathode space of each was charged with a solution of 0.40 g (1.21 mmol) of tetrabutylammonium tetrafluoroborate and 0.4 mL of trifluoromethanesulfonic acid in 6 mL of acetonitrile.

[0187] Anode: BDD; electrode area: 2.5 cm.sup.2.

[0188] Cathode: platinum; electrode area: 2.5 cm.sup.2.

[0189] Amount of charge: 6 F in each case

[0190] Current density: j=15 mA cm.sup.2.

[0191] Temperature: 60 C.

[0192] After the electrolysis time had elapsed, the anode and cathode space of each cell was introduced into a respective pressure tube, and 1 mL (0.86 g, 10.00 mmol, 0.81 equiv.) of piperidine was added and the mixture was heated at 80 C. for 12 h. Subsequently, the five reaction mixtures were combined and the solvent was removed under reduced pressure. The residue was dissolved in ethyl acetate and passed through a filtration column (60 M silica gel; eluent: ethyl acetate; width: 5 cm; length: 12 cm) in order to remove the conductive salt.

[0193] The crude product obtained was dissolved in dichloromethane and adsorbed onto 60 M silica gel. The crude product was separated by column chromatography (column width: 4 cm, length: 55 cm) on 60 M silica gel in the cyclohexane/ethyl acetate eluent mixture. An additional 1% triethylamine was added to the eluent mixture. The following solvent gradient was used: 1000 mL of cyclohexane/ethyl acetate 9:1, 1000 mL of cyclohexane/ethyl acetate 4:1, 900 mL of cyclohexane/ethyl acetate 2:1, 2000 mL of cyclohexane/ethyl acetate 1:1.

2-Aminotriphenylmethane

[0194] .sup.1H-NMR (400 MHz, CDCl.sub.3): (ppm)=3.45 (bs, 2H, NH.sub.2), 5.52 (s, 1H), 6.66-6.70 (m, 1H), 6.70-6.77 (m, 2H), 7.09 (dd, .sup.3J=7.5 Hz, .sup.4J=1.7 Hz, 1H), 7.12-7.17 (m, 4H), 7.22-7.35 (m, 6H).

[0195] .sup.13C-NMR (101 MHz, CDCl.sub.3): (ppm)=52.29, 116.59, 119.05, 126.79, 127.58, 128.69, 129.53, 129.64, 130.12, 142.54, 143.92.

[0196] GC (hard method, HP-5): t.sub.R=14.17 min

[0197] HRMS calculated for C.sub.19H.sub.18N.sup.+: 260.1439; found: 260.1444.

[0198] R.sub.f=0.54 (4:1 cyclohexane/ethyl acetate)

[0199] Yield: 6%

3-Aminotriphenylmethane

[0200] .sup.1H-NMR (400 MHz, CDCl.sub.3): (ppm)=3.67 (bs, 2H, NH.sub.2), 5.47 (s, 1H), 6.49 (d, .sup.4J=2.0 Hz, 1H), 6.53-6.64 (m, 2H), 7.06-7.17 (m, 5H), 7.17-7.32 (m, 6H).

[0201] .sup.13C-NMR (101 MHz, CDCl.sub.3): (ppm)=56.90, 113.33, 116.51, 120.20, 126.35, 128.37, 129.30, 129.60, 144.04, 145.24, 146.41.

[0202] GC (hard method, HP-5): t.sub.R=14.73 min

[0203] HRMS calculated for C.sub.19H.sub.18N.sup.+: 260.1439; found: 260.1431.

[0204] R.sub.t=0.42 (4:1 cyclohexane/ethyl acetate)

[0205] Yield: 3%

4-Aminotriphenylmethane

[0206] .sup.1H-NMR (400 MHz, CDCl.sub.3): (ppm)=3.61 (bs, 2H, NH.sub.2), 5.47 (s, 1H), 6.65 (d, .sup.3J=8.4 Hz, 2H), 6.92 (d, .sup.3J=8.4 Hz, 2H), 7.13 (dd, .sup.3J=7.6 Hz, .sup.4J=1.5 Hz, 4H), 7.18-7.24 (m, 2H), 7.25-7.31 (m, 4H).

[0207] .sup.13C-NMR (101 MHz, CDCl.sub.3): (ppm)=56.16, 115.44, 126.24, 128.33, 129.51, 130.39, 134.53, 144.21, 144.57.

[0208] GC (hard method, HP-5): t.sub.R=14.89 min

[0209] HRMS calculated for C.sub.19H.sub.18N.sup.+: 260.1439; found: 260.1430.

[0210] R.sub.f=0.33 (4:1 cyclohexane/ethyl acetate)

[0211] Yield: 8%

Example 7: Diamination of Triphenylmethane

[0212] According to GP 1, 0.12 g (0.50 mmol, 0.04 equiv.) of triphenylmethane, 0.33 g (1.00 mmol) of tetrabutylammonium tetrafluoroborate, 1 mL (0.98 g, 12.41 mmol, 1 equiv.) of pyridine were dissolved in 5 mL of dry acetonitrile and introduced into the anode space of each of five divided Teflon cells. The cathode space of each was charged with a solution of 0.40 g (1.21 mmol) of tetrabutylammonium tetrafluoroborate and 0.4 mL of trifluoromethanesulfonic acid in 6 mL of acetonitrile.

[0213] Anode: BDD; electrode area: 2.5 cm.sup.2.

[0214] Cathode: platinum; electrode area: 2.5 cm.sup.2.

[0215] Amount of charge: 6 F in each case.

[0216] Current density: j=15 mA cm.sup.2.

[0217] Temperature: room temperature.

[0218] After the electrolysis time had elapsed, the anode and cathode space of each cell was introduced into a respective pressure tube, and 1 mL (0.86 g, 10.00 mmol, 0.81 equiv.) of piperidine was added and the mixture was heated at 80 C. for 42 h. Subsequently, the five reaction mixtures were combined and the solvent was removed under reduced pressure. The residue was dissolved in ethyl acetate and passed through a filtration column (60 M silica gel; eluent: ethyl acetate; width: 10 cm; length: 8 cm) in order to remove the conductive salt and impurities of high molecular weight.

[0219] The crude product obtained was dissolved in dichloromethane and adsorbed onto 60 M silica gel. The crude product (1.04 g) was separated by column chromatography (column width: 4 cm, length: 55 cm) on 60 M silica gel in the cyclohexane/ethyl acetate eluent mixture. An additional 0.1% triethylamine was added to the eluent mixture. The following solvent gradient was used: 1600 mL of cyclohexane/ethyl acetate 2:1 and then, to complete elution, cyclohexane/ethyl acetate 1:1.

[0220] Two mixed fractions (154 mg, R.sub.f=0.36 cyclohexane/ethyl acetate 2:1 and 114 mg, R.sub.f=0.22 cyclohexane/ethyl acetate 2:1) were obtained, which according to GC/MS are diamines. In order to enable a further column chromatography separation, the mixed fractions were reacted with di-tert-butyl dicarbonate:

[0221] 154 mg (0.56 mmol, 1 equiv.) of the mixed fraction, 0.735 g (3.37 mmol, 6 equiv.) of di-tert-butyl dicarbonate and 0.09 g (1.12 mmol, 2 equiv.) of pyridine were dissolved in 20 mL of ethanol, and the mixture was stirred at room temperature for 52 h. TLC monitoring of the reaction solution showed complete conversion after this time. Subsequently, the solvent was removed under reduced pressure, and the crude product (274 mg) was adsorbed onto 60 M silica gel and separated by column chromatography (column length: 45 cm, column width: 3 cm) on 60 M silica gel in the cyclohexane/ethyl acetate 9:1 eluent mixture.

[0222] A pure fraction was obtained.

[0223] .sup.1H-NMR (400 MHz, CDCl.sub.3): (ppm)=1.44 (s, 18H, H-10), 5.65 (s, 1H, H-7), 6.40 (bs, 2H, NH), 6.74 (dd, .sup.3J=7.8 Hz, .sup.4J=1.5 Hz, 2H, H-5, H-5), 6.97-7.06 (m, 4H), 7.24 (d, .sup.4J=1.5 Hz, 1H), 7.27-7.34 (m, 4H), 7.65 (dd, .sup.3J=8.1 Hz, .sup.4J 1.3 Hz, 2H, H-4, H-4).

[0224] .sup.13C-NMR (101 MHz, CDCl.sub.3): (ppm)=28.39 (C-10), 47.65 (C-7), 80.34 (C-9), 124.34, 124.82, 127.23, 127.82, 129.62, 129.70, 134.39 (C-2, C-2), 136.19 (C-1, C-1), 141.35 (C-1), 153.83 (C-8).

[0225] HRMS calculated for C.sub.29H.sub.34N.sub.2O.sub.4Na.sup.+: 497.2416; found: 497.2419.

[0226] R.sup.f=0.25 (9:1 cyclohexane/ethyl acetate)

[0227] Yield: 3 mg (0.006 mmol, <1% based on triphenylmethane).

Example 8: Comparison of Different Electrodes

[0228] The electrochemical amination of m-xylene was conducted in a divided Teflon cell. The anode material used was glassy carbon, BDD (boron-doped diamond electrode) and graphite (see corresponding table). The cathode material used was platinum. The anode space was charged with a solution of 0.106 g (1 mmol, 0.2 mol L.sup.1) of m-xylene and 1 mL of pyridine (2.4 mol L.sup.1) in 0.2 mol L.sup.1 Bu.sub.4NBF.sub.4/acetonitrile (5 mL, dry). The cathode space was charged with a solution of 0.4 mL of trifluoromethanesulfonic acid in 0.2 mol L.sup.1 Bu.sub.4NBF.sub.4/acetonitrile (6 mL, dry). The electrolyses were conducted under galvanostatic conditions at room temperature with an amount of charge of 2.5 F. Current densities of 2-12 mA cm.sup.2 were used (see corresponding table). Once the respective amounts of charge had been attained, the reaction solution (anode and cathode space) was transferred into a pressure tube, and 1 mL of piperidine was added. This was followed by heating at 80 C. for 12 h. On completion of conversion to the amine, the acetonitrile was removed under reduced pressure, the residue was dissolved in ethyl acetate, and 30 L of n-octylbenzene were added as internal standard. After filtration through 2 cm of silica gel, the mixture was analyzed by means of GC and the yield of 2,4-dimethylaniline was ascertained using a calibration line that had been established beforehand. In individual cases, 2,4-dimethylaniline was isolated. For this purpose, the crude product was separated by column chromatography on 60 M silica gel in the cyclohexane/ethyl acetate 9:1 eluent mixture.

Anode: Isostatic Graphite

[0229]

TABLE-US-00001 TABLE 1 Electrochemical amination of m-xylene; 1 mmol of m- xylene; 12 mmol of pyridine; 0.2 mol L.sup.1 Bu.sub.4NBF.sub.4/acetonitrile; anode: isostatic graphite (about 3 cm.sup.2); cathode: platinum; amount of charge: 2.5 F; 22 C. Current density/ Entry mA cm.sup.2 Yield.sup.1/% 1 2 0 2 4 1 3 6 5 4 8 8 5 10 9 6 12 14 .sup.1GC, internal std. n-octylbenzene; mean from two screening experiments in each case.

Anode: Glassy Carbon

[0230]

TABLE-US-00002 TABLE 2 Electrochemical amination of m-xylene; 1 mmol of m- xylene; 12 mmol of pyridine; 0.2 mol L.sup.1 Bu.sub.4NBF.sub.4/acetonitrile; anode: glassy carbon (about 3 cm.sup.2); cathode: platinum; amount of charge: 2.5 F; 22 C. Current density/ Entry mA cm.sup.2 Yield.sup.1/% 1 2 8 2 4 2 3 6 2 4 8 0 5 10 0 6 12 0 .sup.1GC, internal std. n-octylbenzene; mean from two screening experiments in each case.

Anode: Platinum

[0231]

TABLE-US-00003 TABLE 3 Electrochemical amination of m-xylene; 1 mmol of m-xylene; 12 mmol of pyridine; 0.2 mol L.sup.1 Bu.sub.4NBF.sub.4/acetonitrile; anode: platinum (about 3 cm.sup.2); cathode: platinum; amount of charge: 2.5 F; 22 C. Current density/ Entry mA cm.sup.2 Yield.sup.1/% 1 2 3 2 4 4 3 6 3 4 8 2 5 10 3 6 12 2 .sup.1GC, internal std. n-octylbenzene; mean from two screening experiments in each case.
Anode: graphite felt

TABLE-US-00004 TABLE 4 Electrochemical amination of m-xylene; 1 mmol of m- xylene; 12 mmol of pyridine; 0.2 mol L.sup.1 Bu.sub.4NBF.sub.4/acetonitrile; anode: graphite felt (5.0 1.0 0.5 cm); cathode: platinum; amount of charge: 2.5 F; 22 C. Entry Current/mA Yield.sup.1/% 1 6 9 2 12 22 3 18 28 4 24 32 5 30 38 6 36 30 .sup.1GC, internal std. n-octylbenzene; mean from two screening experiments in each case.

Anode: Graphite Nonwoven

[0232]

TABLE-US-00005 TABLE 5 Electrochemical amination of m-xylene; 1 mmol of m- xylene; 12 mmol of pyridine; 0.2 mol L.sup.1 Bu.sub.4NBF.sub.4/acetonitrile; anode: graphite nonwoven (5.0 1.0 cm); cathode: platinum; amount of charge: 2.5 F; 22 C. Entry Current/mA Yield.sup.1/% 1 6 5 2 12 3 3 18 4 4 24 4 5 30 3 6 36 3 .sup.1GC, internal std. n-octylbenzene; mean from two screening experiments in each case.

Anode: BDD

[0233]

TABLE-US-00006 TABLE 6 Electrochemical amination of m-xylene; 1 mmol of m-xylene; 12 mmol of pyridine; 0.2 mol L.sup.1 Bu.sub.4NBF.sub.4/acetonitrile; anode: BDD (about 3 cm.sup.2); cathode: platinum; amount of charge: 2.5 F; 22 C. Current density/ Entry mA cm.sup.2 Yield.sup.1/% 1 2 40 2 4 43 3 6 44 4 8 57 5 10 55 6 12 55 .sup.1GC, internal std. n-octylbenzene; mean from two screening experiments in each case.

[0234] The screening of the current densities and electrode materials gave the following result: if isostatic graphite is used as anode material, it was possible to obtain 2,4-dimethylaniline in a maximum yield of 14% at a current density of 12 mA cm.sup.2 (table 1, entry 6). Glassy carbon as anode material gave 2,4-dimethylaniline in a yield of not more than 8% at an applied current density of 2 mA cm.sup.2 (table 2, entry 1). The use of platinum as anode material gave 2,4-dimethylaniline only in traces. Graphite felt as electrode material produced yields of up to 38% at a current of 30 mA (table 4, entry 5). Graphite nonwoven, by contrast, gave 2,4-dimethylaniline in a yield of up to 5% (table 5, entry 1). If BDD is used as anode material, it was possible to obtain yields of up to 57% at a current density of 8 mA cm.sup.2 of the desired 2,4-dimethylaniline (table 6, entry 4).

[0235] It is therefore clear that only with BDD as the electrode material was it possible to obtain economically viable yields in the electrochemical amination of m-xylene.

[0236] In addition, formation of deposits on the anodes was detected when platinum and glassy carbon were used. When isostatic graphite was used, corrosion of the anode under the given electrolysis conditions was observed. This was not the case with BDD. This also appears to make the use of BDD as electrode material in the amination of aromatics having benzylic CH economically advantageous, since longer service lives with lesser expenditure on cleaning are the result.

[0237] Further anode materials examined in detail for their suitability for electrochemical amination of alkylaromatics were platinum and graphite felt. However, preliminary experiments for this purpose gave distinctly lower yields of amine compared to BDD. The amination of diphenylmethane with one of the abovementioned electrodes did not give any detectable amination products. For this compound, an amination product was detectable exclusively with BDD.

[0238] Thus, the use of BDD as electrode material is advantageous over these other materials in the amination of aromatic rings which contain at least one benzylic CH bond and wherein the amination takes place on the aromatic ring having the benzylic CH bond, because economically viable yields of the desired product are obtainable in this way.