GB2122617A - Method for the preparation of arylethylamines - Google Patents

Method for the preparation of arylethylamines Download PDF

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Publication number
GB2122617A
GB2122617A GB08317345A GB8317345A GB2122617A GB 2122617 A GB2122617 A GB 2122617A GB 08317345 A GB08317345 A GB 08317345A GB 8317345 A GB8317345 A GB 8317345A GB 2122617 A GB2122617 A GB 2122617A
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Prior art keywords
hydrogen
formula
catholyte
cathode
salt
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GB8317345D0 (en
Inventor
Sven Goran Berttil Andersson
Hans Viktor Holmberg
Lars Anders Ragnar Nilsson
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STIFTELSEN IND ORGANISK
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STIFTELSEN IND ORGANISK
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D209/00—Heterocyclic compounds containing five-membered rings, condensed with other rings, with one nitrogen atom as the only ring hetero atom
    • C07D209/02—Heterocyclic compounds containing five-membered rings, condensed with other rings, with one nitrogen atom as the only ring hetero atom condensed with one carbocyclic ring
    • C07D209/04—Indoles; Hydrogenated indoles
    • C07D209/10—Indoles; Hydrogenated indoles with substituted hydrocarbon radicals attached to carbon atoms of the hetero ring
    • C07D209/14—Radicals substituted by nitrogen atoms, not forming part of a nitro radical
    • C07D209/16—Tryptamines
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B3/00—Electrolytic production of organic compounds
    • C25B3/20—Processes
    • C25B3/25—Reduction

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Acyclic And Carbocyclic Compounds In Medicinal Compositions (AREA)

Abstract

Arylethylamines are obtained by electrolytic reduction of the corresponding aryl nitroethene in the presence of a hydroxylamine in the catholyte using a strong negative cathode potential during the entire process.

Description

SPECIFICATION Method for the preparation of arylethylamines This invention relates to an improved method of electro-chemically reducing 1-aryl-2-nitroethenes to arylethylamines.
Although the electrochemical reduction of nitrostyrenes has been described in the chemical literature (cf for instance Japanese Patent 49-13777), the use of this technique as a practical preparation of phenylethylamines has seldom been realised because of insufficient chemical efficiency.
It has now been found that a method for preparing arylethylamines in water solutions in high yields and with excellent purity can be achieved.
This new method is characterized by electrochemical reduction of a 1-aryl-2-nitroethene of the formula
wherein Ar is an aromatic group, X is hydrogen or one or more substituents on the aromatic group selected from alkyl, alkoxy, hydroxy,
(R3 and R4 are the same or different and each representing hydrogen or alkyl),
-CN, -COOR3, -CF3, -NO2 and halogen, R1 is hydrogen or methyl and R2 is hydrogen or an alkyl group with 1-4 carbon atoms, in the presence of hydroxylamine or a salt thereof and with a strong negative cathod potential during the entire process to form an arylethylamine of the formula
or a pharmaceutically acceptable salt thereof, in which formula Ar, R1 and R2 have the meaning given above and Y is as defined for X with the exception that it does not represent -NO2.
The arylethylamines have the general formula
wherein Ar is an aromatic group, Y is hydrogen or one or more substituents in the aromatic group selected from alkyl, alkoxy, hydroxy,
(R3 and R4 are the same or different and each representing hydrogen or alkyl),
-CN, -COOR3, -CF and halogen, R1 is hydrogen or methyl and R2 is hydrogen or an alkyl group with 1-4 carbon atoms.
Aromatic groups of interest in this Application are for instance phenyl, naphthyl or indolyl.
Alkyl groups of interest in this Application are straight or branched alkyl groups with 1-5 carbon atoms, for instance methyl, ethyl, n-propyl and isopropyl.
Alkoxy groups of interest in this Application are alkyl-O- groups where the alkyl moiety is defined as above. Halogeno groups of interest in this Application are chloro, bromo and fiuoro.
The phenylethylamines of formula I obtained by the method of the invention can be in the form of pharmaceutically acceptable salts e.g. a hydrobromide, hydrochloride, phosphate, sulphate, citrate or tartrate.
The compounds of formula I are useful as pharmaceuticals. The nitroarylethenes used as starting material in the process of this invention have the formula
wherein Ar, R1 and R2 have the meaning given above and X is as defined for Y but can also represent -NO2.
The catholyte may consist of a dilute aqueous solution of a strong acid alone or a mixture of a strong acid, water and an organic solvent. The strong acid is for example sulfuric, hydrochloric, hydrobromic, phosphoric or a sulfonic acid. The concentration of acid and organic solvent if the later has acid-base properties should be such that the hydronium ion concentration is between 10-5 M and 20 M, preferably more than 10-3 M.
The relative amounts of water and organic solvent can be varied over a wide range. The organic solvent may be an alcohol, carboxylic acid, ether, amide or nitrite. The ratio between catholyte volume and cathode area should be as small as possible.
The anolyte may consist of diluted aqueous mineral acids, preferably sulfuric or hydrochloric acid. The concentration is from 2%to 10% by volume.
The anode is normally a DSAanode (metal anode overlaid with noble metal oxides) but may also consist of lead, lead dioxide, graphite or platinum metals.
The cathode material must be carefully chosen. It must have an electrode surface with high hydrogen overpotential. This is achieved by making the cathode of a material with high hydrogen overpotential or by electrodeposition of a metal with high hydrogen overpotential on the cathode before or during the process.
The cathode material may be zinc, lead, cadmium, mercury, tin, or conducting materials (for example graphite, lead, nickel, copper, aluminium, titanium) on which deposition of for example zinc, lead, cadmium, tin or mercury can be done.
The electrolytic cell should be a divided one with good mass transport properties. The diaphragm can be of the ion exchanging type or a plastic tissue.
The temperature should be as low as possible. The process is usually carried out at temperatures below 20"C.
Cathode potential, current density, concentration of nitrostyrene and mass transport properties to the cathode surface are a function of each other. According to the invention it has been found that a large negative potential is important to carry out the reduction successfully. Therefore the reduction should be carried out either as a controlled potential electrolysis at a large negative potential or as a constant current electrolysis where the values for current density, concentration of nitrostyrene and mass transport properties to the cathode surface are such, that the potential has a large negative value. The potential should be more negative than - 1.0 V relative to a SCE (saturated calomel electrode) reference electrode.The reference electrode is placed in contact with the cathode at an angle of about 45" to the cathode surface.
Furthermore, it has been found according to the invention that a successful realization of the reduction involves addition of a hydroxylamine our a salt thereof to the catholyte, preferably hydroxylamine. The concentration can vary from traces to saturated solution.
The chemical efficiency increases with increasing concentration of the hydroxylamine. The upper limit of the hydroxylamine concentration is determined by the solubility in the catholyte. We prefer a concentration higher than 0.1 M.
Suitable salts of hydroxylamine are hydroxyl ammonium hydrogen sulfate, hydroxyl ammonium sulfate, hydroxyl ammonium chloride, and hydroxyl ammonium phosphate.
Isolation of the product is accomplished according to well known methods. The pH of the catholyte is properly adjusted (pH 4 in most instances) and then extracted with for example toluene or dichloromethane.
Afterthat the pH of the water phase is increased to about pH 9-10 when the phenethylamine contains a phenolic group and to about pH 12 in other cases and then extracted several times with for example toluene or dichloromethane. The solvent is evaporated and the free amine of high purity is obtained.
According to a preferred embodiment of the invention a compound of the formula
is reduced to
The reduction is carried out with the addition of hydroxylamine to the catholyte and with a strongly negative potential during the entire process ( < -1.2 V).
The following illustrates the principle and the adaption of the invention, however, without limiting it thereto.
Example 1 The electrolytic equipments used were of the filterpress type with DSA0D anodes and lead cathodes. The exposed area of both the anode and cathode were 20 cm2. The equipment had a reference electrode, placed in contact with the cathode at an angle of 45" to the cathode surface. The anode and cathode chambers were separated by a strong cation exchanging diaphragm (Nation z 390). Both the anolyte and catholyte were pumped through the cell with centrifugal pumps. The substrate was placed in a container made of a plastic net. The container dipped into the catholyte solution.
The analyses were carried out with HPLC. The conditions used and the results are shown in table 1. The conversion of the substrate was in all examples 100%.
The catholyte pH was maintained constant during the electrolysis by acid addition.
The anolyte consisted of 1 M H2SO4.
TABLE 1
Run Sub- H2O Catholyte conditions Cathode Current Potentiale) Amp. Chemicno. strate Cosolvent Acidc) Hydroxyl Metalsalt Temp. density VISCE hours al mols ml amm. salt mg pH C effic ml ml mols Aldm iency % 1 0.05 105 - H2SO4 6 - ZNCO3 100 0.2 16 Pb 15 -1.55#-2.00 45.8 66 (NH22 " " - " " OH)2 0.018 " " " " " " " " 80 H2SO4 3 " " - " " " " " " " 23 " 35 -1.60#-1.80 " 80 4 " " - " " " 0.09 " " " " " " -1.60#-1.90 49 86 5 0.14 " - " " " " " " " " " " -1.55#-1.90 79 79 6 0.0045 " - " " 0.018 " " " " 16 " 10.8 -1.40#-1.46 42 81 7 0.05 210 - " 12 " 0.036 " 200 " 23 " 35 -1.72#-1.90 45.5 74 8 0.0045 105 - " 6 " 0.018 " 100 " 16 Graphite 10.8 -1.65#-1.53 4.2 74 9 " " - " " " " " " " 52 Pb 27.5 -1.40#-1.47 " 72 10 " 95 - " 15 " " " " - 16 " 10.8 -1.25#-1.42 " 79 (NH211 " 80 - " 30 OH)2 " " " - " " " -1.28#-1.42 4.2 76 H2SO4 TABLE 1 (cont...) Run Sub- H2O Catholyte conditions Cathode Current Potentiale) Amp. Chemicno. strate Cosolvent Acidc) Hydroxyl Metalsalt Temp. density VISCE hours al mols ml amm. salt mg pH C effic ml ml mols Aldm iency % 12 0.0045 100 - HCl 5 - ZnCO3 100 0.4 16 Pb 15#12.5e)-1.6d) 4.2 78 (NH2OH)2 13 0.014 17 MeOH 89 H2SO4 4.1 H2SO4 0.008 " " " " " 5 =-2.1 11.1 86 14 " 45 EtOH 60 " 6 " " " " " " " 15 - " 83 15 " " i-PrOH " " " " " " " " " " " - " 81 16b) 0.032 27 MeOH 87 40%HBr 20 - a) " " " 13.5 -1.20#-1.70 20.4 61 a) Zinc was electro-depositioned on the cathode surface before the nitrostyrene reduction.
b) The conditions according to Japanese Patent 49-13777.
c) The acid voiume before the electrolysis.
d) Constant potential electrolysis.
e) The arrows show the changes during the electrolysis.
Example 2
The same equipment was used and the experiments were run in the same manner as in example 1.
TABLE 2 Run Sub- H2O Catholyte conditions Cathode Current Cathode Amp. Chemicno. strate Cosolvent Acidc) Hydroxyl Metalsalt Temp. density potentialb) hours al mols ml amm. salt C effic ml ml mg Aldm VISCE iency mols % 1 0.0106 27 MeOH 87 HCl 22 - ZnO 100 16 Pb 13.5 -1.50#-1.54 15.8 60 2 " " " " " " (NH2OH) 0.012 " " " " " -1.49#-1.55 " 81 H2SO4 a) The acid volume before the electrolysis.
b) The arrows show the changes during the electrolysis.
Example 3
The same equipment was used and the experiments were run in the same manner as in example 1.
TABLE 3 Run Sub- H2O Catholyte conditions Cathode Current Cathode Amp. Chem NO. strate CosolventAcidc) Hydroxylamm.Metal salt Temp density potentialb) hours ical mols ml salt effic A/dm V/SCE iency ml ml mols mg C % 1 0.0106 27 MeOH 87 HCl 22 (NH2OH)2 0.012 ZnO 100 16 Pb 13.5 =-1.52 27.8 80 H2SO4 2 " " " " " " " " " " " " 5 -1.0#-1.1 " 57 3 " " " " " " - - " " " " 13.5 =-1.5 " 70 Example 4
The same equipment was used and the experiment was run in the same manner as in example 1.
TABLE 4 Run Sub- H2O Catholyte conditions Cathode Current Cathode Amp. Chemno. strate Cosolvent Acidc) Hydroxyl Metalsalt Temp. density potential hours ical ml amm.salt C effic A/dm V/SCE iency mols ml ml mols mg % 0.0024 27 MeOH 87 HCl 22 (NH2OH)2 0.004 ZnO 100 16 Pb 13.5 -1.32-1.38 27.8 93 H2SO4 Example 5
The experiment was run as in example 1 except that the anolyte consisted of 90% ethanol and 10% concentrated sulfuric acid.
TABLE 5 Run Sub- H2O Catholyte conditions Cathode Current Cathode Amp. Chemno. strate Cosolvent Acidc) Hydroxyl Metalsalt Temp. density potential hours ical ml amm.salt C effic A/dm V/SCE iency mols ml ml mols mg % 0.25 15 MeOH 175 HCl 10 (NH2OH)2 0.02 ZnSO4 300 23 Pb 12.5 -1.8-4.0 45 85 H2SO4 Example 6
The experiment was run as in Example 5.
TABLE 6 Run Sub- H2O Catholyte conditions Cathode Current Cathode Amp. Chemno. strate Cosolvent Acidc) Hydroxyl Metalsalt Temp. density potential hours ical mols ml amm.salt C effic ml ml mols mg A/dm V/SCE iency % 0.25 15 MeOH 175 HCl 10 (NH2OH)2 0.02 ZnSO4 300 24 Pb 12.5 -1.8-4.5 45 85 H2SO4 Example 7
The same equipment was used and the experiment was run in the same manner as in Example 1.
TABLE 7 Run Sub- H2O Catholyte conditions Cathode Current Cathode Amp. Chemno. strate Cosolvent Acidc) Hydroxyl Metalsalt Temp. density potential hours ical mols ml amm.salt C effic ml ml mols mg A/dm V/SCE iency % 0.1 35 MeOH 90 HCl 25 (NH2OH)2 0.01 ZnSO4 100 30 Pb 12.5 -2.0-3.0 10 60 H2SO4 Example 8
The experiment was run as in Example 1. Except that the anolyte consisted of 60% THF and 40% 1 M H2SO4.
TABLE 8 Run Sub- H2O Catholyte conditions Cathode Current Cathode Amp. Chemno. strate Cosolvent Acidc) Hydroxyl Metalsalt Temp. density potential hours ical mols ml amm.salt C effic ml ml mols mg A/dm V/SCE iency % 0.005 35 THF 60 H2SO4 5 (NH2OH)2 0.006 ZnCO3 36 Pb 10 6.7 80 H2SO4 Example 9
The experiment was run as in Example 8.
TABLE 9 Run Sub- H2O Catholyte conditions Cathode Current Cathode Amp. Chem density potential hours ical no. strate Cosolvent Acidc) Hydroxyl Metalsalt Temp. effic mols ml amm.salt C A/dm V/SCE iency ml ml mols mg % 35 THF 60 H2SO4 5 (NH2OH)2 0.006 ZnCO3 36 31 Pb 10 - 4 90 H2SO4

Claims (15)

1. A method for the preparation of an arylethylamine of the formula
or a pharmaceutically acceptable salt thereof, in which formula Ar is an aromatic group, Y is hydrogen or one or more substituents in the aromatic group selected from alkyl, alkoxy, hydroxy,
(R3 and R4 are the same or different and each representing hydrogen or alkyl,
-CN, -COOR3, -CF3 and halogen, R1 is hydrogen or methyl, and R2 is hydrogen or an alkyl group with 1-4 carbon atoms comprising electrochemical reduction of a nitrostyrene of the formula
wherein Ar, R1 and R2 have the meaning given above and X is as defined above for Y but additionally can also represent - NO2, in the presence of hydroxylamine or a salt thereof and with a strong negative cathode potential during the entire process.
2. A method according to claim 1 wherein Ar is a benzene, naphthalene or indene residue.
3. A method according to claim 1 or 2 wherein X is dimethylamino, methyl, hydrogen, hydroxy or methoxy.
4. A method according to any one of the preceding claims wherein R1 is hydrogen.
5. A method according to any one of the preceding claims wherein R2 is hydrogen, methyl or butyl.
6. A process according to claim 1 comprising reduction of a nitrostyrene of the formula
to a phenethylamine of the formula
7. A method according to any one of the preceding claims wherein the catholyte comprises aqueous acid.
8. A method according to claim 7 wherein the hydronium ion concentration in the catholyte is 10-5M to 20M.
9. A method according to claim 7 or 8 wherein the catholyte comprises an organic solvent.
10. A method according to claim 9 wherein the solvent is methanol, ethanol, isopropanol or tetrahydrofuran.
11. A method according to any one of the preceding claims wherein the catholyte comprises more than 0.1 M hydroxylamine or a salt thereof.
12. A method according to any one of the preceding claims wherein the anolyte comprises 2-10% by volume sulphuric acid or hydrochloric acid.
13. A method according to any one of the preceding claims wherein the cathode is lead.
14. A method according to any one of the preceding claims wherein a negative potential more negative than 1 volt, relative to a standard calomel electrode, is used.
15. A method according to claim 1 substantially as hereinbefore described with reference to any one of the Examples.
GB08317345A 1982-06-29 1983-06-27 Method for the preparation of arylethylamines Withdrawn GB2122617A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
SE8204015A SE455604B (en) 1982-06-29 1982-06-29 SET TO MAKE PHENETYLAMINES BY ELECTROCHEMICAL REDUCTION

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GB2122617A true GB2122617A (en) 1984-01-18

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AT (1) ATA236283A (en)
DE (1) DE3323047A1 (en)
DK (1) DK296383A (en)
FI (1) FI832362L (en)
GB (1) GB2122617A (en)
NO (1) NO832350L (en)
SE (1) SE455604B (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003042166A2 (en) * 2001-11-16 2003-05-22 Syngenta Participations Ag PROCESS FOR PREPARATION OF α-HYDROXYCARBOXYLIC ACID AMIDES
US6828351B2 (en) 2000-11-01 2004-12-07 Sention, Inc. Methods and compositions for regulating memory consolidation
US7244769B2 (en) 2000-11-01 2007-07-17 Cognition Pharmaceuticals, Llc Methods for treating an impairment in memory consolidation
US7619005B2 (en) 2000-11-01 2009-11-17 Cognition Pharmaceuticals Llc Methods for treating cognitive impairment in humans with Multiple Sclerosis
US10954234B2 (en) 2018-06-21 2021-03-23 Genentech, Inc. Solid forms of 3-((1R,3R)-1-(2,6-difluoro-4-((1-(3- fluoropropyl)azetidin-3-yl)amino)phenyl)-3-methyl-1,3,4,9-tetrahydro-2H-pyrido[3,4-b]indol-2-yl)-2,2-difluoropropan-1-ol and processes for preparing fused tricyclic compounds comprising a substituted phenyl or pyridinyl moiety, including methods of their use

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008244554A (en) * 2007-03-26 2008-10-09 Toa Corp Overcurrent protection circuit of audio system

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6828351B2 (en) 2000-11-01 2004-12-07 Sention, Inc. Methods and compositions for regulating memory consolidation
US7244769B2 (en) 2000-11-01 2007-07-17 Cognition Pharmaceuticals, Llc Methods for treating an impairment in memory consolidation
US7619005B2 (en) 2000-11-01 2009-11-17 Cognition Pharmaceuticals Llc Methods for treating cognitive impairment in humans with Multiple Sclerosis
WO2003042166A2 (en) * 2001-11-16 2003-05-22 Syngenta Participations Ag PROCESS FOR PREPARATION OF α-HYDROXYCARBOXYLIC ACID AMIDES
WO2003042166A3 (en) * 2001-11-16 2004-03-04 Syngenta Participations Ag PROCESS FOR PREPARATION OF α-HYDROXYCARBOXYLIC ACID AMIDES
US7521579B2 (en) 2001-11-16 2009-04-21 Syngenta Crop Protection, Inc. Process for the preparation of alpha hydroxycarboxylic acid amides
US10954234B2 (en) 2018-06-21 2021-03-23 Genentech, Inc. Solid forms of 3-((1R,3R)-1-(2,6-difluoro-4-((1-(3- fluoropropyl)azetidin-3-yl)amino)phenyl)-3-methyl-1,3,4,9-tetrahydro-2H-pyrido[3,4-b]indol-2-yl)-2,2-difluoropropan-1-ol and processes for preparing fused tricyclic compounds comprising a substituted phenyl or pyridinyl moiety, including methods of their use
US11780834B2 (en) 2018-06-21 2023-10-10 Genentech, Inc. Solid forms of 3-((1R,3R)-1-(2,6-difluoro-4-((1-(3-fluoropropyl)azetidin-3- yl)amino)phenyl)-3-methyl-1,3,4,9-tetrahydro-2H-pyrido[3,4-b]indol-2-yl)-2,2-difluoropropan-1-ol and processes for preparing fused tricyclic compounds comprising a substituted phenyl or pyridinyl moiety, including methods of their use

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GB8317345D0 (en) 1983-07-27
DK296383D0 (en) 1983-06-28
SE455604B (en) 1988-07-25
SE8204015D0 (en) 1982-06-29
ATA236283A (en) 1984-07-15
FI832362L (en) 1983-12-30
DK296383A (en) 1983-12-30
JPS5953689A (en) 1984-03-28
SE8204015L (en) 1983-12-30
DE3323047A1 (en) 1984-02-23
FI832362A0 (en) 1983-06-28
NO832350L (en) 1983-12-30

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