Method for the Production of Primary Amines Comprising a Primary Amino Group Which is Bound to an Aliphatic or Cycloaliphatic C-Atom, and a Cyclopropyl Unit

Abstract

Process for preparing primary amines having a cyclopropyl unit and a primary amino group bound to an aliphatic or cycloaliphatic carbon atom (amine A) by cathodically reducing oximes having a cyclopropyl unit or oxime derivatives in which the hydrogen atom in the oxime group has been replaced by an alkyl or acyl group (oxime O) at a temperature of from 50 to 100° C. in an essentially anhydrous electrolyte solution in a divided electrolysis cell.

Description

EXAMPLE 1

Apparatus:       Electrolysis unit with catholyte and anolyte circuits
                 and two divided electrolysis cells connected in series
Anode:           2 graphite anodes, effective area of each; 300 cm2
Cathode:         2 lead cathodes, effective area of each: 300 cm2
Membrane:        Proton-conducting perfluorinated membrane having
                 sulfonic acid groups, e.g. Nafion 324 from DuPont
Distance between 6 mm
electrode
and membrane:
Current density: 3.4 A/dm2
Voltage:         20-40 V
Temperature:     55° C.
Composition      979.2 g of MeOH, 20.8 g of H2SO4, 96% strength
of anolyte:
Composition      5000 g of MeOH, 400 g of sodium methoxide solution,
of catholyte:    30% in MeOH, 600 g of cyclopropylphenylmethanone
                 oxime 1
Flow rate:       150-200 L/h

In the electrolysis under the conditions indicated, anolyte and catholyte were pumped through the respective half cells for 24 hours (corresponds to an amount of charge of 5 F/mol of 1). Analysis of the reaction product mixture by gas chromatography indicated 95.1% by area of the desired product 2, 0.10% of the ring-opened compound 3, 0.82% of starting material 1 and 3.18% of high boilers.

EXAMPLE 2

Apparatus:       Electrolysis cell with catholyte and anolyte circuits
Anode:           Graphite, effective area: 35 cm2
Cathode:         Lead, effective area: 35 cm2
Membrane         Proton-conducting perfluorinated membrane having
                 sulfonic acid groups, e.g. Nafion 117 from DuPont
Current density: 3.4 A/dm2
Voltage:         15-20 V
Temperature:     40° C.
Composition of   117.5 g of MeOH, 25 g of H2SO4, 96% strength
anolyte:
Composition of   94.0 g of MeOH, 1.0 g of H2SO4, 96% strength, 5 g
catholyte:       of cyclopropylphenylmethanone oxime 1

In the electrolysis under the conditions indicated, anolyte and catholyte were pumped through the respective half cells for 4.11 hours (corresponds to an amount of charge of 6 F/mol of 1). Analysis of the reaction product mixture by gas chromatography indicated 83.3% by area of the desired product 2, 1.3% of the ring-opened compound 3, and 15.6% of high and intermediate boilers.

EXAMPLE 3

(For Comparison)

Apparatus:       Electrolysis cell with catholyte and anolyte circuits
Anode:           Graphite, effective area: 300 cm2
Cathode:         Lead, effective area: 300 cm2
Membrane         Proton-conducting perfluorinated membrane having
                 sulfonic acid groups, e.g. Nafion 324 from DuPont
Current density: 3.4 A/dm2
Voltage:         14-33 V
Temperature:     40° C.
Composition of   783 g of MeOH, 17 g of H2SO4, 96% strength
anolyte:
Composition of   2600 g of MeOH, 100 g of NaOMe, 30% strength in
catholyte:       MeOH, 300 g of cyclopropylphenylmethanone
                 oxime 1

In the electrolysis under the conditions indicated, anolyte and catholyte were pumped through the respective half cells for 27.6 hours (corresponds to an amount of charge of 6.5 F/mol of 1). Analysis of the reaction product mixture by gas chromatography indicated 77.3% by area of the desired product 2, 2.0% of unreacted oxime 1 and 20.7% of high and intermediate boilers.

Claims

1. A process for preparing primary amines having a cyclopropyl unit and a primary amino group bound to an aliphatic or cycloaliphatic carbon atom (amine A) by cathodicallly reducing oximes having a cyclopropyl unit or oxime derivatives in which the hydrogen atom in the oxime group has been replaced by alkyl or acyl group (oxime O) at a temperature of from 50 to 100° C. in an essentially anhydrous electrolyte solution in a divided electrolysis cell.

2. The process according to claim 1, wherein the amines A are compounds of the general formula H2N—CHR1R2 (formula I), where R1 is hydrogen, C3-C8-cycloalkyl, C1-C20-alkyl, C6-C20-aryl or together with R2 and the methine group located between R1 and R2 forms a C5-C6-cycloalkyl group, with the abovementioned hydrocarbon radicals being able to be substituted by C1-C6-alkoxy or halogen, andR2 is C3-C8-cycloalkyl, C1-C20-alkyl, C6-C20-aryl or together with R2 and the methine group located between R1 and R2 forms a C5-C6-cycloalkyl group, with the abovementioned hydrocarbon radicals being able to be substituted by C1-C6-alkoxy, NH2—, C1-C20-alkylamino or halogen,with the proviso that at least one of the radicals R1 and R2 is cyclopropyl or is substituted by cyclopropyl, andthe oxides O are compounds of the general formula R5O—N═CR3R4 (formula II),where R3 has the same meaning as R1 in formula I,R4 has the same meaning as R2 in formula I and the radicals R3 and R4 may be substituted by 1-hydroxyimino(C1-C20)alkyl radicals, 1-(C1-C6-alkoxy imino(C1-C20)alkyl radicals or 1-(C-C6-acyloxyimino(C1-C20)alkyl radicals andR5is hydrogen, C1-C6-alkyl or C1-C6-acyl.

3. The process according to claim 1, wherein the amines A are compounds of the general formula Ia,

4. The process according to claim 1, wherein the catholyte comprises an amine A and an oxime O and also a C1-C4-alkyl alcohol as solvent

5. The process according to claim 1, wherein the catholyte comprises a mineral acid or an alkali metal C1-C4)alkoxide.

6. The process according to claim 1, wherein the cathode surface is formed by a material having a high hydrogen overvoltage.

7. The process according to claim 1, wherein the cathode surface is formed by lead zinc, tin, nickel, mercury, cadmium, copper or alloys of these metals or glassy carbon, graphite or diamond.

8. The process according to claim 1, wherein the water content of the catholyte is less than 2% by weight.