DE1136330B - Process for the preparation of N-phenyl-N'-cycloalkyl-p-phenylenediamines - Google Patents

Description

GERMAN

PATENT OFFICE

V 18958 IVb / 12 ο

REGISTRATION DATE: JULY 8, 1960

ANNOUNCEMENT THE REGISTRATION AND ISSUE OF THE EDITORIAL: SEPTEMBER 13, 1962

The invention relates to the improvement of the process for the preparation of N-phenyl-N'-cycloalkyl-p-phenylenediamines, in particular of N-phenyl-N'-cyclohexyl-p-phenylenediamine, by reacting an N-phenyl-p-phenylenediamine with a Cycloalkanone to Schiff's base and its reduction with formic acid.

Processes for the production of these compounds are already known (German patents 702 618 and 851 344 and German Auslegeschrift 1 078 119), which can also be accessed via the easily available Ship bases go. These compounds are quite simple and with good yields available, but they are very sensitive to moisture, higher temperatures and in particular against acids. Therefore, the required reduction in Schiff's bases is preferably catalytic carried out. It is also known that the reduction with formic acid (German Auslegeschrift 1 078 119, Column 3, lines 18 to 20) to be carried out, which, however, in the manner previously carried out (Leukart) is uneconomical.

It has now surprisingly been found that the reaction of N-phenyl-p-phenylenediamine with a cycloalkanone and the subsequent reduction of the Schiffschen obtained as an intermediate Base succeeds very advantageously if the reaction is carried out in an organic solvent which is very hygroscopic. This makes the reduction with formic acid in particular good adjustable and rapid reaction without pressure at temperatures below 100 ° C with consumption achieved by only almost equivalent amounts of formic acid with approximately theoretical yields. Another advantage is that you do not use a 3 to 4-fold excess of the cycloalkanone to work, only equivalent amounts of the ketone are necessary.

The polyhydric alcohols, for example, are used as hygroscopic organic solvents, such as glycols, glycerine, hexanetriol, into consideration. Due to the hygroscopicity of the solvent obviously the moisture leading to decomposition is absorbed and eliminated, so that thereby the mentioned advantages occur in the reaction.

In addition, it was found that with simultaneous reduction of the Schiff base with nascent Hydrogen, e.g. B. by adding zinc dust, the reaction is even smoother, so that even impure Starting products can be used without prior distillation. This is for example at Method of manufacture

of N-phenyl-N'-cycloalkyl-

p-phenylenediamines

Applicant:

VEB paint factory Wolfen, Wolfen (district of Bitterfeld)

Theodor Waag, Wolfen (district of Bitterfeld),

and Dr. Willy Köhler, Dessau, have been named as the inventor

the case with N-phenyl-p-phenylenediamine obtained by hydrolysis of nerolic acid.

example 1

140 g of crude N-phenyl-p-phenylenediamine (96.5%) are dissolved in 140 g ethylene glycol under heating to 8O ⁰ C. At 8O ⁰ C then 90 g of cyclohexanone are added. The mixture is then stirred for 10 minutes. Then 15 g of formic acid and 1 g of zinc dust are added. The reaction, recognizable by the foam formation, starts immediately and is maintained without further heating by adding a further 45 g of formic acid and adding 5 g of zinc dust. After the addition, which takes about 20 minutes, the mixture is stirred for a further 10 minutes at 80 to 85 ° C., then cooled to 50 to 60 ° C. and diluted with 200 g of 50% aqueous methanol. The product cools to 10 to 20 ° C. with stirring and is then filtered off. Yield of N-phenyl-N'-cyclohexyl-p-phenylenediamine, dried at 70 ° C.: 200 g (98% of theory), mp 112 to 118 ° C.

Example 2

41 g of crude N-phenyl-p-phenylenediamine (89%) are dissolved in 150 g of dimethylformamide, 19.5 g Cyclohexanone is added and the mixture is heated to 80 to 90 ° C. for 30 minutes. Then will 13 g of 85% formic acid were added. The mixture is then stirred for 30 minutes. Then it will be the solution is diluted with methanol and the precipitated N-phenyl-N'-cyclohexyl-p-phenylenedi-

209 640/339

amine filtered off. F. 106 to 110 ⁰ C. Yield: 49 g (92.5 <y ₀ of theory).

Example 3

140 g raw N-phenyl-p-phenylenediamine (96.5%) are dissolved in 140 g of ethylene glycol with heating to 80 ° C. At 80 ° C., 77 g of cyclopentanone are then dissolved admitted. The mixture is then stirred for 10 minutes. Then 60 g of formic acid are added added, and the mixture is stirred for a further 30 minutes. Then the solution is mixed with Diluted methanol and filtered off the precipitated N-phenyl-N'-cyclopentyl-p-phenylenediamine. F.loS up to 169 ° C. Yield: 176 g (95% of theory).

Claims (4)

PATENT CLAIMS: * 5 1. A process for the preparation of N-phenyl-N'-cycloalkyl-p-phenylenediamines by reacting an N-phenyl-p-phenylenediamine with a cycloalkanone and reducing the Schiff base obtained as an intermediate with formic acid in the presence of a solvent, characterized in that a hygroscopic solvent is used as the solvent. 2. The method according to claim 1, characterized in that at the same time one with formic acid nascent hydrogen-forming substance, such as zinc dust, is added, 3. The method according to claim 1 and 2, characterized in that the hygroscopic solvent a polyhydric alcohol is used. 4. The method according to claim 1 to 3, characterized characterized in that N-phenyl-p-phenylenediamine is reacted with cyclohexanone. Considered publications:
German interpretative document No. 1 078 119. θ! W 640/339 9.62