DE1010959B - Process for the preparation of disubstituted maleic acid and fumaric acid dinitriles - Google Patents

Description

Process for the preparation of disubstituted maleic acid and fumaric acid dinitriles The invention relates to an improved process for the preparation of disubstituted Maleic acid and disubstituted fumaric acid dinitriles.

It is from U.S. Patents 2,476,270,2473486 and 2,328,890 known that alkyl esters of fatty acids which are in the t- or 2-position of the alkyl Cyano groups contain, when heated to high temperatures, unsaturated nitriles give while splitting off acetic acid.

It is also known that succinic acid dinitrile on heating easily splits off hydrogen cyanide at high temperature.

For example, a fatty acid t, 2-dicyanoalkyl ester can become like a succinic acid dinitrile behave and give off hydrocyanic acid, or it can turn out to be Cyanalkyl esters behave and split off t moles of fatty acid.

From the Journal of the Chemical Society, Vol. 1935, pp. 400 to 406, it is known that by heating ß-cyanoethyl acetate to 450 to 460 "only 30d / 0 of the starting material transesterified and 19% acrylic acid can be obtained. on the other hand it is known that succinic acid dinitrile easily splits off hydrocyanic acid at 220 ° and Acrylonitrile there. It was therefore to be expected that when a 1,2-dicyano fatty acid ester was heated Hydrocyanic acid would preferably be split off at a high temperature. In contrast for this purpose it has now been found that when heated, one of the following is identified substituted 1, 2-Dicyanäthylfettsäureesters at high temperature the fatty acid molecule and the expected hydrocyanic acid is not split off.

The disubstituted maleic acid and disubstituted fumaric acid dinitriles of the general formula are obtained by the process of the invention: in which R1 is an alkyl or aralkyl radical and R2 is an alkyl, aralkyl or aryl radical, from 1,2-dinitriles of the general formula: in which R1 and R2 have the meaning given above and R3 is an acyl group, by heating to high temperatures.

In the given formulas, R1 can, for example, be a methyl, Ethyl or benzyl radical and R2, for example, a methyl, ethyl, benzy] - or Mean phenyl radical. The acyl group R3 can be saturated or unsaturated aliphatic, cycloaliphatic or aromatic and, for example, acetyl, propionyl, palmityl or be benzoyl.

When carrying out the procedural implementation, one can use the Starting compounds, if desired, alone or, preferably, in the presence of one Diluent, for example an organic acid such as acetic acid heat high temperatures. When the starting compound and the diluent are volatile, the heating is preferably carried out in such a way that the starting compound or the mixture of the starting compound and the diluent passes through a heated pipe, which is optionally filled with an inert solid, for example silica, is filled in order to achieve that the whole amount of the Starting compound is heated to the desired temperature.

The diluent can be obtained from the mixture of the resulting nitriles can be removed by distillation and the individual nitriles can if desired separated from one another by fractional distillation under reduced pressure. The yields of unsaturated dinitriles obtained by the process of the invention obtained are about 900 /, of theory or more, and they are higher than those which can be obtained by the previously known method.

The unsaturated dinitriles obtained by the process of the invention are valuable intermediate products for the production of dyes.

The invention is illustrated in the following examples. The parts are parts by weight.

Example 1 A solution of 291 parts of the acetate of α-methylacetoacetic acid nitrile cyanohydrin in 333 parts of glacial acetic acid is passed into a refractory glass tube, which is filled with silica fragments is filled, and is placed in this tube in an electric oven to 470 to 480 " heated. The solution is introduced into the pipe at such a rate that that the contact time with the hot tube is 10 seconds. The fission products are collected in a vessel that is filled with a mixture of carbon dioxide and Ethanol is cooled.

The reaction mixture, which dimethylfumar- and dimethyhnaleinsäuredinitril contains dissolved in acetic acid, is fractionally distilled to add the acetic acid remove. The yield of the mixed dinitriles obtained is 91,010 the theory. The dinitriles themselves are separated by fractional distillation.

Dimethylfumaric acid dinitrile, which is released under a pressure of 16 mm of mercury distilled at 80 ", melting at 81 °.

Dimethylmaleic dinitrile, which is released under a pressure of 21 mm of mercury distilled at 138 °, melts at 48 °.

The starting material used in the above example, for its Production in the context of this procedure protection is not sought, can by acting of acetic anhydride in the presence of a trace of concentrated sulfuric acid α-Methylacetessigsäurenitrilcyanhydrin, boiling point 124 "at a pressure of 1 mm Mercury column. This connection itself can be preserved through this be that a-Methylacetessigsäurenitril carefully anhydrous hydrogen cyanide is added in the presence of a small amount of potassium hydroxide. The acetate of a-Methylacetessigsäurenitrilcyanhydrins is a colorless viscous liquid which boils at 95 "under a pressure of 0.7 mm of mercury and has a refractive index n200 owns 1.4362.

Example 2 A solution of 121.3 parts of the acetate of α-ethyl acetic acid nitrile cyanohydrin in 124 parts of glacial acetic acid is heated under the conditions described in Example 1.

The cleavage product is fractionally distilled to remove the acetic acid to remove and recover the dinitrile.

Ethylmethylfumaric acid dinitrile distilled under a pressure of 12 mm of mercury at 71.5 to 74 "and ethylmethyl maleic dinitrile under one Pressure of 12 mm of mercury at 131 to 132 ".

The starting material used in this example for its manufacture Protection is not sought after, in a similar way as the acetate of a-Methylacetessigsäurenitrilcyanhydrin be prepared according to Example 1, but instead of a-methylacetoacetic acid nitrile the α-ethyl acetate acetic acid nitrile is used. The acetate of a-Ethylacetessigsäurenitrilcyanhydrin arises as a colorless viscous liquid, which under a pressure of 0.9 mm mercury column distilled at 98 to 100 "and has a refractive index n2D = 1.4395.

Example 3 A solution of 211.1 parts of the acetate of α-benzyl acetic acid nitrile cyanohydrin in 284 parts of glacial acetic acid is heated in the manner described in Example 1. That Reaction mixture, which predominantly from Benzylmethylfumaräuredinitril and a small amount of benzylmethylmaleic acid dinitrile and acetic acid fractionally distilled to remove the acetic acid and separate the dinitriles. Benzylmethylfumaric acid dinitrile distilled under a pressure of 0.1 mm mercury column at 80 to 85 "and benzylmethyl maleic acid dinitrile under a pressure of 0.05 mm Column of mercury in the form of a yellow oily liquid at 137 ". Benzylmethylfumaric acid dinitrile can, if desired, be further purified by dissolving it in methanol and the resulting solution is cooled in a bath made up of a mixture of solid Carbonic acid and ethanol. This produces crystals of pure benzylmethylfumaric acid dinitrile obtained which melt at 40 °.

The starting material used in this example above, for its Manufacturing Protection is not sought after, can be manufactured in a similar way like the acetate of a-Methylacetessigsäurenitrilcyanhydrin described in Example 1, however, α-benzyl acetic acid nitrile is used. The acetate of a-Benzylacetessigsäurenitrilcyanhydrin is obtained in the form of colorless crystals which melt at 103-104 ".

Example 4 A solution of 100 parts of the acetate of α-phenylacetoacetic acid nitrile cyanohydrin in 81 parts of glacial acetic acid is heated under the conditions described in Example 1. The reaction mixture is fractionally distilled to remove the acetic acid and to obtain a mixture of the dinitriles in a yield of 8701, of theory.

The dinitriles are separated by fractional distillation. Phenylmethylfumaric acid dinitrile, Melting point 70 °, distilled under a pressure of 0.05 mm of mercury 80 to 85 ". Phenylmethylmaleic acid dinitrile, melting point 56 °, distilled under a pressure of 0.04 mm of mercury at a temperature of 100 to 110 °.

The starting material used in the above example, for its Manufacture protection is not sought after, can be done in a similar way as in the example 1, but using a-phenylacetoacetonitrile. The acetate of a-Phenylacetessigsäurenitrilcyanhydrin is as colorless, viscous Liquid obtained under a pressure of 0.03 mm of mercury at 1200 boils.

Claims (1)

PATENT CLAIM Process for the production of disubstituted maleic acid and disubstituted fumaric acid dinitriles of the general formula: in which R1 is an alkyl or aralkyl radical and R2 is an alkyl, aralkyl or aryl radical, characterized in that a compound of the general formula: in which R1 and R2 have the meaning given above and R3 represents an aliphatic acyl group, preferably heated to high temperatures in the presence of a diluent. References considered: U.S. Patents No. 2476270, 2473486, 2438019, 2399349, 2328890.