DE2900506A1 - 2-cyanomethyl-benzimidazole prepn. - from 0-phenylenediamine and cyano-acetic acid deriv. without solvent - Google Patents

Abstract

Prepn. of 2-cyanomethylbenzimidazole (I) is carried out by reacting o-phenylenediamine (II) with a cpd. of formula (III) NC-CH2-CO-R1 (where R1 is NH2, NHR2, NR2R3 or OR2; R2 and R3 are H or aliphatic, araliphatic, cycloaliphatic or aromatic gps.). The reaction is effected at 130-150 degrees C in the absence of solvents, and pref. at 130-142 degrees C with a (III) : (II) molar ratio of 1-1.2:1. (I) is an intermediate for dyes and plant protection agents. The process gives good yields (e.g. 76%) using lower reaction temps. and simpler work-up procedures than prior art processes.

Description

Process for the preparation of 2-cyanomethylbenzimidazole

The invention relates to a new process for the preparation of 2-cyanomethylbenzimidazole by reacting o-phenylenediamine with cyanoacetic acid compounds at one temperature from 130 to 1500C and in the absence of solvents.

It is from J. Am. Chem. Soc., Vol. 65 (1943), pp. 1072-1075 known that one o-phenylenediamine and ethyl cyanoacetate in boiling, excess Converts aniline to 2-cyanomethylbenzimidazole. One can in the case of cyanoacetamide instead of ethyl cyanoacetate, the reaction also takes place in the melt without additional React solvent at a temperature of 165 to 209 0C. One moves in the latter case so> that the mixture of o-phenylenediamine and cyanoacetamide during Heated from 170 to 209 ° C. for 6 minutes and then reacted at 2000 ° C. for 9 minutes will. It should be noted that only rubbery, non-separable residues obtained when the heating period is too long. Both methods are satisfactory in terms of simple, economical, reliable and environmentally friendly Operation not.

In the case of the first-mentioned process, the 2-cyanomethylbenzimidazole obtained after the reaction by filtration on the press from the solvent L be separated. During the work-up Often solvent vapors get into the air in the factory and can endanger the health of those working there. This pollution the air in the room can be removed by encapsulating the filter press with a with a pull the cabin provided, but this press must then be used with the aid respiratory protective equipment must be used for those in the cramped cabin Persons poses an additional difficulty.

Another disadvantage of the process is the wastewater pollution associated with it. Part of the solvent used gets through the complex regeneration into the wastewater, there are also distillation residues, their disposal Cause costs. In the case of the process with cyanoacetamide as the starting material it is disadvantageous that high temperatures and in accordance with the aforementioned procedure (loc. cit., page 1 074) nitrobenzene baths and ether used as extractants Need to become. The reaction produces large amounts of ammonia, which and bring sewage problems with them. The aforementioned short-term heating-up times are to be complied with on an industrial scale with great effort.

It has now been found that 2-cyanomethylbenzimidazole is advantageously obtained by reacting o-phenylenediamine with cyanoacetic acid compounds when the reaction is carried out with cyanoacetic acid compounds of the formula where R1 is the radical -NH2, or represents the radical OR2 and the individual radicals R2 can be identical or different and each represent a hydrogen atom, an aliphatic, araliphatic, cycloaliphatic or aromatic radical, is carried out at a temperature of 130 to 150 ° C. and in the absence of solvents.

If ethyl cyanoacetate is used, the reaction can be represented by the following formulas: With regard to the known processes, the process according to the invention provides 2-cyanomethylbenzimidazole in a simpler, more reliable and more economical way in good yield and purity. Solvents are not required. Despite the longer operating time, the process according to the invention is more reliable and simpler compared to the known solvent-free process, since much lower temperatures are used, there is comparatively no or only insignificant formation of rubber-like residues and thus the work-up is simplified. Ether extractions and the associated operational and health damage as well as the formation of significant amounts of ammonia and thus environmental problems are avoided.

Recrystallization of the end product with water using Norit, as prescribed in the aforementioned publication (loc. Cit., Page 1075), is not necessary. The outlay on equipment is lower. All of these beneficial results are surprising in view of the prior art. J 'The starting materials are reacted in a stoichiometric amount or in excess, preferably in an amount of 1 to 1.2 mol of starting material I per mole of o-phenylenediamine. Preferred starting materials I are those. in their formulas R1 the remainder -NH2, the remainder the rest or denotes the radical -OR2 and the individual radicals R2 can be identical or different and each denotes a hydrogen atom, an alkyl radical with 1 to 7 carbon atoms, a cyclohexyl radical, an aralkyl radical or alkylaryl radical with 7 to 12 carbon atoms, a phenyl radical. The abovementioned radicals can also be substituted by groups which are inert under the reaction conditions, for example alkyl groups having 1 to 4 carbon atoms.

For example, the following starting materials I come into question: Methyl-, Xthyl-, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclohexyl, Benzyl, phenyl cyanoacetic acid esters; with the methyl, ethyl, propyl, isopropyl, Butyl, isobutyl, tert. -Butyl, sec-butyl, cyclohexyl, 3enzyl, phenyl groups substituted one or two times identically or differently on the amido nitrogen atom Cyanoacetic acid amides; Cyanoacetic acid, cyanoacetamide.

The reaction is carried out at a temperature of 130 to 15,000, preferably from 130 to 14200> expediently without pressure, continuously or discontinuously carried out.

The reaction can be carried out as follows: A mixture of the two Starting materials is added with thorough stirring of the mixture for 2 to 11 hours kept the reaction temperature. The result is something that is still stirrable at the reaction temperature Crystal slurry of 2-cyanomethylbenzimidazole, which is expediently in the same reaction rräß, expediently in a stirred tank, further processed to the subsequent products. The separation The secondary substances water and alcohol can be improved by passing nitrogen over them will. However, the end product can also be used in the usual way, e.g. by diluting with a solvent that dissolves the end product as little as possible, expediently water, cooling of the mixture and filtration. Will the response in plants like carried out a paddle dryer or a ball mill reactor, the end product can can be discharged directly after cooling the reaction mixture without with Must be diluted with water or a solvent.

The 2-cyanomethylbenzimidazole which can be prepared by the process of the invention is a valuable raw material for the production of dyes and pesticides.

The parts listed in the following example are parts by weight.

Example The mixture of 54 parts of o-phenylenediamine and 62 parts Ethyl cyanoacetate is heated to 140 ° C. for 10 hours while flushing with nitrogen. 75 parts of a crystal slurry of 2-cyanomethylbenzimidazole are obtained. The mixture is stirred with 100 parts of water and cooled, filtered and dried. Man receives 70 parts of 2-cyanomethylbenzimidazole (85 total) (76 β of theory) with a melting point of 180 to 0 200 0.

Claims (1)

Patent claim Process for the production of 2-cyanomethylbenzimidazole by reacting o-phenylenediamine with cyanoacetic acid compounds, characterized> that the reaction with cyanoacetic acid compounds of the formula where R1 is the radical -NH2, or denotes the radical -OR and the individual radicals R can be identical or different and each denotes a hydrogen atom, an aliphatic, araliphatic, cycloaliphatic, aromatic radical, is carried out at a temperature of 130 to 1500C and in the absence of solvents.