DE1932297A1 - Process for the preparation of benzimidazole-2-carbamic acid esters - Google Patents

Description

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COLOR FACTORY BAYERAG

LEVERKUSEN- Beyerwerk "Pttent-AbteUung ST / ΜΗ ^Z * ^J Unl 1969

Process for the production of
Benzimidazole-2-carbamic acid esters

The present invention relates to a chemically peculiar process for the preparation of widely known benzimidazole-2-carbamic acid esters, which are known to be used as fungicides (US Pat. No. 2,593 50 * 0 ·

It has already become known that 2-anilino-benzimidazoles are obtained when o-pbenylenediamines are mixed with aromatic ones
Isocyanide dichlorides in a molar ratio of 1: 1 (BeIg.
Patent 632,578).

It is also known that benzimidazole-2-carbamic acid esters are obtained when o-phenylenediamine is reacted with N-cyano-alkyl carbamates (South African patent 67/6589). However, this method has a number of disadvantages. In order to achieve greater yields, there are excesses
N-cyanoalkyl carbamates and longer reaction times or
higher reaction temperatures required.

It has now been found that the largely known benzimidazole-2-carbamic acid esters can be used the formula

(D

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X stands for hydrogen, halogen, alkyl with 1-4 carbon atoms or alkoxy with 1-4 carbon atoms stands and

R represents alkyl of 1-12 carbon atoms, cycloalkyl of 5-8 carbon atoms and aralkyl,

obtained when using ο-phenylenediamines of the formula

(II)

in which X has the meaning given above, with N-dichloromethylene carbamic acid ester of the formula

(IH)

in which R has the meaning given, at temperatures between -10 ° and + 4-0 ⁰ C in the presence of bases

implements.

It can be described as extremely surprising that side reactions, in particular aminolysis of the ester group, do not occur in this reaction and, accordingly, no by-products are formed. This is because it is known that carbamic acid esters are aminolyzed by amines (Houben-Weyl, Volume VIII, pp. 161-162 (1952)). The method according to the invention therefore has a number of advantages. The Benzimidezol-2-carbamic acid esters are obtained in high purity and quantitative yield , without an excess of one or

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other component would be necessary. There is also no need for a higher energy supply, since the implementation starts at low levels Temperatures runs rapidly.

Use o-phenylenediamine and methoxycarbonyl isocyanide dichloride as starting materials, the course of the reaction can can be represented by the following equation:

In the formula (II), X preferably represents hydrogen, chlorine, alkyl having 1-3 C atoms, such as methyl, isopropyl, and Alkoxy with 1-2 C atoms, such as methoxy. Examples include: o-phenylenediamine, 1,3 »4-tolylenediamine, 4-Cblor-o- ^ phenylenediamine, 4-methoxy-o-phenylenediamine. The phenylenediamines are known.

In the formula (III), R preferably represents alkyl having 1-8 C atoms, such as methyl, ethyl, isopropyl, n-butyl, n-octyl; Cyclohexyl; Phenylalkyl with 1-3 carbon atoms in the alkyl radical, e.g. B. benzyl and phenylethyl.

Examples of these compounds are: N-dichloromethylene carbamic acid methyl ester, ethyl ester, Isopropyl ester, -n-butyl ester, -n-octyl ester, -cyclohexyl ester, benzyl ester and phenyl ethyl ester.

The N-dicbloroethylene carbamic acid esters are not yet known. However, they can be easily prepared by reacting the previously known Dichlormethylencarbamidsäurechlorids with alcohols or phenols in the presence, s ^ inert organic solvent such as ether, dioxane, tetrahydrofuran, benzene, toluene, at temperatures between 0 and +40 ⁰ C.

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An example is the production of the ethyl dichloromethylcarbamate specified:

To the solution of 300 g of dichloromethylene carbamic acid chloride (= 1.88 moles) in 350 ml of ether (dried over Na), 86.5 g of ethanol (absolute) (= 1, 88 moles), (reaction ^{temperature between 15 and 20 0} C). The solution is kept at room temperature for a further 2 hours, the ether is distilled off and the product is rectified. The main fraction of 267 g ( ^e 84 % of theory) (bp ₂₀ 5> 3-68 °) is distilled again through a column: 230 g (= 72 % of theory) bp ₂₀ 68 °.

All inert organic solvents can be used as diluents in question. These include hydrocarbons such as gasoline or toluene, chlorinated hydrocarbons such as chloroform, Ethers such as diethyl ether or dioxane. But it can also be water or aqueous mixtures with organic solvents, such as dioxane, acetone or tetrahydrofuran can be used.

The reaction according to the invention is carried out in the presence of bases carried out. As such, alkali and alkaline earth hydroxides, carbonates and hydrogen carbonates, or tertiary organic Serving bases. Examples include: sodium hydroxide, potassium carbonate, potassium hydrogen carbonate, triethylamine and Pyridine. · ■

The reaction temperatures can be varied over a wide range. In general, one works between -10 and +40 ⁰ C, preferably between Ό and +30 ⁰ C.

When carrying out the method according to the invention, sets one mole of the o-pbenylenediamine in the presence of 2 moles of base with 1 mole of the isocyanide dichloride.

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The still new carbamic acid esters can be used in the same way like those already known to be used as fungicides.

Example 1:

A solution of 15.6 g of metboxycarbonyl isocyanide dichloride in 50 ml of chloroform is added dropwise with stirring to a mixture of 10.8 g of o-pbenylenediamine, 20.2 g of triethylamine and 300 ecm of chloroform, the temperature being kept at about 20 ° C. by cooling with ice will. After stirring for a further 10 minutes, the mixture is filtered off with suction and the precipitate is washed with chloroform. After drying, 19 g of the ester are obtained. The product decomposes somewhat at 215 ~ 220 ^° C., but remains solid.

Be is pie 12:

H Τ °° Λ

10.8 g of o-pbenylenediamine are dissolved together with 8 g of sodium hydroxide in a mixture of 200 ecm of water and 50 ecm of dioxane. 17.0 g Äthoxycarbonylisocyaniddichlorid the temperature being maintained by cooling below 20 ⁰ C are added dropwise in a mixture with 50 cc of dioxane in the cooled to 10 ° C solution. After stirring for 10 minutes, the mixture is filtered off with suction, the precipitate is washed with water and acetone and dried. 20 g ester, melting point: 320 ° (zj.

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In an analogous way ^{we get: 'JO} * - λ- ° '

Benzimidazole-2-carbamic acid n-butyl ester, m.p .: then becomes solid again,

Benzimidazole-2-carbamic acid n-octyl ester, m.p .: then becomes solid again,

Benzimidazole-2-carbamic acid benzyl ester, Scbmp .: then becomes solid again.

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Claims (3)

Patent claims: 1) Process for the preparation of benzimidazole-2-carbamic acid ester of the formula in which X for hydrogen, halogen, alkyl with 1 to 4 carbon atoms or alkoxy with 1 to 4- Carbon atoms and R is alkyl of 1 to 12 carbon atoms, Cycloalkyl of 5 to 8 carbon atoms as well as aralkyl, characterized in that one phenylenediamines of the formula in which X has the meaning given, with N-dichloromethylene carbamic acid esters of the formula Π-0-gN. , _ci in which R has the meaning given above, Reacts at temperatures between -10 ° and +40 ⁰ C in the presence of bases * Le A 12 3 20 - 7 - 009882/2181 2) Method according to claim 1, characterized in that that the reaction is carried out at temperatures between 0 and 30.degree performs. 3) Process according to claim 1 and 2, characterized in that the reaction is carried out in the presence of solvents performs. Le A 12 320 - β - 009882/2181