DE1670946B2 - PROCESS FOR THE PREPARATION OF 2-FURYL-BENZIMIDAZOLES HALOGENATED IN THE FURYL RESIDUE - Google Patents

Description

Hal and R stand for a chlorine or bromine atom,
R 'for a chlorine atom or the methyl

group stands

m stands for the numbers 0,1 or 2 and

ρ stands for the numbers 0 or 1

characterized in that 2-furyl-benzimidazoles the general formula

R.

(H)

in which

R. R 'and ρ have the meaning given above

own and
π stands for the numbers 0,1 or 2,

in the presence of acids and optionally in the presence of solvents at temperatures between 100 and 180 ° C with chlorine or bromine treated.

2. The method according to claim 1, characterized in that that the reaction is carried out at temperatures between 100 and 150 "C.

3. Process according to Claims 1 and 2, characterized in that the acids are organic Sulphonic acids or inorganic acids and, as solvents, high-boiling chlorinated hydrocarbons used.

4. Process according to Claims 1 and 2, characterized in that the acids and solvents are used optionally chlorinated acetic acid is used.

5. Process according to Claims 1, 2 and 4, characterized in that the halogenation is carried out in the presence of trichloroacetic acid.

The invention relates to a chemically peculiar process for the production of widely known, 2-furyl-benzimidazoles halogenated in the furyl radical. It is known that these compounds serve to combat of mushrooms and worms.

It has already become known that one in the furyl radical chlorinated 2-furyl-benziniidazole is obtained if correspondingly chlorinated brenzschleimsäui-en with o-phenylenediamine implemented (South African patent specification 65/3584). However, this method is very disadvantageous, because the production of pyrocucous acids is extremely laborious. These acids are produced by chlorination of ethyl pyroxate to obtain an ester mixture, fractional distillation. Saponification and isolation of the various chloro- and dichloropurenzic acids via their alkaline earth salts and optionally reducing partial elimination of chlorine (cf. South African patent specification 65/3584). This very awkward path is for one

■ 5 technical presentation extremely unsuitable

Furthermore, it has already become known that benzimidazoles halogenated on the benzene ring are obtained when one benzimidazole, ζ. B. the 2-methyl-benzimidazole, in Usually treated with halogen ζ. B. at 0 to 20 ° C in glacial acetic acid (J. Indian Chem. Soc. 42,777).

About the halogenation of 2-furyl-benzimidazole is so far nothing has become known.

It has been found that the largely known 2-furyl-benzimidazoles halogenated in the furyl radical can be used the general formula

Shark

in which

Hai and R stand for a chlorine or bromine atom,

R 'stands for a chlorine atom or the methyl group

stands

m stands for the numbers 0,1 or 2, and

4c ρ stands for the numbers 0 or 1,

obtained in a simple manner if you 2-furyl-benzimidazole the general formula

(ID

in which

R, R 'and ρ have the meaning given above, and

η stands for the numbers 0.1 or 2,

in the presence of acids and optionally in the presence of solvents at temperatures

ho between 100 and 180 ° C with chlorine or bromine treated.

It can be described as extremely surprising that the halogenation takes place exclusively in the furyl radical, since in view of the prior art

ds had to be expected that primarily the Benzene ring would be halogenated. It is also surprising that the desired halogenation especially with the conditions according to the invention

occurs because very similar conditions are not the goal to lead.

If you let z. B. chlorine on 2-furyl- {2) -benziinidazole in chloroform at 0 ° or in carbon tetrachloride at 20 ⁰ C, 2- [5-chlorofuryl- {2)] - benzimidazole can only be detected in traces in the chlorination in chlorobenzene at 130 ⁰ C, in formic acid at 95 ° C, in glacial acetic acid at 90 ⁰ C or in trichloroacetic acid at 70 ⁰ C is produced, despite the use of a top excess of chlorine, the title compound in low yield.

This shows that deviations from the conditions according to the invention, such as. B. the lack of the required acid, or working at temperatures below 100 "C ₁ does not lead to satisfactory results.,

The course of the reaction of the reaction according to the invention can be based on the following formula scheme explained:

Cl ₂
- HCl

The furyl-benzimi- _w dazenes of the formula (H) used as starting materials are largely known. B. around 2-furyl- (2) -benzimidazoI, 5-methyl-, 5-chloro-2-furyl- (2) -benzimidazole and 4-chloro-2-furyI- (2) -benzimidazole the not yet known benzimidazoles can be prepared in the same way as ^ the known benzimidazoles. Examples include: 4-methyl- (F.228-230 ^o C) and 2- [3,4-dichlorofuryl- {2)> benzimidazole (F.220 ^o C).

Both organic acids and inorganic acids can be used to carry out the halogenation. Suitable organic acids are aliphatic carboxylic acids are suitable boiling above 100 ⁰ C, such as acetic acid and propionic acid, especially chlorinated aliphatic carboxylic acids which boil above 100 ° C, such as chloro-, dichloro- and trichloroacetic acid, and chlorinated 4s propionic acids. These organic acids can also serve as solvents.

Sulphonic acids, such as benzene and toluenesulphonic acids, can be used as further organic acids. If necessary, mixtures of acids can also be used; this is advantageous if an acid with a low dissociation constant (e.g. glacial acetic acid with DC of 1.7 x 10 ^s ) is used, an addition of concentrated sulfuric acid or trichloroacetic acid (DC approx. 2 · 10 ') is advantageous here (see example section).

The inorganic acids used are preferably sulfuric or phosphoric acid; these acids can but do not serve as a solvent, it is therefore expedient to add another one with the same acid (> o Add miscible solvent or one of the aforementioned organic acids (see example section).

Suitable solvents are all inert organic solvents which under the reaction conditions do not show any reaction with the reaction partners used. They must also have a boiling point above 100 ⁰ C. The above-mentioned carboxylic acids are particularly appealing, as are chlorinated hydrocarbons, especially chlorinated aromatic hydrocarbons such as chlorobenzene and dichlorobenzene

The reaction temperatures are between 100 and 180 ° C, preferably between 110 and 150 ⁰ C.

When carrying out the process according to the invention, the furylbenzimidazoles are mixed with the acid and optionally together with a solvent and adds chlorine or bromine. Included It does not matter whether the halogen is added in gaseous or liquid form or dissolved in a solvent In the case of gaseous addition, especially of bromine, the halogen can be diluted with other gases, z. B. with carbon dioxide.

The processing of the reaction mixture takes place in usual way.

In the case of chlorination of the unsubstituted 2-Furyl- (2} -benzimidazoles is molten trichloroacetic acid a particularly favorable solvent, which also acts as an acid because here after If the product is immediately diluted with water, i.e. without neutralization, the trichloroacetic acid precipitates can be recovered by evaporation and distillation without further treatment.

In the halogenation of the furyl benzimidazoles, one or more halogen atoms can be present in the Enter furyl residue. The first halogen atom is preferably in the 5-position of the furyl radical. Will the If halogenation is continued, more halogen atoms enter the furyl radical. Partly you get Mixtures of several chlorination products. The constitution of the individual compounds can be determined by the nuclear magnetic resonance spectra are determined, as well as by products of the same constitution, which are based on other Pathways have been synthesized.

The furyl-benzimidazoles obtainable according to the invention can be used for combating fungi and worms can be used in a known manner (see South African patent specification 65/3584). They are particularly suitable to combat phytopathogenic fungi, e.g. B. to combat snow mold. In this case they are used as seed dressing.

example 1

N
H

C!

Is introduced at 120 ⁰ C with stirring in the melt of 36.8 g of 2-furyl (2) -benzimidazole and 250 g of trichloroacetic acid 16 g of chlorine. After cooling to 8O ⁰ C, the reaction mixture is poured under stirring in 900 cc of water, filtered off with suction, the precipitate washed with water. until the filtrate no longer shows an acidic reaction. After drying, 39.3 g of 2- [5-chlorofuryl (2)] benzimidazole with a temperature of 229 ° to 232 ° C. are obtained, which can be purified by recrystallization from carbon tetrachloride or from xylene: colorless, shiny flakes with a melting point of 235 ° to 236 ° C. According to the mixed melting point and 1R spectrum, the substance is identical to the product obtained in the usual way from 5-chloro-pyrocucic acid and o-phenylenediamine.

Example la

Passing Ib g of chlorine at 120 ⁰ C under agitation in the solution of Figure 3b, 8 g of 2-rairyl- (2) -benzimidazole in 250 uem

Jl

Cl

17.5 g of 2- [3,4-dichlorofuryl- (2)] -benzimidazole are chlorinated in 130 g of trichloroacetic acid as in Example 1, but the precipitate precipitated with water is purified by taking it up in 2000 ecm of 5% sodium hydroxide solution with stirring 90 to 95 ⁰ C, filtration and precipitation with solid ammonium chloride. After washing and drying, 13 g of 2- [Trichlorfuryl- (2)] - benzimidazole, mp 194 to 196 ⁰ C, which can be further purified by recrystallization from xylene (mp 197-198 ° C).

Preliminary product

The 2- [3,4-dichlorofuryl- (2)] - benzimidazole can be prepared from 3,4-dichloropyrenzic acid (cf. South African patent 65/3584) by heating with o-phenylenediamine in polyphosphoric acid in the usual way (cf. J. Am . Chem. See. 79, 417). After recrystallization from xylene, the compound has a melting point of 220 ^° C.

CH ₃

Example 3

20 g of 5-methyl-2-furyl- (2) -benzimidazole are chlorinated in 150 g of trichloroacetic acid as in Example 1. It is then diluted with water and neutralized with ammonia as in Example 1a. 14.8 g of 5-methyl-2- [5-chlorofuryl- (2)] -benzimidazoi are obtained, which melts at 199 ° C after recrystallization from toluene.

Glacial acetic acid to which concentrated sulfuric acid was added. After cooling to 80 ⁰ C the solution was poured in 500 cc of water, add concentrated under cooling to ammonia to alkaline reaction and filtered off. After washing with water and drying, 27.5 g of 2- [5-chloro-furyl- {2)] - benzimidazoL are obtained

Example Ib

If you work as indicated in Example la, but replace the sulfuric acid with 28 g of p-toluenesulfonic acid, 36.2 g of the same end product can be isolated in this way.

Example Ic

36.8 g of 2-furyl- (2) -benzimidazole are passed into the suspension in the solution of 28 g of p-folaolsulfonic acid 16 g of chlorine in 300 ecm of chlorobenzene at 130 ° C. with stirring, then the chlorobenzene is distilled in vacuo and works through the remaining oily residue with aqueous concentrated ammonia. To Suction and drying gives 37 g of 2- [5-chlorofuryl- (2)] - benzimidazole.

Example 2
Cl Cl

Example 4

Mixture of

CH ₃

VAn / °

Longer chlorination with a total of 25 g of chlorine results in the usual procedure (cf. Examples 1,1a and 3) instead of the compound obtained according to Example 3, 5-methyl-2- [4,5-dichlorofuryl- (2)] benzimidazole mixed with a little 5-methyl-2- [3,5-dichlorofuryl- (2)] benzimidazole obtain.

Example 5

Cl

As in Example 3, 22.4 g of 5-chloro-2-furyl- (2) -benzimidazole are chlorinated in trichloroacetic acid and, after recrystallization from carbon tetrachloride, 53-dichloro-2-furyl- (2) -benzimidazole with a melting point of 200 ⁰ C.

Example 6

Is passed under stirring into the melt of 18.4 g of 2-furyl (2) -benzimidazole in 150 g of trichloroacetic acid at 120 ⁰ C with a CO ₂ stream 16 g of bromine, the batch is poured after cooling to below ⁰ C to 8O Stir in 500 ecm of water and suck off the precipitate. After washing with water, it is treated with 350 ecm of 3% aqueous ammonia solution and again suctioned off after 2 hours. After washing with water and drying, 22.6 g of 2- [5-BromfuryI- (2)] - benzimidazole are obtained, Recrystallization from xylene shows a melting point of 225-227 ° C.

According to the mixed melting point and IR spectrum, the substance is identical to that of 5-bromopyrumic acid (cf. R. 52,352) and o-phenylenediamine product obtained in the usual way

Example 6a

The bromination is carried out as in Example 6, but in 150 ecm glacial acetic acid as the solvent. At the Working up analogously to Example 2 gives 10 g of 2- [5-bromofuryl- (2)] benzimidazole.

Example 7 Cl Cl

* - Br 15 g of 2- [3,4-dichlorofuryl- (2)] benzimidazole are brominated as in Example 6a (see Example 4). After diluting the batch with water, it is neutralized with ammonia, then filtered off with suction and washed with water. The dried 2- [5-bromo-3,4-dichlorfuryl- (2)] - benzimidazole is obtained from a benzene-ligroin mixture (3: 1) to give yield 13.7 g, mp 200 ⁰ C.

Xö 520/470

Claims (1)

Patent claims: 1. Method of making im Furyfrest halogenated 2-furyl-benzimidlazoIen of the general a formula Hal in which