DE2137553C3 - Process for the production of tetrachlorophthalide - Google Patents

Description

Cl

CH, C1

Representation of the starting product in the o-XyloI molecule eight chlorine atoms are introduced, of which four again in the subsequent acidic saponification Form of hydrochloric acid can be split off. This gaseous hydrochloric acid, which occurs at a higher temperature leads to considerable problems with regard to corrosion and wastewater treatment and thus pollutes it Procedures with additional costs, which is a serious disadvantage.

It has now been found that tetrachlorophthalide is advantageously obtained by 2-chloromethyl-tetrachlorobenzoyl chloride of the formula

with 1 to 4 moles of an alkali metal hydroxide per mole of starting compound at a temperature of 60 to 120 ⁰ C and then cyclized the salt obtained without isolation at a temperature of 10 to 40 ° C by acidification to the lactone

20th

It is already known that derivatives of 2-hydroxymethyl-tetrachlorobenzoic acid are obtained if aromatic compounds which have at least two dichloromethyl groups in the ortho position and whose hydrogen atoms can be completely substituted by further CHCb groups and / or chlorine atoms, with at least 75 % Sulfuric acid or oleum saponified in the temperature range from 80 to 200 ⁰ C (cf. German Offenlegungsschrift 16 43 347). For example, tetrachloro-1,2-bis (dichloromethyl) benzene and concentrated sulfuric acid of tetrachlorophthalide can be prepared, a compound which is of interest as a fungicidal active ingredient (cf. German Offenlegungsschrift 19 03 169). To this end, however, 1 to 4 moles of an alkali metal hydroxide per mole of starting compound must first be ^{reacted at a temperature of 60 to 120 °} C. and then the salt obtained must be cyclized to the lactone by acidification ^{at a temperature of 10 to 40 ° C. without isolation}

It is extremely surprising that the saponification of the chlorocarbonyl group and the chloromethyl group takes place simultaneously under relatively mild conditions The chlorine atoms on the nucleus are - despite their accumulation and mutual influence - not exchanged.

In contrast to the previously known method, the method according to the invention has the advantage that only two instead of four chlorine atoms are split off per mole of starting product and no free hydrochloric acid accrues.

If sodium hydroxide solution is used as the saponifying agent and hydrochloric acid for the cyclization reaction, this takes place Reaction according to the following equation:

CO- Cl

+ 3 NaOH

-2NuCl

Cl Γ CIhOH CI H ₂ O

Cl \ Cl Cl co / CH, / I. \ 4 HCl YiI NaCi λ J 2 H ₂ O [ CI

The 2-chloromethyltetrachlorobenzoyl chloride required as the starting product can by nuclear chlorination of o-toluic acid chloride and subsequent side chain chlorination can be obtained (cf. US Pat. No. 3,253,900).

The process can be carried out without the use of solvents or diluents, preferably however, the reaction is in aqueous solution or suspension. Organic miscible with water Solvents, e.g. B. alcohols, ketones, cyclic ethers (ζ. B. dioxane) can advantageously be added will.

Alkali hydroxides suitable for saponification are, for example, sodium, lithium and potassium hydroxide.

Organic acids, such as formic acid or acetic acid, or acidic inorganic acids are sufficient for acidification Salts of sulfuric or phosphoric acids. The cyclization to the lactone and its deposition can can also be done with mineral acids such as hydrochloric acid, sulfuric acid or phosphoric acid. The acids will preferably used in aqueous dilution.

The saponification takes place at 60 to 120 ° C. The

«The reaction temperature for the cyclization is 10 to 40 ° C.

The implementation is expediently carried out as a »one-pot reaction« carried out; the sodium salt of the 2-hydro-

6ü xymethyl-tetrachlorobenzoic acid not isolated.

In the process according to the invention, 2-chloromethyl-tetrachlorobenzoyl chloride is used first with at least 1 mol of alkali metal hydroxide. A faster one with a better yield However, conversion is achieved with 2 to 4 mols of alkali metal hydroxide. Then you put that in solution or Suspension obtained salt without isolation with the required amount of acid. A bigger one

An excess of acid is not required, it is sufficient when a pH range of 2 to 4 is reached.

The tetrachlorophthalide is an effective fungicide, especially against those fungi, the rice plants infected, known (cf. German Offenlegungsschrift 19 03 169).

example

A mixture of 16.4 g (0.05 mol) of 2-chloromethyl-tetrachlorobenzoyl chloride, 6 g (0.15 mol) of sodium hydroxide in 60 ml of water and 60 ml of dioxane was refluxed for 15 hours. The resulting suspension was diluted with 150 ml of water , cooled to room temperature and acidified to pH 3 with 10% hydrochloric acid. The precipitated tetrachlorophthalide was suction filtered, washed with water and dried at 110 ⁰ C The crude yield is 12.3 g (90% of theory). After recrystallization from benzene, 10 g (= 79% of theory) of colorless crystals with a melting point of 207 ° C. were obtained.

The connection is with the tetrachlorophthalide produced by the known process of DE-OS 16 43 347 identical.

Claims (1)

Claim: Process for the production of tetrachlorophthalide, characterized in that one 2-chloromethyltelrachlorobenzoyle chloride of the formula CO-CI 10