DD297955A5 - PROCESS FOR PREPARING CHLORINE DIPHENYL ETHER - Google Patents

Abstract

Chlorinated diphenyl ethers of the formula I in which R 1 is hydrogen, C 1 -C 6 -alkyl or C 3 -C 7 -cycloalkyl or C 1 -C 6 -alkoxy, R 2 is hydrogen or chlorine can be prepared by reacting 1 mol of a phenolate of the formula II in which X is an alkali metal cation and R1 and R2 have the above meaning, with 1.1 to 10 mol of a dichlorobenzene of the formula III in a polar aprotic solvent in the temperature range of 190 to 240C, in the absence of metal catalysts. Formulas I to III

Description

in a polar aprotic solvent in the temperature range from 190 to 240 ⁰ C, preferably 205 to 225 ⁰ C, in the absence of metal catalysts.

2. The method according to claim 1, characterized in that as aprotic solvent of eggs several from the group of dimethylformamide, dimethylacetamide, Hexamethylphosphorsäurethamid, N-methylpyrrolidone, dimethyl sulfoxide, sulfolane, diethylene glycol dimethyl ether, glycol dimethyl ether, ethylene carbonate and propylene carbonate, preferably from Group of N-methyl-pyrrolidone, dimethylformamide, dimethylacetamide and dimethyl sulfoxide, is used.

3. The method according to claim 2, characterized in that per part by weight of phenolate from 1.5 to lOgew.-parts, preferably 2 to 6 parts by weight of solvent are used.

4. The method according to claim 1, characterized in that 1.2 to 5MoI, preferably 1.8 to 3.5 mol, dihalobenzene are used per mole of phenolate.

5. The method according to claim 1, characterized in that in addition to the phenol bound phenol free phenol in an amount of 0.05 to 0.6 mol, preferably 0.15 to 0.4 mol, per mole of phenol bound phenol is used ,

6. The method according to claim 1, characterized in that the phenolate is formed in a mixture with other reactants of phenol and aqueous alkali metal hydroxide solution and the water contained is distilled off azeotropically before the reaction is started.

The invention relates to a process for preparing chlorinated diphenyl ethers by reacting the underlying alkali metal phenolates with dichlorobenzenes in the absence of metal catalysts.

This reaction has been known without catalyst so far only in the event that both the alkali metal phenolate with potassium as the cation and the chlorobenzene were strongly activated as an example of a halogenobenzene by one nitro group, at least one of the nitro groups o- or p-constantly to the phenolate or chlorine group must be. The reaction was carried out in boiling dimethylformamide (DMF) and gave for the different position isomers yields of 60 to 72% of the theoretical yield (J. Org. Chem. 27 (1962), 4098).

The expansion to non-activated phenolates and halobenzenes is known as the so-called Ullmann reaction (Krauch-Kunz "name reactions in organic chemistry", D. Huig Verlag GmbH, Heidelberg, 2nd edition 1962, p.474) the reaction of alkali metal phenolates with aryl halides in the presence of copper or copper compounds as a catalyst This Ullmann reaction, in turn, is known in a number of different embodiments.

It is thus known to react 1,4-dichlorobenzene with 3-chlorophenol under CuCl / KJ catalysis to give 3,4'-dichlorodiphenyl ether (US Pat. No. 3,472,782, US Pat. No. 3,371,120).

An improvement of the Ullmann catalyst is proposed in EP 51 235 by using basic copper carbonates or copper salts of lower aliphatic carboxylic acids.

Furthermore, it is known to produce chlorinated diphenyl ethers from chlorophenolates and dichlorobenzenes in the presence of a copper catalyst and an aprotic solvent as co-catalyst at temperatures of 120 to 220 ° C.

It has been a process for the preparation of chlorinated diphenyl ethers of the formula

Xl ^ _{f % t} (I),

R ¹ is hydrogen, C | -C _e alkyl, Cr-C ₇ cycloalkyl or C ₁ -C ₆ -alkoxy, R ² are hydrogen or chlorine, found, which is characterized in that 1 mol of a phenolate of formula

(II)

X is an alkali metal cation and R ¹ and R ² are as defined above, with from 1.1 to 1 mole of a dichlorobenzene of the formula

(III)

in a polar aprcuischen solvent in the temperature range from 190 to 2 <10 ° C, preferably 205 to 225 ⁰ C, in the absence of metal catalysts.

It was surprising and not foreseeable that when using a polar iprotic solvent according to the invention in the absence of metal catalyst, in particular in the absence of a Ki nferkatalysators, phenolates can be reacted with non-activated halobenzenes to the corresponding diphenyl ethers with excellent yield.

The advantages of the new process are its relatively simple feasibility and the very good yield hr.:·? Economics.

In carrying out the diphenyl ether production neon methods that correspond to the prior art, complex measures for the disposal of forcibly resulting copper-containing wastewater are required. It is a particular advantage of the erfii, the inventive method that, due to its copper-free operation, such additional work and expenses omitted.

Polar aprotic solvents for the process according to the invention include: dimethylformamide (DMF), dimethylacetamide, diethyiformamide, diethylacetamide, hexamethylphosphoric triamide, N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), sulfolane, diethylene glycol dimethyl ether, glycol dimethyl ether, ethylene carbonate, Propylene carbonate and others, preferably DMF, dimethylacetamide, hexamethylphosphoric triamide, NMP, DMSO, sulfolane, DimethylenplyKul dimethyl ether, glycol dimethyl ether, ethylene carbonate and propylene carbonate, more preferably NMP, DMF, dimethylacetamide and DMSO. Such solvents can be used both individually and in admixture.

The amount of the polar aprotic solvent to be used according to the invention can vary within wide limits. It depends mainly on the solubility of the phenolate (II). In general, the amount of the solvent is 1 to 10 parts by weight, preferably 2 to 6 parts by weight per part by weight of the phenolate (II) used.

The phenolates of the formula (II) to be used according to the invention are preferably the sodium or potassium salts, particularly preferably the potassium salts, of the phenols on which they are based. In these C, -C ₆ alkyl methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, amyl, branched amyl, hexyl, branched hexyl, preferably the said Ci-C ^ alkyl, more preferably methyl or Ethyl, C ₃ -C ₇ -cycloalkyl /! herein is cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, methylcyclopropyl, dimethylcyclopropyl, methylcyclopentyl, dimethylcyclopentyl, methylcyclohexyl, preferably cyclopropyl, cyclopentyl or cyclohexyl or diene methyl substituted derivatives. C 1 -C ₆ -alkoxy means methoxy, ethoxy, propoxy, isopropoxy, buyloxy, isobutoxy, tert-butoxy, amyloxy, branched amyloxy, hexyloxy or branched hexyloxy, preferably the cited Ci-CrAlkoxyreste, more preferably methoxy or ethoxy.

Such underlying phenols include: phenol, o-, m-, p-cresol, o-, m-, p-ethylphenol, o-, m-, p-isopropylphenol, o-, m-, p-, tert Butylphenyl, o-, m-, p-cyclohexylphenol, o-, m-, p-chlorophenol, the different isomeric chlorocresols and others.

Dichlorobenzene of the formula (III) are: o-dichlorobenzene. m-dichlorobenzene, p-dichlorobenzene.

In the process according to the invention, the dichlorobenzene (III) is used in excess of the phenolate (1!). The molar ratio of dihalobenzene to phenolate is 1.1-10: 1, preferably 1.2-5: 1, more preferably 1.8-3.5: 1.

The reaction temperature of the inventive process is in the range from 190 to 24O ⁰ C, preferably in the range of 205 to 225 ⁰ C. The reaction is generally carried out at atmospheric pressure. Of course, it is also possible, in particular if the boiling point of the chosen solvent or of the dichlorobenzene is below the chosen reaction temperature, to carry out the reaction under pressure. In such a case, it is preferable to work under the autogenous autogenous pressure of the reaction system.

It has been found that it is advantageous to carry out the process according to the invention in the presence of additional free phenol, the free phenol being the same as the phenolate (II). The amount of such a free phenol present is in the range of 0.05 to 0.6 mol, preferably 0.15 to 0.4 mol, of free phenol per mole of the phenolate.

To carry out the process according to the invention can be made of conventional techniques. For example, you can the reactants, preferably under anhydrous conditions, submit and the reaction mixture for several hours, often between 8 and 20 hours, in each case, but also depends on the batch size, at the desired temperature

stir. In this case, the phenolate must be prepared beforehand in a separate process step, for example from phenol and alkali hydroxide.

In an advantageous variant of the process according to the invention, however, it is also possible to prepare phenol and dichlorobenzene and alkali hydroxide in the form of an aqueous solution, dehydrate this mixture azeotropically and then react the entire reaction mixture at the desired temperature after addition of the polar aprotic solvent , In such a case, if the polar aprotic solvent boils higher than the azeotrope of water-dichlorobenzene, the polar aprotic solvent can also be added at the beginning of the phenolate formation. Of course, it is also possible to use additional entrainers for the azeotrope to be removed water, such as toluene or xylene. As a result, the azeotropic dehydration of the reaction mixture can also be carried out at lower temperatures.

The workup of the final reaction mixture can also be done in different variants. For example, it is possible first to distill off the polar aprotic solvent and the excess dichlorobenzene and any existing free phenol. The salt-containing residue is then treated with water, excess phenolate is converted by acidification into phenol and the organic phase formed after a phase separation is worked up by distillation

 In a further work-up form, the salt-containing residue obtained after distilling off the polar aprotic solvent, the dichlorobenzene and any free phenol is freed from the salt by filtration, optionally after addition of a non-water-miscible solvent, such as benzene, toluene or xylene. The filtrate is then washed with dilute sodium hydroxide solution and water, the solvent is removed (for example in vacuo) and the residual crude product is distilled under high vacuum.

The chlorinated diphenyl ethers which can be prepared by the process according to the invention are valuable chemical intermediates in the pharmaceutical and crop protection sector (EP 51235, EP 65485, EP 126430). Furthermore, chlorodiphenyl ethers have also been proposed as growth regulators (US 3,371,120, US 3,472,782).

example 1

3,4'-Dlchlor-diphenyl ether

In a 2-liter autoclave 257g 4-chlorophenyl, 588g m-dichlorobenzene, 168g 50% aqueous potassium hydroxide solution and

700 g of N-methylpyrrolidone (NMP) are azeotropically dehydrated over a water separator for 3 hours. During this drainage, the sump temperature rose from 132 to 193 ° C. The autoclave was then closed and stirred at 220 ^° C. for 17 hours.

It set a pressure of about 2 bar. After cooling, NMP, excess m-dichlorobenzene and 4-chlorophenol were distilled off. To the residue was added 800 ml of water, stirred for 15 min. At 70 ° C and acidified with dilute sulfuric acid.

After separation, the organic phase was worked up by distillation.

There were obtained 308.2 g (86%) of the above compound

Example 2

2,4'-dichloro-diphenyl ether

257 g of 4-chlorophenol, 588 g of o-dichlorobenzene, 168 g of 504 aqueous potassium hydroxide solution and 700 g of NMP were treated as in Example 1. The final distillation yielded 321 g (89.5%) of the above compound.

Example 3

2-chloro-4'-teri.-butyl-diphonylethar

300 g of 4-tert-butylphenol, 588 g of o-dichlorobenzene, 168 g of 50% aqueous potassium hydroxide solution and 800 g of NMP were added as in

Example 1 treated. 358.9 g (91.8%) of the above compound was isolated.

Example 4

4-chloro-3-methyl-3'-chloro-diphenyl ether

285 g of 4-chloro-3-methyl-phenol, 588 g of m-dichlorobenzene, 168 g of 50% aqueous potassium hydroxide solution and 700 g of NMP were treated as in Example 1. It isolated 304.1 g (80.2%) of the above compound.

Claims (1)

1. A process for the preparation of chlorinated Diphenylethem of the formula R ^{1 is} hydrogen, C ₁ -C ₆ -alkyl, C ₃ -C ₇ -cycloalkyl or C ₁ -C ₆ -alkoxy, R ^{2 is} hydrogen or chlorine, characterized in that 1 mol of a phenolate of the formula X is an alkali metal cation and R ¹ and R ^{2 have} the above meaning, with from 1.1 to 10 mol of a dichlorobenzene of the formula _J - M ^cl Cl C) t