WO2018141642A1

WO2018141642A1 - Process for the preparation of 2-chloro-4-fluoro-5-nitrobenzotrichloride

Info

Publication number: WO2018141642A1
Application number: PCT/EP2018/051928
Authority: WO
Inventors: Swapnil Yerande; Prashant KAPSE; Sukunath Narayanan; Roland Goetz; Christopher Koradin
Original assignee: BASF Agro BV
Current assignee: BASF Agro BV
Priority date: 2017-02-06
Filing date: 2018-01-26
Publication date: 2018-08-09
Anticipated expiration: 2019-08-06
Also published as: AR111093A1

Abstract

The present invention relates to an improved process for the preparation of 2-chloro-4-fluoro-5-nitrobenzotrichloride. The present invention further relates to a process for the purification of 2-chloro-4-fluoro-5-nitrobenzotrichloride, which reduces the isomeric impurities and acidic by-products.

Description

Process for the preparation of 2-chloro-4-fluoro-5-nitrobenzotrichloride

The present invention relates to an improved process for the preparation of 2-chloro-4-fluoro- 5-nitrobenzotrichloride. The present invention further relates to a process for the purification of 2-chloro-4-fluoro-5-nitrobenzotrichloride, which reduces the isomeric impurities and acidic byproducts.

Background of the Invention

2-Chloro-4-fluoro-5-nitrobenzotrichloride is reported in the literature as an intermediate in the preparation of 2-chloro-4-fluoro-5-nitrobenzoic acid. WO 2006/090210 A1 discloses the preparation of 2-chloro-4-fluoro-5-nitrobenzoic acid and derivatives thereof, by nitration of 2-chloro-4- fluorobenzo trichloride. The nitration is effected by a 'sulfonitric mixture' which is composed of concentrated nitric acid and oleum. The drawback of using oleum in the sulfonitric mixture is the generation of considerable amount of undesired, isomeric impurity. The reaction is quenched in water, leading to the hydrolysis of the trichloride group, thereby increasing the amount of undesired side-product, i.e. the acid 2-chloro-4-fluoro-5-nitrobenzoic acid. The yield of 2-chloro-4- fluoro-5-nitrobenzotrichloride reported in WO 2006/090210 A1 is 93% but that includes about 20% of the aforementioned acid and thus the yield of the desired product is very low. Hence, the process of the prior art suffers from the drawbacks of low yield and poor quality of the prod- uct due to formation of a substantial amount of corresponding acid and isomeric nitro impurity. Further, quenching the reaction in water generates huge quantities of aqueous waste, the disposal of which is a concern when the process is applied to a large manufacturing scale.

Preparing 2-chloro-4-fluoro-5-nitrobenzotrichloride in high yield and high purity is a challenge. Thus, there is a need of an improved process for preparing 2-chloro-4-fluoro-5- nitrobenzotrichloride which obviates the drawbacks of the prior art.

Accordingly, it was an object of the presently claimed invention to provide a method of preparation and purification of 2-chloro-4-fluoro-5-nitrobenzotrichloride which gives the product in a high yield and minimizes the side products and isomeric impurities such as 2-chloro-4-fluoro-3- nitrobenzotrichloride, 2-chloro-4-fluoro-3 nitrobenzoic acid, 2-chloro-4-fluoro-5-nitrobenzoic acid and 2-chloro-4-fluoro benzoic acid.

Further, the process of the present invention is a cost effective, industrially applicable and an environmentally friendly process.

Summary of the Invention

Surprisingly it was found that 2-chloro-4-fluoro-5-nitrobenzotrichloride can be obtained in a high yield, i.e. > 85 %, and with high purity, i.e. > 99 %, by a process that involves nitrating 2- chloro-4-fluorobenzotrichloride with a mixture of red fuming nitric acid and concentrated sulfuric acid, adding a halogenated organic solvent, separating the organic layer comprising 2-chloro-4- fluoro-5-nitrobenzotrichloride and washing it with a basic aqueous solution and subsequent crystallization of 2-chloro-4-fluoro-5-nitrobenzotrichloride from an organic solvent and water.

Therefore, in an embodiment, the present invention relates to an improved process for the preparation of 2-chloro-4-fluoro-5-nitrobenzotrichloride comprising

A) reacting 2-chloro-4-fluorobenzotrichloride with sulfonitric mixture at a temperature in the range of ≥ 0 °C to≤ 15 °C to obtain a reaction mixture;

B) adding a halogenated organic solvent to the reaction mixture of step (A) at a temperature in the range of ≥ 0 °C to≤ 15 °C to obtain an organic layer and an acidic layer;

C) separating the organic layer and the acidic layer of step (B);

D) washing the organic layer of step (C) with an aqueous solution of an inorganic base at a temperature in the range of ≥ 10 °C to≤ 15 °C;

E) concentrating the organic layer of step (D) to obtain a crude product;

F) mixing the crude product of step (E) with at least one organic solvent and water and heating to a temperature in the range of≥ 60 °C to≤ 70 °C to obtain a crude mixture;

G) storing the crude mixture at a temperature in the range of≥ 0 °C to≤ 10 °C;

H) obtaining 2-chloro-4-fluoro-5-nitrobenzotrichloride from the crude mixture.

In another embodiment, the present invention relates to an improved process for the preparation of 2-chloro-4-fluoro-5-nitrobenzotrichloride comprising

A) reacting 2-chloro-4-fluorobenzotrichloride with sulfonitric mixture at a temperature in the range of ≥ 5 °C to < 10 °C to obtain a reaction mixture;

B) adding a halogenated organic solvent to the reaction mixture of step (A) at a temperature in the range of ≥ 10 °C to < 15 °C to obtain an organic layer and an acidic layer;

C) separating the organic layer and the acidic layer of step (B);

D) washing the organic layer of step (C) with an aqueous solution of an inorganic base at a temperature in the range of≥ 10 °C to < 15 °C;

E) concentrating the organic layer of step (D) to obtain a crude product;

F) mixing the crude product of step (E) with at least one organic solvent and water and heat- ing to a temperature in the range of≥ 60 °C to < 70 °C to obtain a crude mixture;

G) storing the crude mixture at a temperature in the range of ≥ 0 °C to < 5 °C;

H) obtaining 2-chloro-4-fluoro-5-nitrobenzotrichloride from the crude mixture.

The term 'high purity' implies≥ 99% purity of 2-chloro-4-fluoro-5-nitrobenzotrichloride.

The term 'sulfonitric mixture' denotes a mixture of red fuming nitric acid and concentrated sulfuric acid.

'Halogenated organic solvent' denotes class of organic solvent which contains halogens- chlorine (CI), fluorine (F), bromine (Br) or iodine (I).

The 'purity' is the purity of the compound as determined by High performance liquid chroma- tography (HPLC).

Detailed description of the Invention

In an aspect, the present invention relates to an improved process for the preparation of 2- chloro-4-fluoro-5-nitrobenzotrichloride of high purity.

Thus, in an embodiment, the present invention relates to a process for the preparation of 2- chloro-4-fluoro-5-nitrobenzotrichloride comprising

A) reacting 2-chloro-4-fluorobenzotrichloride with sulfonitric mixture at a temperature in the range of ≥ 0 °C to≤ 15°C to obtain a reaction mixture; B) adding a halogenated organic solvent to the reaction mixture of step (A) at a temperature in the range of≥ 0 °C to≤ 15 °C to obtain an organic layer and an acidic layer;

C) separating the organic layer and the acidic layer of step (B);

D) washing the organic layer of step (C) with an aqueous solution of an inorganic base at a temperature in the range of≥ 10 °C to≤ 15 °C;

E) concentrating the organic layer of step (D) to obtain a crude product;

H) obtaining 2-chloro-4-fluoro-5-nitrobenzotrichloride from the crude mixture.

In another embodiment, the present invention relates to a process for the preparation of 2- chloro-4-fluoro-5-nitrobenzotrichloride comprising A) reacting 2-chloro-4-fluorobenzotrichloride with sulfonitric mixture at a temperature in the range of≥ 5 °C to < 10 °C to obtain a reaction mixture;

B) adding a halogenated organic solvent to the reaction mixture of step (A) at a temperature in the range of≥ 10 °C to < 15 °C to obtain an organic layer and an acidic layer;

C) separating the organic layer and the acidic layer of step (B);

E) concentrating the organic layer of step (D) to obtain a crude product;

F) mixing the crude product of step (E) with at least one organic solvent and water and heat- ing to a temperature in the range of≥ 60 °C to <70 °C to obtain a crude mixture;

G) storing the crude mixture at a temperature in the range of≥ 0 °C to < 5 °C;

H) obtaining 2-chloro-4-fluoro-5-nitrobenzotrichloride from the crude mixture.

The starting material, 2-chloro-4-fluorobenzotrichloride, can be synthesized by the photochlo- rination of the corresponding toluenic derivative as described in the patent US 4,71 1 ,905.

According to an embodiment, the 'sulfonitric mixture is composed of concentrated nitric acid and concentrated sulfuric acid. The concentrated nitric acid is preferably 90% red fuming nitric acid and the concentrated sulfuric acid is 98 %.

The sulfonitric mixture comprises concentrated nitric acid and concentrated sulfuric acid preferably in a weight ratio of 1 :3 to 1 :7, more preferably in a weight ratio of 1 :3 to 1 :6, even more preferably in a weight ratio of 1 :3.5 to 1 :5

In a most preferred embodiment, the sulfonitric mixture comprises concentrated nitric acid and concentrated sulfuric acid in a weight ratio of 1 :4 to 1 :5.

The weight ration of the sulfonitric mixture to 2-chloro-4-fluorobenzotrichloride is preferably in the range of 1 :1 to 3:1 , more preferably in the range of 1 :1 to 2.8:1 or 1 .2:1 to 2.8:1 , even more preferably in the range of 1 .4:1 to 2.5:1 , most preferably in the range of 1 .4:1 to 2.2:1 or 1 .4:1 to 2:1 .

In a particular preferred embodiment, the weight ratio of the sulfonitric mixture and 2-chloro-4- fluorobenzotrichloride is in the range of 1.5:1 to 2:1. The sulfonitric mixture is preferably prepared by adding red, fuming nitric acid to concentrated sulfuric acid at a temperature of less than 10 °C.

The temperature of the nitration reaction (A) is preferably in the range of≥ 5 °C to≤ 10 °C. It is observed that if the reaction temperature is below 5 °C, the reaction times are increased. On the other hand, if the reaction is carried out at a temperature above 10 °C, the acid impurity formation is more, to the effect of even 10 %.

Preferably, the nitration step (A) is carried out without solvent. It is observed that if a solvent, such as halogenated organic solvent is used as a reaction solvent, the nitration reaction does not proceed to completion.

Halogenated organic solvent used in the extraction step (B) is preferably selected from the group consisting of dichloromethane, chloroform, monochlorobenzene, ethylenedichloride more preferably dichloromethane and ethylenedichloride are used as halogenated organic solvent.

Halogenated organic solvent used in the extraction step (B) is preferably selected from the group consisting of dichloromethane, chloroform, monochlorobenzene, more preferably di- chloromethane is used as halogenated organic solvent.

The weight ratio of halogenated organic solvent to 2-chloro-4-fluorobenzotrichloride is preferably in the range of 1 :1 to 10:1 , more preferably in the range of 2:1 to 8:1 , even more preferably in the range of 2:1 to 6:1 , most preferably in the range of 3:1 to 6:1 and in particular in the range of 3:1 to 5:1 .

In an embodiment, the weight ratio of the halogenated organic solvent to 2-chloro-4- fluorobenzotrichloride is preferably in the range of 3.5:1 to 5:1 .

Step (B) is preferably carried out at a temperature in the range of≥ 10 °C to≤ 15 °C.

The extraction step (B) is preferably done only once and thus it obviates the need to use additional solvent.

The organic layer is separated from the acidic layer in Step (C). The acidic layer removed in step (C) contains a mixture of sulfuric acid and nitric acid and can preferably be reused, thereby reducing the waste generation and waste disposal issues. This is advantageous over the prior art in which the product is isolated by quenching the reaction in water which results in substantial aqueous waste generation.

The inorganic base in step (D) is preferably selected from alkali metal salts, more preferably the inorganic base is selected from the group consisting of alkali metal hydroxides, alkali metal carbonates and bicarbonates, even more preferably the inorganic base is selected from the group consisting of sodium carbonate and sodium bicarbonate and most preferably the inorganic base is sodium carbonate. Strong inorganic bases such as alkali metal hydroxides, though can be used, but when employed result in higher acidic impurity formation.

Step (D) is preferably carried out at a temperature in the range of≥ 10 °C to≤ 15°C.

The inorganic base is used in form of a saturated aqueous solution.

By the term 'saturated aqueous solution' it is meant that the inorganic base is added to water until the inorganic base no longer dissolves in water. Preparation techniques of saturated aque- ous solution is well known to a person skilled in the art.

In an embodiment, the aqueous solution of an inorganic base comprises inorganic base in an amount preferably in the range of 10 % to 20%, by weight. The weight ratio of aqueous solution of inorganic base to 2-chloro-4-fluorobenzotrichloride is preferably in the range of 1 :1 to 4:1 , more preferably in the range of 1 .5:1 to 3.5:1 , even more preferably in the range of 1.5:1 to 3:1 and most preferably in the range of 1 .5:1 to 2.5:1 .

In a particular preferred embodiment, the weight ratio of aqueous solution of inorganic base to 2-chloro-4-fluorobenzotrichloride is in the range of 1 .7:1 to 2.5:1 .

The organic layer containing 2-chloro-4-fluorobenzotrichloride is concentrated in step E). Preferably the organic solvent is removed in step (E) by preferably using conventional techniques, such as distillation or distillation under vacuum, to remove the halogenated organic solvent and obtain 2-chloro-4-fluorobenzotrichloride as a crude product. In case a halogenated organic sol- vent such as dichloromethane is used the organic solvent can be removed by simple distillation at a comparatively low temperature such as 40°C without applying any vacuum.

The crude product obtained after step (E) has a purity of≥ 90 % and contains≤ 5 % isomeric impurities and≤ 5 % acid impurities. The crude product is subjected to further purification by crystallizing the crude product from an organic solvent mixture comprising at least one organic solvent and water.

The organic solvent used for crystallization in step (F) preferably is a polar protic solvent, more preferably an alkanol, even more preferably an alkanol selected from the group consisting of methanol, ethanol and isopropanol, most preferably methanol. The weight ratio of the organic solvent to 2-chloro-4-fluorobenzotrichloride is preferably in the range of 0.5:1 to 3:1 , more pref- erably in the range of 1 :1 to 3:1 , even more preferably in the range of 1 :1 to 2.5:1 and most preferably in the range of 1 :1 to 2:1 .

In a particular preferred embodiment, the weight ratio of the organic solvent to 2-chloro-4- fluorobenzotrichloride is in the range of 1 :1 to 1.5:1

The weight ratio of water to 2-chloro-4-fluorobenzotrichloride is preferably in the range of 0.04:1 to 0.1 :1 , more preferably in the range of 0.04:1 to 0.09:1 , even more preferably in the range of 0.04:1 to 0.08:1 , and most preferably in the range of 0.04:1 to 0.075:1.

In a particular preferred embodiment, the weight ratio of water and 2-chloro-4- fluorobenzotrichloride is in the range of 0.04:1 to 0.07:1.

Step (F) is carried out by dissolving the crude product in the at least one organic solvent, pref- erably at a temperature in the range of≥ 60°C to≤ 70°C, preferably followed by addition of water.

In a preferred embodiment, the crude mixture is optionally seeded with 2-chloro-4-fluoro-5- nitrobenzotrichloride.

In step (G), the crude mixture is preferably stored at a temperature in the range of≥ 0 °C to ≤ 5 °C. The crude mixture can be stored for any time period that is long enough to ensure sufficient and proper crystallization of 2-chloro-4-fluoro-5-nitrobenzotrichloride. Preferably the crude mixture is stored for a period of 30 minutes to 8 hours, more preferably for a period of 30 minutes to 4 hours, even more preferably for a period of 30 minutes to 2 hours, most preferably for a period of 30 minutes to 90 minutes.

Using the conventional separation techniques, such as filtration, filtration under vacuum, de- cantation or centrifugation, the pure product, 2-chloro-4-fluoro-5-nitrobenzotrichloride, is obtained from the crude mixture in a high yield of≥ 85 % with a high purity of preferably≥ 99 %, in step (H).

By using the above described process following advantages are achieved: 1 . The aqueous waste generation is minimized and the acidic layer can be reused/recycled. Thus, the process is an environmental friendly and sustainable process.

2. The process of the present invention leads to higher yield and higher selectivity, making it a cost-effective process.

3. The process is applicable for manufacturing at large scale.

The invention is now illustrated in detail by the working examples which follow. More particularly, the test methods specified hereinafter are part of the general disclosure of the application and are not restricted to the specific working examples. Examples:

Methods

High-performance liquid chromatography (HPLC) Chromatographic parameters:

Column: Symmetry Cie 250 X 4.6 mm, 5 micron

Column Temperature: Ambient

Flow Rate: 1 .0 ml/min

Mobile Phase: A = 1 ml of 85 % Phosphoric Acid in Water

B = 1 ml of 85 % Phosphoric Acid in Acetonitrile

Run Time: 35 minutes

A

2-chloro-4- 2-chloro-4-fluoro-5- 2-chloro-3-nitro-4- 2-chloro-4-fluoro-5- 2-chloro-3-nitro-4- 2-chloro^- fluorobenzotrichloride nitro-benzotrichloride fluoro-benzotrichloride nitro-benzoic acid fluoro-benzoic acid fluoro-benzoic acid

Example 1

Preparation of 2-chloro-4-fluoro-5-nitrobenzotrichloride:

Into a 1.6 I reactor, equipped with mechanical means of stirring, means of cooling, thermometer and dropping funnel, containing 98 % concentrated sulfuric acid (4.0 equivalent, 7.24 mole, 710 g), was added 90 % red fuming nitric acid (1 .14 equivalent, 2.062 mole, 144.8 g) at a temperature below 10 °C. To the sulfonitric mixture thus obtained, 2-chloro-4-fluorobenzotrichloride (1 .0 equivalent, 1 .81 mole, 450 g) was added over two hours while maintaining the temperature between 6 °C to 8 °C. The reaction mixture was stirred at said temperature for a further 6 hours. Dichloromethane (1800 g) was added to the reaction mass between 10 °C to 15 °C and the contents were stirred for 10 minutes. The two layers were allowed to settle and the organic layer was separated from the aqueous, acidic layer. The organic phase was washed with 15% aqueous solution of Na2C03 (900 g) between 10 °C to 15 °C and evaporated to dryness at 40 °C, to give the crude product (497 g). To the crude product obtained was added methanol (497 g) and the contents were heated at 65°C followed by addition of water (29.8 g). The contents were cooled to 5°C and maintained at 0°C to 5°C for an hour followed by filtration to obtain the desired product (yield = 86 %, purity (by HPLC) = 99.33 %, isomeric impurity = 0.28 %) obtained as a white solid.

The HPLC analysis data is as follows:

I I % Product distribution in HPLC (% by area) I Un¬

2-chloro-4- 2-chloro-4-

2-chloro-4- 2-chloro-4- known 2-chloro-4- fluoro-3-nitro fluoro-5- fluoro- fluoro-5- impurity fluoroben-

Sample benzotrichlo- nitroben- benzoic nitroben- (RRT: zotrichlo- ride zotrichlo- acid zoic acid 0.859 ) ride

ride

Reaction

2.036 2.037 0.725 1 .023 4.455 89.028 Monitoring

Organic Lay¬

1 .469 0.572 0.784 0.931 4.445 91.539 er

After Na₂C0₃

wash -

0.031 Nil 0.756 0.959 4.858 93.215 Crude product

Crystallized

Nil Nil Nil 0.017 0.285 99.339 Product

Example 2

Preparation of 2-chloro-4-fluoro-5-nitrobenzotrichloride using ethylenedichloride as extraction solvent:

Into a flask 98 % concentrated sulfuric acid (4.0 equivalent, 1.5867 mole, 158.8 g) was charged. Reaction mass was cooled to 0 °C). To it was added 90 % red fuming nitric acid (1.16 equivalent, 0.4599 mole, 32.2 g) in a dropwise manner at a temperature below 5 °C.

Stirring was done for 30 mins after addition of fuming nitric acid.

To the sulfonitric mixture thus obtained, 2-chloro-4-fluorobenzotrichloride (1.0 equivalent, 0.3964 mole, 100 g) was added over two hours while maintaining the temperature between 5 °C to 7 °C. The reaction mixture was stirred at said temperature for 6 to 8 hours.

Ethylenedichloride (400 g) was added to the reaction mass between 10 °C to 15 °C and the contents were stirred for 15 minutes. The two layers were allowed to settle and the top organic layer (517 g) was separated from the bottom, aqueous, acidic layer (165 g).

The organic phase was washed with 15% aqueous solution of Na2CC"3 (200 g) between 10 °C to 15 °C and evaporated to dryness at 40 °C, to give the crude product (1 17.3 g). More specifically, organic layer (517 g) was charged back to flask. 15 % Na2C03 aqueous solution (200 g) was charged slowly to organic layer. Stirring was done for 15 min. Stirring was stopped and settling of layers was allowed. The bottom organic layer (512 g) was separated. Aqueous layer (205 g) was discarded. Organic layer was concentrated to residue. Residue (crude product) (1 14.3g) obtained was used for recrystallization.

To the crude product (1 14.3 g) obtained was added methanol (1 14.3 mL/ 89.89 g) and the contents were heated at 65 °C to get a clear solution, followed by addition of water (6.27 g). Stirring was done for 15 mins. The contents were gradually cooled to 45 °C. Pure 2-chloro-4- fluoro-5-nitrobenzotrichloride (10 mg) was charged as seed at 45 °C and the contents were gradually cooled to 0 °C in 90 mins, further maintained at 0 °C to 5 °C for an hour followed by filtration and suction drying under vacuum to obtain the desired product. Wet cake (104.3g) was unloaded and charged into flask and heated melt the solid. Vacuum was applied and main- tained for 1 hour under vacuum. The dry 2-chloro-4-fluoro-5-nitrobenzotrichloride was unloaded, (yield = 87.17 %, purity (by High-performance liquid chromatography) = 99.68 %, isomeric impurity = 0.24 %, 2-chloro-4-fluorobenzotrichloride = 0.08%).

Claims

Claims:

A process for the preparation of 2-chloro-4-fluoro-5-nitrobenzotrichloride comprising the steps of

A) reacting 2-chloro-4-fluorobenzotrichloride with an sulfonitric mixture at a temperature in the range of≥ 0 °C to≤ 15 °C to obtain a reaction mixture;

C) separating the organic layer and the acidic layer of step (B);

E) concentrating the organic layer of step (D) to obtain a crude product;

F) mixing the crude product of step (E) with at least one organic solvent and water and heating to a temperature in the range of ≥ 60 °C to≤ 70 °C to obtain a crude mixture;

G) storing the crude mixture at a temperature in the range of≥ 0 °C to≤ 15 °C; and

H) obtaining 2-chloro-4-fluoro-5-nitrobenzotrichloride from the crude mixture.

The process according to claim 1 , wherein in step A) the sulfonitric mixture comprises concentrated nitric acid and concentrated sulfuric acid in the weight ratio range of 1 :3 to 1 :7.

The process according to one or more of claims 1 to 2, wherein in step A) the weight ratio of sulfonitric mixture to 2-chloro-4-fluorobenzotrichloride is in range of 1 :1 to 3:1.

The process according to one or more of claims 1 to 3, wherein in step B) the halogenated organic solvent is selected from the group consisting of dichloromethane, ethylenedichlo- ride, chloroform and monochlorobenzene.

The process according to one or more of claims 1 to 4, wherein in step B) the weight ratio of halogenated organic solvent to 2-chloro-4-fluorobenzotrichloride is in range of 1 :1 to 10:1 . 6. The process according to one or more of claims 1 to 5, wherein in step D) the inorganic base is selected from the group consisting of sodium carbonate and sodium bicarbonate.

7. The process according to one or more of claims 1 to 6, wherein in step D) the aqueous solution of the inorganic base comprises the inorganic base in the range of 10 % to 20%, by weight.

8. The process according to one or more of claims 1 to 7, wherein in step D) the weight ratio of the aqueous solution of the inorganic base to 2-chloro-4-fluorobenzotrichloride is in the range of 1 :1 to 4:1 .

9. The process according to one or more of claims 1 to 8, wherein in step F) the organic layer is concentrated by distillation. 10. The process according to one or more of claims 1 to 9, wherein in step F) the at least one organic solvent is selected from the group consisting of methanol, ethanol and isopropa- nol.

The process according to one or more of claims 1 to 10, wherein in step F) the weight ratio of the at least one organic solvent to 2-chloro-4-fluorobenzotrichloride is in the range of 0.5:1 to 3:1 .

12. The process according to one or more of claims 1 to 1 1 , wherein in step F) the weight ratio of water and 2-chloro-4-fluorobenzotrichloride is in the range of 0.04:1 to 0.1 :1.

13. The process according to one or more of claims 1 to 12, wherein in step G) the crude mixture is seeded with 2-chloro-4-fluoro-5-nitrobenzotrichloride.