Method for producing substituted anthranilic acid derivatives

Abstract

The present invention relates to a process for preparing substituted anthranilic acid derivatives of the formula (I)

Description

BACKGROUND

Field of the Invention

The present invention relates to a novel process for preparing substituted anthranilic acid derivatives of the formula (I)

in which

• • R¹ is optionally singly or multiply, identically or differently fluorine- or chlorine-substituted C₁-C₆-alkyl, or C₆-C₁₀-aryl, or is a hetaryl radical of the general formula (II)

• • R¹ is preferably C₁-C₃-alkyl, C₆-aryl or a hetaryl radical of the general formula (II),
  • R¹ is more preferably C₁-C₂-alkyl or a hetaryl radical of the general formula (II),where
  • R⁸ is C₁-C₆-alkyl, C₃-C₆-cycloalkyl, C₁-C₄-alkoxy, C₁-C₄-alkylthio, C₁-C₄-alkylsulphinyl, C₁-C₄-alkylsulphonyl, which may optionally be mono- or polysubstituted identically or differently by fluorine or chlorine, or is fluorine, chlorine, cyano, alkylamino, dialkylamino, cycloalkylamino or C₃-C₆-trialkylsilyl,
  • R⁸ is preferably fluorine, chlorine or C₁-C₆-alkyl,
  • R⁸ is more preferably fluorine or chlorine,
  • Z is CH or N,
  • Z is preferably and more preferably N,and
  • Y is hydrogen, fluorine, chlorine, optionally singly or multiply, identically or differently fluorine- or chlorine-substituted C₁-C₆-alkyl, C₃-C₆-cycloalkyl, C₁-C₄-alkoxy, C₁-C₄-alkylthio, C₁-C₄-alkylsulphinyl, C₁-C₄-alkylsulphonyl, or is cyano, alkylamino, dialkylamino, cycloalkylamino, C₃-C₆-trialkylsilyl or a radical of the general formula (III)

where

• • R⁹ is C₁-C₅-alkyl which may optionally be mono- or polysubstituted identically or differently by halogen,
  • R⁹ is preferably C₁-C₃ perfluoroalkyl,
  • R⁹ is more preferably CF₃ or C₂F₅,
  • R² is an OR⁵ or NR⁶R⁷ radical,
  • R² is preferably and more preferably OR⁵,
  • R² is likewise preferably and more preferably NR⁶R⁷,where
  • R⁵, R⁶ and R⁷ are each independently hydrogen, C₁-C₆-alkyl, or C₆-C₁₀-aryl,
  • R⁵, R⁶ and R⁷ are preferably each independently hydrogen, C₁-C₃-alkyl or C₆-aryl,
  • R⁵, R⁶ and R⁷ are more preferably each independently hydrogen or C₁-C₂-alkyl,
  • R³ is hydrogen, optionally singly or multiply, identically or differently fluorine- or chlorine-substituted C₁-C₆-alkyl, C₁-C₆-alkoxy or C₃-C₆-cycloalkyl,
  • R³ is likewise halogen,
  • R³ is preferably C₁-C₅-alkyl,
  • R³ is more preferably methyl, ethyl or tert-butyl,
  • R³ is likewise preferably and more preferably chlorine,
  • R⁴ is hydrogen, fluorine, chlorine, cyano, optionally singly or multiply, identically or differently fluorine- or chlorine-substituted C₁-C₄-alkyl, C₁-C₄-alkoxy, C₁-C₄-alkylthio, C₁-C₄-alkylsulphinyl, C₁-C₄-alkylsulphonyl, C₁-C₄-alkylamino, di(C₁-C₄-alkyflamino, C₃-C₆-cycloalkylamino, (C₁-C₄-alkoxy)imino, (C₁-C₄-alkyl)(C₁-C₄-alkoxy)imino, SF₅ or C₃-C₆-trialkylsilyl,
  • R⁴ is preferably hydrogen, chlorine or cyano,
  • R⁴ is more preferably chlorine or cyano,characterized in that substituted anthranilic acid derivatives of the formula (IV)

in which the R¹, R³ and R⁴ radicals are each as defined above and

• • X is chlorine, bromine or iodine, preferably bromine or iodine, more preferably bromine,are reacted in the presence of a palladium catalyst and optionally of a phosphine ligand simultaneously with carbon monoxide and a compound of the general formula (V)R⁵—OH   (V)in which R⁵ is as defined aboveor a compound of the general formula (VI)HNR⁶R⁷   (VI)in which R⁶ and R⁷ are each as defined above.

Description of Related Art

The literature already states that it is possible to obtain substituted anthranilic acid derivatives of the formula (I) by reaction of anthranilic acid derivatives of the general formula (VII)

with carboxylic acids of the general formula (VIII)R¹—COOH   (VIII)in the presence of agents which activate the carboxyl group for the desired reaction, for example thionyl chloride, oxalyl chloride, phosgene, methanesulphonyl chloride or toluenesulphonyl chloride (WO 2003/015519; WO 2003/106427; WO 2004/067528; WO 2006/062978; WO 2008/010897; WO 2008/070158; WO 2008/082502; WO 2009/006061; WO 2009/061991; WO 2009/085816; WO 2009 111553; Bioorg. & Med. Chem. Lett. 15 (2005) 4898-4906; Bioorg. & Med. Chem. 16 (2008) 3163-3170).

The known reactions can be illustrated by the following reaction schemes, where R¹, R³, R⁴, R⁶ and R⁷ have, for example, the definitions given above:

• • a) R²═OR⁵ where R⁵ is not H, or NR⁶R⁷

• • b) R²═OR⁵ where R⁵═H

These known methods for preparation of substituted anthranilic acid derivatives of the formula (I) require the availability of the corresponding substituted anthranilic acid derivatives of the general formula (VII). These substituted anthranilic acid derivatives of the general formula (VII) are either known or can be prepared by known organic chemistry methods. Some of these substituted anthranilic acid derivatives of the general formula (VII), however, can be prepared only in a complex manner, in multiple stages and at high cost, which can lead to uneconomically high costs for the end products as a result of unavoidable yield losses.

Substituted anthranilic acid derivatives of the formula (I) are of high interest as compounds having known insecticidal efficacy (see, for example, Bioorg. & Med. Chem. Lett. 15 (2005) 4898-4906; Biorg. & Med. Chem. 16 (2008) 3163-3170). Further, it is already known, that substituted anthranilic acid derivatives of the general formula (VII) can be obtained by reacting substituted anthranilic acid derivatives of the general formula (IX) with carbon monoxide in the presence of a palladium catalyst, of a ligand, of a primary amine and a base (WO 2012/103436). However, it is not known whether anthranilic acid amides of the general formula (IV) can be used correspondingly.

SUMMARY

It is therefore an object of the present invention to provide a novel, more economically viable process for preparing substituted anthranilic acid derivatives of the formula (I).

The object was achieved according to the present invention by a process for preparing anthranilic acid derivatives of the general formula (I), characterized in that substituted anthranilic acid derivatives of the general formula (IX)

in which X, R³ and R⁴ are each as defined aboveare reacted with acids of the general formula (VIII) to give the substituted anthranilic acid derivatives of the formula (IV)

and the latter are then reacted in the presence of a palladium catalyst and optionally of a phosphine ligand simultaneously with carbon monoxide and a compound of the general formula (V)R⁵—OH   (V)in which R⁵ is as defined aboveor a compound of the general formula (VI)HNR⁶R⁷   (VI)in which R⁶ and R⁷ are each as defined aboveto give the substituted anthranilic acid derivatives of the general formula (I).

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The process according to the invention can be illustrated by the following scheme:

The present invention likewise provides novel compounds of the general formula (IV)

in which the R¹, R³, R⁴ and X radicals are each as defined above.

Preference is given to compounds of the general formula (IV) in which

• • R¹ is optionally singly or multiply, identically or differently fluorine- or chlorine-substituted C₁-C₆-alkyl, or C₆-C₁₀-aryl, or is a hetaryl radical of the general formula (II)

where

• • R⁸ is optionally singly or multiply, identically or differently fluorine- or chlorine-substituted C₁-C₆-alkyl, C₃-C₆-cycloalkyl, C₁-C₄-alkoxy, C₁-C₄-alkylthio, C₁-C₄-alkylsulphinyl, C₁-C₄-alkylsulphonyl, or is fluorine, chlorine, cyano, alkylamino, dialkylamino, cycloalkylamino or C₃-C₆-trialkylsilyl, preferably fluorine, chlorine or C₁-C₆-alkyl, more preferably fluorine or chlorine,
  • Z is CH or N, preferably N,and
  • Y is hydrogen, fluorine, chlorine, optionally singly or multiply, identically or differently fluorine- or chlorine-substituted C₁-C₆-alkyl, C₃-C₆-cycloalkyl, C₁-C₄-alkoxy, C₁-C₄-alkylthio, C₁-C₄-alkylsulphinyl, C₁-C₄-alkylsulphonyl, or is cyano, alkylamino, dialkylamino, cycloalkylamino, C₃-C₆-trialkylsilyl or a radical of the general formula (III)

in which

• • R⁹ is C₁-C₅-alkyl which may be mono- or polysubstituted identically or differently by halogen,
  • R⁹ is preferably C₁-C₃-perfluoroalkyl,
  • R⁹ is more preferably CF₃ or C₂F₅,
  • R³ is chlorine,
  • R³ is likewise methyl,
  • R⁴ is chlorine or cyano,and
  • X is bromine or iodine.

Particular preference is given to compounds of the general formula (IV) in which

• • R¹ is a hetaryl radical of the general formula (II)

where

• • R⁸ is fluorine or chlorine,
  • Z is N,and
  • Y is hydrogen, fluorine, chlorine or a radical of the general formula (III)

where

• • R⁹ is CF₃ or C₂F₅,
  • R³ is methyl,
  • R⁴ is chlorine or cyano,and
  • X is bromine.

Examples of the particularly preferred compounds of the general formula (IV) include:

• N-(2-bromo-4-cyano-6-methylphenyl)-1-(3-chloropyridin-2-yl)-3-{[5-(trifluoromethyl)-2H-tetrazol-2-yl]methyl}-1H-pyrazole-5-carboxamide
• N-(2-bromo-4-chloro-6-methylphenyl)-1-(3-chloropyridin-2-yl)-3-{[5-(pentafluoroethyl)-2H-tetrazol-2-yl]methyl}-1H-pyrazole-5-carboxamide.

General definitions: Alkyl groups substituted by one or more fluorine or chlorine atoms (=fluoro- or chloroalkyl groups) are selected, for example, from trifluoromethyl (CF₃), difluoromethyl (CHF₂), CCl₃, CFCl₂, CF₃CH₂, C₁CH₂, CF₃CCl₂.

Alkyl groups in the context of the present invention, unless defined differently, are linear or branched hydrocarbyl groups.

The definition alkyl and C₁-C₁₂-alkyl encompasses, for example, the meanings of methyl, ethyl, n-, isopropyl, n, iso-, sec- and t-butyl, n-pentyl, n-hexyl, 1,3-dimethylbutyl, 3,3-dimethylbutyl, n-heptyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl.

Cycloalkyl groups in the context of the present invention, unless defined differently, are cyclic saturated hydrocarbyl groups.

Aryl radicals in the context of the present invention, unless defined differently, are aromatic hydrocarbyl radicals which may have one, two or more heteroatoms selected from O, N, P and S and may optionally be substituted by further groups.

Arylalkyl groups and arylalkoxy groups in the context of the present invention, unless defined differently, are, respectively, alkyl and alkoxy groups which are substituted by aryl groups and may have an alkylene chain. Specifically, the definition arylalkyl encompasses, for example, the meanings of benzyl and phenylethyl, and the definition arylalkoxy, for example, the meaning of benzyloxy.

Alkylaryl groups (alkaryl groups) and alkylaryloxy groups in the context of the present invention, unless defined differently, are, respectively, aryl groups and aryloxy groups which are substituted by alkyl groups, may have a C_1-8-alkylene chain and may have, in the aryl skeleton or aryloxy skeleton, one or more heteroatoms selected from O, N, P and S.

Step 1

Anthranilic acid derivatives of the formula (IV) can be prepared as follows:

The reaction is performed in the presence of a condensing agent. Suitable agents for this purpose are all agents customary for such coupling reactions. Examples include acid halide formers such as phosgene, phosphorus tribromide, phosphorus trichloride, phosphorus pentachloride, phosphorus oxychloride, oxalyl chloride or thionyl chloride; anhydride formers such as ethyl chloroformate, methyl chloroformate, isopropyl chloroformate, isobutyl chloroformate or methanesulphonyl chloride; carbodiimides such as N,N′-dicyclohexylcarbodiimide (DCC) or other customary condensing agents such as phosphorus pentoxide, polyphosphoric acid, 1,1′-carbonyldiimidazole, 2-ethoxy-N-ethoxycarbonyl-1,2-dihydroquinoline (EEDQ), triphenylphosphine/carbon tetrachloride, bromotripyrrolidinophosphonium hexafluorophosphate, bis(2-oxo-3-oxazolidinyl)phosphine chloride or benzotriazol-1-yloxytris(dimethylamino)phosphonium hexafluorophosphate. It is likewise possible to use polymer-supported reagents, for example polymer-bound cyclohexylcarbodiimide Preference is given to phosgene, mesyl chloride and thionyl chloride.

Process step 1 can optionally be performed in the presence of an inert organic diluent customary for such reactions. These preferably include aliphatic, alicyclic or aromatic hydrocarbons, for example petroleum ether, hexane, heptane, cyclohexane, methylcyclohexane, benzene, toluene, xylene or decalin; halogenated hydrocarbons, for example chlorobenzene, dichlorobenzene, dichloromethane, chloroform, carbon tetrachloride, dichloroethane or trichloroethane; ethers such as diethyl ether, diisopropyl ether, methyl tert-butyl ether, methyl tert-amyl ether, dioxane, tetrahydrofuran, 1,2-dimethoxyethane, 1,2-diethoxyethane or anisole; ketones such as acetone, butanone, methyl isobutyl ketone or cyclohexanone; nitriles such as acetonitrile, propionitrile, n- or isobutyronitrile or benzonitrile; amides such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methylformanilide, N-methylpyrrolidone or hexamethylphosphoramide, or mixtures thereof.

Process step 1 is generally performed in the presence of a base.

Suitable bases are alkali metal hydroxides, for example lithium hydroxide, sodium hydroxide or potassium hydroxide, alkali metal carbonates, for example Na₂CO₃, K₂CO₃, and acetates, for example NaOAc, KOAc, LiOAc, and also alkoxides, for example NaOMe, NaOEt, NaOt-Bu, KOt-Bu. Likewise suitable bases are organic bases such as trialkylamines, alkylpyridines, phosphazenes and 1,8-diazabicyclo[5.4.0]undecene (DBU). Preference is given to organic bases such as pyridines, alkylpyridines, for example 2,6-dimethylpyridine, 2-methyl-5-ethylpyridine or 2,3-dimethylpyridine.

Process step 1 of the invention is performed preferably within a temperature range from 20° C. to +100° C., more preferably at temperatures of 30° C. to +80 ° C., more preferably at 30-60° C.

Process step 1 of the invention is generally performed under standard pressure. Alternatively, however, it is also possible to work under vacuum or under elevated pressure in an autoclave.

The reaction time may, according to the batch size and the temperature, be selected within a range between 1 hour and several hours.

Process step 1 can optionally be performed in the presence of a catalyst. Examples include 4-dimethylaminopyridine or 1-hydroxybenzotriazole.

Step 2

Substituted anthranilic acid derivatives of the general formula (I) can be prepared in accordance with process step 2 as follows:

The reaction is performed in the presence of a palladium catalyst. The palladium catalysts used in the process according to the invention are palladium(II) salts, for instance palladium chloride, bromide, iodide, acetate or acetylacetonate, which may optionally be stabilized by further ligands, for example alkyl nitriles, or Pd(0) species, for example palladium on activated carbon, Pd(PPh₃)₄, bis(dibenzylideneacetone)palladium or tris(dibenzylideneacetone)dipalladium. Preference is given to bis(dibenzylideneacetone)palladium, tris(dibenzylideneacetone)dipalladium, palladium chloride, palladium bromide and palladium acetate; particular preference is given to bis(dibenzylideneacetone)palladium, palladium chloride and palladium acetate.

The amount of palladium catalyst used in the process according to the invention is 0.001 to 20 mole per cent, based on substituted anthranilic acid derivative of the general formula (IV) used. Preferably 0.005 to 10 mole per cent is used, more preferably 0.01 to 5 mole per cent.

The phosphine ligands used in the process according to the invention are ligands of the general formula (X)PR¹⁰R¹¹R¹²   (X)where the R¹⁰, R¹¹ and R¹² radicals are each independently hydrogen, linear or branched C₁-C₈-alkyl, vinyl, aryl or heteroaryl from the group of pyridine, pyrimidine, pyrrole, thiophene and furan, which may in turn be substituted by further substituents from the group of linear or branched C₁-C₈-alkyl or C₆-C₁₀-aryl, linear or branched C₁-C₈-alkyloxy or C₁-C₁₀-aryloxy, halogenated linear or branched C₁-C₈-alkyl or halogenated C₆-C₁₀-aryl, C₆-C₁₀-aryloxycarbonyl, linear or branched C₁-C₈-alkylamino, linear or branched C₁-C₈-dialkylamino, C₁-C₈-arylamino, C₁-C₈-diarylamino, hydroxyl, carboxyl, cyano and halogen such as fluorine or chlorine.

Further useful phosphine ligands include chelating bisphosphines. Examples of these include 1,2-bis(diphenylphosphino)ethane, 1,2-bis(diphenylphosphino)propane, 1,2-bis(diphenylphosphino)butane, 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl and 1,1′-bis(diphenylphosphino)ferrocene.

Preferred phosphine ligands are trialkylphosphines such as tri-tert-butylphosphine and triadamantylphosphine, and also triarylphosphines such as triphenylphosphine, tri(ortho-tolyl)phosphine or tri(para-methoxyphenyl)phosphine. Particular preference is given to triphenylphosphine.

As an alternative to this, it is also possible to use defined palladium complexes which have been obtained from the abovementioned ligands in one or more process steps.

In the process according to the invention, 1-20 molar equivalents of phosphine are used, based on the amount of palladium used. Preferably 2-15 molar equivalents are used.

Process step 2 of the process according to the invention is performed in the presence of carbon monoxide (CO). The carbon monoxide is typically introduced in gaseous form, and so the reaction is usually performed in an autoclave. It is customary to work at CO pressure 0.1 to 50 bar, preferably at 1 to 25 bar.

It is alternatively also possible in principle to introduce the carbon monoxide in the form of suitable metal carbonyl complexes, for example dicobalt octacarbonyl or molybdenum hexacarbonyl. Preference is given to working with gaseous carbon monoxide.

Process step 2 is generally performed in the presence of a base. Suitable bases are organic bases such as trialkylamines, alkylpyridines, phosphazenes and 1,8-diazabicyclo[5.4.0]undecene (DBU). Preference is given to organic bases such as triethylamine, tripropylamine, tributylamine, diisopropylethylamine, pyridine, alkylpyridines, for example 2,6-dimethylpyridine, 2-methyl-5-ethylpyridine or 2,3-dimethylpyridine.

The compounds of the general formula (V) or (VI) required for preparation of the substituted anthranilic acid derivatives of the general formula (I) are typically used in an excess, based on the substituted anthranilic acid derivative of the general formula (IV). It is also possible to use the compounds of the general formula (V) or (VI) in such an amount that they simultaneously serve as solvents.

PREPARATION EXAMPLES

The Preparation Examples which follow illustrate the invention without limiting it.

Example 1

2-Acetamido-5-cyano-3-methylbenzoic acid

In a 30 ml autoclave, under nitrogen as protective gas, 2.54 g [10 mmol] of N-(2-bromo-4-cyan-6-methylphenyl)acetamide, 3.89 g [21 mmol] of tri-n-butylamine, 0.131 g [0.5 mmol] of triphenylphosphine, 0.035 g [0.05 mmol] of bis(triphenylphosphine)palladium(II) chloride and 2 g of water are combined. After closure, the autoclave is purged with carbon monoxide and heated to 110° C., and a carbon monoxide pressure of 10 bar is maintained. After 18 hours, the mixture is allowed to cool to room temperature, the autoclave is depressurized, the reaction mixture is stirred with methylene chloride and filtered through kieselguhr, and the filtrate is washed, first with dilute hydrochloric acid and then with water, dried over sodium sulphate and concentrated under reduced pressure. This gives 1.14 g of the title compound.

LC/MS: m/e=219 (MH⁺).

GC/MS(sil.): m/e=362 (M⁺, 2×sil., 10%), 347 (M⁺−15, 2×sil., 45%).

Example 2

N-(2-Bromo-4-cyano-6-methylphenyl)-1-(3-chloropyridin-2-yl)-3-{[5-(trifluoromethyl)-2H-tetrazol-2-yl]methyl}-1H-pyrazole-5-carboxamide

To a solution of 3.74 g of 1-(3-chloropyridin-2-yl)-3-{[5-(trifluoromethyl)-2H-tetrazol-2-yl]methyl}-1H-pyrazole-5-carboxylic acid in 20 ml of acetonitrile are added 1.86 g of 3-methylpyridine. Then 1.37 g of methanesulphonyl chloride are added dropwise at 0° C. After 30 minutes at 0° C., the red solution thus obtained is slowly added dropwise to a solution of 2.11 g of 4-amino-3-bromo-5-methylbenzonitrile and 1.12 g of 3-methylpyridine in 20 ml of acetonitrile. The reaction mixture is stirred at room temperature for one hour and at 40° C. for 1 hour and cooled to room temperature, water and methylene chloride are added thereto, and the organic phase is removed, washed with dilute hydrochloric acid, dried and concentrated. The crude product thus obtained is purified by chromatography on silica gel (cyclohexane/ethyl acetate). This gives 1.30 g of the title compound as a pale beige solid.

LC/MS: m/e=566 (MH⁺ with ⁷⁹Br and ³⁵Cl).

Example 3

Methyl 2-({[1-(3-chloropyridin-2-yl)-3-{[5-(trifluoromethyl)-2H-tetrazol-2-yl]methyl}-1H-pyrazol-5-yl]carbonyl}amino)-5-cyano-3-methylbenzoate

In a 30 ml autoclave, under nitrogen as protective gas, 0.567 g of N-(2-bromo-4-cyano-6-methylphenyl)-1-(3-chloropyridin-2-yl)-3-{[5-(trifluoromethyl)-2H-tetrazol-2-yl]methyl}-1H-pyrazole-5-carboxamide, 0.463 g of tri-n-butylamine, 0.066 g of triphenylphosphine, 0.035 g of bis(triphenylphosphine)palladium(II) chloride and 10 ml of methanol are combined. After closure, the autoclave is purged with carbon monoxide and heated to 110° C., and a carbon monoxide pressure of 10 bar is maintained After 18 hours, the mixture is allowed to cool to room temperature, the autoclave is depressurized, the reaction mixture is stirred with methylene chloride and filtered through kieselguhr, and the filtrate is washed, first with dilute hydrochloric acid and then with water, dried over sodium sulphate and concentrated under reduced pressure. This gives 0.49 g of the title compound.

LC/MS: m/e=546 (MH⁺ with ³⁵Cl).

Example 4

1-(3-Chloropyridin-2-yl)-N-[4-cyano-2-(dimethylcarbamoyl)-6-methylphenyl]-3-{[5-(trifluoromethyl)-2H-tetrazol-2-yl]methyl}-1H-pyrazole-5-carboxamide

In a 30 ml autoclave, under nitrogen as protective gas, 0.567 g of N-(2-bromo-4-cyano-6-methylphenyl)-1-(3-chloropyridin-2-yl)-3-{[5-(trifluoromethyl)-2H-tetrazol-2-yl]methyl}-1H-pyrazole-5-carboxamide, 0.463 g of tri-n-butylamine, 0.066 g of triphenylphosphine, 0.035 g of bis(triphenylphosphine)palladium(II) chloride and 2 ml of dimethylamine are combined. After closure, the autoclave is purged with carbon monoxide and heated to 110° C., and a carbon monoxide pressure of 10 bar is maintained. After 18 hours, the mixture is allowed to cool to room temperature, the autoclave is depressurized, the reaction mixture is stirred with methylene chloride and filtered through kieselguhr, and the filtrate is washed, first with dilute hydrochloric acid and then with water, dried over sodium sulphate and concentrated under reduced pressure. This gives 0.475 g of the title compound.

LC/MS: m/e=559 (MH⁺ with ³⁵Cl).

Claims

1. A compound of formula (IV)

2. A compound of formula (IV) according to claim 1, wherein R8 is fluorine.

3. A compound of formula (IV) according to claim 1, wherein R8 is chlorine.

4. A compound of formula (IV) according to claim 1, wherein R9 is CF3.

5. A compound of formula (IV) according to claim 1, wherein R9 is C2F5.

6. A compound of formula (IV) according to claim 1, wherein R4 is chlorine.

7. A compound of formula (IV) according to claim 1, wherein R4 is cyano.