WO1991000266A1 - Esters of 2,3,4,5-tetrafluoro-6-cyano-1-benzene carboxylic acids and process for preparing them - Google Patents

Abstract

Compounds of formula (I), where R denotes an alkyl group with 1 to 8 carbon atoms or a possibly substituted phenyl group, and process for preparing them, in which compounds of formula (II), where R has the above-mentioned meaning, are reacted with an alkali metal fluoride or with mixtures of alkali metal fluorides in polar aprotic solvents at temperatures of approximately 80 to 300°C, if necessary in the presence of phase transfer catalysts.

Description

description

2,3,4,5-tetrafluoro-6-cyano-1-benzene-carboxylic acid ester and process for its preparation

The present invention relates to new 2,3,4,5-tetrafluoro-6-cyano-1-benzenecarboxylic acid esters and a process for their preparation in good yields. With saponification and

Subsequent decarboxylation gives 2,3,4,5-tetrafluorobenzoic acid, which is an important one

Preproduct for the production of antibacterial agents

represents.

The invention relates to new compounds of the general formula

in welcher R eine Alkylgruppe von 1 bis 8

in which R is an alkyl group from 1 to 8

 Carbon atoms or an optionally substituted phenyl group, and a process for their

 Manufacture by using compounds of general

 Formula (II)

in welcher R die vorstehend genannten Bedeutungen hat, mit einem Alkalimetallfluorid oder mit Mischungen aus

in which R has the meanings given above, with an alkali metal fluoride or with mixtures of

Alkali metal fluorides in polar aprotic solvents at temperatures from about 80 ° C to about 300 ° C, preferably from about 100 ° C to about 200 ° C, optionally in the presence of phase transfer catalysts.

Suitable alkali metal fluorides are LiF, NaF, KF, RbF or CsF or any mixtures thereof. About 100 to about 200 mole percent, preferably about 100 to about 120 mole percent, of alkali metal fluoride are advantageously used per chlorine atom to be exchanged. A larger amount of alkali metal fluoride can also be used, but there is practically no discernible influence on the

Degree of fluorination and the process is becoming increasingly uneconomical.

Examples of polar, aprotic solvents are sulfolane, chlorobenzene, dichlorobenzene, trichlorobenzene,

Dimethyl sulfone, diphenyl sulfone, dimethyl sulfoxide,

 N, N'-dimethylethylene urea, tetramethyl urea,

N, N'-dimethylpropyleneurea, N-methylpyrrolidone,

Dimethylformamide, acetonitrile or benzonitrile in question. Usually the solvent is in excess

 used, preferably in an amount of about 100 to about 500 weight percent, based on the

 Tetrachlorobenzene compound. These solvents can also be used as mixtures, with up to 50%, based on the total amount of solvent, of other inert substances

 Solvents such as toluene or xylene can be added. In Sulfolan or

 N-methylpyrrolidone worked.

Phase transfer catalysts can be added in an amount of, for example, about 0.5 to about 40 percent by weight, based on the alkali metal fluoride used become. Such phase transfer catalysts are

for example in Dehmlow / Dehmlow "phase transfer

Catalysis ", Verlag Chemie, Weinheim 1983 and are usually quaternary ammonium or

Phosphonium compounds, as well as crown ethers or

 Pyridinium compounds. As examples of this

Tetraalkylammonium chloride or bromide,

Tetraalkylphosphonium chloride or bromide,

Tetraphenylphosphonium chloride or bromide,

Distearyldimethylammonium chloride or bromide,

 Hexadecyltributylphosphonium chloride or bromide,

Pyridinium chloride or bromide or 18-crown-6 called. The phase transfer catalysts can be used individually or in a mixture.

The reaction can be carried out under pressure or under pressure. For low-boiling solvents that is

Printing procedure advantageous. In most cases

 however, working at normal pressure is sufficient.

Response times range from about 2 to about 25 hours.

The in the inventive method as

 2,3,4,5-Tetrachloro-6-cyano-1-benzene-carboxylic acid esters used as starting compounds can be prepared by the processes known from DE 3 700 675 and DE 2 112 778.

example 1

5 g (0.016 mol) of 2,3,4,5-tetrachloro-6-cyanobenzoic acid methyl ester are heated with 4.65 g (0.08 mol) of KF in 100 ml of sulfolane at 160 ° C. for 10 hours.

 When the reaction has ended, the reaction mixture

 gaschromatographiεch examined, with 87% of

corresponding tetrafluoro, 9% of the trifluoro and 3% of the difluoro compound (characterized by GC / MS) can be detected (GC calculation without solvent peak) ("GC" means gas chromatography; "MS" means

Mass spectroscopy). Example 2

5 g (0.017 mol) of 2,3,4,5-tetrachloro-6-cyanobenzoic acid ethyl ester are heated with 4.9 g (0.085 mol) of KF in 100 ml of N-methylpyrrolidone at 170 ° C. for 12 hours. When the reaction has ended, the reaction mixture is examined by gas chromatography, 89% of the

corresponding tetrafluoro, 7% of the trifluoro and 2% of the di-fluorine compound (characterized by GC / MS)

be detected.

Claims

Claims 1. Compounds of the general formula

in which R represents an alkyl group of 1 to 8 carbon atoms or an optionally substituted phenyl group. 2. Compounds of the general formula

in soft R 'denotes a methyl or ethyl group, 3. Process for the preparation of compounds of  general formula I.

in which R is an alkyl group of 1 to 8 carbon atoms or an optionally substituted phenyl group means, characterized in that compounds of the general formula

in which R has the meanings given above, with an alkali metal fluoride or with mixtures of Alkali metal fluorides in polar aprotic  Solvents at temperatures from about 80 ° C to about 300 ° C, optionally in the presence of Phase transfer catalysts. 4. The method according to claim 3, characterized in that at Tem

temperatures from about 100 ° C to about 200 ° C implemented. 5. The method according to at least one of claims 3 and 4, characterized in that reacting with sodium fluoride or potassium fluoride. 6. The method according to at least one of claims 3 to 5, characterized in that one with about 100 to about 200 mole percent alkali metal fluoride per to be exchanged  Chlorine atom. 7. The method according to at least one of claims 3 to 6, characterized in that one with about 100 to about 120 Mole percent alkali metal fluoride per exchanged Chlorine atom. 8. The method according to at least one of claims 3 to 7, characterized in that in sulfolane, chlorobenzene, Dichlorobenzene, trichlorobenzene, dimethyl sulfone, diphenyl sulfone, dimethyl sulfoxide, N, N'-dimethylethylene urea, Tetramethylurea, N, N'-dimethylpropyleneurea, N-methylpyrrolidone, dimethylformamide, acetonitrile or Benzonitrii or mixtures thereof as a polar aprotic solvent. 9. The method according to at least one of claims 3 to 8, characterized in that polar aprotic  Solvents mixed with other inert  Implement solvents. 10. The method according to at least one of "claims 3 to 9, characterized in that polar aprotic  Solvents mixed with toluene or xylene as  further inert solvents. 11. The method according to at least one of claims 3 to 10, characterized in that in the presence of a  quaternary ammonium or phosphonium compound, one  Pyridinium compound or a crown ether or  Mixtures thereof implemented as phase transfer catalysts. 12. The method according to at least one of claims 3 to 11, characterized in that in the presence of  Tetraalkylammonium chloride or bromide  Tetraalkylphosphonium chloride or bromide,  Tetraphenylphosphonium chloride or bromide,  Distearyldimethylammonium chloride or bromide,  Hexadecyltributylphosphonium chloride or bromide, Pyridinium chloride or bromide or 18-crown-6 or Mixtures thereof implemented as phase transfer catalysts. 13. The method according to at least one or claims 3 to 12, characterized in that one implements at normal or positive pressure.