HK1036971B - Production of organic compounds which are low in fluoride - Google Patents

Description

Preparation of fluoride-depleted organic compounds

The present invention relates to a catalytic process for the preparation of fluoride-poor organic compounds, in particular fluoro organic compounds such as carboxylic acids and derivatives thereof.

Fluoroorganic compounds are of great interest in many industrial fields. For example, in the field of refrigeration engineering and fire fighting, and as a cleaning agent, a fluorine organic compound (fluorinated hydrocarbon, fluorochlorohydrocarbon, fluorine-containing ether, fluorine-containing surfactant, etc.) is used. Fluorocarbons are used as propellants in the manufacture of foams or aerosols, also in the pharmaceutical field. The fluoroorganic compounds are not only used as end products as described above, but also as intermediates in the preparation of useful further processed products. In particular in the agricultural sector, carboxylic acids containing fluorine and, if appropriate, chlorine, have an important role as intermediates. Such carboxylic acids and reactive derivatives, such as the corresponding carboxylic acid chlorides, can often be further processed in condensation reactions into interesting materials such as esters or ring systems.

Many carboxylic acids and esters have found industrial application per se. For example, acetates and other carboxylates are used as solvents or cleaning agents, and other esters such as succinates are used for aromatization. Ethyl trifluoroacetate is, for example, a solvent for the chlorination of alkanes or the polymerization of alkylene oxides. Many carboxylic acid esters are also intermediates in chemical synthesis. Hydrogenation of methyl trifluoroacetate and trifluoroacetic acid-1, 1, 1-trifluoroethyl ester yields trifluoroethanol (and possibly methanol). Trifluoroethanol is used as a solvent and as an intermediate product, for example in the preparation of solvents and the narcotic isoflurane. Esters of trifluoroacetic acid and trifluoroacetoacetic acid are also useful for the introduction and preparation of compounds having CF₃-a radical of a biologically active substance. For example, one can prepare peptides with hormonal activity by N-acylation with methyl trifluoroacetate. The trifluoroethyl ester was reacted with a camphor derivative to give a shifting reagent for NMR-analysis. Phenyl trifluoroacetate after Fries displacement with aluminum chloride gives the corresponding trifluoroacetylated phenol which can be used as starting material for the synthesis of pharmaceuticals. Many other industrial applications of esters are known to the skilled person, for example the reaction of esters with amines to amides, which are starting materials for the synthesis of pharmaceuticals, photosensitizers and dyes.

The ester of chlorodifluoroacetic acid is likewise the starting material for the synthesis. Ethyl esters are used, for example, for structuring liquid crystals, see DE-OS 4023106, for preparing pharmaceuticals, see U.S. Pat. No. 3, 5006563, methyl esters are likewise used for structuring liquid crystals, as starting compounds for the microbiological preparation of chiral secondary alcohols, see T.Kitazume et al, J.Fluorine chem.56 (1992), p.271-284, or for preparing fluorinated enol ethers in Wittig synthesis reactions, see J.P.Beque et al, J.Org.chem.57 (1992), after p.3807. Chlorodifluoroacetate is also a precursor for difluorocarbene.

Carboxylic acid chlorides, in particular those containing fluorine, can be reacted with ketene to give RC (O) CH₂C (O) Cl, which is further esterified and likewise is the starting material for the synthesis. The preparation of haloacetoacetyl chlorides and their esterification is known from DE-AS 1158490. These esters are intermediates in dye chemistry, pharmaceutical chemistry and plant protection chemistry.

The fluoroorganic compounds can be prepared, for example, by reacting with F₂High-valence metal fluorides are directly fluorinated and prepared by fluorine-chlorine exchange, HF-addition and other methods. Any fluorine containing a hydrolyzable group, whether dependent on the production conditions or by hydrolysis of fluorine from the molecule, can cause corrosion of glass, ceramic and metal containers or equipment.

The hydrogen fluoride reacts with the glass and ceramic to form H₂SiF₆Which react with water under certain conditions to regenerate HF and SiO₂. The released HF, in turn, corrodes the glass and therefore can cause large losses, corrosion of the metal container also being undesirable.

Problems can also occur not only with storage vessels but also during derivatization of the fluoroorganic compounds, for example, in the condensation reaction, HF is also liberated, albeit as a secondary product.

If the carboxylic acid chlorides have small amounts of carboxylic acid fluoride, free HF or hydrolysable fluoride due to the preparation conditions, for example, esterification of the carboxylic acid chlorides with alcohols in the absence of catalysts also leads to corrosion problems. Even in carboxylic acids or their esters, the impurities can be troublesome due to corrosion problems.

The above description explains the problems with fluoroorganic compounds. Even in the compounds not substituted with fluorine, the problems may occur as long as fluoride is introduced during the preparation thereof.

It has been surprisingly found that corrosion is often due to hydrolysable fluoride.

The object of the invention is to provide a technically simple and easy process by means of which organic compounds, in particular fluoroorganic compounds, containing a reduced amount of hydrolyzable fluoride can be purified or prepared. A particular object is to provide a process by which carboxylic acids, carboxylic acid chlorides and their derivatives, in particular derivatives from condensation reactions, such as carboxylic acid esters, can be purified or prepared in high yields with the corresponding carboxylic acids, carboxylic acid chlorides or their derivatives, such as esters, containing impurities as starting materials, which are depleted in fluoride or contain reduced amounts of carboxylic acid fluoride and free HF. The method of the present invention accomplishes this task.

The process of the invention for preparing organic compounds depleted in hydrolysable fluoride consists in contacting a fluoroorganic compound contaminated with hydrolysable fluoride with at least one separating agent for hydrolysable fluoride selected from inorganic oxide sorbents and carboxylic "onium" salts.

The process of the present invention is suitable for purifying organic compounds contaminated with fluoride or hydrolysable fluoride. These impurities may be due to the preparation process and/or hydrolysis of fluorine in the molecule. Preference is given to purifying the fluoroorganic compounds, i.e. they are compounds containing at least one fluorine atom. Other halogen substituents may also be present. The invention is further explained with the aid of this embodiment.

The invention comprises two aspects: the already prepared fluoroorganic compound is purified (for example before its use or before further processing or during storage) and the fluoroorganic compound is prepared simultaneously with the purification according to the invention.

The process is preferably applied to the preparation or purification of fluorine-containing carboxylic acids, fluorine-containing carboxylic acid chlorides and derivatives for the preparation or purification of fluorine-containing carboxylic acids and fluorine-containing carboxylic acid chlorides. Derivatization preferably means condensation reactions such as esterification of fluorine-containing carboxylic acids, carboxylic acid chlorides, condensation with hydrazine derivatives, hydrolysis, etc.

May also be well suited for use with compositions containing one or more CF₃-、CF₂H-or CF₂Organic compounds of Cl-groups.

"hydrolyzable fluoride" also refers to alkali metal fluorides, such as those formed in an alkaline (lye) catalyzed reaction.

The process of the present invention is preferably used for the preparation or purification of carboxylic acid, carboxylic acid chloride and carboxylic acid ester depleted in carboxylic acid fluoride, free HF or hydrolysable fluoride from carboxylic acid, carboxylic acid chloride and carboxylic acid ester contaminated with carboxylic acid fluoride, HF or hydrolysable fluoride, wherein the former is contacted with at least one separating agent for carboxylic acid fluoride, free HF and hydrolysable fluoride selected from inorganic oxide sorbents and the corresponding "onium" salts of carboxylic acid.

Preferred inorganic oxide sorbents are silica, in particular amorphous silica, for example precipitated as hydrates or in the form of silica gel beads. As mentioned above, condensation reactions often release water. This can lead to the formation of HF and thus to corrosion. In the purification of substances or reaction mixtures which, apart from the condensation water, contain no further water, finely divided SiO₂If necessary, it exists as a hydrate and can be used as a good HF scavenger. In systems containing large amounts of water, silica gel beads (or other materials of coarse particle size) are preferably used. The beads, particles or compacts may be added directly to the reactor. The material or reaction mixture to be purified is preferably circulated through a separately disposed bed of sorbent particles. It has been observed that the corrosion caused by HF is greatly reduced even in systems containing large amounts of water (for example formation of hexafluorosilicic acid or its renewed decomposition).

When an "onium" salt is used, the HF scavenger is regenerated as long as the ratio of HF to "onium" salt exceeds 2: 1.

The process of the invention is particularly suitable for the preparation (purification)Formula R¹C (O) OH, a carboxylic acid of formula (I) R¹C (O) carboxylic acid chloride of Cl and R of formula (II)¹C(O)CH₂C (O) Cl carboxylic acid chlorides and their derivatives obtained by condensation, of formula (III) R¹C(O)OR²And esters of formula (IV) R¹C(O)CH₂C(O)OR²Esters of (a); r¹And R²The meaning of (a) is explained further below. If desired, purification can also be achieved by using both the oxidizing sorbent and an "onium" salt or by using an "onium" salt and oxidizing sorbent in either order sequentially.

It can be purified by the process of the invention after the preparation and, if desired, isolation of the ester. According to one embodiment, the carboxylic acid fluoride, HF and hydrolyzable fluoride are separated during the preparation of the ester from the carboxylic acid chloride and the alcohol.

This embodiment of the preparation of fluoride-depleted carboxylic acid esters from alcohols and carboxylic acid chlorides contaminated with carboxylic acid fluorides or HF and hydrolyzable fluorides is characterized in that the reaction is carried out in the absence of water and in the presence of an "onium" salt of the carboxylic acid corresponding to the carboxylic acid chloride used as separating agent and/or inorganic oxide sorbent. The carboxylic ester formed can then be separated off by distillation. Fluoride remains in the residue.

Wherein the "onium" salt of the carboxylic acid can be used simultaneously as a catalyst. One possibility is that the reaction of the acid chloride and the alcohol is carried out in the presence of the "onium" salt and the reaction mixture is circulated through the sorbent. It is of course also possible to operate without catalyst or with other catalysts, the reaction mixture being circulated through a sorbent, for example SiO₂。

If desired, the "onium" salts can be prepared in situ from a carboxylic acid and a base corresponding to the "onium" cation. If a labile acid is involved, for example a β -keto-carboxylic acid which is readily decarboxylated, another carboxylic acid may be used first. For example, trifluoroacetic acid can first be used in place of 4, 4, 4-trifluoroacetylacetic acid to provide an "onium" salt. It has been shown that the "onium" salt of 4, 4, 4-trifluoroacetylacetic acid is then formed in a mild manner by addition of 4, 4, 4-trifluoroacetylacetic acid or of an ester without decarboxylation occurring.

It is not necessary to add an acid, such as a carboxylic acid, and it is preferred not to add it.

The process of the present invention can in principle be used for the preparation and purification of any carboxylic acid, carboxylic acid chloride and the formation of esters from any carboxylic acid with any alcohol. In a preferred embodiment, the formula R is used¹C (O) OH or R¹C(O)CH₂C (O) OH, a carboxylic acid of formula (I) R¹C (O) Cl or R of formula (II)¹C(O)CH₂C (O) a carboxylic acid chloride of Cl, R of formula (III)¹C(O)OR²Or of the formula (IV) R¹C(O)OH₂C(O)OR²In which R is¹Represents an alkyl radical of 1 to 6 carbon atoms substituted by at least one halogen atom, in particular by at least one fluorine atom, R²The meaning of the expression is the same as above. The process is particularly suitable for use with the formula R¹C (O) OH, formula (I), formula (II) (wherein the compound of formula (II) is obtained, for example, by addition of a compound of formula (I) onto ketene), a compound of formula (III) or (IV), wherein R is¹Represents an alkyl group of 1 to 6 carbon atoms, in particular 1 to 4 carbon atoms, polyfluoro, perfluoro or polyfluorochloro. Wherein "polyfluoro" refers to R¹At least the hydrogen atom of 2/3 is replaced by fluorine. "perfluoro" means R¹Wherein all hydrogen atoms are replaced by fluorine. "Polyfluorochloro" means R¹At least 2/3, and the remaining hydrogen atoms are at least largely or entirely replaced by chlorine atoms.

In addition, preference is given to using an ester or the formula R²Alcohols of OH (II) in which R²Represents an alkyl or alkenyl group of 1 to 8 carbon atoms; an alkyl or alkenyl group of 1 (or at least 2 carbon atoms in the case of an alkenyl group) to 8 carbon atoms substituted by at least one halogen atom; phenyl, tolyl, benzyl; phenyl, tolyl or benzyl substituted by at least 1 halogen atom and/or at least one nitro group.

It is particularly preferred that R¹Denotes a polyfluoroalkyl, perfluoroalkyl or polyfluorochloroalkyl radical having 1 to 4 carbon atoms, R²Represents 1 (orAn alkyl or alkenyl group of at least 2 carbon atoms in the case of an alkenyl group) to 4 carbon atoms; an alkyl or alkenyl group of 1 (or at least 2 carbon atoms in the case of an alkenyl group) to 4 carbon atoms substituted by at least 1 halogen atom; a phenyl group; phenyl substituted by at least 1 halogen atom and/or at least one nitro group. R¹Particularly preferably a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group or a chlorodifluoromethyl group. R²Particularly preferably represents an alkyl or alkenyl group of 1 (or at least 2 carbon atoms in the case of an alkenyl group) to 3 carbon atoms; an alkyl or alkenyl group of 1 (or at least 2 carbon atoms in the case of an alkenyl group) to 3 carbon atoms substituted by at least 1 fluorine atom; a phenyl group; phenyl substituted by at least 1 fluorine atom and/or at least one nitro group.

Carboxylic acid chlorides substituted by fluorine and, if desired, chlorine can be prepared in a known manner.

"onium" means a cation having a positively charged nitrogen, for example a protonated aromatic nitrogen base such as pyridinium or a protonated alkyl, dialkyl, trialkyl ammonium cation of up to 20 carbon atoms, or a cycloalkyl-substituted ammonium compound or a cycloaliphatic nitrogen base such as piperidinium or quaternary ammonium cation.

Very suitable as carboxylates are "onium" salts, in which "onium" represents the formula R^IR^IIR^IIIR^IVN⁺Of nitrogen, wherein R is^I、R^II、R^IIIAnd R^IVIndependently of one another, hydrogen, alkyl, aryl or aralkyl having 1 to 20 carbon atoms, or R in the formula^IAnd R^IIOr R^IIIAnd R^IVOr R^I、R^IIAnd R^IIIOr R^I、R^II、R^IIIAnd R^IVIf desired together with the nitrogen atom, form a saturated or unsaturated ring system. "aryl" here denotes in particular phenyl or phenyl substituted by one or more C1-C2 alkyl groups. In particularly suitable salts, "onium" means ammonium, pyridinium or R¹’R²’R³’R⁴’N⁺In the formula, R¹’、R²’、R³' and R⁴' independently of one another denotes hydrogen, alkyl having 1 to 15 carbon atoms, phenyl or benzyl. As examples of such cations, mention may be made of pyridinium, piperidinium, anilinium, benzyltriethylammonium and triethylammonium.

The process of the invention is particularly suitable for the preparation or purification of difluoroacetic acid, 4, 4-difluoroacetoacetic acid, trifluoroacetic acid, chlorodifluoroacetic acid, 4, 4, 4-trifluoroacetoacetic acid and 4-chloro-4, 4-difluoroacetoacetic acid, the carboxylic acid chlorides thereof and their derivatives obtained by condensation reactions (hydrolysis, esterification, hydrazinolysis to form a ring containing a heteroatom), for example with 1, 1, 1-trifluoroethanol, methanol, ethanol, isopropanol, n-propanol, 4-nitrophenol, pentafluorophenol and allyl alcohol.

In the preparation of esters, the molar ratio of carboxylic acid halide to alcohol is preferably greater than 0.9. The alcohol may be used in higher excess and as solvent, particularly when an alcohol substituted by an electron-withdrawing group such as a fluorine atom is involved. The molar ratio of alcohol to carboxylic acid halide is generally in the range from 0.9: 1 to 1.1: 1, or may be up to 5: 1 if alcohol is used as solvent.

The reaction (or purification) is carried out at a temperature from ambient temperature (about 20 ℃) to the boiling point of the mixture, for example to 100 ℃. For unstable acids or carboxylic acid chlorides, the procedure is carried out below the decarboxylation temperature. This applies, for example, to the esterification of 4, 4, 4-trifluoro-, 4-chloro-4, 4-difluoro-and 4, 4-difluoroacetoacetyl chloride; the esterification here is carried out at room temperature or under cooling of the reaction mixture. The operation is carried out at ambient pressure (about 1 bar absolute) or, if necessary, at elevated pressure, for example up to 5 bar.

The "onium" salts may be present in catalytic or molar amounts. The molar ratio of acid halide to carboxylic acid salt is generally from 1: 1 to 20000: 1.

In addition to the already mentioned distillation which can be used for separating the esters, it is possible for certain esters to use the following, i.e. two-phase formation: one phase contains very pure ester (> 94% purity) and the other phase contains catalyst, alcohol and fluoride. Two phases are formed, for example, in the case of the methyl and ethyl esters of trifluoro and chlorodifluoroacetic acid and the n-propyl ester of chlorodifluoroacetic acid. Its advantage is simple post-treatment.

This embodiment of the process of the invention is used for the preparation of the methyl or ethyl esters of trifluoro and chlorodifluoroacetic acid and the n-propyl ester of chlorodifluoroacetic acid, the carboxylic acid chloride is reacted with an excess of alcohol in the presence of an "onium" salt of the corresponding acid, the molar ratio of alcohol to carboxylic acid chloride being chosen such that two phases are formed, one of which contains the ester in a purity of at least 95% without having to distill it, the ester being obtained by separating the ester phase from the other. In this way, the ester is obtained in a certain purity without the need for a distillation step. Thus, a preferred embodiment of the invention is to isolate the resulting ester without distillation.

In the preparation of methyl trifluoroacetate, the molar ratio of methanol to trifluoroacetyl chloride is from 1.03: 1 to 4: 1. In the preparation of ethyl trifluoroacetate, the molar ratio of ethanol to trifluoroacetyl chloride is from 1.01: 1 to 5: 1. In the preparation of methyl chlorodifluoroacetate, the molar ratio of methanol to chlorodifluoroacetyl chloride is from 1.06: 1 to 2.5: 1. In the preparation of ethyl chlorodifluoroacetate, the molar ratio of ethanol to chlorodifluoroacetyl chloride is from 1.02: 1 to 2.5: 1. Two phases are formed in the range described, wherein one phase contains esters always at least 95% pure, as described above. Methyl esters always form in the lower phase; ethyl chlorodifluoroacetate likewise forms the lower phase, while ethyl trifluoroacetate forms the upper phase.

The present invention provides acids, acid chlorides and esters with greatly reduced fluoride content (e.g., less than 70ppm, even 10ppm or less), depending on the original levels of HF, carboxylic acid fluoride and hydrolyzable fluoride. On the one hand, the product is very pure and, on the other hand, has no corrosion problems (or a much reduced corrosivity), as is the case, for example, in esterification in ceramic or glass installations and installation components.

The use of "onium" salts as catalysts in esterification is known from EP-A623582 (═ US 5405991). In this way not only very easy preparation is possible, but also fluoride-poor results are obtained when starting materials containing carboxylic acid fluoridesProducts and reduced corrosion are not known from the above-mentioned documents. This also applies to DE 19732031, not previously published, which relates to the two-phase process for the preparation of CF₃C (O) Cl and CF₂Methyl and ethyl esters of ClC (O) Cl.

The "onium" salts of 4, 4, 4-trifluoroacetoacetic acid, 4-chloro-4, 4-difluoroacetoacetic acid and the free acids themselves are novel and can be used in the process according to the invention, which are likewise subject matter of the invention.

The following examples further illustrate the invention but should not be construed as limiting its scope.

Preparation of fluoride-depleted Ethyl trifluoroacetate catalyzed by trifluoroacetyl chloride and ethanol for examples 1-3 General experimental description of

Starting materials (applicable to examples 1-3):

0.2mol of pyridine 15.8g

22.8g of 0.2mol trifluoroacetic acid (TFA)

2.0mol of ethanol p.A 92.1.1 g

1.8mol of trifluoroacetyl chloride (TFAC) 238.5g

The operation is as follows:

pyridine was placed in a 250ml three-necked flask with a magnetic stir bar, thermowell and dry ice cooler and TFA was added dropwise. The reaction was exothermic and ethanol was added to keep the salt in solution before it completely precipitated. To increase the reaction rate, the solution was warmed to 50 ℃ in an oil bath, at which temperature TFAC was introduced through a frit.

Two phases formed at 20% of the desired TFAC, with the upper phase being almost pure ethyl trifluoroacetate.

After the end of the introduction, the solution was stirred for a further half an hour and then transferred to a separating funnel. The two phases separated and became clear and the catalyst phase was pale yellow.

Example 1:

TFAC with a fluoride content of 570ppm was used. The test was carried out as described above, giving after reaction an ester phase with a fluoride content of 61ppm and a phase containing 1850ppm F^-The catalyst phase of (1).

This percentage distribution indicates that fluoride preferentially enters the catalyst phase; there was 86.03% of the total fluoride content and the ester phase contained 15.27%.

Example 2:

TFAC with the same fluoride content of 570ppm was used here. The test was carried out as described above, but the stirring was significantly more intense and an ester phase with a fluoride content of 10ppm and 3670ppm F were obtained after the reaction^-The catalyst phase of (1).

This percentage distribution indicates that fluoride preferentially enters the catalyst phase; there was 97.28% of the total fluoride; the fluoride content in the ester phase was reduced to 2.72% of the original value.

Example 3:

TFAC with a fluoride content of 71ppm was used here. The test was carried out as described above, giving after reaction an ester phase with a fluoride content of 10ppm and having a F content of 130ppm^-The catalyst phase of (1).

This percentage distribution indicates that fluoride preferentially enters the catalyst phase; there was 76.66% of the total fluoride; the fluoride content in the ester phase was reduced to 23.35% of the original value.

These examples show that the fluoride content in the ester can be reduced to very low values, not only when the original fluoride content in the carboxylic acid fluoride is high, but also when the original fluoride content in the carboxylic acid fluoride is already quite low.

Example 4:

raw materials:

0.1mol of pyridine 7.9g

11.4g of 0.1mol trifluoroacetic acid

2.0mol of ethanol p.A 92.1.1 g

1.8mol of trifluoroacetyl chloride 238.5g

TFAC with a fluoride content of 570ppm was also used here. The amount of catalyst was reduced from 10 mol% to 5 mol% used. The test was carried out as described above, but with stirring being distinctly intense, an ester phase having a fluoride content of 32ppm was obtained after the reaction.

Example 5:

using SiO in a ceramic stirred vessel₂Preparation of fluoride-poor trifluoroacetates

5.1. A solution was prepared from 0.10kg of pyridinium trifluoroacetate in 1.90kg of methanol and mixed with a further 4.80kg of methanol. 0.02kg of precipitated SiO with a particle size of < 0.1mm was added₂Hydrate (product "1.00656.000 kieselsaeuure gefaellt reenst schwer", Merck KGaA from Darmstadt; bulk density about 30-50g/100ml) and 19.2kg of trifluoroacetyl chloride (1000ppm of hydrolyzable fluoride) are introduced with stirring. The hydrolysable fluoride content of the methyl ester after distillation is less than 40 ppm. No corrosion was observed on the ceramic parts of the stirred vessel after repeated cycles.

5.2. Example 5.1 was repeated. The same molar amount of ethanol was used instead of methanol. After distillation, ethyl esters having a hydrolysable fluoride content of less than 30ppm are obtained.

Example 6:

separation of hydrolyzable fluoride from trifluoroacetyl chloride

A bed of 100g of KC-dry beads AF125 from Hannover EngelhardProcess Chemicals GmbH was prepared in a glass tube with an internal diameter of 1.5 cm. The dry beads are made of SiO₂-gel formation, diameter 2-5 mm. The pore size was 125  (12.5 nm). They are commonly used as desiccants or catalyst carriers.

Trifluoroacetyl chloride containing 570ppm of hydrolysable fluoride was passed through the bed at room temperature. The product leaving the feed contained 98ppm hydrolysable fluoride.

Examples 7 to 9:

purification of 4, 4, 4-Trifluoroacetoacetic acid Ethyl ester

630g of ester (3.4mol) was mixed with 2.6g of HF (0.1mol) to simulate an ester containing 4125ppm of hydrolyzable fluoride.

Example 7:

Py.TFA as F-separating agent

In a 250ml Teflon flask with a magnetic stirring bar, 2.1g of pyridine (0.027mol) was placed in advance and mixed with 3.1g of trifluoroacetic acid (0.027mol) (4, 4, 4-trifluoroacetoacetic acid readily decarboxylates when a salt is prepared directly from pyridine and 4, 4, 4-trifluoroacetoacetic acid). To pyridinium trifluoroacetate was added 50.2g of ethyl 4, 4, 4-trifluoroacetoacetate, and stirred at room temperature for 3 hours. The solution was thereafter heated at 70 ℃ water bath temperature for 1 hour and distilled under vacuum. "onium" salts containing 4, 4, 4-trifluoroacetoacetic acid(s) (ii)¹⁹F-NMR) contained 14500ppm of fluoride in the bottom sample. The distilled ester contained 1460ppm fluoride.

"onium" salts of 4, 4-difluoroacetoacetate and 4-chloro-4, 4-difluoroacetoacetate are likewise obtainable. Can be separated according to the conventional method.

Example 8:

precipitated SiO₂-hydrates as sorbents

In a Teflon flask equipped with a magnetic stirring bar, 50.1g of ethyl 4, 4, 4-trifluoroacetoacetate (0.27mol) was placed. To the ethyl 4, 4, 4-trifluoroacetoacetate was added 6.57g of precipitated SiO from Merck₂Hydrate (see example 5) and stirred at room temperature for 3 hours. The solution was then heated at 80 ℃ water bath temperature for 1 hour. After the stirring, the solution was filtered hot and the fluoride content of the solution was measured. The fluoride content obtained was 9 ppm.

Example 9:

SiO₂-gel beads as sorbent

In a Teflon flask equipped with a magnetic stirring bar, 50.7g of ethyl 4, 4, 4-trifluoroacetoacetate (0.28mol) was placed. To the ethyl 4, 4, 4-trifluoroacetoacetate was added 10.2g of dry beads "AF 125" see example 6), and stirred at room temperature for 3 hours. After this time ethyl 4, 4, 4-trifluoroacetoacetate was filtered off with a fluoride content of 47 ppm.

Example 10:

purification of trifluoroacetic acid

Trifluoroacetyl chloride containing about 1000ppm of hydrolyzable fluoride is stirred with an almost equimolar amount of water. The reaction mixture was continuously circulated through "AF 125". The hydrolysable fluoride content of the product is less than 50 ppm. Thus, although the reaction mixture contains water, SiO₂Fluoride is also adsorbed.

Example 11:

preparation and isolation of 4, 4, 4-trifluoroacetoacetic acid

Raw materials:

4.0mol of ethyl alpha, alpha-trifluoroacetoacetate 736.4g

2.0mol of trifluoroacetic acid 228.0g

0.9mol sulfuric acid 95-97%, 90.0g

Synthesis and operation:

in a 1 liter flask equipped with a distillation apparatus were placed ethyl α, α, α -trifluoroacetoacetate and trifluoroacetic acid in advance. Concentrated sulfuric acid is carefully added dropwise. The previously clear solution became turbid. Thereafter, cooking is carried out at 70-90 ℃ for 1.5 hours. The temperature was slightly lowered when the appearance of individual bubbles was observed in the bubble counter.

After boiling, the light brown solution was taken out of the oil bath and cooled in an ice bath to form white fine needle crystals after a short time. The crystals were suction filtered through a frit and confirmed to be trifluoroacetoacetic acid by means of NMR and mass spectrometry analysis.

4, 4-difluoroacetoacetic acid and 4-chloro-4, 4-difluoroacetoacetic acid can be obtained in a similar manner from ethyl ester and trifluoroacetic acid and then by conventional purification procedures.

Claims (29)

1. Process for the preparation of fluorinated organic compounds poor in hydrolysable fluoride, characterised in that an organic compound contaminated with hydrolysable fluoride is brought into contact with at least one material selected from amorphous SiO₂And a separating agent for hydrolyzable fluoride of an "onium" carboxylate salt.

2. The process as claimed in claim 1, wherein the carboxylic acid or carboxylic acid chloride is purified.

3. The process as claimed in claim 1, wherein derivatives of carboxylic acids or carboxylic acid chlorides are purified.

4. A process according to any one of claims 1 to 3, characterized in that the derivatives of carboxylic acids or carboxylic acid chlorides are purified in the preparation of the derivatives of carboxylic acids or carboxylic acid chlorides.

5. The process according to claim 1 for the preparation of carboxylic acid, carboxylic acid chloride and carboxylic acid ester depleted in carboxylic acid fluorides, wherein carboxylic acid, carboxylic acid chloride and carboxylic acid ester contaminated with carboxylic acid fluorides are reacted with at least one compound selected from the group consisting of amorphous SiO₂And a separating agent for carboxylic acid fluorides of an "onium" salt of the corresponding carboxylic acid.

6. The process as claimed in claim 1, wherein silica gel beads or precipitated SiO are used₂-a hydrate.

7. The process as claimed in claim 5, wherein the onium salt and/or amorphous SiO of the corresponding carboxylic acid₂Carboxylic acid esters are prepared from carboxylic acid chlorides and alcohols in the presence of a catalyst.

8. The process as claimed in any of the preceding claims, wherein the compound of the formula R is purified¹C (O) OH or by using a carboxylic acid of the formula (I) R¹C (O) Cl or R of formula (II)¹C(O)CH₂C (O) carboxylic acid chloride of Cl, in which R¹Represents an alkyl group of 1 to 6 carbon atoms substituted by at least one fluorine atom.

9. The process as claimed in claim 8, wherein R is¹Represents a polyfluoroalkyl, perfluoroalkyl or polyfluorochloroalkyl group having 1 to 6 carbon atoms.

10. The process as claimed in claim 7, wherein the formula R is used²An alcohol of OH (II), wherein R²Represents an alkyl or alkenyl group of 1 to 8 carbon atoms; by substitution of at least one halogen atomAlkyl or alkenyl of 1 to 8 carbon atoms; phenyl, tolyl, benzyl; phenyl, tolyl or benzyl substituted by at least 1 halogen atom and/or at least one nitro group.

11. The process as claimed in claim 5, wherein R of the formula (III)¹C(O)OR²Or of the formula (IV) R¹C(O)CH₂C(O)OR²In which R is¹Represents an alkyl group of 1 to 6 carbon atoms substituted by at least one fluorine atom, and R²Represents an alkyl or alkenyl group of 1 to 8 carbon atoms; an alkyl or alkenyl group of 1 to 8 carbon atoms substituted by at least one halogen atom; phenyl, tolyl, benzyl; phenyl, tolyl or benzyl substituted by at least 1 halogen atom and/or at least one nitro group.

12. The method as set forth in claim 11, wherein R is¹Denotes a polyfluoroalkyl, perfluoroalkyl or polyfluorochloroalkyl group of 1 to 4 carbon atoms, R²Represents an alkyl or alkenyl group of 1 to 4 carbon atoms; an alkyl or alkenyl group of 1 to 4 carbon atoms substituted by at least one halogen atom; a phenyl group; phenyl substituted by at least 1 halogen atom and/or at least one nitro group.

13. The method as set forth in claim 12, wherein R is¹Represents a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group or a chlorodifluoromethyl group.

14. The method as set forth in claim 13, wherein R is²Represents an alkyl or alkenyl group of 1 to 3 carbon atoms; an alkyl or alkenyl group of 1 to 3 carbon atoms substituted by at least one fluorine atom; a phenyl group; phenyl substituted by at least 1 fluorine atom and/or at least one nitro group.

15. The process as claimed in claim 7, wherein the molar ratio of carboxylic acid chloride to onium salt is from 1: 1 to 20000: 1.

16. A process as claimed in any of the preceding claims, characterized in that pyridinium or piperidinium salts are used.

17. The process as claimed in claim 7, wherein the "onium" salts are prepared in situ from the corresponding carboxylic acids and the bases corresponding to the "onium" cations.

18. The process as claimed in claim 17, wherein the preparation is carried out starting from decarboxylation-stable carboxylic acids in the case of readily decarboxylated carboxylic acids.

19. The process as claimed in claim 11, characterized in that esters of the formula (IV) are prepared in which R of the formula (II) is used¹C(O)CH₂C (O) Cl, the carboxylic acid chloride being formed by R¹C (O) Cl with ketene.

20. The process as claimed in claim 1, wherein the CF is purified or prepared as a fluorinated organic compound₃C (O) Cl or CF₃C(O)CH₂C(O)Cl。

21. The process as claimed in claim 1, wherein CF is used₃C (O) Cl or CF₃C(O)CH₂C (O) Cl as a fluorinated organic compound.

22. The process as claimed in claim 7, for preparing methyl or ethyl esters of trifluoroacetic acid and chlorodifluoroacetic acid, characterized by the presence of an "onium" salt and optionally amorphous SiO₂Reacting the acid chloride with a stoichiometric excess of an alcohol in the presence of a molar ratio of alcohol to carboxylic acid chloride selected such that two phases are formed, one of which comprises at least 95% by weight of the ester without distillation, and separating the ester by separating the ester phase from the other phases.

23. The process as set forth in claim 22, characterized in that the methyl ester of trifluoroacetic acid is prepared in a molar ratio of methanol to trifluoroacetyl chloride in the range of from 1.03: 1 to 4: 1.

24. The process as set forth in claim 22, characterized in that the ethyl ester of trifluoroacetic acid is prepared in a molar ratio of ethanol to trifluoroacetyl chloride in the range of from 1.01: 1 to 5: 1.

25. The process as set forth in claim 22, characterized in that the methyl ester of chlorodifluoroacetic acid is prepared in a molar ratio of methanol to chlorodifluoroacetyl chloride ranging from 1.06: 1 to 2.5: 1.

26. The process as set forth in claim 22, characterized in that the ethyl chlorodifluoroacetate is prepared in a molar ratio of ethanol to chlorodifluoroacetyl chloride ranging from 1.02: 1 to 2.5: 1.

27. The process of claim 22, wherein the reaction mixture is circulated and contacted with the sorbent.

28. The process as claimed in claim 6, wherein silica gel beads are used in the aqueous system and the purification is carried out in the circulation stream.

4-chloro-4, 4-difluoroacetoacetate, 4-difluoroacetoacetate and the "onium" salts thereof.