Method for preparing oxysulphide and fluorinated derivatives by sulphination

Abstract

The invention concerns a method for preparing an oxysulphide and fluorinated derivative, said method comprising the reacting, in the presence of an organic solvent, of: i) at least one compound of formula Ea-COOR (I), in which Ea represents the fluorine atom or a group having 1 to 10 carbon atoms chosen from fluoroalkyls, perfluoroalkyls and fluoroalkenyls and R represents hydrogen, a monovalent cation or an alkyl group, and ii) a sulphur oxide, said method being such that the initial molar ratio (sulphur oxide/compound of formula (I)) is less than 0.4 and the concentration of sulphur oxide dissolved in the reaction medium is kept constant for the entire duration of the reaction to a value of between 0.2% and 3% by weight by means of continually adding said sulphur oxide to the reaction medium.

Claims

1. A process for the preparation of an oxysulfide and fluorinated derivative, comprising the reaction, in the presence of an organic solvent, of: i) at least one compound of formula Ea-COOR (I), wherein Ea represents a fluorine atom or a group having from 1 to 10 carbon atoms selected from the group consisting of fluoroalkyls, perfluoroalkyls and fluoroalkenyls, and R represents hydrogen, a monovalent cation or an alkyl group, and ii) a sulfur oxide, wherein the initial sulfur oxide/compound of formula (I) molar ratio is less than 0.4 and the concentration of dissolved sulfur oxide in the reaction medium is kept constant throughout the duration of the reaction at a value of between 0.2 weight % and 3 weight % by a continuous addition of said sulfur oxide to the reaction medium.

2. The process according to claim 1, wherein the compound of formula (I) is a salt of a fluorocarboxylic acid in which the R group is a monovalent cation selected from the group consisting of alkali metal cations, quaternary ammonium cations and quaternary phosphonium cations.

3. The process according to claim 2, wherein R is an alkali metal cation.

4. The process according to claim 1, wherein the Ea group is selected from the group consisting of a fluorine atom, a CH.sub.2F radical, a CHF.sub.2 radical and a CF.sub.3 radical.

5. The process according to claim 1, wherein the sulfur oxide is sulfur dioxide.

6. The process according to claim 1, wherein the initial sulfur oxide/compound of formula (I) molar ratio is less than 0.2.

7. The process according to claim 1, wherein the concentration of dissolved sulfur oxide in the reaction medium is monitored in line or in situ by Raman spectrometry, by near infrared spectroscopy or by UV spectroscopy.

8. The process according to claim 1, wherein the organic solvent is a polar aprotic solvent.

9. The process according to claim 8, wherein the solvent is N,N-dimethylformamide (DMF), N,N-diethylformamide or N,N-dimethylacetamide.

10. The process according to claim 1, wherein the concentration of the compound of formula (I) in the organic solvent is between 1 weight % and 40 weight %.

11. The process according to claim 1, wherein the process is carried out continuously or semicontinuously.

12. The process according to claim 1, wherein the reaction is carried out at an absolute total pressure between 1 and 20 bar.

13. The process according to claim 1, wherein the reaction is carried out at a pressure below atmospheric pressure.

14. A process for the preparation of a compound selected from the group consisting of a sulfonimide compound (Ea-SO.sub.2).sub.2NH, its salts (Ea-SO.sub.2).sub.2NMe, Me representing an alkali metal, a fluorinated compound having a sulfonic acid functional group SO.sub.2OH and exhibiting a formula Ea-SO.sub.2OH, and an anhydride compound of formula (Ea-SO.sub.2).sub.2O, wherein Ea represents a fluorine atom or a group having from 1 to 10 carbon atoms selected from the group consisting of fluoroalkyls, perfluoroalkyls and fluoroalkenyls, said process comprising: preparation of an oxysulfide and fluorinated derivative according to the process of claim 1, using the oxysulfide and fluorinated compound as reactive compound for the synthesis of a sulfonimide compound (Ea-SO.sub.2).sub.2NH and of its salts (Ea-SO.sub.2).sub.2NMe, Me representing an alkali metal, of a fluorinated compound having a sulfonic acid functional group SO.sub.2OH and exhibiting a formula Ea-SO.sub.2OH, or of an anhydride compound of formula (Ea-SO.sub.2).sub.2O.

15. The process according to claim 14, wherein the salt of a sulfonimide compound of formula (Ea-SO.sub.2).sub.2NMe is prepared from the oxysulfide and fluorinated derivative the process comprising: a) the preparation of the oxysulfide and fluorinated derivative; b) oxidation of the oxysulfide and fluorinated derivative in order to obtain the compound (Ea-SO.sub.2)X, where X is chlorine or fluorine; c) ammonolysis of Ea-SO.sub.2X to give (Ea-SO.sub.2).sub.2N.HNR.sub.3; d) acidification of (Ea-SO.sub.2).sub.2N.HNR.sub.3 to give (Ea-SO.sub.2).sub.2NH; e) neutralization, by an alkali metal base, of (Ea-SO.sub.2).sub.2NH to give (Ea-SO.sub.2).sub.2NMe; and f) optionally drying (Ea-SO.sub.2).sub.2NMe; wherein R represents a linear or branched alkyl group having from 1 to 20 carbon atoms and Me represents an alkali metal.

16. The process according to claim 14, wherein the fluorinated compound of formula Ea-SO.sub.2OH is prepared from the oxysulfide and fluorinated derivative the process comprising: a) the preparation of the oxysulfide and fluorinated derivative; b) the oxidation of the oxysulfide and fluorinated derivative in order to obtain the fluorinated compound of formula Ea-SO.sub.2OH.

17. The process according to claim 14, wherein the anhydride compound of formula (Ea-SO.sub.2).sub.2O is prepared from the oxysulfide and fluorinated derivative the process comprising: a) the preparation of the oxysulfide and fluorinated derivative; b) the oxidation of the oxysulfide and fluorinated derivative in order to obtain a fluorinated compound of formula Ea-SO.sub.2OH; c) the anhydrization of the fluorinated compound of formula Ea-SO.sub.2OH in order to obtain an anhydride compound of formula (Ea-SO.sub.2).sub.2O.

Description

EXAMPLE 1 (COMPARATIVE)

Preparation of Potassium Trifluoromethylsulfinate CF3SO2K by Sulfination of Potassium Trifluoroacetate in the Presence of SO2 According to a Batch Implementation

(1) 125.5 g of dimethylformamide are charged, at ambient temperature (approximately 20 C.), to a 500 cm.sup.3 reactor provided with a jacket, with a central mechanical stirrer and with outlet to the atmosphere and with an acetone/dry ice condenser which makes possible the reflux of the sulfur dioxide. 25.5 g of potassium trifluoroacetate are introduced into the DMF. 6.9 g of sulfur dioxide are subsequently charged via a capillary connected to a pressurized sulfur dioxide cylinder. Heating is carried out to 140 C. at atmospheric pressure. The SO.sub.2/KTFA molar ratio is equal to 0.64.

(2) After 4 hours 25 minutes, ion chromatographic analysis gives the following results: Degree of conversion of the potassium trifluoroacetate: 57.1% Yield of potassium trifluoromethylsulfinate: 52.8%

EXAMPLE 2 (INVENTION)

Preparation of Potassium Trifluoromethylsulfinate CF3SO2K by Sulfination of Potassium Trifluoroacetate in the Presence of SO2 According to a Semicontinuous Implementation

(3) The following are introduced at ambient temperature into a 500 ml jacketed reactor equipped with a condenser having an aqueous glycol solution at 15 C., with a stirrer and with baffles: 200 g of anhydrous dimethylformamide (DMF) 50 g of potassium trifluoroacetate (KTFA), i.e., a KTFA concentration equal to 20 weight % in the DMF-KTFA mixture.

(4) The reactor is equipped with a Raman probe which makes it possible to monitor, in the medium, the concentration of dissolved SO.sub.2; this probe is connected by an optical fiber to the Raman spectrometer.

(5) The medium is stirred and brought to a temperature of 100 C.

(6) Via a dip pipe connected to the SO.sub.2 cylinder, an amount of 1.25 g of gaseous SO.sub.2 is continuously introduced into the reactor through a micrometric regulating valve, so as to have a concentration of dissolved SO.sub.2 equal to 0.5 weight % and an initial SO.sub.2/KTFA molar ratio of 0.059.

(7) The temperature is brought to 145 C. while keeping the SO.sub.2 concentration constant at 0.5 weight %. The reaction is allowed to take place for 5 hours while regulating the SO.sub.2 concentration at 0.5 weight %.

(8) After 5 hours, the reaction mixture is cooled and analyzed by NMR, and the results are as follows: Degree of conversion of the potassium trifluoroacetate: 90% Yield of potassium trifluoromethylsulfinate: 64.8%

(9) A marked improvement in the reaction yield and conversion is observed.