EP0203851B1 - Electrochemical process for the preparation of organic trifluoro (or chlorodifluoro or dichlorofluoro) methylated derivatives - Google Patents

Electrochemical process for the preparation of organic trifluoro (or chlorodifluoro or dichlorofluoro) methylated derivatives Download PDF

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EP0203851B1
EP0203851B1 EP86401046A EP86401046A EP0203851B1 EP 0203851 B1 EP0203851 B1 EP 0203851B1 EP 86401046 A EP86401046 A EP 86401046A EP 86401046 A EP86401046 A EP 86401046A EP 0203851 B1 EP0203851 B1 EP 0203851B1
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process according
compound
formula
aprotic solvent
dichlorofluoro
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EP0203851A1 (en
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Francis Leroux
Michel Jaccaud
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Arkema France SA
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Atochem SA
Elf Atochem SA
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B3/00—Electrolytic production of organic compounds
    • C25B3/20—Processes
    • C25B3/27—Halogenation
    • C25B3/28—Fluorination
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B3/00—Electrolytic production of organic compounds
    • C25B3/20—Processes
    • C25B3/29—Coupling reactions
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B3/00—Electrolytic production of organic compounds
    • C25B3/20—Processes
    • C25B3/25—Reduction

Definitions

  • the invention relates to a process for trifluoro (or chlorodifluoro or dichlorofluoro) methylation of non-electroactive electrophilic substrates.
  • the invention relates to the preparation of methyl trifluoro (or chlorodifluoro or dichlorofluoro) methyl derivatives, useful in particular as synthesis intermediates.
  • the trifluoromethylation reaction can be carried out by radical route starting from CF 3 1 by initiating the reaction by raising the temperature or by irradiation with UV rays (J. Chem. Soc. 1953, p, 1199; U.S. Patents 3,016,406 and 3,016,407); however; this method has not yet been industrialized since access to trifluoromethyl iodide from trifluoroacetyl fluoride according to the scheme: is difficult and expensive.
  • the olefin trifluoromethylation was moreover carried out by electrochemical oxidation of the trifluoroacetate anion according to a radical mechanism, as described by BROOKES et al. (J. Chem. Soc. Chem. Commun. 1974, 323) and RENAUD et al. (Can. J. Chem 53, 1975, 529).
  • ISHIKAWA Choemistry Letters 1984, 517-520
  • phosphines a generator of polluted effluents
  • the present invention therefore relates to a process for the preparation of trifluoro (or chlorodifluoro or dichlorofluoro) methylated organic derivatives, characterized in that a compound of formula (1) is reduced electrochemically in the presence of a non-electroactive electrophilic substrate and a support electrolyte in an aprotic solvent.
  • non-electroactive electrophilic substrate is understood here to mean any organic electron-attracting compound which under operating conditions has a reduction potential more negative than the potential at which the operation is carried out.
  • substrates mention may be made more particularly of carbon dioxide, aldehydes such as formaldehyde and acetaldehyde, ketones such as acetone and benzophenone, and activated olefins (i.e. comprising at least one electron-withdrawing group) such as allyl alcohol and methyl acrylate.
  • the support electrolyte whose role is to ensure the passage of the current can be chosen from all the mineral or organic salts known for this purpose (cf. for example, Organic Electrochemistry by MM BAIZER , 1973, pp. 227-230) and, more particularly, among the bromides, chlorides, perchlorates or arylsulfonates of alkali metals (preferably lithium) or of tetraalkylammonium (C 1 to C 4 alkyl radicals).
  • the amount of support electrolyte in the aprotic solvent can range from 0.01 mole / liter until saturation; preferably, the support electrolyte is used at a concentration of 0.1 to 1 mole per liter of aprotic solvent.
  • the reaction can be carried out in any aprotic solvent or mixture of such solvents provided that its cathode limit is less than the reduction potential of the compound (1).
  • amides such as dimethylformamide (DMF), dimethylacetamide (DMA), N-methylpyrrolidone (NMP) or hexamethylphosphorotriamide (HMPT), sulfoxides such as dimethyl sulfoxide (DMSO), nitriles such as acetonitrile (ACN) and ethers such as tetrahydrofuran (THF).
  • aprotic solvents mention may be made of pyridine, nitromethane, nitrobenzene, propylene carbonate, 1,2-dimethoxyethane, methylene chloride, tetrahydrothiophene-dioxide.
  • the cathode which constitutes the working electrode can be a carbon, graphite, platinum, nickel, gold, lead or mercury electrode.
  • the anode can be identical to the working electrode, but can also be made of any usual electrode material insofar as it is inert under the reaction conditions.
  • the electrochemical reduction according to the present invention can be carried out in the various usual cell types. Although one can operate in a cell with a single compartment, it is preferred to conduct the operation in a cell with two compartments to avoid free circulation between the cathode and the anode; the separator is generally made of an inert material, for example porcelain, sintered glass or ion exchange membrane.
  • the operation can be carried out according to a potentiostatic or intensiostatic control and is preferably carried out at the reduction potential of the compound of formula (I) under the operating conditions, this potential being able to be determined in a manner known per se by polarography or by cyclic voltammetry.
  • the range of temperatures at which the electrochemical reduction according to the invention can be carried out can vary within wide limits depending on the nature of the substrates and solvents used. In general, one operates at a temperature which can range from ⁇ 15 ° C to the boiling point of the aprotic solvent or even at a higher temperature by operating under pressure (from 0 to 50 bars). However, it is preferred to operate at a temperature between 0 and 80 ° C.
  • the molar ratio: electrophilic substrate / compound of formula (I) can vary between 1 and 20 and is advantageously between 3 and 10.
  • the reaction medium is preferably carried out when the reaction medium is saturated with the compound of formula (1), this saturation possibly being able to be maintained during operation by continuous or discontinuous addition of compound (1).
  • the product formed can be isolated by any conventional method, in particular by liquid-liquid extraction and / or by distillation, etc.
  • anode compartment of the cell 40 ml of a 0.1 mol / liter solution of LiCl0 4 in DMF are introduced as anolyte.
  • cathode compartment 550 ml of a solution containing 0.055 mole of LiCl0 4 and 0.55 mole of acetaldehyde in DMF are introduced as catholyte.
  • the reactor is closed, the stirring is started and brought to 3 ° C. by circulation of a water-glycol mixture (2/1 weight ratio) in the double jacket of the reactor, then the catholyte is saturated with bromo-trifluoromethane.
  • the electrolysis potential is - 2.00 volts / DHW.
  • the reaction solution is hydrolyzed in an acid medium (HCl, pH 1), neutralized with sodium hydroxide and added sodium chloride until saturation. Then extracted with ethyl ether and dried over sodium sulfate. After evaporation of the ether and distillation, the trifluoro-1,1,1 propanol-2 (PEb. 78 ° C.) is obtained, the structure of which has been identified by NMR and by mass spectrography coupled to gas chromatography.
  • the current yield that is to say the ratio: mass of product identified by analysis / theoretical mass, is 35%.
  • Carbon dioxide is used as the electrophilic substrate and operates under the following conditions:
  • reaction solution is then hydrolyzed in an acid medium, then subjected to distillation.
  • the water-trifluoroacetic acid azeotrope changes to 105.5 ° C at atmospheric pressure.
  • Example 1 The following table summarizes seven operations carried out by operating as in Example 1 with other solvents, other electrolytes and / or other substrates.
  • the abbreviation TBAB stands for tetrabutylammonium bromide.
  • the other operating conditions are the same as at example 1.
  • the products were all identified by NMR.

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  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
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  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)

Abstract

A process for the preparation of an organic trihalomethyl derivative comprising electrolytically reducing a compound of the formula: ClxF3-xC-Br in which x is equal to 0, 1 or 2, in a reaction medium also containing an electrophilic substrate which is void of electrochemical activity at the reduction potential of said compound, and a support electrolyte in an aprotic solvent for a time and at a temperature sufficient to form the desired organic trihalomethyl derivative.

Description

L'invention concerne un procédé de trifluoro (ou chlorodifluoro ou dichlorofluoro) méthylation de substrats électrophiles non électroactifs. En particulier, l'invention a pour objet la préparation de dérivés organiques trifluoro (ou chlorodifluoro ou dichlorofluoro) méthylés, utiles notamment comme intermédiaires de synthèse.The invention relates to a process for trifluoro (or chlorodifluoro or dichlorofluoro) methylation of non-electroactive electrophilic substrates. In particular, the invention relates to the preparation of methyl trifluoro (or chlorodifluoro or dichlorofluoro) methyl derivatives, useful in particular as synthesis intermediates.

On connaît déjà plusieurs procédés pour introduire un groupe trifluorométhyle, mais ces procédés font en général appel à des produits difficiles d'accès et/ou doivent être réalisés en présence de catalyseurs et/ou de réducteurs chimiques. Ainsi, par exemple, la réaction de trifluorométhylation peut être effectuée par voie radicalaire à partir de CF31 en initiant la réaction par élévation de la température ou par irradiation par les rayons U.V. (J. Chem. Soc. 1953, p, 1199 ; brevets US 3016406 et 3 016 407) ; cependant ; cette méthode n'a pas encore été industrialisée car l'accès à l'iodure de trifluorométhyle à partir du fluorure de trifluoroacétyle suivant le schéma :

Figure imgb0001
est difficile et onéreux.Several processes are already known for introducing a trifluoromethyl group, but these processes generally use products which are difficult to access and / or must be carried out in the presence of catalysts and / or chemical reducers. Thus, for example, the trifluoromethylation reaction can be carried out by radical route starting from CF 3 1 by initiating the reaction by raising the temperature or by irradiation with UV rays (J. Chem. Soc. 1953, p, 1199; U.S. Patents 3,016,406 and 3,016,407); however; this method has not yet been industrialized since access to trifluoromethyl iodide from trifluoroacetyl fluoride according to the scheme:
Figure imgb0001
 is difficult and expensive.

Ont également été proposés comme agents de trifluorométhylation des composés complexes tels que

Figure imgb0002
(UMEMOTO et al., Toyo Soda Kenkyu Hokoku 1983, 27(2), 69-73 et CA 100: 67911 z) ou CH3Si-ftl=N-CF3 (HARTKOPF et al., Angew. Chem. 1982, 94(6), 444 ou CA 97: 127170 p).Complex compounds such as trifluoromethylation agents have also been proposed.
Figure imgb0002
 (UMEMOTO et al., Toyo Soda Kenkyu Hokoku 1983, 27 (2), 69-73 and CA 100: 67911 z) or CH3Si-ftl = N-CF3 (HARTKOPF et al., Angew. Chem. 1982, 94 (6 ), 444 or CA 97: 127 170 p).

La trifluorométhylation d'oléfines a par ailleurs été effectuée par oxydation électrochimique de l'anion trifluoroacétate selon un mécanisme radicalaire, comme décrit par BROOKES et al. (J. Chem. Soc. Chem. Commun. 1974, 323) et RENAUD et al. (Can. J. Chem 53, 1975, 529).The olefin trifluoromethylation was moreover carried out by electrochemical oxidation of the trifluoroacetate anion according to a radical mechanism, as described by BROOKES et al. (J. Chem. Soc. Chem. Commun. 1974, 323) and RENAUD et al. (Can. J. Chem 53, 1975, 529).

La réaction de trifluorométhylation peut également être effectuée à partir de CF31 ou de CF3Br en présence de réducteurs et/ou d'activateurs. Ainsi, ISHIKAWA (Chemistry Letters 1984, 517-520) utilise des réducteurs à base de zinc et des catalyseurs à base de sels de nickel ou de palladium complexés avec des phosphines ; l'emploi de zinc, générateur d'effluents pollués, rend cette technique peu attractive industriellement.The trifluoromethylation reaction can also be carried out using CF 3 1 or CF 3 Br in the presence of reducing agents and / or activators. Thus, ISHIKAWA (Chemistry Letters 1984, 517-520) uses zinc-based reducers and catalysts based on nickel or palladium salts complexed with phosphines; the use of zinc, a generator of polluted effluents, makes this technique unattractive industrially.

Il a maintenant été trouvé que les composés de formule :

Figure imgb0003
dans laquelle x est égal à 0,1 ou 2, peuvent être réduits directement par voie électrochimique et qu'on obtient ainsi de façon simple (sans réducteur chimique comme le zinc) et à partir de composés facilement accessibles, une source commode d'anions ClxF3-xC⊖ conduisant à des réactions d'addition nucléo- phile en présence de substrats électrophiles non électroactifs.It has now been found that the compounds of formula:
Figure imgb0003
 in which x is equal to 0.1 or 2, can be reduced directly electrochemically and so that a convenient source of anions is obtained in a simple manner (without chemical reducing agent such as zinc) Cl x F 3 - x C⊖ leading to nucleophilic addition reactions in the presence of non-electroactive electrophilic substrates.

La présente invention a donc pour objet un procédé de préparation de dérivés organiques trifluoro (ou chlorodifluoro ou dichlorofluoro) méthylés, caractérisé en ce que l'on réduit par voie électrochimique un composé de formule (1) en présence d'un substrat électrophile non électroactif et d'un électrolyte support dans un solvant aprotique.The present invention therefore relates to a process for the preparation of trifluoro (or chlorodifluoro or dichlorofluoro) methylated organic derivatives, characterized in that a compound of formula (1) is reduced electrochemically in the presence of a non-electroactive electrophilic substrate and a support electrolyte in an aprotic solvent.

Par substrat électrophile non électroactif, on entend ici tout composé organique attracteur d'électrons qui dans les conditions opératoires présente un potentiel de réduction plus négatif que le potentiel auquel est effectuée l'opération. Comme exemples de tels substrats, on peut mentionner plus particulièrement le dioxyde de carbone, des aldéhydes tels que le formaldéhyde et l'acétaldéhyde, des cétones telles que l'acétone et la benzophénone, et des oléfines activées (c'est-à-dire comportant au moins un groupe électroattracteur) telles que l'alcool allylique et l'acrylate de méthyle.The expression “non-electroactive electrophilic substrate” is understood here to mean any organic electron-attracting compound which under operating conditions has a reduction potential more negative than the potential at which the operation is carried out. As examples of such substrates, mention may be made more particularly of carbon dioxide, aldehydes such as formaldehyde and acetaldehyde, ketones such as acetone and benzophenone, and activated olefins (i.e. comprising at least one electron-withdrawing group) such as allyl alcohol and methyl acrylate.

Pourvu qu'il ait un potentiel de réduction plus négatif que celui auquel est effectuée l'opération et qu'il soit suffisamment soluble dans le milieu, l'électrolyte support dont le rôle est d'assurer le passage du courant peut être choisi parmi tous les sels minéraux ou organiques connus à cet effet (cf. par exemple, Organic Electrochemistry par M. M. BAIZER, 1973, p. 227-230) et, plus spécialement, parmi les bromures, chlorures, perchlorates ou arylsulfonates de métaux alcalins (de préférence lithium) ou de tétraalkylam- monium (radicaux alkyle en C1 à C4). La quantité d'électrolyte support dans le solvant aprotique peut aller de 0,01 mole/litre jusqu'à la saturation ; de préférence, on utilise l'électrolyte support à une concentration de 0,1 à 1 mole par litre de solvant aprotique.Provided it has a more negative reduction potential than that at which the operation is carried out and that it is sufficiently soluble in the medium, the support electrolyte whose role is to ensure the passage of the current can be chosen from all the mineral or organic salts known for this purpose (cf. for example, Organic Electrochemistry by MM BAIZER , 1973, pp. 227-230) and, more particularly, among the bromides, chlorides, perchlorates or arylsulfonates of alkali metals (preferably lithium) or of tetraalkylammonium (C 1 to C 4 alkyl radicals). The amount of support electrolyte in the aprotic solvent can range from 0.01 mole / liter until saturation; preferably, the support electrolyte is used at a concentration of 0.1 to 1 mole per liter of aprotic solvent.

Conformément à la présente invention, la réaction peut être réalisée dans tout solvant aprotique ou mélange de tels solvants pourvu que sa limite cathodique soit inférieure au potentiel de réduction du composé (1). On préfère cependant le choisir parmi les amides comme le diméthylformamide (DMF), le diméthylacétamide (DMA), la N-méthylpyrrolidone (NMP) ou l'hexaméthylphosphorotriamide (HMPT), les sulfoxydes comme le diméthylsulfoxyde (DMSO), les nitriles comme l'acétonitrile (ACN) et les éthers comme le tétrahydrofuranne (THF). Comme autres exemples de solvants aprotiques, on peut citer la pyridine, le nitrométhane, le nitrobenzène, le carbonate de propylène, le diméthoxy-1,2 éthane, le chlorure de méthylène, le tétrahydrothiophène-dioxyde.According to the present invention, the reaction can be carried out in any aprotic solvent or mixture of such solvents provided that its cathode limit is less than the reduction potential of the compound (1). However, it is preferred to choose it from amides such as dimethylformamide (DMF), dimethylacetamide (DMA), N-methylpyrrolidone (NMP) or hexamethylphosphorotriamide (HMPT), sulfoxides such as dimethyl sulfoxide (DMSO), nitriles such as acetonitrile (ACN) and ethers such as tetrahydrofuran (THF). As other examples of aprotic solvents, mention may be made of pyridine, nitromethane, nitrobenzene, propylene carbonate, 1,2-dimethoxyethane, methylene chloride, tetrahydrothiophene-dioxide.

Dans le procédé selon l'invention, la cathode qui constitue l'électrode de travail peut être une électrode en carbone, graphite, platine, nickel, or, plomb ou mercure. L'anode peut être identique à l'électrode de travail, mais peut aussi être constituée de tout matériau usuel pour électrode dans la mesure où il est inerte dans les conditions réactionnelles.In the method according to the invention, the cathode which constitutes the working electrode can be a carbon, graphite, platinum, nickel, gold, lead or mercury electrode. The anode can be identical to the working electrode, but can also be made of any usual electrode material insofar as it is inert under the reaction conditions.

La réduction électrochimique selon la présente invention peut être effectuée dans les différents types de cellules habituels. Bien qu'on puisse opérer dans une cellule à un seul compartiment, on préfère conduire l'opération dans une cellule à deux compartiments pour éviter la libre circulation entre la cathode et l'anode ; le séparateur est en général réalisé en une matière inerte, par exemple en porcelaine, verre fritté ou membrane échangeuse d'ions.The electrochemical reduction according to the present invention can be carried out in the various usual cell types. Although one can operate in a cell with a single compartment, it is preferred to conduct the operation in a cell with two compartments to avoid free circulation between the cathode and the anode; the separator is generally made of an inert material, for example porcelain, sintered glass or ion exchange membrane.

L'opération peut être conduite selon un contrôle potentiostatique ou intensiostatique et est de préférence réalisée au potentiel de réduction du composé de formule (I) dans les conditions opératoires, ce potentiel pouvant être déterminé de façon connue en soi par polarographie ou par voltamétrie cyclique.The operation can be carried out according to a potentiostatic or intensiostatic control and is preferably carried out at the reduction potential of the compound of formula (I) under the operating conditions, this potential being able to be determined in a manner known per se by polarography or by cyclic voltammetry.

Le domaine de températures auxquelles peut être effectuée la réduction électrochimique selon l'invention peut varier dans de larges limites selon la nature des substrats et solvants mis en ceuvre. En général, on opère à une température pouvant aller de ―15°C jusqu'au point d'ébullition du solvant aprotique ou même à une température plus élevée en opérant sous pression (de 0 à 50 bars). Cependant, on préfère opérer à une température comprise entre 0 et 80 °C.The range of temperatures at which the electrochemical reduction according to the invention can be carried out can vary within wide limits depending on the nature of the substrates and solvents used. In general, one operates at a temperature which can range from ―15 ° C to the boiling point of the aprotic solvent or even at a higher temperature by operating under pressure (from 0 to 50 bars). However, it is preferred to operate at a temperature between 0 and 80 ° C.

Le rapport molaire : substrat électrophile/composé de formule (I) peut varier entre 1 et 20 et est avantageusement compris entre 3 et 10. On opère de préférence à saturation du milieu réactionnel en composé de formule (1), cette saturation pouvant éventuellement être maintenue en cours d'opération par addition continue ou discontinue de composé (1).The molar ratio: electrophilic substrate / compound of formula (I) can vary between 1 and 20 and is advantageously between 3 and 10. The reaction medium is preferably carried out when the reaction medium is saturated with the compound of formula (1), this saturation possibly being able to be maintained during operation by continuous or discontinuous addition of compound (1).

L'isolement du produit formé peut être réalisé par toute méthode conventionnelle, en particulier par extraction liquide-liquide et/ou par distillation, etc...The product formed can be isolated by any conventional method, in particular by liquid-liquid extraction and / or by distillation, etc.

Les exemples suivants qui illustrent l'invention sans la limiter, ont été réalisés en utilisant comme cellule d'électrolyse à compartiments séparés un réacteur en verre de 1 litre, muni d'un dispositif de reflux, d'un système d'agitation énergique, d'une double enveloppe et des tubulures. nécessaires à l'introduction des réactifs. Sauf indication contraire, on a travaillé avec une cathode en graphite (plaque rectangulaire de 30 cm2) et une anode en platine (disque de 10 cm2), en utilisant comme séparateur une membrane perfluorée NAFIONO commercialisée par la Société DU PONT DE NEMOURS et en contrôlant le potentiel d'électrolyse avec une électrode de référence au calomel saturé (ECS).The following examples which illustrate the invention without limiting it, were produced using as an electrolysis cell with separate compartments a 1 liter glass reactor, provided with a reflux device, with a vigorous stirring system, a double envelope and tubing. necessary for the introduction of the reagents. Unless otherwise indicated, we worked with a graphite cathode (30 cm 2 rectangular plate) and a platinum anode (10 cm 2 disc), using as a separator a NAFIONO perfluorinated membrane marketed by the company DU PONT DE NEMOURS and by checking the electrolysis potential with a saturated calomel reference electrode (DHW).

Exemple 1Example 1

Dans le compartiment anodique de la cellule, on introduit comme anolyte 40 ml d'une solution à 0,1 mole/litre de LiCI04 dans le DMF. D'autre part, dans le compartiment cathodique, on introduit comme catholyte 550 ml d'une solution contenant 0,055 mole de LiCl04 et 0,55 mole d'acétaldéhyde dans le DMF. On ferme le réacteur, met en route l'agitation et porte à 3°C par circulation d'un mélange eau-glycol (rapport pondéral 2/1) dans la double enveloppe du réacteur, puis on sature le catholyte en bromo- trifluorométhane.In the anode compartment of the cell, 40 ml of a 0.1 mol / liter solution of LiCl0 4 in DMF are introduced as anolyte. On the other hand, into the cathode compartment, 550 ml of a solution containing 0.055 mole of LiCl0 4 and 0.55 mole of acetaldehyde in DMF are introduced as catholyte. The reactor is closed, the stirring is started and brought to 3 ° C. by circulation of a water-glycol mixture (2/1 weight ratio) in the double jacket of the reactor, then the catholyte is saturated with bromo-trifluoromethane.

On met sous tension et maintient pendant 5 heures sous une densité de courant cathodique de 1 A/dm2, tout en introduisant 2,2 NI/h de CF3Br par barbotage dans le catholyte. Le potentiel d'électrolyse est de - 2,00 volts/ECS.It is powered up and maintained for 5 hours under a cathode current density of 1 A / dm 2 , while introducing 2.2 NI / h of CF 3 Br by bubbling into the catholyte. The electrolysis potential is - 2.00 volts / DHW.

L'électrolyse terminée, on hydrolyse la solution réactionnelle en milieu acide (HCI, pH 1), neutralise avec de l'hydroxyde de sodium et ajoute du chlorure de sodium jusqu'à saturation. On extrait ensuite à l'éther éthylique et sèche sur sulfate de sodium. Après évaporation de l'éther et distillation, on obtient le trifluoro-1,1,1 propanol-2 (PEb. 78 °C) dont la structure a été identifiée par RMN et par spectrographie de masse couplée à la chromatographie en phase gazeuse.Once the electrolysis is complete, the reaction solution is hydrolyzed in an acid medium (HCl, pH 1), neutralized with sodium hydroxide and added sodium chloride until saturation. Then extracted with ethyl ether and dried over sodium sulfate. After evaporation of the ether and distillation, the trifluoro-1,1,1 propanol-2 (PEb. 78 ° C.) is obtained, the structure of which has been identified by NMR and by mass spectrography coupled to gas chromatography.

Le rendement en courant, c'est-à-dire le rapport : masse de produit identifié par analyse/masse théorique, est de 35 %.The current yield, that is to say the ratio: mass of product identified by analysis / theoretical mass, is 35%.

Exemple 2Example 2

On utilise comme substrat électrophile le dioxyde de carbone et opère dans les conditions suivantes :

Figure imgb0004
Carbon dioxide is used as the electrophilic substrate and operates under the following conditions:
Figure imgb0004

La solution réactionnelle est ensuite hydrolysée en milieu acide, puis soumise à distillation. L'azéotrope eau-acide trifluoroacétique passe à 105,5 °C à pression atmosphérique.The reaction solution is then hydrolyzed in an acid medium, then subjected to distillation. The water-trifluoroacetic acid azeotrope changes to 105.5 ° C at atmospheric pressure.

On obtient ainsi, avec un rendement en courant de 52 %, l'acide trifluoroacétique dont la structure a été identifiée par RMN du 19F.There is thus obtained, with a current yield of 52%, trifluoroacetic acid, the structure of which has been identified by 19 F NMR.

Exemples 3 à 9Examples 3 to 9

Le tableau suivant résume sept opérations réalisées en opérant comme à l'exemple 1 avec d'autres solvants, d'autres électrolytes et/ou d'autres substrats. L'abréviation TBAB désigne le bromure de tétrabutylammonium. A l'exception de la température indiquée dans la cinquième colonne du tableau et de l'exemple 3 pour lequel on a utilisé comme cathode une plaque rectangulaire de platine (30 cm2), les autres conditions opératoires sont les mêmes qu'à l'exemple 1. Les produits ont tous été identifiés par RMN.

Figure imgb0005
The following table summarizes seven operations carried out by operating as in Example 1 with other solvents, other electrolytes and / or other substrates. The abbreviation TBAB stands for tetrabutylammonium bromide. With the exception of the temperature indicated in the fifth column of the table and of Example 3 for which a rectangular plate of platinum (30 cm 2 ) was used as the cathode, the other operating conditions are the same as at example 1. The products were all identified by NMR.
Figure imgb0005

Claims (11)

1. Process for the preparation of organic trifluoro (or chlorodifluoro or dichlorofluoro) methyl derivatives, characterized in that a compound of formula :
Figure imgb0007
in which x is equal to 0, 1 or 2, is reduced electrochemically in the presence of an electrophilic substrate which is electrically unreactive at the reduction potential of the compound (I), and a support electrolyte in an aprotic solvent.
2. Process according to Claim 1, in which the compound of formula (I) is bromotrifluoromethane.
3. Process according to Claim 1 or 2, in which the electrically unreactive electrophilic substrate is carbon dioxide, an aldehyde, a ketone or an activated olefin.
4. Process according to one of Claims 1 to 3, in which the support electrolyte is a lithium or tetraalkylammonium salt.
5. Process according to one of Claims 1 to 4, in which the aprotic solvent is chosen from amides, sulphoxides, nitriles, ethers and mixtures thereof.
6. Process according to one of Claims 1 to 5, in which the cathode is made of carbon, graphite, platinum, nickel, gold, lead or mercury.
7. Process according to one of Claims 1 to 6, in which the cathode and the anode are separated by an ion exchange membrane, procelain or sintered glass.
8. Process according to one of Claims 1 to 7, in which the operation is carried out at a temperature of 0 to 80 °C.
9. Process according to one of Claims 1 to 8, in which the quantity of support electrolyte in the aprotic solvent ranges from 0.01 mole/litre up to saturation and is preferably between 0.1 and 1 mole/litre.
10. Process according to one of Claims 1 to 9, in which the molar ratio of electrophilic substrate to the compound of formula (I) is between 1 and 20, preferably between 3 and 10.
11. Process according to one of Claims 1 to 10, in which the reaction medium is saturated with the compound of formula (I).
EP86401046A 1985-05-21 1986-05-15 Electrochemical process for the preparation of organic trifluoro (or chlorodifluoro or dichlorofluoro) methylated derivatives Expired EP0203851B1 (en)

Priority Applications (1)

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AT86401046T ATE37048T1 (en) 1985-05-21 1986-05-15 ELECTROCHEMICAL PROCESS FOR THE PREPARATION OF ORGANIC TRIFLUORO (OR CHLORODIFLUOROOR DICHLOROFLUORO) METHYLATED COMPOUNDS.

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FR8507595A FR2582320B1 (en) 1985-05-21 1985-05-21 ELECTROCHEMICAL PROCESS FOR THE PREPARATION OF ORGANIC DERIVATIVES TRIFLUORO (OR CHLORODIFLUORO OR DICHLOROFLUORO) METHYLES
FR8507595 1985-05-21

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EP0203851B1 true EP0203851B1 (en) 1988-09-07

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FR2582320B1 (en) 1987-06-26
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JPS61291987A (en) 1986-12-22
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FR2582320A1 (en) 1986-11-28
DE3660684D1 (en) 1988-10-13
ES8703946A1 (en) 1987-03-01

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