EP1402087A2 - Method for electrolytic heterocoupling between an aryl(pseudo) halide and an ester containing an ethylenic unsaturation, use of cobalt in order to carry out said coupling and composition therefor - Google Patents

Abstract

The invention relates to a method for the electrochemical production of vinyl aryl derivatives. Said method is defined by the fact that it consists in subjecting a composition comprising cobalt salt, aromatic halide and vinyl ester to electrolysis on an inert cathode. The invention can be used for organic synthesis.

Description

 ELECTROLYTIC HETEROCOUPLING METHOD BETWEEN

AN ARYL HALIDE (PSEUDO) AND A CARRYING ESTER

OF AN ETHYLENIC UNSATURATION, USE OF COBALT

TO PERFORM SUCH COUPLING AND COMPOSITION FOR THIS

The present invention relates to a process for the synthesis of vinyl or allyl aryl compound from a heterogeneous coupling reaction by electrolytic route between aryl compounds and vinyl compounds or allyl compounds.

It relates more particularly to the use of cobalt salts, in particular cobaltous, as catalysts for the electrochemical coupling between an aryl derivative and a vinyl derivative.

The coupling between vinyl derivatives and aryl derivatives to give vinyl aryl derivatives is hardly described. The only document to mention this is the communication published in the Tetrahedron, volume 48, n ° 4, pages 719 to 726, where a reaction of this type is described in the presence of palladium II salts supported on a silylated montmorillonite. No mechanism is proposed, and the absence of elements described above does not allow even a balanced reaction equation to be proposed since all the reaction equations proposed, once they are completed, lead to aporias.

These reactions would however allow easy and particularly advantageous access to useful complex derivatives, in particular in pharmacy and agrochemical activities. This is why one of the aims of the present invention is to provide a coupling process between vinyl derivatives and aryl derivatives which does not require the use of expensive catalysts. Another object of the present invention is to provide a process of the above type which gives good yields. Another object of the present invention is to provide a process of the above type which is doubly ipso, the connection between the vinyl molecule and the aryl molecule being carried out at the place where the two leaving groups were located. Another object of the present invention is to provide a process which gives few parasitic reactions; in particular a reaction which gives little symmetrical coupling and which gives few reductions to lead to hydrogenated compounds in place of the leaving groups. The coupling between allylic derivatives and aryl derivatives to give allylic aryl derivatives, meanwhile, is almost not described.

These reactions would however allow easy and particularly advantageous access to useful complex derivatives, in particular in pharmacy and agrochemical activities. This is why another object of the present invention is to provide a coupling process between allylic derivatives and aryl derivatives which does not require the use of expensive catalysts. Another object of the present invention is to provide a process of the above type which gives good yields. Another object of the present invention is to provide a process of the preceding type which is doubly ipso (here, the ablative from the Latin "ipse" is used to indicate that the functionalization is carried out on the same carbon as that which carried the leaving group ), the link between the molecule carrying the unsaturation, in particular allylic, even homoallylic, and the aryl molecule being produced at the place where the two leaving groups were located.

Another object of the present invention is to provide a process which gives few parasitic reactions; in particular a reaction which gives little symmetrical coupling and which gives little reduction to lead to hydrogenated compounds in place of the leaving groups. These aims, and others which will appear subsequently, are achieved by means of an electrolytic heterocoupling process between an aryl (pseudo) halide and a carrier of ethylenic unsaturation and of a leaving group, advantageously an ester, or even an ether, in particular of allyl and of vinyl, which consists in subjecting the two substrates to cathodic reduction in the presence of cobalt cobaltous.

Although the form of cobalt in the vicinity of the cathode has not been completely clarified, it has been possible to show that the presence of cobalt coordinating agents appears to be important and makes it possible to modify very significantly returns. It could be that this presence could have a role on the possible coordination between ethylenic unsaturation and cobalt.

Recalling that an ester is defined as the product of condensation between a carrier of a hydroxyl function and a Bronstedt acid, that is to say a carrier of an acidic hydrogen, the unsaturation is advantageously close to the atom which was a carrier of acidic hydrogen, that is to say that said carrier atom is advantageously in vinyl, allylic, or even homoallylic position; preferably in vinyl or allylic position.

The reaction can be roughly written as follows:

Formulas in which L represent a divalent arm ensuring the link between the vinyl unsaturation and the rest of the acid (noted here Y) after having ignored the hydrogen. So when the ester is vinyl, L is a nothing, -L- then symbolizing the single bond linking Y and the vinyl unsaturation. When -L- represents something other than a single bond, advantageously L is an alkylene group; preferably ethylene or methylene, more preferably methylene. In the latter case, the ester is allylic.

Formulas in which Y corresponds to a leaving group, capable of existing in the form Y ^" , such as phenate, or even alcoholate but advantageously chosen from halogens and lato sensu carboxylates and pseudohalogens. It is desirable that it be such that the acid YH has a pKa (measured in water) at most equal to 9, advantageously to 7, preferably to 5. It is advantageously chosen from halogens and carboxylates lato sensu and (pseudo) halogens.

The case where Y is such that it forms an ether with the compounds carrying an ethylenic double bond is hardly to be considered except when the aryl-allyl coupling is aimed at.

The term “pseudohalogen” is intended to denote a group the departure of which leads to an oxygenated anion, the anionic charge being carried by the chalcogen atom and the acidity of which is at least equal to that of acetic acid, advantageously at the second acidity of sulfuric acid, and preferably that of trifluoroacetic acid. To be placed on the acidity scale, reference should be made to pKa for medium to high acidities from carboxylic acids to acetic acid and to be placed on the scale of Hammett constants from l trifluoroacetic acid.

By lato sensu carboxylate is meant any radical such that its anionic form contains the atomic sequence -CO-O ^" ; thus not only are the carboxylate functions linked to a carbon atom, but also carbamic acids and alkylcarbonates. 'We want to avoid any parasitic reaction, it is preferable to avoid that the substituents include reactive hydrogens such as hydrogens on the amides (which are therefore advantageously protected or peralkylated) or on an oxygen.

Formulas in which Ri, R ₂ and R _3j, different or not, are chosen from hydrogen, the functions which are more difficult to reduce than the function Y and from hydrocarbon radicals, in particular alkyls and aryls.

Thus, among the functions which are more difficult to reduce than Y, there may be mentioned, when y forms an ester, the ether functions, the carboxylic functions (linked or not to the rest of the molecule by carbon), the functions among which Y is chosen on the condition that these functions are less reducible than Y. The order of reducibility can be easily determined under the operating conditions by routine experiments. By way of indication only, it can be noted that as regards the halides, the higher the atomic number, the more the halide is reducible and, more generally (and coarser), the more the acid corresponding to the group. therefore the stronger, the more the corresponding vinyl ester is reducible (however, it should be noted that the anions can themselves be reduced and cause parasitic reactions).

Among the relatively reducible groups for which attention should be paid, mention may be made of perfluorinated groups; one of the solutions is to play on the current density.

The hydrocarbon radicals are preferably either of aromatic nature or of aliphatic nature, that is to say that the carbon ensuring the link with the rest of the molecule is sp ³ hybridization; these aliphatic radicals are in general of alkyls (alkyl is taken in its etymological sense of an alcohol from which the OH function has been removed), including aralkyls. It should be noted that the hydrocarbon radicals having a double bond conjugated with the double bond give only very poor results. To be effective, it is desirable that the cobalt be present at a minimum concentration of at least 10 ^"3 M.

To be economical, it is preferable that the cobalt is not too concentrated, so we prefer that the cobalt content is at most equal to 0.2 M.

The reaction medium advantageously comprises a solvent, this solvent must be sufficiently polar to dissolve the metals or more exactly the metal salts used, and it must be sufficiently lipophilic to dissolve, at least in part, the substrates whose aryl is to be formed vinyl.

It is preferable to use solvents which are sufficiently weak in acid, so that the reactions with hydrogen are as weak as possible. Thus, primary alcohols are too acidic.

More specifically, preference is given to so-called polar aprotic solvents such as, for example, alone or as a mixture:

• purely oxygenated solvents, in particular ethers, preferably polyethers such as dimethoxy-1, 2-ethane, or cyclic ethers such as THF or dioxane;

• amides or ureas (DMF, N-methylpyrrolidone-2, imidazolidone, tetramethylurea, dimethoxypropylene-urea, etc.);

• sulfones (for example sulfolane) or sulfoxides (such as DMSO);

• and, insofar as they are liquid under the operating conditions, nitrogen derivatives, nitrogen heterocycles, in particular pyridine and compounds with a nitrile function (for those which are preferred, see below);

• and, insofar as they are liquid under the operating conditions, complexing agents (crown ether, HMPT, tris- (dioxa-3,6-heptyl) amine (TDA-1) which improve the smooth running of the reaction by increasing the conductivity, increasing the reactivity of the anion, preventing metal deposition at the cathode. Without this explanation being limiting, it would seem that these advantageous phenomena are correlated with the ability to complex metal cations or in a mixture.

As indicated above, the solvents used can themselves play the role of complexing agents or coordinating agents. They can in particular, and this is advantageous, present one or more of the coordination functions mentioned above.

The solvent can be a mixture of an apolar solvent and a polar solvent as defined above by the donor index. To facilitate the separation of the products from the reaction media, it is preferable that said solvent has a boiling point which is substantially different from the compound to be synthesized and from the starting compound.

To facilitate the reaction and improve the conductivity of the medium, saline electrolytes are sometimes used, sometimes called bottom salts, possibly modified by the presence of complexing agents. These electrolytes are chosen so as not to disturb the reactions at the anode and at the cathode. The latter is advantageously inert.

According to one of the most economical implementations of the present invention, it is possible to use, as the bottom salt, in the case where a soluble anode is used, a salt whose cations correspond to the metals of the anode. Among the soluble anodes, mention may be made of anodes containing iron and / or cobalt, and in particular anodes made of cobalt alloy, of cobalt itself, or of ferro-cobalt.

The electrolyte can be chosen so as to have as cations metals with strong transporting power such as divalent, advantageously trivalent, of the aluminum type, and this provided that this does not disturb the basic reaction.

Among the metals used in the base salts, it is desirable to use those which exhibit, in addition to degree 0, only one stable degree of oxidation.

The electrolyte can be chosen so that these cations are directly soluble in the reaction medium. Thus, in particular when the medium is not very polar, rather than making the metal cations soluble by means of adjuvants, it may be advantageous to use stable "oniums" in the field of electrical inactivity. By "onium" means positively charged organic compounds whose name assigned to them by the nomenclature has an affix, generally suffix, "onium" (such as sulfonium [trisubstituted sulfur], phosphonium [tetrasubstituted phosphorus], ammonium [tetrasubstituted nitrogen] ). The most used are tetraaicoyiammoniums, the alkyl groups taken in their etymological sense generally have from 1 to 12 carbon atoms, preferably from 1 to 4 carbon atoms. Phase transfer agents can also be used.

The anions can be usual anions for the indifferent electrolytes, but it is preferable that they are chosen from those released by the reaction, essentially halides, or for example by complex anions of type BF ₄ -, PF ₆ -, CI0 ₄ - Among the preferred anions, mention may be made of those derived from fluorinated acids or their imides (TFSI, triflate, etc.). As an indication, it should be noted that DMF, used with tetrafluoroborate tetrabutylammonium as a background salt at a concentration of 0.01 M, has given good results.

Said electrolysis can be carried out at numerous temperatures, but it is preferable to conduct this electrolysis at a temperature at most equal to 100 ° and at most equal to the boiling point of the solvent. An interval giving good results is the interval between 0 and 50 ° C; it is a closed interval, that is to say comprising the limits.

Pressure is of little importance on electrolysis, unless one of the reactants or the solvent has particularly low boiling points.

However, for practical reasons, it is preferable to place yourself at atmospheric pressure in the place where you are.

In the case mentioned above where one of the constituents of the reaction medium is particularly volatile and where it is desired to maintain this constituent in the reaction medium, it is then possible to increase the pressure; this pressure is generally then an autogenous pressure resulting from the reaction in a closed enclosure.

The aryl substrates (Ar-X) capable of being coupled with the compounds carrying ethylenic unsaturation according to the present invention represent a wide range of compounds. Halides are generally halides corresponding to relatively heavy halogens, that is to say halogens heavier than fluorine.

It can also be given as an indication that when the halogen is linked to an aromatic nucleus depleted in electrons, it is preferable to use bromines or chlorines as halogen, the chlorines being reserved for nuclei particularly depleted in electrons. The condition is almost always fulfilled by six-membered heterocycles; but in the case of homocyclic aryl hexacyclic substrates, to use a chloride, it is preferable that the sum of the Hammett constants σ _p of the substituents (without taking into account the leaving halide) is at least equal to 0.40, preferably to 0.50. On the other hand, nuclei that are particularly enriched in electrons can use iodine as the halide.

For more details on the Hammett constants, one can for example refer to the third edition of the manual written by professor Jerry March "Advanced organic chemistry" (pages 242 to 250) and edited by JohnWiley and sons.

Five-membered heterocycles, comprising a chalcogen as heteroatom (such as furan and thiophene), also give acceptable results. As mentioned above, the electron depletion of the nucleus may be due either to the presence of electron-withdrawing groups as substituents or, in the case of six-membered nuclei, to the replacement of a carbon by a heteroatom . In other words, the electron-depleted nucleus can be a six-membered heterocyclic nucleus, in particular heterocyclic nuclei having a nitrogen column atom and more particularly nitrogen.

Among the electron-withdrawing groups leading to good results, mention should be made of acyl groups, nitrile groups, sulfone groups, carboxylate groups, trifluoromethyl groups or more generally perfluoroalkyl groups and halogens of lower rank than the halide. , which will be replaced by the allylic radical. Among the donor groups, that is to say giving poor results with chlorine but good with bromine, mention may be made of alkyloxy groups, alkyl groups, amino and dialkoylamine groups.

The aromatic substrate derivative of the present process advantageously corresponds to the following formula: where:

- Z represents a trivalent link -CfR ^ ≈, an atom of column V, advantageously a nitrogen; - X represents the leaving halogen;

- A represents either a link chosen either from the ZH groups or from the chalcogens advantageously of a rank at least equal to that of sulfur, or from the divalent unsaturated groups with two links CR _g ≈CRg, N = CR ₂ CR ₂ = N. Insofar as they are carried by contiguous atoms, two of the radicals R, R _{1 (} R ₂ , R ₃ can be linked to form rings. Thus the aryls can be in particular of formula:

or :

- Zi is chosen from the same meanings as those given for Z;

- The radicals Ri, R ₂ , R ₃ are chosen from the substituents mentioned above and in particular: • the electron-withdrawing groups, in particular the acyl groups, the nitrile groups, the sulfone groups, the carboxylate groups, the trifluoromethyl groups, or more generally the perfluoroalkyl groups and the halogens of lower rank than the halide which will be transformed into coupling product; ^" The donor groups, in particular the aryloxyl, alkyloxyl groups, the hydrocarbyl groups such as aryl and alkyl (the latter word being taken in its etymological meaning), the amino groups, including the mono and disubstituted by alcoylamine hydrocarbon groups. It is desirable that the substrates have at most 50 carbon atoms, advantageously at most 30 carbon atoms, preferably at most 20 carbon atoms.

Among the particularly interesting substrates are the halides, preferably aryl chlorides, carrying in particular in the meta position, an aliphatic carbon (ie sp ³ ) carrying at least two fluorines. For example halides, preferably trifluoromethylaryl chlorides.

It is preferable that the cobalt is coordinated, however the optimal conditions of coordination are a little different for the vinyl esters on the one hand and for the other esters, in particular of allyl, on the other hand. The present description now focuses more specifically on the implementation in which the ester is vinyl; in this case, L is a nothingness and therefore -L- is a simple bond: the above equation then becomes:

R2 Ri R2 Ri

\ / \ __ /

Ar-X + / ^C = ^C _N + 2 e- - p— <+ Y + X

R3 Y R3 Ar Vinyl, seat of the reaction, gives only very poor results when it is conjugated with an ethylenic double bond to give a butadiene skeleton.

In general, the number of carbons in the vinyl derivative is less than fifty, advantageously thirty.

In fact, during studies which led to the present invention, it has been shown that in the presence of cobalt, the above coupling takes place with good yields.

Although the form of cobalt in the vicinity of the cathode has not been completely clarified, it has been possible to show that the presence of cobalt coordinating agents appears to be important and makes it possible to very significantly increase the yields. It could be that this presence could have a role on the possible coordination between ethylenic unsaturation and cobalt.

Although an effect can be demonstrated when using solvents with the property of coordinating cobalt, it is preferable to use specific coordinating agents.

Returning to the solvents or agents which make it possible to improve the yield significantly, it can be indicated that compounds with a high donor index can be used. More precisely, it may be indicated that it is preferable for the donor index D of these solvents, or of these solvating agents, to be greater than or equal to 10, preferably less than or equal to 30, advantageously between 20 and 30, the terminals being included. Said donor index corresponds to the ΔH (enthalpy variation) expressed in kilocalories of the association of said polar aprotic solvent or of said coordinator with antimony pentachloride.

This is described more precisely in Christian Reichardt's book: "Solvents and Solvent effects in organic chemistry" - VCH, page 19, 1988. On this page, we find the definition of the donor index expressed in Anglo-Saxon terms by "Donor number". The results are better if the atom coordinating the cobalt in said solvent or solvating agent is an atom from the column of nitrogen, and advantageously nitrogen itself. When a specific coordinating agent is used, which does not act as a solvent, mention may be made of the functions, or group, of pyridine, nitrile, phosphine, stibine and imine.

To be effective, it is desirable that the cobalt be present at a minimum concentration of at least 10 ^"3 M.

To be economical, it is preferable that the cobalt is not too concentrated, so we prefer that the cobalt content is at most equal to 0.2 M.

The reaction medium advantageously comprises a solvent, this solvent must be sufficiently polar to dissolve the metals, or more exactly the metal salts used, and it must be sufficiently lipophilic to dissolve, at least in part, the substrates for which it is desired to form the vinyl aryl.

It is preferable to use solvents which are sufficiently weak in acid, so that the reactions with hydrogen are as weak as possible. Thus, primary alcohols are too acidic. More specifically, preference is given to so-called polar aprotic solvents such as, for example, alone or as a mixture:

• purely oxygenated solvents, in particular ethers, preferably polyethers such as dimethoxy-1, 2-ethane or cyclic ethers such as THF or dioxane; • amides or ureas (DMF, N-methylpyrrolidone-2, imidazolidone, tetramethylurea, dimethoxypropylene-urea, etc.);

• sulfones (for example sulfolane) or sulfoxides (such as DMSO);

• and, insofar as they are liquid under the operating conditions, nitrogen derivatives, nitrogen heterocycles, in particular pyridine and compounds with a nitrile function (for those which are preferred, see below);

• and, insofar as they are liquid under the operating conditions, complexing agents (crown ether, HMPT, tris- (dioxa-3,6-heptyl) amine (TDA-1)) which improve the smooth running of the reaction by increasing the conductivity, increasing the reactivity of Panion, preventing metal deposition at the cathode.

Without this explanation being limiting, it would seem that these advantageous phenomena are correlated with the ability to complex metal cations or in a mixture. As indicated above, the solvents used can themselves play the role of complexing agents or coordinating agents. They can in particular, and this is advantageous, present one or more of the coordination functions mentioned above. The solvent can be a mixture of an apolar solvent and a polar solvent as defined above by the donor index.

When the solvent is not in itself a cobalt complexing agent strong enough to obtain optimal results, it is then desirable to use one of the cobalt-specific complexing agents, advantageously polydent, most often bidental. As functions playing the role of teeth, mention should be made of nitriles (preferably aromatic and / or bidentes) or else pyridines and derivatives of the pyridine nucleus, such as quinoline.

Thus, the bipyridyls being bidentes, also give very good results as coordinators distinct from the solvent. The preferred complexing agents are those which do not carry a charge, especially a negative charge, on the atom, or the atoms carrying the bond, coordinating the cobalt; it is also preferable that when said complexing agent carries a charge, the latter is located by the shortest route at least 4, and even advantageously at least 5 atoms, preferably 6, especially when said charge is negative. Thus cyanides are not desirable as complexing cobalt.

To obtain improved results and yields, it is preferable that the ratio (coordinator (s) / cobalt) between coordinator (s), expressed in moles for monodentates and in equivalent for polydents and cobalt ions (expressed in moles) , or at least equal to 0.5, advantageously to 1, preferably to 2, more preferably to 4.

To facilitate the separation of the products from the reaction media, it is preferable that said solvent has a boiling point which is substantially different from the compound to be synthesized and from the starting compound.

To facilitate the reaction and improve the conductivity of the medium, saline electrolytes, sometimes called background salts, are generally used, possibly modified by the presence of complexing agents. These electrolytes are chosen so as not to disturb the reactions at the anode and at the cathode. The latter is advantageously inert. According to one of the most economical implementations of the present invention, it is possible to use, as the bottom salt, in the case where a soluble anode is used, a salt whose cations correspond to the metals of the anode. Among the soluble anodes, mention may be made of anodes containing iron and / or cobalt, and in particular anodes made of cobalt alloy, of cobalt itself, or of ferro-cobalt.

The electrolyte can be chosen so as to have as cations metals with strong transporting power such as divalent, advantageously trivalent, of the aluminum type, and this provided that this does not disturb the basic reaction. Among the metals used in the base salts, it is desirable to use those which exhibit, in addition to degree 0, only one stable degree of oxidation.

The electrolyte can be chosen so that these cations are directly soluble in the reaction medium. Thus, in particular when the medium is not very polar, rather than making the metal cations soluble by means of adjuvants, it may be advantageous to use stable "oniums" in the field of electrical inactivity.

By "onium" means positively charged organic compounds whose name assigned to them by the nomenclature has an affix, generally suffix, "onium" (such as sulfonium [trisubstituted sulfur], phosphonium [tetrasubstituted phosphorus], ammonium [tetrasubstituted nitrogen] ). The most used are tetraaicoyiammoniums, the alkyl groups taken in their etymological sense generally have from 1 to 12 carbon atoms, preferably from 1 to 4 carbon atoms. Phase transfer agents can also be used. The anions can be usual anions for the indifferent electrolytes, but it is preferable that they are chosen from those released by the reaction, essentially halides, or for example by complex anions of type BF ₄ -, PF ₆ -, CI0 ₄ -. Among the preferred anions, mention may be made of those derived from fluorinated acids or their imides (TFSI, triflate, etc.). As an indication, it should be noted that DMF, used with tetrafluoroborate -tetrabutylammonium at the background salt of 0.01 M, has given good results. Said electrolysis can be carried out at numerous temperatures, but it is preferable to conduct this electrolysis at a temperature at most equal to 100 ° and at most equal to the boiling point of the solvent.

An interval giving good results is the interval between 0 and 50 ° C; it is a closed interval, that is to say comprising the limits.

Pressure is of little importance on electrolysis, unless one of the reactants or the solvent has particularly low boiling points.

However, for practical reasons, it is preferable to place yourself at atmospheric pressure in the place where you are. In the case mentioned above where one of the constituents of the reaction medium is particularly volatile and where it is desired to maintain this constituent in the reaction medium, it is then possible to increase the pressure; this pressure is generally then an autogenous pressure resulting from the reaction in a closed enclosure. Advantageously, the vinyl ester has the following formula (II):

R2 R1

\ / P = C (Formula II)

R3 Y

Another object of the present invention is to provide a medium which can be used for carrying out electrolysis and which leads to heterocouplings. This object was achieved by means of a composition, comprising at least: • a cobalt salt,

• a conductive solvent, or made conductive, and

• a cobalt coordinator,

• a vinyl ester

The solvent and the cobalt coordinating agent can constitute a single entity, and even a single compound when the solvent is a single compound.

The cobalt content is advantageously between and 2.10 ^"3 and 10 ^{" 1} M, preferably between 5.10 ^"3 and 5.10 ^{" 2} M (closed interval, that is to say including the limits). When using soluble cobalt anodes, the upper limit values may be exceeded. Said composition further comprises an aryl halide, the preferred chemical characteristics of which will be detailed later. This aryl halide is advantageously present at a concentration of 0.1 to 1 M. It is desirable that the molar ratio (dissolved species) of cobalt to vinyl ester ranges from 10 ^"2 to 1/2, preferably 0.05 at 0.2 (closed interval, that is to say including the limits). The important limit values are the minimum values. If using a cobalt soluble anode, these values can be exceeded. It is also advised that the molar ratio (of course species) of vinyl ester on aryl halide is at least equal to 1, and advantageously to 1.5, preferably to 2, and is at most equal to 5, advantageously to 4, preferably to 3. Thus, it is customary, so that this ratio goes from 1 to 5 (closed interval, that is to say including the limits). Those skilled in the art will optimize this parameter, in particular as a function of the nature of Y and the aromatic with which we want to condense the vinyl.

According to an advantageous implementation of the invention, the intensity and the surface of the reactive electrode, more precisely of the electrode where the reaction takes place, are chosen, so that the current density / is between 5 and 5.10 ² A / m ² , preferably between 20 and 200 A / m ² (closed interval, that is to say including the terminals).

By routine tests, a person skilled in the art can determine the reduction potential of cobalt in the reaction medium and that of aryl halide. This determination made, it will preferably be placed between the reduction potential of cobalt and that of aryl halide.

The aryl substrates capable of being coupled with the vinyls according to the present invention represent a wide range of compounds. The halides are generally halides corresponding to relatively heavy halogens, that is to say to halogens heavier than fluorine; these substrates are denoted by formula (I):

Ar— X (Formula I)

It can also be given as an indication that when the halogen is linked to an aromatic nucleus depleted in electrons, it is preferable to use as halogen from bromine or chlorine, chlorine being reserved for nuclei particularly depleted in electrons. The condition is almost always fulfilled by six-membered heterocycles; but in the case of homocyclic aryl hexacyclic substrates, to use a chloride, it is preferable that the sum of the Hammett constants σ _p of the substituents (without taking into account the leaving halide) is at least equal to 0.40, preferably to 0.50. On the other hand, nuclei that are particularly enriched in electrons can use iodine as the halide.

For more details on the Hammett constants, one can for example refer to the 3 ^rd edition of the manual written by Professor Jerry March

"Advanced organic chemistry" (pages 242 to 250) and edited by John Wiley & sons.

Five-membered heterocycles, comprising a chalcogen as heteroatom (such as furan and thiophene), also give acceptable results. As mentioned above, the electron depletion of the nucleus may be due either to the presence of electron-withdrawing groups as substituents or, in the case of six-membered nuclei, to the replacement of a carbon by a heteroatom . In other words, the electron-depleted nucleus can be a six-membered heterocyclic nucleus, in particular heterocyclic nuclei having a nitrogen column atom and more particularly nitrogen.

Among the electron-withdrawing groups leading to good results, mention should be made of acyl groups, nitrile groups, sulfone groups, carboxylate groups, trifluoromethyl groups, or more generally perfluoroalkyl groups and halogens of lower rank than halide, which will be replaced by the vinyl radical.

Among the donor groups, that is to say giving poor results with chlorine but good with bromine, mention may be made of alkyloxy groups, alkyl groups, amino and dialkylamine groups. The aromatic substrate derivative of the present process advantageously corresponds to the following formula:

or :

- Z represents a trivalent link -C (Rι) =, an atom from column V, advantageously nitrogen;

- X represents the leaving halogen;

- A represents either a link chosen either from the ZH groups or from the chalcogens advantageously of a rank at least equal to that of sulfur, or from the divalent unsaturated groups with two links CR ₂ = CR ₃ , N = CR ₂ CR ₂ = N.

Insofar as they are carried by contiguous atoms, two of the radicals R, R. ,, R ₂ , R ₃ can be linked to form rings.

Thus the aryl compounds can be chosen in particular from those of the following formulas:

(formula A)

(formula B)

(PC formula)

or :

- Zi is chosen from the same meanings as those given for Z;

the radicals Ri, R ₂ , R ₃ are chosen from the substituents mentioned above and in particular: • electron-withdrawing groups, in particular acyl groups, nitrile groups, sulfone groups, carboxylate groups, trifluoromethyl groups, or more generally perfluoroalkyl groups and halogens of lower rank than the halide which will be transformed into a product of coupling;

• the donor groups, in particular the aryloxyl, alkyloxyl groups, the hydrocarbyl groups such as aryl and alkyl (the latter word being taken in its etymological meaning), the amino groups, including the mono and disubstituted by alcoylamine hydrocarbon groups.

It is desirable that the substrates have at most 50 carbon atoms, advantageously at most 30 carbon atoms, preferably at most 20 carbon atoms.

Among the particularly interesting substrates are the halides, preferably aryl chlorides, carrying in particular in the meta position, an aliphatic carbon (ie sp ³ ) carrying at least two fluorides, for example halides, preferably trifluoromethylaryl chlorides .

One of the advantages of the present invention is that it requires only complexing agents, or coordinators, which are easy to access, such as nitriles (preferably aromatic or bidental) or else pyridines and derivatives of the pyridine nucleus, such as quinoline. Furthermore, the bipyridyls being bidentes, also give good results as a separate coordinator of the solvent.

The present description now deals with the implementation of the electrolytic heterocoupling between an aryl (pseudo) halide and an allyl ester, or even an ether, which consists in subjecting the two substrates to cathodic reduction in the presence of cobalt. cobaltous.

The reaction can be roughly written as follows:

Formulas in which:

- Y corresponds to a leaving group capable of existing in the Y ^" form, such as phenate, or even alcoholate, but advantageously chosen from halogens and lato sensu carboxylates and pseudohalogens.

- Ra and Rb, which may be identical or different, are chosen from hydrocarbyles (that is to say the groups whose open bond is carried by a carbon and which comprises both hydrogen and oxygen) and hydrogens. It is desirable to avoid steric hindrance problems that at least one, preferably two, of the Ra and Rb is hydrogen. The term pseudohalogen is intended to denote a group the departure of which leads to an oxygenated anion, the anionic charge being carried by the chalcogen atom and the acidity of which is most often at least equal to that of acetic acid, advantageously at the second acidity of sulfuric acid and preferably that of trifluoroacetic acid. To be placed on the acidity scale, reference should be made to pKa for medium to high acidities from carboxylic acids to trifluoroacetic acid and to be placed on the scale of Hammett constants from l trifluoroacetic acid. By lato sensu carboxylate is meant any radical such that its anionic form contains the atomic sequence -CO-O ^" ; thus, not only are the carboxylate functions linked to a carbon atom, but also carbamic acids and alkylcarbonates. one wishes to avoid any parasitic reaction, it is preferable to avoid that the substituents comprise reactive hydrogens such as hydrogens on the amides (which are therefore advantageously protected or peralkylated) or on an oxygen.

- Ri, R ₂ and R ₃ , different or not, are chosen from hydrogen, the functions which are more difficult to reduce than the function Y and from the hydrocarbon radicals, sometimes designated in the present application by the term

"Hydrocarbyls" in particular alkyls and aryls; alkyls being taken in its etymological sense from an alcdol from which the OH function has been removed, and of course comprises the aralkyls Thus, among the functions which are more difficult to reduce than Y, there may be mentioned the ether and carboxylic functions, the functions from which Y is chosen provided that these functions are less reducible than Y. The order of reducibility can be easily determined under the operating conditions by routine experiments. As an indication, it can be indicated that with regard to halides, the higher the atomic number, the more the halide is reducible and more generally (and coarser), the more the acid corresponding to the group. leaving is strong, more the corresponding allyl ester is reducible, (it is however necessary to pay attention to the fact that the anions can themselves be reduced and to cause parasitic reactions).

Among the relatively reducible groups for which attention should be paid, mention may be made of perfluorinated groups; one of the solutions is to play on the current density. The hydrocarbon radicals are preferably either of aromatic nature or of aliphatic nature, that is to say that the carbon ensuring the link with the rest of the molecule is sp ³ hybridization; these aliphatic radicals are generally alkyls (alkyl is taken in its etymological sense from an alcohol from which the OH function has been removed), including aralkyls. It should be noted that the hydrocarbon radicals having a double bond conjugated with the allyl seat of the reaction give only very poor results.

In general, the number of carbons of the allylic derivative is less than fifty, advantageously thirty.

In fact, during studies which led to the present invention, it has been shown that in the presence of cobalt, the above coupling takes place with good yields.

The reaction is indeed an ipso reaction (here, the ablative from the Latin "ipse" is used to indicate that the functionalization is done on the same carbon as that which carried the halide or pseudohalide leaving), but in certain cases, of course when the allyl group is not palindromic, small amounts of product corresponding to SN'2 have been observed.

Although the form of cobalt in the vicinity of the cathode has not been fully elucidated, it has been shown that the presence of coordinating agents cobalt was found to be important and made it possible, when they were not very complexing, to significantly increase the yields. On the other hand, strong coordinators and especially strong bidentes are likely to reduce the yield. By strong bidentate is meant bidentes, one of whose teeth is at least as complexing with respect to cobalt as pyridine. Pyridine itself when not engaged in bidentate gives excellent results. When we refer to the concept of bidentity, of course, we mean that the geometry of the molecule allows the two teeth to cooperate and therefore to form a cycle at most, advantageously less than 7 centers with the cobalt.

Although an effect can be demonstrated when using solvents with the property of coordinating cobalt, it is sometimes preferable to use specific coordinating agents.

Returning to the solvents or agents which make it possible to improve the yield significantly, it can be indicated that compounds with a high donor index can be used. More precisely, it may be indicated that it is preferable for the donor index D of these solvents, or of these solvating agents, to be greater than or equal to 10, preferably less than or equal to 30, advantageously between 20 and 30, the terminals being included. Said donor index corresponds to the ΔH (enthalpy variation) expressed in kilocalories of the association of said polar aprotic solvent or of said coordinator with antimony pentachloride.

This is described more precisely in Christian Reichardt's book: "Solvents and Solvent effects in organic chemistry" - VCH, page 19, 1988. On this page, we find the definition of the donor index expressed in Anglo-Saxon terms by "Donor number".

The results are better if the atom coordinating the cobalt in said solvent or solvating agent is an atom from the column of nitrogen, and advantageously nitrogen itself. When a specific coordinating agent is used, which does not act as a solvent, mention may be made of the functions, or group, of pyridine, nitrile, phosphine, stibine and imine. To be effective, it is desirable that the cobalt be present at a minimum concentration of at least 10 ⁻³ M. Except in the case of strong bidentes, it is preferable that the ratio between the coordinators and the cobalt expressed in moles

(coordinator (s) / Co) is at least equal to 1, advantageously 2, preferably 5.

To be economical, it is preferable that the cobalt is not too concentrated, so we prefer that the cobalt content is at most equal to 0.2 M.

The reaction medium advantageously comprises a solvent, this solvent must be sufficiently polar to dissolve the metals or more exactly the metal salts used, and it must be sufficiently lipophilic to dissolve, at least in part, the substrates whose aryl is to be formed allyl.

It is preferable to use solvents which are sufficiently weak in acid, so that the reactions with hydrogen are as weak as possible. Thus, primary alcohols are too acidic. More specifically, preference is given to so-called polar aprotic solvents such as, for example, alone or as a mixture:

• purely oxygenated solvents, in particular ethers, preferably polyethers such as dimethoxy-1, 2-ethane or cyclic ethers such as THF or dioxane; • amides or ureas (DMF, N-methylpyrrolidone-2, imidazolidone, tetramethylurea, dimethoxypropylene-urea, etc.);

• sulfones (for example sulfolane) or sulfoxides (such as DMSO);

^• and, insofar as they are liquid under the operating conditions, nitrogen derivatives, nitrogen heterocycles, in particular pyridine and compounds with a nitrile function (for those which are preferred, see below);

^• and, insofar as they are liquid under the operating conditions, complexing agents (crown ether, HMPT), which improve the smooth running of the reaction by increasing the conductivity, increasing the reactivity of the anion, preventing metal deposition at the cathode. Without this explanation being limiting, it would seem that these advantageous phenomena are correlated with the ability to complex metal cations or in a mixture. As indicated above, the solvents used can themselves play the role of complexing agents or coordinating agents. In particular, they may present one or more of the coordination functions mentioned above. The solvent can be a mixture of an apolar solvent and a polar solvent as defined above by the donor index.

When the solvent is not in itself a cobalt complexing agent strong enough to obtain optimal results, it is then desirable to use one of the specific cobalt complexing agents, advantageously non-polydent, and even non-bidental, especially when the one of the teeth is a pyridine function. As functions playing the role of teeth, mention should be made of nitriles (preferably aromatic and / or bidentes) or else pyridines and derivatives of the pyridine nucleus, such as quinoline. Alone, dinitriles give very good results. Thus bipyridyls, being bidentes, give poor results as complexing agents distinct from the solvent. It is preferable for the complexing agents of bidentate cobalt comprising at least a pyridine tooth to be in an amount less than that of cobalt (expressed in moles per liter).

More precisely, according to the present invention, when vinyl compounds are not treated, it is preferable that the complexing agents of pyridine nature expressed in equivalent of pyridine or strong function are less than twice the amount expressed in mole of cobalt salts , preferably less than once.

It is also desirable that the same rules apply to strong complexing agents of cobalt, such as amines and possibly bidentate phosphines.

The preferred complexing agents are those which do not carry a charge, especially a negative charge, on the atom, or on the atoms carrying the bond coordinating cobalt; it is also preferable that when said complexing agent carries a charge, the latter is located by the shortest route at least 4, and even advantageously at least 5 atoms, preferably 6, especially when said charge is negative. Thus cyanides are not desirable as complexing agents for cobalt. To facilitate the separation of the products from the reaction media, it is preferable for said solvent to have a boiling point which is substantially different from the compound to be synthesized and from the starting compound.

To facilitate the reaction and improve the conductivity of the medium, saline electrolytes are sometimes used, sometimes called bottom salts, possibly modified by the presence of complexing agents. These electrolytes are chosen so as not to disturb the reactions at the anode and at the cathode. The latter is advantageously inert.

According to one of the most economical implementations of the present invention, it is possible to use, as the bottom salt, in the case where a soluble anode is used, a salt whose cations correspond to the metals of the anode. Among the soluble anodes, mention may be made of anodes containing iron and / or cobalt, and in particular anodes made of cobalt alloy, of cobalt itself, or of ferro-cobalt. The electrolyte can be chosen so as to have as cations metals with strong transporting power such as divalent, advantageously trivalent, of the aluminum type, and this provided that this does not disturb the basic reaction.

Among the metals used in the base salts, it is desirable to use those which exhibit, in addition to degree 0, only one stable degree of oxidation. The electrolyte can be chosen so that these cations are directly soluble in the reaction medium. Thus, in particular when the medium is not very polar, rather than making the metal cations soluble by means of adjuvants, it may be advantageous to use stable "oniums" in the field of electrical inactivity. By "onium" means positively charged organic compounds whose name assigned to them by the nomenclature has an affix, generally suffix, "onium" (such as sulfonium [trisubstituted sulfur], phosphonium [tetrasubstituted phosphorus], ammonium [tetrasubstituted nitrogen] ). The most used are tetraaicoyiammoniums, the alkyl groups taken in their etymological sense generally have from 1 to 12 carbon atoms, preferably from 1 to 4 carbon atoms. Phase transfer agents can also be used. The anions can be usual anions for indifferent electrolytes, but it is preferable that they are chosen from those released by the reaction, essentially halides, or for example by complex anions of type BF ₄ -, PFβ-, CI0 ₄ -. Among the preferred anions, mention may be made of those derived from fluorinated acids or their imides (bis-trifluoromethylsulfonimide, triflate, etc.). As an indication, it should be pointed out that DMF, used with tetrabutylammonium tetrafluoroborate as a background salt at a concentration of 0.01 M, has given good results.

Said electrolysis can be carried out at numerous temperatures, but it is preferable to conduct this electrolysis at a temperature at most equal to 100 and at most equal to the boiling point of the solvent.

An interval giving good results is the interval between 0 and 50 ° C; it is a closed interval, that is to say comprising the limits.

Pressure is of little importance on electrolysis, unless one of the reactants or the solvent has particularly low boiling points. However, for practical reasons, it is preferable to place yourself at atmospheric pressure in the place where you are.

In the case mentioned above where one of the constituents of the reaction medium is particularly volatile and where it is desired to maintain this constituent in the reaction medium, it is then possible to increase the pressure; this pressure is generally then an autogenous pressure resulting from the reaction in a closed enclosure.

Another object of the present invention is to provide a medium which can be used for carrying out electrolysis and which leads to heterocouplings. This object was achieved by means of a composition, comprising at least:

• a cobalt salt,

• a conductive solvent, or made conductive, and

• a cobalt coordinator,

• an allyl or even homoallyl ester or ether; The solvent and the cobalt coordinating agent can constitute a single entity, and even a single compound when the solvent is a single compound. The cobalt content is advantageously between 2.10 ^"3 and 10 ^{" 1} M, preferably between 5.10 ^"3 and 5.10 ^{" 2} M (closed interval, that is to say including the limits). When using soluble cobalt anodes, the upper limit values may be exceeded. Said composition further comprises an aryl halide (Ar-X) whose preferred chemical characteristics will be detailed later. This aryl halide is advantageously present at a concentration of at least 0.01 M, preferably 0.1 to 1 M.

It is desirable that the ester or allyl ether is at least at a (dissolved) concentration of 0.01 M.

It is desirable that the molar ratio (dissolved species) of cobalt to allyl ester should be from 10 ^"2 to 1/2, preferably from 0.05 to 0.2 (closed interval, that is to say including the limits) The important limit values are the minimum values, when using a cobalt soluble anode these values may be exceeded.

It is also advised that the molar ratio (of course species) of ester, or ether, of allyl on aryl halide is at least equal to 1 and advantageously to 1.5, preferably to 2 and to be at most equal to 5, advantageously to 4, preferably to 3. Thus, it is customary, so that this ratio goes from 1 to 5 (closed interval, that is to say comprising the terminals). Those skilled in the art will optimize this parameter, in particular as a function of the nature of Y and of the aromatic with which it is desired to condense the allyl.

According to an advantageous implementation of the invention, the intensity and the surface of the reactive electrode, more precisely of the electrode where the reaction takes place, are chosen, so that the current density / is between 5 and

5.10 ² A / m ² , preferably between 20 and 200 A / m ² (closed interval, that is to say including the terminals).

By routine tests, a person skilled in the art can determine the reduction potential of cobalt in the reaction medium and that of aryl halide. This determination made, it will preferably be placed between the reduction potential of cobalt and that of aryl halide.

The aryl substrates (Ar-X) capable of being coupled with the allyls according to the present invention represent a wide range of compounds. The halides are generally halides corresponding to relatively heavy halogens, that is to say halogens heavier than fluorine.

It can also be given as an indication that when the halogen is linked to an aromatic nucleus depleted in electrons, it is preferable to use bromines or chlorines as halogen, the chlorines being reserved for nuclei particularly depleted in electrons. The condition is almost always fulfilled by six-membered heterocycles; but in the case of homocyclic aryl hexacyclic substrates, to use a chloride, it is preferable that the sum of the Hammett constants σ _p of the substituents (without taking into account the leaving halide) is at least equal to 0.40, preferably to 0.50. On the other hand, nuclei that are particularly enriched in electrons can use iodine as the halide.

For more details on the Hammett constants, one can for example refer to the 3 ^rd edition of the manual written by Professor Jerry March "Advanced organic chemistry" (pages 242 to 250) and edited by JohnWiley & sons.

Five-membered heterocycles, comprising a chalcogen as heteroatom (such as furan and thiophene), also give acceptable results.

As mentioned above, the electron depletion of the nucleus may be due either to the presence of electron-withdrawing groups as substituents or, in the case of six-membered nuclei, to the replacement of a carbon by a heteroatom . In other words, the electron-depleted nucleus can be a six-membered heterocyclic nucleus, in particular heterocyclic nuclei having a nitrogen column atom and more particularly nitrogen.

Among the electron-withdrawing groups leading to good results, mention should be made of acyl groups, nitrile groups, sulfone groups, carboxylate groups, trifluoromethyl groups or more generally perfluoroalkyl groups and halogens of lower rank than the halide. , which will be replaced by the allylic radical.

Among the donor groups, that is to say giving poor results with chlorine but good with bromine, mention may be made of groups alkyloxy, alkyl groups, amino groups and dialkoylamines.

The aromatic substrate derivative of the present process advantageously corresponds to the following formula:

or :

- Z represents a trivalent link -C (Rι) =, an atom from column V, advantageously nitrogen;

- X represents the leaving halogen;

- A represents either a link chosen either from the ZH groups or from the chalcogens advantageously of a rank at least equal to that of sulfur, or from the divalent unsaturated groups with two links CR ₂ = CR ₃ , N = CR ₂ CR ₂ = N.

Insofar as they are carried by contiguous atoms, two of the radicals R, RR ₂ , R ₃ can be linked to form rings. Thus the aryls can be in particular of formula:

where: - Zi is chosen from the same meanings as those given for Z - The radicals Ri, R ₂ , R ₃ are chosen from the substituents mentioned above and in particular:

• The electron-withdrawing groups, in particular the acyl groups, the nitrile groups, the sulfone groups, the carboxylate groups, the trifluoromethyl groups, or more generally the perfluoroalkyl groups and the halogens of lower rank than the halide which will be transformed into a product of coupling.

• Donor groups, in particular aryloxy, alkyloxy groups, hydrocarbyl groups such as aryl and alkyl (the latter word being taken in its etymological meaning), amino groups, including mono and disubstituted by alkylamino hydrocarbon groups.

It is desirable that the substrates have at most 50 carbon atoms, advantageously at most 30 carbon atoms, preferably at most 20 carbon atoms.

Among the particularly interesting substrates are the halides, preferably aryl chlorides, carrying in particular in the meta position, an aliphatic carbon (ie sp ³ ) carrying at least two fluorines. For example halides, preferably trifluoromethylaryl chlorides. One of the advantages of the present invention is that it requires only complexing agents, or coordinators, which are easy to access, such as nitriles (preferably aromatic or bidental) or else pyridines and derivatives of the pyridine nucleus, such as quinoline. Furthermore, the bipyridyls being bidentes, also give good results as a separate coordinator from the solvent.

The following nonlimiting examples illustrate the invention. ARYLE-ALLYLE COUPLING EXAMPLES

General procedure in the case of aromatic bromides

GF represents a functional group corresponding to R in the general formula and Y is here a carboxylate of formula Y-COO-

Apparatus

Single compartment electrolysis cell with an iron anode and a cathode made up of a stainless steel grid (cathodes made of nickel foam or a gold grid can also be used). Solvent: acetonitrile- pyridine (45 ml-5 ml)

Temperature: 50 ° C

Aryl bromide: 7.5 millimoles

Cobalt bromide: 1 millimole

Allylic acetate: 20 millimoles Constant intensity: 0.2A

Electrolyte indifferent: tetrabutyl ammonium tetrafluoroborate (10 ^"2 M)

Electrode surface: 20 cm ²

Duration of electrolysis: 4 hours

The conditions deviating from the general procedure are specified in the tables below, which give a sample of the results obtained (Table 1). Table 1

a: the ec ro yse time is 8 hours

General procedure in the case of aromatic chlorides

Apparatus

Single compartment electrolysis cell with an iron anode and a cathode made up of a stainless steel grid (cathodes made of nickel foam or a gold grid can also be used). Solvent: acetonitrile- pyridine (45 ml-5 ml)

Temperature: 50 ° C

Aryl bromide: 5 millimoles

Cobalt bromide: 2 millimoles Allyl acetate: 10 millimoles

Constant intensity: 0.2A

Electrolyte indifferent: tetrabutyl ammonium tetrafluoroborate (10 v ^" 2 * M")

Electrode surface: 20 cm ²

Duration of the electrolysis: 7 hours The conditions deviating from the general operating mode are specified in the tables below, which give a sample of the results obtained (Table 2).

Table 2

General procedure in the case of heteroaromatic halides

HetAr-X R2

Y is here a carboxylate of formula Y'-COO-

Apparatus

Single compartment electrolysis cell with an iron anode and a cathode made up of a stainless steel grid (cathodes made of nickel foam or a gold grid can also be used). Solvent: acetonitrile-pyridine (45 ml-5 ml) Temperature: 50 ° C

Heroaryl halide: 5 millimoles

Cobalt bromide: 2 millimoles Allyl acetate: 10 millimoles

Constant intensity: 0.2A

Electrolyte indifferent: tetrabutyl ammonium tetrafluoroborate (10 ^"2 M)

Electrode surface: 20 cm ²

Duration of electrolysis: 4 hours The conditions deviating from the general operating mode are specified in the tables below, which give a sample of the results obtained (Table 3).

Table 3

General procedure in the case of other allylic derivatives

Y is here a carboxylate of formula Y'-COO-

Apparatus

Single compartment electrolysis cell with an iron anode and a cathode made up of a stainless steel grid (cathodes made of nickel foam or a gold grid can also be used). Solvent: acetonitrile- pyridine (45 ml-5 ml)

Temperature: 50 ° C

Aromatic bromide: 7.5 millimoles (aromatic chloride: 5 millimoles)

Cobalt bromide: 1 millimole (2 millimoles for aromatic chloride) allyl derivative: 20 millimoles (10 millimoles for aromatic chloride) Constant intensity: 0.2A

Electrolyte indifferent: tetrabutyl ammonium tetrafluoroborate (10 ^"2 M)

Electrode surface: 20 cm ²

Duration of electrolysis: 4 hours

The conditions deviating from the general procedure are specified in the tables below, which give a sample of the results obtained (Table 4).

Table 4

EXAMPLES OF AROMATIC VINYLATION

Procedure for the examples of vinylation of aromatic bromides

Apparatus

Single compartment electrolysis cell with an iron anode and a cathode made up of a stainless steel grid (cathodes made of nickel foam or a gold grid can also be used).

Solvent Operating Conditions: acetonitrile- pyridine (45ml-5ml)

Ambient temperature (20 to 25 ° C)

Constant intensity: 0.2A

Electrolyte indifferent: tetrabutylammonium tetrafluoroborate (10 ^"2 M)

Electrode surface: 20 cm ² Duration of electrolysis: 4 hours

Reagents

Aryl bromide: 10 millimoles Cobalt bromide: 1 millimole 2,2'-bipyridine: 10 millimoles Vinyl acetate: 25 millimoles

The conditions deviating from the general procedure are specified in the tables below, which give a sample of the results obtained (Table 1).

Table 5

General procedure in the case of aromatic chlorides

Apparatus

Single compartment electrolysis cell, provided with an iron anode and a cathode constituted by a stainless steel grid (cathodes constituted by nickel foam or a gold grid can also be used).

Solvent: acetonitrile- pyridine (45 ml-5 ml)

Ambient temperature (20 to 25 ° C) Aryl bromide: 10 millimoles

Cobalt bromide: 2 millimoles

2,2'Bipyridine: 10 millimoles

Vinyl acetate: 25 millimoles Constant intensity: 0.2A

Electrolyte indifferent: tetrabutylammonium tetrafluoroborate (10 ^"2 M)

Electrode surface: 20 cm ²

Duration of electrolysis: 4 hours

The conditions deviating from the general operating mode are specified in the tables below, which give a sample of the results obtained (Table 2).

Table 6

1) Use of cobalt as an electrolytic heterocoupling catalyst between an aryl (pseudo) halide and a vinyl ester.

Electrolytic heterocoupling process between an aryl (pseudo) halide and a vinyl ester which consists in subjecting the two substrates to cathodic reduction in the presence of cobalt cobalt.

Claims

1. Use of cobalt as an electrolytic heterocoupling catalyst between an aryl (pseudo) halide and a derivative carrying a double bond and of a group leaving in vinyl, allylic or even homoallylic position of said double bond.

2. Use according to claim 1, characterized in that the cobalt is present in the oxidation state 2.

3. Use according to claims 1 and 2, characterized in that the cobalt is present in a coordinated form.

4. Use according to claim 3, characterized in that the coordination of cobalt is carried out by a solvent or solvating compound having a high donor index.

5. Use according to claim 4, characterized in that the atom responsible for the good donor index is chosen from atoms in the nitrogen column.

6. Use according to claims 3 to 5, characterized in that the coordination of cobalt is carried out by a specific coordinating agent.

7. Use according to claim 6, characterized in that said coordinating agent has functions chosen from pyridine, nitrile, phosphine, stibine and imine functions.

8. Use according to claims 1 to 7, characterized in that the anode is a soluble anode.

9. Use according to claim 8, characterized in that said soluble anode contains iron and / or cobalt.

10. Use according to claims 8 and 9, characterized in that said soluble anode is an alloy of cobalt or cobalt itself, advantageously a ferro-cobalt.

11. Use according to claims 1 to 10, characterized in that said derivative carrying a double bond and a leaving group is a vinyl ester.

12. Use according to claim 11, characterized in that the ratio (coordinator (s) / cobalt) between coordinator (s), expressed in moles for monodentates and in equivalent for polydents and cobalt ions (expressed in moles) is at least equal to 0.5; advantageously to 1, preferably to

2, more preferably 4.

13. Use according to claims 1 to 10, characterized in that said derivative carrying a double bond and a leaving group is an ester or an allylic ether.

14. Use according to claim 13, characterized in that the ratio [cobalt] / [coordinating at least bidentate of which at least one tooth is pyridine, expressed in pyridine equivalent] is greater than 1, advantageously 2.

15. Use according to claim 13, characterized in that the cobalt / pyridine equivalent ratio is greater than 1, advantageously than 2.

16. Composition comprising at least one cobalt salt, a conductive or made conductive solvent, a cobalt coordinator, and a derivative carrying a double bond and a leaving group.

17. Composition according to Claim 16, characterized in that the cobalt content is between 2 x 10 ^"3 and 10 ^{" 1} M.

18. Composition according to Claims 16 and 17, characterized in that it comprises a solvent chosen from the following components, alone or as a mixture:

- purely oxygenated solvents, in particular ethers, preferably polyethers such as dimethoxy-1, 2-ethane or cyclic ethers such as THF or dioxane; - amides, including ureas;

- sulfones or sulfoxides;

- nitrogen derivatives, in particular nitrogen heterocycles, in particular pyridine and compounds with nitrile functions;

- complexing agents.

19. Composition according to Claims 16 to 18, characterized in that the molar ratio in dissolved species between the cobalt and a derivative carrying a double bond and a leaving group ranges from 10 ^"2 to 0.5.

20. Process for the electrolytic synthesis of aryl and a derivative carrying a double bond and a leaving group,. characterized in that it consists in subjecting a composition according to one of claims 16 to 19, further comprising an aryl (pseudo) halide to electrolysis on an inert cathode.

21. The method of claim 20, characterized in that the cathodic current density is in the closed range from 5 to 5 x 10 ² A / m ² .