EP1507898A1

EP1507898A1 - Electrochemical method for the production of organofunctional silanes

Info

Publication number: EP1507898A1
Application number: EP03755089A
Authority: EP
Inventors: Thomas Kammel; Bernd Pachaly; Christa Grogger; Bernhard Loidl; Harald STÜGER
Original assignee: Consortium fuer Elektrochemische Industrie GmbH
Current assignee: Consortium fuer Elektrochemische Industrie GmbH
Priority date: 2002-05-29
Filing date: 2003-04-17
Publication date: 2005-02-23
Also published as: WO2003100134A1; CN1656252A; JP2005527706A; US20050234255A1; DE10223939A1

Abstract

The invention relates to a method for producing organofunctional silanes of general formula (1), according to which a silane of general formula (2) is electrochemically reacted with a compound of general formula R1-Y by using an undivided electrolysis cell, provided that a maximum of 0.1 mol of a complexing agent is present per mol of X. R1, R2, R3, R4, X, and Y have the meanings defined in claim 1.

Description

Electrochemical process for the production of organofunctional silanes

The invention relates to an electrochemical method for producing organofunctional silanes using a sacrificial anode.

Shono et al. {Chem. Letters 1985, 463-466) describe that it is possible, by electrochemical reduction of benzyl and allyl halides in the presence of trimethylchlorosilane, to give the corresponding benzyl (e.g. PhCH2SiMe3) and allylsilanes in a divided electrolysis cell using an inert anode in good To produce yields.

Furthermore, Biran, Bordeau et al. (J. Chim. Phys. 1996, 93, 591-600, Organometallics, 2001, 20 (10), 1910-1917) describes the electrochemical display of organofunctional silanes using a sacrificial anode and in the presence of complexing agents such as HMPT.

The electrochemical production of substituted aromatic halides using the silane dimethyl dichlorosilane (silane M2) was also described by Bordeau, Biran et al. (Organometallics, 2001, 20 (10), 1910-1917). The advantage of electrochemical imaging compared to traditional methods is the high selectivity in Si-C bond formation. In contrast, in the classic chemical processes the Si-C bond formation takes place through a coupling reaction with organometallic nucleophiles, which have to be generated beforehand with BuLi or Mg. Biran et al. Succeeded in forming silylated aromatics such as p-methoxyphenyldimethylchlorosilane. however only if the electrolysis is not only in the presence of a complexing agent like HMPT and a guiding principle (tetrabutylammonium bromide), but in addition a nickel catalyst (nickel bipyridine dichloride) and as co-catalyst 2, 2 '-bipyridine is used (see reaction equation below).

In addition, the silane must be used in large excess in order to obtain the desired product in acceptable yields: hitherto only bromides could be successfully reacted as starting materials under these conditions.

The invention relates to a process for the preparation of organofunctional silanes of the general formula (1)

in which a silane of the general formula (2)

with a compound of general formula (3) R ^x -Y (3),

is implemented electrochemically using an undivided electrolytic cell, where

R is a radical of the general formula (4)

R ^β R ⁷ R ⁸ C (4),

R *>, R ⁷ and R8 individually or together monomer, oligomer or polymer residues, R ² and R-3 individually or together optionally substituted Cι-C3 _Q hydrocarbon residues in which one or more, not adjacent methylene units by groups - 0-, -CO-, -COO-, -OCO-, or -OC00-, -S-, -CO-NR ⁵ -, -NH- or -NC] _- C20 ^_κ ° hl ^enwasserst ° ff ^e can and in which one or more non-adjacent methine units can be replaced by groups, -N =, -N = N-, or -P =, R ^ hydrogen or an optionally substituted C ~ C3 _Q hydrocarbon radical, in which a or more, not adjacent methylene units by groups -0-, -CO-, -COO-, -OCO-, or -0C00-, -S-, -CO-NR ⁵ -, -NH- or -NC] _- C20 ^-K ° hl ^enwasserst ° f ^' f ^e can be replaced and in which one or more, not adjacent to each other

Methine units can be replaced by groups, -N =, -N = N-, or -P =, X and Y are selected from Br, Cl, I, OR ⁵ and R ^{5 are} a Ci-CiQ-alkyl radical, with the proviso that at most 0.1 mole of complexing agent is present per mole of X. The process manages with small amounts and also without the use of complexing agents such as the health-threatening HMPT (hexamethylphosphoric triamide) or DMPH (N, N'-dimethylpropylene urea) and can also be carried out without a catalyst or co-catalyst. The silanes of the general formula (1) can thus be prepared in a simple and efficient manner.

Furthermore, this method is very widely applicable, i.e. Both aromatic and aliphatic halides (and therefore not only bromides), which carry a wide variety of substituents, can be used. The reactions are stoichiometric (no excess of silane necessary), the process is very selective, i.e. By-products are not detected at all or only in extremely small amounts, and the organosilanes of the general formula (1) formed can be isolated in good to very good yields (usually 70-90%).

Monomeric radicals R ⁶ , R ⁷ and R ^ are preferably hydrogen, cyano or optionally substituted C1-C3Q-

Hydrocarbon radicals in which one or more, not adjacent methylene units by groups -0-, -CO-, - COO-, -OCO-, or -OCOO-, -S-, -CO-NR ⁵ -, -NH- or - -C1-C20- hydrocarbons can be replaced, in which one or more non-adjacent methine units can be replaced by groups, -N =, -N = N-, or -P = and in which one or more, not each other neighboring carbon atoms can be replaced by silicon atoms.

Halogens, in particular fluorine, chlorine, bromine and iodine, cyano, amino, are suitable as substituents. Particularly preferred monomeric residues R ^6, R ⁷ and R ⁸ are C_-C2o ^_ aryl and C] _- C2n-alkyl radicals, which may be in non-adjacent methylene units by groups -0- and nonadjacent carbon atoms are replaced by silicon atoms.

Oligomers and polymeric radicals R ^, R ⁷ and R ⁸ are, for example, polymers, synthetic oligomers and polymers such as polyvinyl chloride, polyethylene, polypropylene, polyvinyl acetate, polycarbonate, polyacrylate, polymethacrylate, polymethyl methacrylate, polystyrene, polyacrylonitrile, polyvinylidene chloride (PVC), polyvinyl fluoride, polyvinylidene fluoride, Polyvinylidene cyanide, polybutadiene, polyisoprene, polyether, polyester, polyamide, polyimide, silicone, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, polyethylene glycol and their derivatives and the like including copolymers such as styrene-acrylate copolymers, vinyl acetate-acrylate copolymers, ethylene-vinyl acetate-copolymers, ethylene Terpolymers (EPDM), Ethylene Propylene Rubber (EPM), Polybutadiene (BR), Poly Isobutene Isoprene (Butyl Rubber, JJR), Polyisoprene (IR) and Styrene Butadiene Rubber (SBR);

Oligomers and polymeric radicals R *>, R ⁷ and R ⁸ are, for example, also natural oligomers and polymers, such as cellulose, starch, casein and natural rubber, as well as semi-synthetic oligomers and polymers such as cellulose derivatives, e.g. B. methyl cellulose, hydroxymethyl cellulose and carboxymethyl cellulose.

The spellings of the general formulas (1) and (2) include that the radicals R ² R ³ and R ⁴ are bonded to the silicon atom directly or via an oxygen atom. Examples of hydrocarbon radicals R ² , R ³ and R ⁴ are alkyl radicals, such as the methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, tert. -Butyl-, n-pentyl-, iso-pentyl-, neo-pentyl-, tert. -Pentyl radical, hexyl radicals, such as the n-hexyl radical, heptyl radicals, such as the n-heptyl radical, octyl radicals, such as the n-octyl radical and iso-octyl radicals, such as the 2, 2, 4-trimethylpentyl radical, nonyl radicals, such as the n-nonyl radical, decyl radicals, such as the n-decyl radical, dodecyl radicals, such as the n-dodecyl radical, octadecyl radicals, such as the n-octadecyl radical; Alkenyl groups such as the vinyl and allyl groups; Cycloalkyl radicals, such as cyclopentyl, cyclohexyl,

Cycloheptyl and methylcyclohexyl; Aryl radicals, such as the phenyl, naphthyl and anthryl and phenanthryl radical; Alkaryl residues, such as o-, m-, p-tolyl residues, xylyl residues and ethylphenyl residues; Aralkyl radicals, such as the benzyl radical, the alpha and the β-phenylethyl radical. As radicals R ² , R ³ and R ⁴ , Cχ-Cg-alkyl radicals, in particular methyl and ethyl radicals or phenyl radicals are preferred.

Any mixtures or combinations of compounds of the general formulas (2) and (3) can of course also be used.

In the process, preferably at most 0.01 mol, in particular no complexing agent, are present per mol of X. Complexing agents are, for example, hexamethylphosphoric triamide (HMPT), N, N '-dimethylpropylene urine _. toff or tetrahydro-l, 3-dimethyl-2 (1H) pyrimidinone (DMPH), tris (3,6-dioxaheptyl) amine (TDA-1), tetramethyl urea (TMU).

The anode can consist of all materials that have sufficient electrical conductivity and are chemically inert under the selected reaction conditions. A sacrificial anode is preferably used as the anode. The Sacrificial anode comprises a metal or an alloy of metals that dissolve to form cations in the process. Preferred metals are Mg, Fe, Ti, Zn, Al, Cu, Sn, especially Mg.

The counter electrode (cathode) can also consist of all materials that have sufficient electrical conductivity and are chemically inert under the selected reaction conditions. Preferred are graphite or an inert metal such as gold, silver, platinum, rhenium, ruthenium, rhodium, osmium, iridium, and palladium or another metal or alloy that is fairly inert, e.g. stainless steel.

In order to achieve sufficient conductivity of the reaction mixture at the start of the reaction, a conductive salt is preferably added. Inert salts or mixtures thereof which do not react with the reaction components are used as conductive salts.

Examples of conductive salts are salts of the general formula M ⁺ Y ^~ , where M is, for example, Mg, Li, Na, NBU4, NMe4, NEt4, and Y, for example

CIO4, Cl, Br, I, NO3, BF ₄ , ASF ₆ , BPh, PFg, AICI4, CF3SO3 and

SCN means in which Bu, Me, Et or Ph denotes a butyl, methyl, ethyl or phenyl group. Examples of more suitable

Electrolytes include tetraethylammonium tetrafluoroborate and tetrabutylammonium tetrafluoroborate. Particularly preferred conductive salts are MgCl2 and LiCl.

The process preferably takes place in a solvent. All aprotic solvents which do not react with the compounds of the general formulas (1) to (3) and which themselves only react with one can be used as solvents more negative potential than the compounds of the general formula (2) can be reduced. Suitable solvents are all in which the compounds used are at least partially soluble under operating conditions with regard to concentration and temperature. In a special embodiment, the compounds of the general formulas (2) and (3) themselves can also serve as solvents. An example of this is dimethyldichlorosilane. Examples of suitable solvents are ethers such as tetrahydrofuran, 1, 2-dimethoxyethane, 1, 3-dioxolane, bis (2-methoxyethyl) ether, dioxane, acetonitrile, γ-butyrolactone, nitromethane, liquid SO2, tris ( dioxa-3, 6-heptyl) amine, trimethyl urea, dimethylformamide, dimethyl sulfoxide, and mixtures of these solvents. The solvents are preferably dry. Tetrahydrofuran is particularly preferred.

The concentration of compound of the general formula (3) in the solvent is preferably 0.05 to 5 mol / 1, in particular 0.1 to 2 mol / 1.

Based on 1 mol of compound of the general formula (3), the amount of compound of the general formula (2) used is preferably 0.8 to 1.5 mol, in particular 0.9 to 1.2 mol.

The method can be carried out in any conventional way using an electrolytic cell with a cathode and a sacrificial anode. The electrolytic cell can be a divided or undivided electrolytic cell, the undivided electrolytic cell being preferred since it is the simplest in construction. The process preferably takes place under an inert gas atmosphere, nitrogen, argon or Helium are preferred. The electrolysis cell is preferably provided with a potentiostat or a galvanostat (constant current flow) in order to regulate the potential or the intensity of the current. The implementation can be carried out with and without controlled potential.

Based on the compound of the general formula (3), the amount of charge Q is preferably 1.1 to 5 F / mol, in particular 1.5 to 3 mol / F.

The process preferably takes place under the influence of ultrasound.

The temperature in the process is preferably 5 ° C to 50 ° C, in particular 10 to 30 ° C.

All of the above symbols of the above formulas have their meanings independently of one another. In all formulas, the silicon atom is tetravalent.

Unless otherwise stated, all quantities and percentages in the following examples are based on weight, all pressures 0.10 MPa (abs.) And all temperatures 20 ° C.

The reactions are carried out under a protective gas atmosphere (argon,

Nitrogen), all solvents used are dry, the starting materials used are each highly pure.

Electrolysis setup: An undivided electrolysis cell is used for the electrolysis, in which the rod-shaped sacrificial anode (8 mm diameter) made of high-purity magnesium is arranged in the middle and the cathode, which is made of a cylindrical stainless steel sheet with 4 cm diameter is attached to the anode. The electrolysis is carried out galvanostatically, the current density at the cathode not exceeding 0.5 mA / cm ² . The electrolysis cell is sonicated for the entire duration of the electrolysis in an ultrasonic bath, which is cooled by water so that the temperature does not rise significantly above RT (20 ° C).

Example 1: Preparation of (p-methoxyphenyl) dimethylsilane

1.2 g (28.3 mmol) of anhydrous lithium chloride are dissolved in 50 ml of dry THF and flushed into a dry, inert gas

Electrolysis cell transferred. After adding 5.00 g (35.1 mmol) of p-chloroanisole and 3.32 g (35.1 mmol) of chlorodimethylsilane, electrolysis is carried out at a constant current of 15 mA (current density i = 0.4 mA / cm ² ). After a total reaction time of 138 h (note: this corresponds to a quantity of charge Q of 2.2 F / mol), the electrolysis is stopped.

Work-up: After removing the solvent THF in vacuo, the remaining residue is mixed with 75 ml of a saturated, aqueous ammonium chloride solution and then shaken out a total of 3 times with 50 ml each of n-pentane. The organic phases are combined and dried over sodium sulfate. After removal of the solvent n-pentane, 4.95 g of the desired product (p-methoxyphenyl) dimethylsilane are obtained (yield: 85% of theory).

H ₃ Example 2: Preparation of (p-methoxyphenyl) dimethylsilane

Analogously to Example 1, 10.00 g (53.5 mmol) of 4-bromoanisole are reacted electrochemically with the stoichiometric amount of 5.06 g (53.5 mol) of chlorodimethylsilane. After an electrolysis time of 48 h and workup analogous to that in Example 1, the desired product p-methoxyphenyldimethylsilane is obtained in 85% yield.

Example 3: Synthesis of [4- (N, N-

Dirrtethylamino) phenyl] dimethylsilane

Analogously to Example 1, starting from 5.00 g (25.0 mmol) of 4-bromo-N, N-dimethylaniline, electrochemically reacting with 2.36 g (25 mmol) of chlorodimethylsilane. After an electrolysis time of 98 h (charge quantity Q = 2.2 F / mol) and working up analogously to that in Example 1, 3.12 g of [4- (N, -Dimethylamino) phenyl] dimethylsilane are obtained, which corresponds to a yield of 70 % (th.).

Example 4: Preparation of [4- (dimethylsilyl) phenoxy] - tert-butyldimethylsilane

In analogy to Example 1, 7.50 g (26.1 mmol) of (4-bromophenoxy) tert-butyldimethylsilane are reacted electrochemically with 2.47 g (26.1 mmol) of chlorodimethylsilane. After an electrolysis time of a total of 103 h (charge quantity Q = 2.2 F / mol) and working up analogously as in Example 1, 6.40 g of [4- (dimethylsilyl) phenoxy] -ert-butyldimethylsilane are obtained. This corresponds to a yield of 90% of theory. Th.

C (CH ₃ ) ₃ r C-Si-Cm

I o

H ₃ C-Si-CH ₃ H

Example 5: Preparation of n-pentyldimethylsilane

Analogously to Example 1, starting from 4.00 g (37.5 mmol) of 1-chloropentane and 3.55 g (37.5 mmol) of chlorodimethylsilane after an electrolysis time of 147 h (charge quantity Q = 2.2 F / mol) and Working up analogously as in Example 1, a total of 4.15 g of the desired product n-pentyldimethylsilane was obtained. This corresponds to a yield of 85%.

Example 6: Preparation of n-hexyldimethylsilane

Analogously to Example 1, starting from 5.00 g (30.3 mmol) of hexyl bromide and the stoichiometric amount of 2.86 g (30.3 mmol) of chlorodimethylsilane, a total of 22 hours and analogous working up as in Example 1 are obtained 2.90 g of the product n-hexyldimethylsilane. This corresponds to a yield of 66% of theory

Example 7: Synthesis of (p-methoxyphenyl) methoxy-di ethy1si1an

5.00 g (35.1 mmol) of p-chloroanisole and 4.22 g (35.1 mmol) of dimethoxydimethylsilane are reacted with one another in an analogous manner to Example 1. After an electrolysis time of a total of 138 h (charge quantity Q = 2.2 F / mol) and working up analogously as in Example 1, 5.50 g of the product p-methoxyphenylmethoxydimethylsilane are obtained (yield: 80% of theory).

Example 8: Synthesis of (p-methoxyphenyl) methoxydimethylsilane

Starting from 5.00 g (26.7 mmol) of p-bromoanisole and the stoichiometric amount of 3.20 g (26.7 mmol) of dimethoxydimethylsilane, analogously to Example 1, after an electrolysis time of 24 h and the same working up as in the example 1 2.72 g of the desired product (52% of theory).

Example 9: Preparation of [4- (methoxydimethylsilyl) phenoxy] tert-butyldimethylsilane

Analogously to Example 1, 7.50 g (26.1 mmol) of (4-bromophenoxy) tert-butyldimethylsilane with a stoichiometric amount

Dimethoxydimethylsilane (3.14 g (26.1 mmol)) electrolyzed.

After a total electrolysis time of 103 hours (Q = 2.2

F / mol) and analogous work-up as in Example 1

4.60 g of the desired product [4- (methoxydimethylsilyl) phenoxy] tert-butyldimethylsilane obtained. This corresponds to a yield of 60% of theory. Th.

Example 10: Synthesis of (N, N-diethylamino) -p-methoxyphenyldimethylsilane In analogy to Example 1, 2.80 (15.1 mmol) p-bromoanisole and the stoichiometric amount of 2.50 g (15.1 mmol ) (N, N-diethylamino) dimethylchlorosilane implemented electrochemically. The electrolysis is ended after 24 h. After working up analogously to Example 1, 1.62 g of the desired product (N, N-diethylamino) -p-methoxyphenyldimethylsilane (45% of theory) are obtained.

Example 11: Synthesis of (3-butenyl) methoxydimethylsilane

4.00 g (29.6 mmol) of 4-bromo-1-butene are reacted electrochemically analogously to Example 1 with 3.56 g (29.6 mmol) of dimethoxydimethylsilane. After an electrolysis time of 116 h (charge quantity Q = 2.2 F / mol) and working up analogously to that in Example 1, 3.50 g of the desired product (3-butenyl) methoxydimethylsilane are obtained. This corresponds to a yield of 83%.

Example 12: Preparation of Pol [(dimethylsilyl) ethylene-co-vinyl chloride

Analogously to Example 1, starting from 1.00 g (16 mmol of Cl) polyvinyl chloride and 1.51 g (16 mmol) of chlorodimethylsilane, the electrolysis is carried out at a constant current of 15 mA. After a total reaction time of 63 h (charge quantity Q = 2.2 F / mol), the electrolysis is ended. The reaction solution is concentrated to half by partially removing the solvent in vacuo. The concentrated solution is then slowly added dropwise, with vigorous stirring, to 250 ml of methanol, the polymer formed precipitating out. The precipitated polymer is washed a total of three times with 150 ml of methanol each time and then dried in vacuo to constant weight.

Example 13: Synthesis of n-pentyldimethylsilane

Analogously to Example 5, but using a titanium anode instead of a magnesium anode, 4.00 g (37.5 mmol) of 1-chloropentane and 3.55 g (37.5 mmol) of chlorodimethylsilane are electrolyzed for a total of 8 d under the same conditions. GC / MS analysis detects the desired product in addition to the educt in the raw product (composition: 55% of the target product n-pentyldimethylsilane, 45% of the educt 1-chloropentane).

Comparative example: synthesis of p-methoxyphenyldimethylchlorosilane (from Biran, Bordeau et al. Organometalllcs 2001, 20 (10), 1910-1917)

In an undivided electrolysis cell (100 ml), which has a cylindrical aluminum or magnesium rod (1 cm diameter) as a sacrificial anode and a concentric stainless steel grid (or

Carbon) as cathode (area: 1.0 ± 0.2 dm ² ), the reaction is carried out under a nitrogen atmosphere as follows: a constant current flow of 0.1 A (current density: 0.1 ± 0.05 A dm ^{- 2} ) is applied and dry THF (20 ml), HMPA (6 ml) and the silane (40-60 ml) are added successively to the dried cell. After degassing the reaction solution and _; Pre-electrolysis (removal of traces of water to form the corresponding, electrochemically inert siloxane) 0.45 g (1.2 mmol) of the nickel catalyst NiBr2 (bpy) and an excess of the cocatalyst 2, 2'-bipyridine (0.78 g, 5 mmol) was added. The electrolysis (i = 0.1 A) is carried out until the theoretical amount of charge is reached. After working up analogously to the above examples, the desired product p-methoxyphenyldimethylchlorosilane is obtained. The yield is 86%. In the absence of the catalyst and the cocatalyst, the conversion rates are between 8-13%, with the catalysts 98%.

Claims

Claims:

1. Process for the preparation of organofunctional silanes of the general formula (1)

in which a silane of the general formula (2)

with a compound of general formula (3)

R ^X - (3),

is implemented electrochemically using an undivided electrolytic cell, where

R ^{1 is} a radical of the general formula (4)

R ⁶ R ⁷ R ⁸ C (4),

R *>, R ⁷ and R ⁸ individually or together monomer, oligomer or

Polymer radicals, R ² and R ^3, individually or together, optionally substituted C -C3o hydrocarbon radicals, in which one or more methylene units which are not adjacent to one another are represented by groups -0-, -CO-, -COO-, -OCO-, or -0C00- , -S-, -CO-NR ⁵ -, -NH- or -NC -C20 ^-κ ° hydrogen can be replaced and in which one or more, not adjacent methine units can be replaced by groups, -N =, -N = N-, or -P =, R ^{4 is} hydrogen or an optionally substituted C ~

C3 _Q hydrocarbon residue, in which one or more, not adjacent methylene units by groups

-0-, -CO-, -COO-, -OCO-, or -0C00-, -S-, -CO-NR ⁵ -, -NH- or -N-Cχ-C20 ^-κ ° cooling hydrogens can be replaced and in which one or more, not adjacent to each other

Methine by groups -N =, -N = N-, or -P = may be replaced, X and Y is OR are selected from Br, Cl, I, and R5 represent a C ⁵ -Cχo ~ ^A l ^k yl ^radical, with the proviso that at most 0.1 mole of complexing agent is present per mole of X.

2. The method according to claim 1, wherein the monomeric radicals R ^, R ⁷ and R ^{8 are} selected from preferably hydrogen, cyano or optionally substituted Cχ-C3Q-

Hydrocarbon radicals in which one or more methylene units, which are not adjacent to one another, are separated by groups

-0-, -CO-, -COO-, -OCO-, or -0C00-, -S-, -CO-NR ⁵ -, -NH- or -N-Cι-C20 ^_Kon l ^enwasserst ° ff ^{e be} replaced can, in which one or more, not adjacent to each other

Methine units can be replaced by groups, -N =, -N = N-, or -P = and in which one or more carbon atoms which are not adjacent to one another can be replaced by silicon atoms.

3. The method according to claim 1, in which oligomeric and polymeric radicals R ⁶ , R ⁷ and R ^{8 are} selected from polyvinyl chloride, polyethylene, polypropylene, polyvinyl acetate, polycarbonate, polyacrylate, polymethacrylate, polymethyl methacrylate, polystyrene, polyacrylonitrile, polyvinylidene chloride (PVC), polyvinyl fluoride , Polyvinylidene fluoride,

Polyvinylidene cyanide, polybutadiene, polyisoprene, polyether, polyester, polyamide, polyimide, silicone, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, polyethylene glycol and their derivatives and the like including copolymers such as styrene-acrylate copolymers, vinyl acetate-acrylate copolymers, ethylene-vinyl acetate-copolymers, ethylene Terpolymers (EPDM), ethylene-propylene rubber (EPM), polybutadiene (BR), poly-isobutene-isoprene (butyl rubber, JJR), polyisoprene (IR) and styrene-butadiene rubber (SBR).

4. The method of claims 1 to 3, wherein the anode is a sacrificial anode comprising a metal or an alloy of metals selected from Mg, Fe, Ti, Zn, Al, Cu and Sn.

5. The method according to claim 1 to 4, in which a conductive salt of the general formula M ⁺ Y ^~ , where M is Mg, Li, Na, NBU, NMe4, NEt4, and Y is C10, Cl, Br, I, NO3, BF4, ASFs, BPh, PFg, AICI4, CF3SO3 and SCN, where Bu, Me, Et and Ph denotes a butyl, methyl, ethyl and phenyl group.

6. The method according to claim 1 to 5, in which an aprotic solvent is present which does not react with the compounds of the general formulas (1) to (3) and which itself only at a more negative potential than the compounds of the general formula (2) is reduced.

7. The method according to claim 1 to 6 in which, based on 1 mol of compound of the general formula (3), the amount of compound of the general formula (2) used is 0.8 to 1.5 mol.

3. The method according to claim 1 to 7, which is carried out under the influence of ultrasound.