FR2841245A1 - Preparation of organodialkyloxysilane, e.g. starting material for preparation of sulfur-containing organosilicon compounds, comprises reaction of omega-halogenoalkyl dialkyl-halogenosilane with alkanol - Google Patents

Abstract

Process for obtaining an organodialkylalkoxysilane by a continuous reaction countercurrently of an omega-halogenoalkyl dialkylalkoxysilane with an alkanol in the absence of a base. The process for obtaining an organodialkylalkoxysilane of formula (IX) ;- R 1>O-(R 2>R 3>)Si-(CH 2) 3-A ; - consists in contacting counter-currently an alcohol(VIII), R 1>OH, with a silane of formula (VII) : Hal-(R 2>R 3>)Si-(CH 2) 3-A, to effect an alcoholysis by the reaction :- Hal-(R 2>R 3>)Si-(CH 2) 3-A + R 1>OH ---------------R 1>O-(R 2>R 3>)Si-(CH 2) 3-A + H-Hal - operating with a stripping of the product H-Hal formed and recovery of the organodialkylalkoxy-silane in the reactor, and in which Hal : Cl, Br or I(preferably Cl); R 1>1 - 15C alkyl or 2 - 8C alkoxyalkyl; R 2>, R 3>1 - 6C alkyl or phenyl; A : a detachable group from Hal, a radical para-R 0>-C 6H 4-SO 2-O- or R 0>-SO 2-O-(preferably tosylate or mesylate) or R 0>-CO-O-(R 0>= 1 - 4C alkyl). A is preferably Cl. Independent claims are also included for the preparation of the silane(VII) and polysulfides derived from the dialkylalkoxysilanes.

Description

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PROCESS FOR PREPARING ORGANO DIALKYLALCOXYSILANE
The present invention relates to a process for the preparation of organo dialkylalkoxysilane by reactive distillation in the presence of an alkanol on an omegahalogenoalkyl dialkylhalosilane.

The invention relates more particularly to the manufacture of an ethoxypropylsilane from a chloropropylsilane. Methods known on this synthesis relate more specifically to dichloropropylsilane and trichloropropylsilane. The process according to the invention makes it possible to use 3-chloropropyl dimethylchlorosilane as reagent while obtaining ethoxydimethyl-3-chloropropylsilane with very high yields. The chemical reaction is as follows: CIMe2Si-CH2CH2CH2Cl + EtOH # (EtO) Me2Si-CH2CH2CH2Cl + HCl The ethoxylation of 3-chloropropyl dimethylchlorosilane can be conducted quantitatively and selectively in the presence of a base. The use, for example, of a tertiary amine-type organic base (including triethylamine) makes it possible stonically to neutralize the acid formed. However, the use of a base and the lengthening and complication of the process related to its use and final disposal is a definite disadvantage. Moreover, in the absence of base, the reaction leads to unsatisfactory performance under conditions conventionally used for this type of reaction: ethanol flow on a foot of 3-chloropropyl dimethylchlorosilane. This is a batch reactor process which gives excellent results only if the raw material is dichloropropylmethylchlorosilane or trichloropropylchlorosilane: conversion rate (TT) = 100% and selectivity (RT)> 95%. Indeed, the specificity of the dimethylchlorosilane group, compared for example with the trichlorosilane group, leads to a lower reactivity with respect to ethanol and consequently generates the more important formation of by-products. These secondary products are essentially derived from an oligomerization of the silane function, reaction following the reaction:
EtOH + HCI # EtCI + H20 2 [CIMe2Si-CH2CH2CH2Cl] + H2O # ClCH2CH2CH2-SiMe2-O-Me2Si- CH2CH2CH2Cl + HCI

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 The main object of the present invention is precisely to provide a high performance process of the above type whose starting material is a monochloro triorganosilane, in particular 3-chloropropyl dimethylchlorosilane and can be used in the absence of base.

 This and other objects are achieved by the present invention which relates to a process for the preparation of organo dialkylalkoxysilane by reactive distillation in the presence of an alkanol on an omega-haloalkyl dialkylhalosilane.

The conversions obtained are generally greater than 90% and can reach 100%, and the selectivities obtained are also very high.

uu . The alkanolysis reaction carried out using a reactive distillation process according to the invention can be schematized by the following equation:
Step b):

uu.

the symbol Hal represents a halogen atom chosen from among the chlorine, bromine and iodine atoms, the chlorine atom being preferred, the R1 symbols, which are identical or different, each represent a monovalent hydrocarbon group chosen from an alkyl radical; linear or branched, having 1 to 15 carbon atoms and a linear or branched alkoxyalkyl radical having 2 to 8 carbon atoms; the symbols R 2 and R 3, which are identical or different, each represent a monovalent hydrocarbon group chosen from a linear or branched alkyl radical having
1 to 6 carbon atoms and a phenyl radical - A represents a removable group selected from: either a Hal halogen atom belonging to the chlorine, bromine and iodine atoms, the chlorine atom being preferred; or a radical para-R0-C6H4-SO2-O- where R is an alkyl radical, linear or branched in
C1-C4, the para-CH3-C6H4-SO2-O- tosylate radical being preferred; or a radical R - S02 - O - where R is as defined above, the mesylate radical CH3 - SO2 - O - being preferred; is a radical R -CO-O- where R is as defined above, the acetate radical CH3-CO-
0- being preferred, the most preferred radical A being the chlorine atom.

 According to the invention, the reactive distillation reaction makes it possible to carry out in the distillation column, both the alkoxylation reaction and the separation of the alkanol stream of formula (VIII) and of H-Hal (generally HCl) flow of silanes. Then it is possible, if desired, to subsequently separate the alkanol from the H-Hal. Subsequently, the alkanol thus purified can be reinjected into the column. Silane can be introduced at the top or bottom of

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 column and the alkanol also can be introduced at the top or at the bottom of the column. Inside the column, fluid flows (liquids or gases) can be co-current or countercurrent. The column normally distils at least one of the products involved in the reaction, including the reactants and the products formed. In other words, inside the column, at least one of the products of formula H-Hal, (VII), (VIII), or (IX) is in the vapor state. The alkanolysis reaction is carried out inside the column at a temperature between the boiling point of the alkanol of formula (VIII) and the boiling point of the starting silane of formula (VII ), the reaction being carried out in the column either at atmospheric pressure or at reduced pressure or at superatmospheric pressure.

 According to a preferred embodiment of the invention, in particular when the alkanol is ethanol and the silane is 3-chloropropyldimethylchlorosilane, the alcohol is introduced into the boiler and / or at a tray level. from the foot of the column. The silane is preferably introduced at the top of the column at a plateau. In this case, the silane descends against the current column and reacts countercurrently with vaporized ethanol which causes the HCI formed either to a condenser at the top of the column, or the mixture in the form of steam is separated separately. The alkoxylated silane is recovered at the bottom of the column in the boiler and / or by side racking.

 The method comprises a stripping or steam distillation of the HCl formed by the reaction medium and a displacement of the equilibrium by increasing the concentration of alkanol (ethanol) by distillation of the ethanol from the reaction medium to remove the HCl.

 It is preferable, in order to always be in excess of alkanol, to operate the column by working with an alkanol / silane molar ratio greater than 1 and preferably greater than 1.2. In the case of the ethanol / 3-chloropropyldimethylchlorosilane pair, this alkanol / silane molar ratio is greater than 1.2 and, preferably, greater than 3 and, generally less than 20. It is moreover preferable to introduce ethanol into foot of the column and the silane at the top of the column. In the column, ethanol and silane are countercurrent. It should be noted that the silane can be indifferently in gaseous or liquid phase. The ethanol is preferably in the gaseous phase and entrains the HCl formed, while the starting silane and the ethoxylated silane are in the liquid state.

 The column may be a loose or ordered packed column or a tray column with a preference for the latter having from 5 to 50 trays. The reflux rate controls the temperature level in the column but especially the amount of HCl solubilized in ethanol. The increase in reflux leads to an increase in yield but at the expense of selectivity. That's why he

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 It is recommended according to the present invention to work at a low or no reflux rate which further reduces the parasitic chemical reactions.

 As indicated above, in the case where the products corresponding to formulas (VII), (VIII) and (IX) have R1 ethyl groups R1 and R3methyl and A and Hal represent a chlorine atom, the alkanol is ethanol , and the silane is 3chloropropyldimethylchlorosilane with the formation of HCl, the silane is introduced at the top of the column, the ethanol at the bottom of the column, the reaction temperature in the column is greater than 77.80 ° C. and less than 178 ° C. under pressure atmospheric and the hydrochloric acid formed is stripped with vaporized ethanol.

 If the reactive distillation is carried out at atmospheric pressure, the reaction temperature inside the column must be greater than that of the stripping vector gas, ie, for example 78 C in the case of ethanol, and below the temperature. It is thus recommended to work at reduced pressure to limit the solubility of HCl in ethanol and to make the reaction at a temperature below that corresponding to an atmospheric pressure, which makes it possible to limit the parasitic reactions and gain selectivity.

Ethanol acid, that is to say loaded with HCl, must be purified before recycling into the reaction medium, by optionally azeotropic distillation, by adsorption on resin, by neutralization or by separation on membrane, The stripping of HCl can be coupled with a stripping of the water present in the medium, working at a temperature above the boiling point of the water at the pressure in question.

 The alkanolysis reaction carried out by means of a reactive dithigration process may be carried out optionally in the presence of an organic solvent and / or an inert gas. The solvent is of the aprotic and low polar type such as aliphatic and / or aromatic hydrocarbons. the solvent used has a boiling temperature at the operating pressure (atmospheric pressure) between the boiling point of the alkanol of formula (VIII), for example 77. 8 C for ethanol and that of the silane of formula (VII) e.g. 178 C for 3-chloropropyl dimethylchlorosilane. Suitable solvents for the ethanol / 3-chloropropyl dimethylchlorosilane pair include toluene, monochlorobenzene and xylene. The role of the solvent is to stripper hydrochloric acid (HCl) mechanically (ethanol is also entrained and recycling after purification is possible) and also to create a zone of exhaustion (no or very little HCI in foot of column) to minimize parasitic chemical reactions.

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 The solvent is boiled in the boiler of the column to be distilled for example by electrical resistors. This start-up phase takes place at full reflux in order to load the trays of the column.

 It is possible to carry out the reaction in a distillation column operating continuously, semi-continuously or discontinuously.

dans laquelle : x est un nombre, entier ou fractionnaire, allant de 1,5 + 0,1 à 5 ~ 0,1 ; et les symboles R1, R2, R3, Hal et A sont tels que définis supra,
Dans la formule (I) précédente, les radicaux R1 préférés sont choisis parmi les radicaux : méthyle, éthyle, n-propyle, isopropyle, n-butyle, CH30CH2-, CH30CH2CH2- et CH30CH(CH3)CH2- ; de manière plus préférée, les radicaux R1 sont choisis parmi les radicaux : méthyle, éthyle, n-propyle et isopropyle. The organodialkylalkoxysilane of formula (IX) thus obtained is more particularly usable as a starting material for the preparation of organosilicon compounds containing sulfur, corresponding to the average general formula (I):

wherein: x is an integer or fractional number ranging from 1.5 + 0.1 to 5 ~ 0.1; and the symbols R1, R2, R3, Hal and A are as defined above,
In the above formula (I), the preferred radicals R 1 are chosen from the following radicals: methyl, ethyl, n-propyl, isopropyl, n-butyl, CH 3 OCH 2 -, CH 3 OCH 2 CH 2 - and CH 3 CH (CH 3) CH 2 -; more preferably, the radicals R 1 are chosen from the radicals: methyl, ethyl, n-propyl and isopropyl.

 The preferred R 2 and R 3 radicals are chosen from the radicals: methyl, ethyl, n-propyl, isopropyl, n-butyl, n-hexyl and phenyl; more preferably, the radicals R2 and R3 are methyls.

 The number x, integer or fractional, is preferably from 3 + 0.1 to 5 ~ 0.1, and more preferably from 3.5 + 0.1 to 4.5 0.1.

The polysulfide monoorganoxysilanes corresponding to formula (1) which are especially targeted by the present invention, are those of formula

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dans lesquelles le symbole x est un nombre entier ou fractionnaire allant de 1,5 0,1 à 5
0,1, de préférence de 3 0,1 à 5 0,1, et de manière plus préférée de 3,5 0,1 à 4,5 ~ 0,1.

in which the symbol x is an integer or fractional number ranging from 1.5 to 5
0.1, preferably from 0.1 to 0.1, and more preferably from 0.1 to 4.5 to 0.1.

 In the present specification, it will be pointed out that the symbol x of formulas (1), (II), (III) and (IV) is an integer or fractional number which represents the number of sulfur atoms present in a molecule of formula (1), (II), (III) and (IV).

 In practice, this number is the average of the number of sulfur atoms per molecule of compound under consideration, insofar as the chosen synthesis route gives rise to a mixture of polysulfide products each having a different number of sulfur atoms. The polysulfurized monoorganoxysilanes synthesized consist in fact of a distribution of polysulphides, ranging from monosulphide to heavier polysulphides (such as for example S> 5), centered on a mean value in mole (value of the symbol x) lying in the domains general (x ranging from 1.5 + 0.1 to 5 + 0.1), preferential (x ranging from 3 + 0.1 to 5 ~ 0.1) and more preferential (x ranging from 3.5 ~ 0, 1 to 4.5 + 0.1) mentioned above.

où : - les symboles R1, R2, R3, A et x sont tels que définis supra, - le symbole M représente un métal alcalin, - la réaction est réalisée : # en faisant réagir à une température allant de 20 C à 120 C, soit le milieu réactionnel obtenu à l'issue de l'étape (b), soit le dérivé de The products of formula (I) can be prepared in the following manner from the organo dialkylalkoxysilane of formula (IX), previously prepared during step b) by the reactive distillation process of the invention, by reaction during of step c) of said product of formula (IX) on an alkali polysulfide of formula (X) according to the following reaction scheme: Step c):

where: - the symbols R1, R2, R3, A and x are as defined above, - the symbol M represents an alkali metal, - the reaction is carried out: # by reacting at a temperature ranging from 20 C to 120 C, the reaction medium obtained at the end of step (b), or the derivative of

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 monoorganoxydiorganosilylpropyl of formula (IX) taken alone after separation of said medium, with the metal polysulfide of formula (X) in the anhydrous state, using 0.5 15 mol% of metal polysulfide of formula (X) per mole of the reagent of formula (IX) and optionally operating in the presence of an inert polar (or nonpolar) organic solvent, # and isolating the bis (monoorganoxysilylpropyl) polysulfide of formula (I) formed.

 The process according to the present invention provides access to bis (monoorganoxysilylpropyl) polysulfides of formula (1). The diorganohalosilanes of formula (VII) can advantageously be prepared on an industrial scale by a process such as in particular that described in WO-A-99/31111, cited as a reference.

le symbole Hal représente un atome d'halogène choisi parmi les atomes de chlore, brome et iode, l'atome de chlore étant préféré, et les symboles A, R2et R3 sont tels que définis supra, la réaction est réalisée : # en faisant réagir à une température allant de -10 C à 200 C une mole du diorganohalogénosilane de formule (V) avec une quantité molaire st#chiométrique ou différente de la st#chiométrie du dérivé d'allyle de formule (VI) en opérant, en milieu homogène ou hétérogène, en présence d'un initiateur consistant : - soit dans un activateur catalytique consistant dans : (i) au moins un catalyseur comprenant au moins un métal de transition ou un dérivé The process according to the invention for the preparation of the products of formula (I) proceeds almost quantitatively, without using reagents and / or without forming secondary products which are toxic or polluting compounds for the environment (such as H 2 S and alkali metals in the case of the polysulfuration step), # The starting material in step b) of formula (VII) can be prepared according to the following method: step a)

the symbol Hal represents a halogen atom chosen from chlorine, bromine and iodine atoms, the chlorine atom being preferred, and the symbols A, R 2 and R 3 are as defined above, the reaction is carried out by: # reacting at a temperature ranging from -10 ° C. to 200 ° C., one mole of the diorganohalosilane of formula (V) with a stoichiometric molar quantity or different from the stoichiometry of the allyl derivative of formula (VI) operating in a homogeneous medium or heterogeneous, in the presence of an initiator consisting of: - either in a catalytic activator consisting of: (i) at least one catalyst comprising at least one transition metal or a derivative

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said metal, taken from the group consisting of Co, Ru, Rh, Pd, Ir and Pt; andoptionally (2i) at least one hydrosilylation reaction promoter, either in a photochemical activator, in particular in suitable ultraviolet radiation or in suitable ionizing radiation, and optionally isolating the diorganohalosilylpropyl derivative of formula (VII) formed ;
According to a particularly suitable embodiment of the invention, the method which has just been described consists in following steps (a), (b) and (c), in the definition of which the removable group A corresponds to the symbol Hal representing a halogen atom selected from chlorine, bromine and iodine atoms, and preferably a chlorine atom.

 Step (a) consists in reacting the diorganohalosilane of formula (V) with the allyl derivative of formula (VI) in the presence of a chosen initiator. The initiator used includes all the initiators, of the types listed above, which are effective in activating the reaction between a Si SiH function and an ethylenic unsaturation.

According to a preferred arrangement concerning the initiator, the latter is chosen from catalytic activators. These catalytic activators comprise: (a) catalyst (s) (i): (i-1) at least one finely divided elementary transition metal; and / or (i-2) a colloid of at least one transition metal; and / or (i-3) an oxide of at least one transition metal; and / or (i-4) a salt derived from at least one transition metal and a carboxylic mineral acid; and / or (i-5) a complex of at least one transition metal equipped with organic ligand (s) capable of possessing one or more heteroatom (s) and / or organosilicon ligand (s); and / or (i-6) a salt as defined above wherein the metal part is equipped with ligand (s) as defined (s) also supra; and / or (i-7) a metal species chosen from the above-mentioned species (elementary transition metal, oxide, salt, complex, complexed salt) where the transition metal is associated this time with at least one other metal chosen from the family elements of groups 1b, 2b, 3a, 3b, 4a, 4b, 5a, 5b, 6b, 7b, and 8 (except Co, Ru, Rh,
Pd, Ir and Pt) of the Periodic Table as published in "Hanbook of
Chemistry and Physics, 65th Edition, 1984-1985, CRC Press, Inc. ", said other metal being taken in its elemental form or in a molecular form, said combination being able to give rise to a bi-metallic or multi-metallic species, and / or (i-8) a metal species selected from the above-mentioned species (elementary transition metal and transition metal association - other metal, oxide, salt,

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 complex and salt complexed on a transition metal base or on a transition metal - other metal base combination which is supported on an inert solid support such as, for example, alumina, silica, carbon black, a clay, oxide titanium, an aluminosilicate, a mixture of oxides of aluminum and zirconium, a polymeric resin; under the optional promoter (s) (2i): a compound, which may for example be in the form of a ligand or of an ionic compound, taken in particular from the group formed by: an organic peroxide; a carboxylic acid; a carboxylic acid salt; a tertiary phosphine; an amine; a friend of ; a linear or cyclic ketone; a trialkylhydrogensilane; benzothriazole; phenothiazine; a trivalent metal compound (C6H5) 3 where metal = As, Sb or P; a mixture of amine or cyclohexanone with an organosilicon compound comprising one or more group (s) = Si-H; the compounds CH2 = CH-CH2-OH or CH2 = CH-CH2-OCOCH3; a lactone; a mixture of cyclohexanone with triphenylphosphine; an ionic compound such as, for example, an alkali metal or imidazolinium nitrate or borate, a phosphonium halide, a quaternary ammonium halide, a tin halide II.

 According to a more preferred provision relating to the initiator, the latter is chosen from the preferred catalytic activators mentioned above which comprise, under the catalyst (s) (i), one and / or the other metal species (i-1) to (i-8) where the transition metal belongs to the following subgroup: Ir and Pt.

According to an even more preferred embodiment concerning the initiator, the latter is chosen from the preferred catalytic activators mentioned above which comprise, under the catalyst (s) (i), one and / or the other metal species (i-1) to (i-8) where the transition metal is Ir. Within the framework of this even more preferred arrangement, suitable Ir-based catalysts are in particular: [IrCl (CO ) (PPh3) 2] [Ir (CO) H (PPh3) 3] [Ir (C8H12) (C5H5N) P (C6H11) 3] PF6 [IrCl3], nH2O
H2 [IrCl6], nH2O (NH4) 2IrCl6
Na2lrCI6 K2ClCI6
Klr (NO) Cl5 [Ir (C8H12) 2] + BF4-

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[IRCl (CO) 3] n H2IrCl6
Ir 4 (CO) 12 1 (CO) 2 (CH 3 COCHCOCH 3) Ir (CH 3 COCHCOCH 3)
IrBr3
IrCl 3
IrCl4
IrO2 (C6H7) (C8H12) Ir.

 Within the framework of the still more preferred arrangement mentioned above, other Ir-based catalysts which are even more suitable are taken from the group of iridium complexes of the formula: [lr (R 4) Hal] 2 ( XI) in which: the symbol R4 represents a conjugated or non-conjugated polyene ligand, linear or cyclic (mono or polycyclic), having from 4 to 22 carbon atoms and from 2 to 4 ethylenic double bonds; the symbol Hal is as defined above.

 Examples of the iridium complexes of formula (XII) which are more particularly suitable are those in the formula of which: # the symbol R 4 is chosen from 1,3-butadiene, 1,3-hexadiene, cyclohexadiene- 1,3, 1,3-cyclooctadiene, 1,5-cyclooctadiene, 1,5,9-cyclododecatriene and norbornadiene, and # the Hal symbol represents a chlorine atom.

di--chtorobis(Ti-1,5-hexadiene)diiridium, di-u-bromobis(rl-1,5-hexadiene)düridium, di-p-iodobis(rl-1,5-hexadiene)düridium, di-jj-chtorobis(T)-1,5-cyctooctadiene)diiridium, di-p,-bromobis(rl-1,5-cyclooctadiene)düridium, di-Il-iodobis( fI-1 ,5-cyclooctadiene )diiridium, di-p,-chlorobis(rl-2,5-norbornadiene)düridium, di-p,-bromobis(rl-2,5-norbornadiene)diiridium, As specific examples of iridium complexes which are even more suitable, mention may be made of the following catalysts:

di-Chtorobis (Ti-1,5-hexadiene) diiridium, di-u-bromobis (1H-1,5-hexadiene) ditridium, di-p-iodobis (1H-1,5-hexadiene) dichloride, di-d -chtorobis (T) -1,5-cyctooctadiene) diiridium, di-p, -bromobis (α-1,5-cyclooctadiene) dichloridium, di-II-iodobis (1H-1,5-cyclooctadiene) diiridium, di-p , -chlorobis (R1-2,5-norbornadiene) dichloridium, di-p, -bromobis (R1-2,5-norbornadiene) diiridium,

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di--iodobis(rl-2,5-norbornadiene)düridium.

di - iodobis (rl-2,5-norbornadiene) düridium.

 The catalyst can be used, and this is another preferred arrangement, in a homogeneous medium, as described in JP-B-2,938,731. In this context, the reaction can be carried out either continuously, semi-continuously or discontinuously. At the end of the operation, the product of the reaction is separated and collected by distillation of the reaction medium, and it is possible to recycle the catalyst by carrying out a new batch of reactants on a distillation residue containing the catalyst resulting from the reaction stage. distillation of the product of the preceding operation, with possible additional addition of new catalyst. In the case of the use of complexes, the recycling of the catalyst can be improved by also adding a small amount of ligand.

 The catalyst can be used again in a heterogeneous medium. This procedure uses in particular the implementation of a catalyst which is supported on an inert solid support of the type defined above. This procedure makes it possible to carry out the reaction in a fixed bed reactor operating continuously, semi-continuously or discontinuously with recycling. It is also possible to carry out the reaction in stirred standard reactor operating continuously, semi-continuously or discontinuously.

 As regards the other reaction conditions, the reaction is carried out in a wide temperature range preferably ranging from -10 ° C. to 100 ° C., operating under atmospheric pressure or at a pressure greater than atmospheric pressure which can reach or even exceed 20.105Pa.

 The amount of the allyl derivative of formula (VI) used is preferably 1 to 2 moles per 1 mole of organosilicon compound. As for the amount of catalyst (s) (i), expressed as weight of transition metal taken from the group formed by Co, Ru, Rh, Pd, Ir, and Pt, it is in the range from 1 to 10,000 ppm, preferably from 10 to 2000 ppm and more preferably from 50 to 1000 ppm, based on the weight of organosilicon compound of formula (V) or (IX).

The amount of promoter (s) (2i), when one or more is used, expressed in number of moles of promoter (s) per gram atom of transition metal taken from the group consisting of Co, Ru, Rh, Pd , Ir and Pt, is in the range from 0.1 to 1000, preferably from 0.5 to 500 and more preferably from 1 to 300. The diorganohalogénosilylpropyl derivative of formula (VII) is obtained with a molar yield at least equal to 80% based on the organosilicon compound of formula (V) starting.

 According to a preferred arrangement, the anhydrous metal polysulfides of formula (X) are prepared by reaction of an alkali metal sulphide, optionally containing water of crystallization, of formula M2S (XII) where the symbol M has the meaning given above.

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 (alkali metal), with elemental sulfur operating at a temperature ranging from 60 C to 300 C, optionally under pressure and optionally again in the presence of an anhydrous organic solvent.

 Advantageously, the alkali metal sulphide M2S used is the commercially available compound which is generally in the form of a hydrated sulphide; a suitable alkali metal sulfide of this type is the commercially available Na2S sulfide which is a hydrated sulfide containing 55 to 65% by weight of Na2S.

 According to a more preferred embodiment of step (c), the anhydrous metal polysulfides of formula (X) are prepared beforehand from an alkali metal sulphide M2S in the form of a hydrated sulphide, according to a process consisting in sequence the following operating phases (1) and (2): # phase (1), where dehydration of the hydrated alkali sulphide is carried out by applying the appropriate method which makes it possible to eliminate the water of crystallization while retaining the alkaline sulphide in the solid state, during the duration of the dehydration phase; # phase (2), which is then put into contact with a mole of dehydrated alkali sulfide obtained with n (x-1) moles of elemental sulfur, operating at a temperature ranging from 20 C to 120 C, optionally under pressure and optionally again in the presence of an anhydrous organic solvent, the above-mentioned factor n being in the range from 0.8 to 1.2 and the symbol x being as defined above.

 With regard to phase (1), as a dehydration protocol which is suitable, mention may be made in particular of the drying of the hydrated alkali sulphide, operating under a partial vacuum ranging from 1.33 × 10 2 Pa to 40 × 10 2 Pa and by bringing the compound to be dried to a temperature ranging, at the beginning of drying, from 70 ° C. to 85 ° C., and then gradually raising the temperature during drying from 70 ° C. to 85 ° C. until reaching the zone ranging from 125 ° C. to 135 ° C. , following a program providing for a first temperature rise of +10 C to +15 C after a first period varying from 1 hour to 6 hours, followed by a second temperature rise from +20 C to +50 C after a second time ranging from 1 hour to 4 hours.

 As regards the phase (2), as a suitable sulfurization protocol, mention may be made of carrying out this reaction in the presence of an anhydrous organic solvent; suitable solvents are in particular anhydrous aliphatic alcohols C1-C4 anhydrous, such as methanol or anhydrous ethanol. The number of elemental sulfur atoms Sx in the metal polysulfide M2Sx is a function of the molar ratio of S with respect to M2S; for example, the use of 3 moles of S (n = 1 and x-1 = 3) per mole of M2S gives the alkaline tetrasulfide of formula (X) where x = 4.

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 To come back to the realization of step (c), the latter is carried out in a wide temperature range preferably ranging from 50 ° C. to 90 ° C., more preferably operating in the presence of an organic solvent and, in this case, frame, we will advantageously use the alcohols mentioned above about the conduct of the phase (2).

 The product M-A, and in particular the halide M-Hal, formed during the reaction is generally removed at the end of the stage, for example by filtration.

 The bis (monoorganoxydiorganosilylpropyl) polysulfide of formula (I) formed is obtained with a molar yield at least equal to 80%, based on the monoorganoxydiorganosilylpropyl derivative of formula (IX) starting.

 The following examples illustrate the present invention without limiting its scope, reference will be made to the accompanying drawing, wherein the single figure shows schematically the reaction device comprising a distillation column used in said examples.

 In the single figure we see that the device 1 has at its base a boiler 2 and a column 3 40mm in diameter having a lower portion 4 including the column foot, and a rising portion 5, including the column head. The column comprises 15 trays rated 1 to 15. The trays are perforated glass. Column 3 is equipped with a feed tank ethanol 6 supplying the boiler 2 and some trays of the lower part 4 of the column, as well as a liquid recovery tank 7. Column 3 is equipped with a second tank 8 for optional supply of liquid ethanol for feeding some of the trays of the upper part of the column 3 to simulate a reflux of purified ethanol. Column 3 has a tray 9 for recovering the ethanol constituting the distillate and a silane feed tank 10 starting. It is seen that the silane is introduced on a plateau of the upper part of the column, in fact at the last plateau 15 in Examples 1 to 10 below. The upper part 5 of the column is capped with a condenser 11 connected by line 12 to the slagging column of HCI 13 (HCl trap).

Example 1
This example describes the preparation of bis (monoethoxydimethylsilylpropyl) tetrasulfide of formula (III) in which the number x is centered on

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Etape (c) :

The reaction scheme concerned by this example is the following: Step (a):

Step (c):

7 where the reagent 6 is obtained according to the equation:

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1) Step (a): synthesis of 3:
In a stirred reactor of 1 liter, made of glass, equipped with a jacket and a stirrer, surmounted by a distillation column, 165 g of allyl chloride 2 are charged to 97.5 g. % by weight of purity (2.10 moles) and 0.229 g of catalyst [Ir (COD) Cl] 2 where COD = 1,5-cyclooctadiene, and stirred to completely dissolve the catalyst. The temperature of the mixture is adjusted to 20 C using the thermal fluid circulating in the jacket.

 The dimethylhydrochlorosilane 1, purity 99% by weight is introduced by a dip tube into the reaction medium, using a pump: 196.5 g (2.06 moles) are introduced in 2 hours 35 minutes. The feed rate is adjusted to maintain the temperature of the reaction medium between 20 and 25 C, taking into account the high exotherm of the reaction. The reaction medium is stirred for 20 minutes after the end of the introduction of dimethylhydrochlorosilane 1.

 At the end of the holding time, a sample is taken for analysis. The results are as follows: degree of conversion of dimethylhydrochlorosilane 1 = 99.8%, and selectivity to chloropropyldimethylchlorosilane 3 = 92.7% (by gas chromatographic analysis).

 The reaction mixture is then distilled under vacuum (approximately 35 × 10 2 Pa) at about 40 ° C. in order to obtain two main fractions: light (allyl chloride 2 and traces of residual dimethylhydrochlorosilane 1, accompanied essentially by chloropropyldimethylchlorosilane 3, chloropropyldimethylchlorosilane 3, with a molar purity greater than 98%, there remains a distillation pellet consisting of heavier products and catalyst Molar yield: 85%.

2) Step (b): Synthesis of 5: As indicated above, a distillation column is used as shown in the single figure.

The chloropropyldimethylchlorosilane stored in the feed tank 10 and the ethanol stored in the feed tanks 1 and 3 are injected directly into the column 1, respectively to the trays 13 and 3. Column 1 is loaded with a suitable inert solvent in this case toluene. The role of the solvent is to stripper hydrochloric acid (HCl) by mechanical drive, the ethanol is also entrained and optionally recycled after purification. The solvent also creates a zone of exhaustion (no or very little HCI at the bottom of the column) which makes it possible to limit enormously the appearance of parasitic chemical reactions.

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Toluene is boiled in the boiler (2) by electrical resistors. This startup phase is carried out at total reflux of the column in order to load the trays of the column. The reflux flow rate is then adjusted by a valve located between the condenser (6) and the distillate recovery tank (4) and not shown in the single figure.

 The ethanol is injected into the column in the liquid or vapor phase at the plate n 3 of the lower part 4 of the column. The flow rate of ethanol is 100 g / h. Chloropropyldimethylchlorosilane is injected onto plate n 13 in the liquid phase, with a flow rate of 120 g / h. The molar ratio EtOH: silane is 3.17.

 Ethanol vaporizes in the column and meets during its ascent the chloropropyldimethylchlorosilane liquid phase which goes down to the boiler.

The experiment lasts for 5 hours and the overall conversion rate of chloropropyldimethylchlorosilane to chloropropyldimethylethoxysilane is 92 to 94% with a selectivity greater than 90%.

3) Step (c): synthesis of 7:
3. 1) Preparation of anhydrous Na2S4 6: # Phase 1: hydrated Na2S:
In a 1-liter glass flask of a rotary evaporator is charged 43.6 g of industrial hydrated Na2S in flakes containing about 60.5% by weight of Na2S. The flask is placed under an argon atmosphere and then placed under reduced pressure at 13.3.102 Pa.

 The balloon soaks in an oil bath, whose temperature is then raised to 76 C.

This temperature is maintained for 2 hours. Then, a protocol for increasing the temperature of the oil bath is applied, in order to avoid the melting of Na2S, which occurs between 85 and 90 C approximately. The gradual increase in temperature is intended to accompany the change in the melting temperature of the product to be dried, which increases when the product dehydrates. The protocol applied is as follows: 1 hour at 82 ° C., 2 hours at 85 ° C., 1 hour at 95 ° C., 1 hour at 115 ° C. and finally 1 hour at 130 ° C. Note that this protocol can be modified according to the quantity drying, operating pressure, and other parameters that influence the rate of water removal. The amount of water removed, measured by difference in mass, is 17.2 g, which corresponds to a moisture of 39.5% by weight.

# Phase (2): synthesis of Na2S4 6:
The dried Na2S (26 g), according to the protocol described above, is suspended in 400 ml of anhydrous ethanol, and transferred, by suction, into a stirred glass vessel of one liter, double wrapped, equipped with a condenser with possibility of reflux. We

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 In addition, 31.9 g of sulfur and 200 ml of anhydrous ethanol are added to this reactor. The temperature of the mixture is brought to about 80 ° C. (low boiling of ethanol), and it is stirred at 600 rpm. The mixture is maintained at 80 ° C. for 2 hours.

Gradually, the solids (Na2S and sulfur) disappear and the mixture changes from yellow to orange, then brown. At the end of the reaction, the mixture is homogeneous at 80 ° C.: about 58 g of anhydrous Na.sub.2S.sub.4 (0.33 mol) are available in 600 ml of ethanol.
3. 2) Preparation of 7:
To the anhydrous Na 2 S 4 in 600 ml of ethanol prepared previously, maintained in its preparation reactor at 80 ° C. (low boiling of ethanol) and stirred at 600 rpm, is introduced by a dip tube, using a pump, 114 g of chloropropyldimethylethoxysilane at 96.6% molar purity (ie 0.61 mol). A precipitate of sodium chloride appears. After the end of the introduction of chloropropyldimethylethoxysilane 5, the mixture is maintained at 80 ° C. for 2 hours. Then, the mixture is cooled to room temperature, withdrawn and filtered to remove suspended solids, including sodium chloride. The filter cake is washed with ethanol to extract the best organic products. The filtrate is reintroduced into the reactor to be distilled under reduced pressure (about 20.102 Pa) in order to remove the ethanol, and any light. 114 g of pellet is recovered, which corresponds to bis (monoethyoxydimethylsilylpropyl) tetrasulfide, assayed at 97% purity (molar).

 A mass yield of bis (monoethyoxydimethylsilylpropyl) tetrasulfide of 87% is obtained.

 Control by 1 H-NMR, 29 S-NMR and 13 C-NMR makes it possible to verify that the structure obtained is in accordance with the formula (III) given in the description.

 The average number of S atoms per molecule of formula (III) is equal to 3.9 0.1 (x = 3.9 0.1).

Example 2 to 8:
Step b) of Example 1 is repeated, except that the injection level of the alcohol in the column and / or the EtOH / silane molar ratio and / or the reflux ratio are changed. The results obtained are collated in Table 1 below or TT and RT respectively represent the degree of conversion and the selectivity:

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Table 1

<Tb>
<tb> Example <SEP> Tray <SEP> Tray <SEP> ratio <SEP> molar <SEP> TT <SEP> RT <SEP> Rate <SEP> of
Injection <SEP> injection <SEP> EtOH / silane <SEP> reflux
<tb> EtOH <SEP> silane
<tb> 1 <SEP> 12 <SEP> 13 <SEP> 1,2 <SEP> 20 <SEP> 88 <SEP> 0,5
<tb> 2 <SEP> 12 <SEP> 13 <SEP> 3 <SEP> 70 <SEP> 93 <SEP> 0.5 <SEP>
<tb> 3 <SEP> 12 <SEP> 13 <SEP> 6 <SEP> 68 <SEP> 91 <SEP> 0.5
<tb> 4 <SEP> 3 <SEP> 13 <SEP> 1,2 <SEP> 35 <SEP> 89 <SEP> 0,5
<tb> 5 <SEP> 3 <SEP> 13 <SEP> 3 <SEP> 92 <SEP> 91 <SEP> 0.5 <SEP>
<tb> 6 <SEP> 3 <SEP> 13 <SEP> 6 <SEP> 91 <SEP> 91 <SEP> 0.5 <SEP>
<tb> 7 <SEP> 3 <SEP> 13 <SEP> 10 <SEP> 89 <SEP> 90 <SEP> 0.5
<tb> 8 <SEP> 3 <SEP> 13 <SEP> 3 <SEP> 93.5 <SEP> 86 <SEP> 1
<Tb>

From Table 1, it appears that it is preferable to have an EtOH / silane molar ratio of greater than 3 in order to be assured of achieving TT and RT values greater than 90.

 We also see that it is preferable to inject EtOH on the plate 3 rather than on the plate 12. It is assumed that in the latter case, the reaction volume is insufficient.

 Another important parameter is the reflux ratio. This reflux rate controls the temperature level in the column but especially the amount of HCl (solubilized in ethanol). And this acid is the activator of parasitic chemical reactions: Example 8 is carried out with a reflux twice as great as Example 5, and all other things being equal, leads to a slight increase in yield but to the detriment of selectivity (respectively 86 and 91% for Examples 8 and 5).

 Example 9: A reactive distillation is carried out in the same column as the preceding examples but without inert solvent. This time, the boiler (2) is charged with ethanol (1200ml). Column (1) is charged by boiling the ethanol of the boiler (2) and working at total reflux. Once the steady state is reached, the reflux is adjusted and 3chloropropyldimethylchlorosilane is injected onto the plate 13.

The flow rate of ethanol (gas phase) is controlled by keeping the level in the boiler constant. The flow rate of ethanol is 1000 g / h, and the rate of chloropropyldimethylchlorosilane 150 g / h, a molar ratio EtOH: silane 25. The reaction yield is 100% regardless of the reflux ratio. On the other hand,

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 The selectivity is a function of this reflux ratio: from 50% for reflux from 750 g / h to over 85% for no reflux. It should be noted that in the column used, even at zero reflux, a fraction of the ethanol is condensed directly in the column. This can be avoided by introducing chloropropyldimethylchlorosilane preheated to 80 ° C to prevent cooling of the ethanol and its condensation.

Example 10
Same experiment as Example 3 with introduction of chloropropyldimethylchlorosilane to plate n 7. The results are identical to the previous example: TT 100% and RT> 85%.

Claims (21)

1. Process for preparing an organodialkylalkoxysilane of formula (IX) R1O ------- (R2R3) Si --- (CH2) 3 --- A by reactive distillation, during a step b), of a silane of formula (VII): Hal --- (R2R3) Si- (CH2) 3 --- A in the presence of an alcohol of formula (VIII): R'-OH and by carrying out the alkanolysis reaction of said silane inside of a distillation column, with stripping of the product of formula H-Hal formed and recovery of the organodialkylalkoxysilane formed in the column, formulas in which: the symbol Hal represents a halogen atom chosen from chlorine atoms, bromine; and iodine, the chlorine atom being preferred, the symbols R 1, which are identical or different, each represent a monovalent hydrocarbon group chosen from a linear or branched alkyl radical having from 1 to 15 carbon atoms and a linear alkoxyalkyl radical; or branched, having from 2 to 8 carbon atoms; the symbols R 2 and R 3, which are identical or different, each represent a monovalent hydrocarbon group chosen from a linear or branched alkyl radical having 1 to 6 carbon atoms and a phenyl radical - A represents a removable group selected from: either a Hal halogen atom belonging to the chlorine, bromine and iodine atoms, the chlorine atom being preferred; or a radical para-R0-C6H4-SO2-O- where R is an alkyl radical, linear or branched in C1-C4, the para-CH3-C6H4-SO2-O- tosylate radical being preferred; a radical R - SO2-O- wherein R is as defined above, the mesylate radical CH3-SO2-0- being preferred; is a radical R -CO-O- where R is as defined above, the acetate radical CH3-CO- 0- being preferred, the most preferred radical A being the chlorine atom. 2. Method according to claim 1, characterized in that within the column at least one of the products of formula H-Hal, (VII), (VIII), or (IX) is in the vapor state . 3. Method according to claim 1 or 2, characterized in that the alkanolysis reaction is carried out inside the column at a temperature between the boiling point of the alkanol of formula (VIII) and the boiling point of the starting silane of formula (VII), the reaction being carried out in the column either at atmospheric pressure or at reduced pressure or at superatmospheric pressure <Desc / Clms Page number 21>  4. Method according to any one of claims 1 to 3, characterized in that the products of formulas (I) to (XI) have ethyl groups R1, R2 and R3 methyl and A and Hal represent a chlorine atom. 5. Process according to claim 4, characterized in that the silane 3chloropropyldimethylchlorosilane is introduced at the top of the column, ethanol at the bottom of the column, the reaction temperature in the column is greater than 77.80 ° C. and less than 178 ° C. atmospheric pressure and the hydrochloric acid formed is stripped with ethanol. 6. Process according to claim 1 to 3, characterized in that the reaction is carried out in the presence in the presence of an organic solvent or an inert gas, said solvent having a boiling point at the operating pressure. between the boiling point of ethanol of formula (VIII) and that of the silane of formula (VII). 7. Process according to claim 6, characterized in that the solvent is toluene, monochlorobenzene, or xylene and the products corresponding to formulas (I) to (XI) have R1, R2 and R3 methyl groups and A and Hal represent a chlorine atom. 8. Process according to claim 1, 2, 6 or 7, characterized in that the pressure inside the column is the atmospheric pressure. 9. The method of claim 1,2, 6 or 7 characterized in that the pressure inside the column is less than or greater than the atmospheric pressure.  10. Process according to any one of claims 4,5, 7,8 or 9, characterized in that the molar ratio of ethanol / silane is greater than 3.  11. Method according to any one of claims 4,5, 7,8, 9, or 10, characterized in that the reflux ratio is zero.  12. Process according to any one of claims 1 to 11, characterized in that the distillation column is a tray column comprising from 5 to 50 trays or a bulk packed column or ordered. <Desc / Clms Page number 22>  13. Process for the preparation of bis (monoorganoxysilypropyl) polysulfides of formula:

 wherein: x is an integer or fractional number ranging from 1.5 + 0.1 to 5 ~ 0.1; and the symbols R1, R2, R3, Hal and A are as defined above, by implementing step (c) which proceeds according to the equation:

 the symbols R 1, R 2, R 3, A and x are as defined above, and the symbol M represents an alkali metal, the reaction being carried out: by reacting at a temperature ranging from 20 ° C. to 120 ° C., ie the reaction medium obtained after step (b) as defined in any one of claims 1 to 12, the monoorganoxydiorganosilylpropyl derivative of formula (IX) taken separately after separation from said reaction medium, with the metal polysulfide of formula (X) in the anhydrous state, using 0.5 15 mol% of metal polysulfide of formula (X) per mole of the reagent of formula (IX) and optionally operating in the presence of a polar (or non-polar) organic solvent ) and - isolating the bis- (monoorganoxysilylpropyl) polysulfide of formula (1) formed. <Desc / Clms Page number 23>  or: the symbol Hal represents a halogen atom chosen from among the chlorine, bromine and iodine atoms, the chlorine atom being preferred, and the symbols A, R2 and R3 are as defined above, the reaction being carried out by reacting at a temperature ranging from -10 ° C. to 200 ° C. one mole of the diorganohalosilane of formula (V) with a stoichiometric molar quantity or different from the stoichiometry of the allyl derivative of formula (VI) by operating, in a homogeneous or heterogeneous medium, in the presence of an initiator consisting of: either in a catalytic activator consisting of: (i) at least one catalyst comprising at least one transition metal or a derivative of said metal, taken from the group formed by Co Ru, Rh, Pd, Ir and Pt; andoptionally (2i) at least one hydrosilylation reaction promoter, either in a photochemical activator, in particular in suitable ultraviolet radiation or in suitable ionizing radiation, and optionally isolating the diorganohalosilylpropyl derivative of formula (VII) formed;

 14. The method of claim 13, characterized in that the starting material in step b) of formula (VII) can be prepared during step a) according to the following method: 15. Process according to claim 14, characterized in that it is carried out by chaining either the steps (a), (b) and (c), in the definition of which the removable group A corresponds to the symbol Hal representing an atom of halogen is a chlorine atom.  16. Process according to claim 14, characterized in that step (a) is carried out by operating in the presence of a catalytic activator which <Desc / Clms Page number 24>  comprises, as catalyst (s) (i), one or both of the following metal species: (i-1) at least one finely divided elemental transition metal; and / or (i-2) a colloid of at least one transition metal; and / or (i-3) an oxide of at least one transition metal; and / or (i-4) a salt derived from at least one transition metal and a carboxylic mineral acid; and / or (i-5) a complex of at least one transition metal equipped with organic ligand (s) capable of possessing one or more heteroatom (s) and / or organosilicon ligand (s); and / or (i-6) a salt as defined above wherein the metal part is equipped with ligand (s) as defined (s) also supra; and / or (i-7) a metal species chosen from the above-mentioned species (elementary transition metal, oxide, salt, complex, complexed salt) where the transition metal is associated this time with at least one other metal chosen from the family elements of Groups 1b, 2b, 3a, 3b, 4a, 4b, 5a, 5b, 6b, 7b, and 8 (except Co, Ru, Rh, Pd, Ir and Pt) of the Periodic Table (same reference), said other metal being taken in its elemental form or in a molecular form, said combination being able to give rise to a bimetallic or multi-metallic species; and / or (i-8) a metal species selected from the above-mentioned species (elemental transition metal and transition metal association other metal; oxide, salt, complex and salt complexed on a transition metal basis or on a transition metal association basis) other metal) which is supported on an inert solid support such as alumina, silica, carbon black, clay, titanium oxide, aluminosilicate, a mixture of aluminum oxides and zirconium, a polymer resin.  17. The method of claim 16, characterized in that step (a) is carried out operating in the presence of a catalytic activator which comprises, under (or) catalyst (s) (i), one of and / or the other metal species (i-1) to (i-8) where the transition metal belongs to the subgroup formed by Ir and Pt.  18. Process according to claim 16, characterized in that step (a) is carried out operating in the presence of a catalytic activator which comprises, as (or) catalyst (s) (i), one of and / or the other metal species (i-1) to (i-8) where the transition metal is Ir.  19. The method of claim 18, characterized in that step (a) is carried out in the presence of a catalytic activator which comprises, as (or) catalyst (s) (i), at least one type (i-5) metal species belonging to the iridium complexes of formula: <Desc / Clms Page number 25>  where: - the symbol R4 represents a conjugated or unconjugated polyene ligand, linear or cyclic (mono or polycyclic), having from 4 to 22 carbon atoms and from 2 to 4 ethylenic double bonds; the symbol Hal is as defined above. 20. Process according to any one of claims 13 to 19, characterized in that step (c) is carried out by engaging anhydrous metal polysulfides of formula (X) which are prepared beforehand from an alkaline sulfide M2S in the form of a hydrated sulphide, according to a process consisting in linking the following operating phases (1) and (2): # phase (1), in which the hydrated alkali sulphide is dehydrated by applying the appropriate method which allows to eliminate the water of crystallization while retaining the alkali metal sulphide in the solid state, during the duration of the dehydration phase; # phase (2), which is then put into contact with a mole of dehydrated alkali sulfide obtained with n (x-1) moles of elemental sulfur, operating at a temperature ranging from 20 C to 120 C, optionally under pressure and optionally again in the presence of an anhydrous organic solvent, the above-mentioned factor n being in the range from 0.8 to 1.2 and the symbol x being as defined above 21. Process according to any one of Claims 13 to 20, characterized in that the products corresponding to formulas (I) to (XI) have ethyl groups R1, R2 and methyl R3 and A and Hal represent a chlorine atom.