FR2710339A1 - Process for the preparation of fuchsones - Google Patents

Abstract

The subject of the present invention is a process for the preparation of fuchsones. The process for the preparation of a fuchsone according to the invention, which consists in reacting a phenol compound having at least one hydrogen atom in the para position and a non-enolisable ketone compound in the presence of an acid catalyst, is characterised in that the reaction is carried out in the presence of an effective amount of an ionisable sulphur-containing compound.

Description

PROCESS FOR THE PREPARATION OF FUCHSONES
The present invention relates to a process for preparing fuchsones.

In the following description of the present invention, the term "fuchsone" means any chemical compound comprising the following 1,4-methylene quinone unit:

 The applicant proposed in French patent application No. 93 00120, filed on January 8, 1993, a new process for the preparation of a fuchsone, the characteristic of which is to react a phenolic compound having a hydrogen atom in the para position of the hydroxyl group and a non-insoluble ketone compound, in the presence of an effective amount of an acid.

 By "non-enolisable ketone compound" is meant a ketone which has two tertiary carbon atoms in position a of the carbonyl group.

 Continuing her research, the Applicant has found that the said process could be improved, by conducting the reaction in the presence of an additive, namely an ionizable sulfur compound.

 Thus, it has now been found, and this is what is the subject of the present invention, a process for the preparation of a fuchsone which consists in reacting a phenolic compound having at least one hydrogen atom in the para position and a non-insoluble ketone compound, in the presence of an acid catalyst, characterized in that the reaction is carried out in the presence of an effective amount of an ionizable sulfur compound.

 By "ionizable sulfur compound" is meant any sulfur compound which ionizes in the presence of water to give an ion having a free valence on the sulfur atom.

 In accordance with the invention, it has been found that the use of such a compound makes it possible to increase the reaction kinetics. Thus, it has been found that the speed of formation of fuchsone was considerably increased and that it could be multiplied by ten or even more.

dans ladite formule (I) - la position en para est libre, - R1, R2, R3 et R4, identiques ou différents représentent un atome d'hydrogène ou un substituant quelconque, - deux groupes R1 et R2 et/ou R3 et R4 placés sur deux atomes de carbone vicinaux peuvent former ensemble et avec les atomes de carbone qui les portent un carbocycle saturé, insaturé ou aromatique ayant de 4 à 7 atomes de carbone, - R' représente un atome d'hydrogène, un radical alkyle linéaire ou ramifié ayant de 1 à 12 atomes de carbone, un radical carbocyclique éventuellement substitué qui peut être un radical cycloalkyle ayant de 5 à 12 atomes de carbone, un radical aryle ayant de 6 à 12 atomes de carbone, un radical aralkyle ayant de 7 à 14 atomes de carbone.A phenolic compound and a ketone compound are therefore reacted according to the invention, in the presence of an acid catalyst and a sulfur compound.
The present invention applies very particularly to the phenolic compound of general formula (I):

in said formula (I) - the position in para is free, - R1, R2, R3 and R4, identical or different, represent a hydrogen atom or any substituent, - two groups R1 and R2 and / or R3 and R4 placed on two vicinal carbon atoms can form together and with the carbon atoms which carry them a saturated, unsaturated or aromatic carbocycle having from 4 to 7 carbon atoms, - R 'represents a hydrogen atom, a linear or branched alkyl radical having from 1 to 12 carbon atoms, an optionally substituted carbocyclic radical which may be a cycloalkyl radical having from 5 to 12 carbon atoms, an aryl radical having from 6 to 12 carbon atoms, an aralkyl radical having from 7 to 14 atoms of carbon.

The process of the invention applies to any phenolic compound corresponding to the general formula (I) and, more particularly, to the phenolic compounds of formula (I) in which - the radical R 'represents one of the following groups:
a hydrogen atom
a linear or branched alkyl radical having from 1 to 6 carbon atoms,
a cyclohexyl radical,
a phenyl radical,
a benzyl radical, - R1, R21 R3 and R4, identical or different, represent Rg, one of the following groups
a hydrogen atom,
an alkyl radical, linear or branched, having from 1 to 6 carbon atoms, of
preferably from 1 to 4 carbon atoms, such as methyl, ethyl, propyl,
isopropyl, butyl, isobutyl, sec-butyl, tert-butyl,
a linear or branched alkenyl radical having from 2 to 6 carbon atoms,
preferably from 2 to 4 carbon atoms, such as vinyl, allyl,
a linear or branched alkoxy radical having from 1 to 6 carbon atoms, of
preferably from 1 to 4 carbon atoms such as methoxy radicals,
ethoxy, propoxy, isopropoxy, butoxy,
an acyl group having from 2 to 6 carbon atoms,
a radical of formula:
-Rs-OH
- R5-COOR6
-Rs-X
-R5-CF3
in said formulas, R5 represents a valential bond or a radical
divalent hydrocarbon, linear or branched, saturated or unsaturated, having from 1 to 6
carbon atoms such as, for example, methylene, ethylene, propylene,
isopropylene, isopropylidene; R6 represents a linear alkyl radical or
branched having from 1 to 6 carbon atoms; X symbolizes an atom
halogen, preferably a chlorine, bromine or fluorine atom.

dans lequel R5 représente un lien valentiel ou un radical hydrocarboné divalent, linéaire ou ramifié, saturé ou insaturé ayant de 1 à 6 atomes de carbone tel que par exemple, méthylène, éthylène, propylène, isopropylène, isopropylidène et Rg ayant la signification donnée précédemment et m est un nombre entier de O à 4, un radical - R5 - A - R8 dans lequel R5 a la signification donnée précédemment, R8 représente un radical alkyle linéaire ou ramifié ayant de 1 à 6 atomes de carbone ou un radical

et A symbolise l'un des groupes suivants:

dans ces formules, Rg représente un atome d'hydrogène ou un radical alkyle ayant de 1 à 4 atomes de carbone, un radical cyclohexyle ou phényle. - R1, R2, R3 and R4, identical or different, represent R7, one of the following more complex radicals:
a cyclohexyl radical,
a radical of formula

in which R5 represents a valential bond or a divalent, linear or branched, saturated or unsaturated hydrocarbon radical having from 1 to 6 carbon atoms such as, for example, methylene, ethylene, propylene, isopropylene, isopropylidene and Rg having the meaning given above and m is an integer from O to 4, a radical - R5 - A - R8 in which R5 has the meaning given above, R8 represents a linear or branched alkyl radical having from 1 to 6 carbon atoms or a radical

and A symbolizes one of the following groups:

in these formulas, Rg represents a hydrogen atom or an alkyl radical having from 1 to 4 carbon atoms, a cyclohexyl or phenyl radical.

- two groups R1 and R2 and / or R3 and R4 placed on two vicinal carbon atoms can form together and with the carbon atoms which carry them a saturated, unsaturated or aromatic carbocycle having 6 carbon atoms,
The phenolic compound of formula (I) can carry one or more substituents. Examples of substituents are given above, but this list is in no way limiting. Any substituent can be present on the cycle as long as it does not interfere with the desired product.

Among the compounds of formula (I), use is more particularly made of those corresponding to formula (I) in which: the radical R ′ represents one of the following groups:
a hydrogen atom
a linear or branched alkyl radical having from 1 to 4 carbon atoms,
a cyclohexyl radical,
a phenyl radical, - R1, R2 (R3 and R4, identical or different, represent one of the following groups:
a hydrogen atom,
an alkyl radical, linear or branched having from 1 to 4 carbon atoms ,.
a linear or branched alkoxy radical having from 1 to 4 carbon atoms,
a hydroxyl group,
a halogen atom, a group -CF3
a cyclohexyl radical,
a phenyl radical, - two groups R1 and R2 and / or R3 and R4 placed on two vicinal carbon atoms can form together and with the carbon atoms which carry them a benzene ring.

Even more preferably, the compounds of formula (I) are chosen in which R ′ represents a hydrogen atom and R1 represents a hydrogen atom, a hydroxyl group, a methyl radical, a methoxy radical and R2,
R3 and R4 represent a hydrogen atom.

By way of illustration of phenolic compounds of formula (I) capable of being used in the process of the invention, there may be mentioned more particularly:
- those corresponding to formula (I) in which R1, R2, R3 and R4
represent a hydrogen atom, such as phenol or an isolate,
- those corresponding to formula (I) with a substituent on the cycle
benzene, such as ortho-cresol, metacresol, 2-methoxyphenol,
Ethyl 2-phenol, ethyl 3-phenol, propyl-2 phenol, sec-butyl-2-phenol,
tert-butyl-2 phenol, tert-butyl-3 phenol, methoxy-2 phenol, methoxy-3
phenol, methyl salicylate, 2-chloro-phenol, 3-chloro-phenol,
- those corresponding to formula (I) with two substituents on the cycle
benzene, such as 2,3-dimethylphenol, 2,5-dimethylphenol,
2,6-dimethyl phenol, 3,5-dimethyl phenol, 2,3-dichloro phenol,
2,5-dichloro-phenol, 2,6-dichloro-phenol, 3,5-dichloro-phenol,
- those corresponding to formula (I) with three substituents on the cycle
benzene, such as 2,3,5,5-trimethylphenol, 2,3,6-trimethylphenol,
ditert-butyl-2,6 phenol, ditert-butyl-3,5 phenol, trichloro-2,3,5 phenol,
2,3,6-trichloro phenol,
- those corresponding to formula (I) in which R1 and R2 form a ring
benzene, such as hydroxy-naphthalene,
- those corresponding to formula (I) in which R1 represents a radical of
type R7, such as phenoxy-2 phenol, phenoxy-3 phenol.

Among the phenolic compounds of formula (I) which may be used in the process of the invention, non-limiting mention may be made of phenol,
Anisole, orthocresol, metacresol.

 As mentioned above, the characteristic of the ketone compound involved in the process of the invention is that it is a non-insoluble ketone.

dans ladite formule (Il) - Ra et Rb, identiques ou différents sont des radicaux hydrocarbonés ayant chacun de 3 à 30 atomes de carbone; les atomes de carbone de chaque radical
Ra et Rb en position a par rapport au groupe carbonyle étant des carbones tertiaires.More specifically, it corresponds to the following formula (II):

in said formula (II) - Ra and Rb, identical or different are hydrocarbon radicals each having from 3 to 30 carbon atoms; the carbon atoms of each radical
Ra and Rb in position a with respect to the carbonyl group being tertiary carbons.

 Examples of radicals Ra and Rb which are very suitable for the present invention, there may be mentioned, among others, branched alkyl radicals having at least 3 carbon atoms and aryl radicals having at least 6 carbon atoms and more particularly radicals tert-butyl, tert-pentyl, tert-hexyl or optionally substituted phenyl.

dans ladite formule (Il') - Rai, Ra2, Ra3 et Rabi, Rb2, Rb3 identiques ou différents, représentent des radicaux alkyle linéaires ou ramifiés ayant de 1 à 10 atomes de carbone, des radicaux cyclohexyle, phényle ou napthyle éventuellement substitués, Ral, Ra2, Ra3 et/ou Rbl, Rb2, Rb3 peuvent former ensemble et avec l'atome de carbone qui les porte un cycle benzénique ou naphtalénique éventuellement substitué ; éventuellement les deux groupes Ral et Rbl peuvent être liés ensemble par un lien valentiel ou par un groupe -CH2- formant ainsi un cycle cétonique qui peut être saturé ou insaturé.The ketone compounds suitable for the present invention can be represented more precisely by the following general formula (II ′):

in said formula (II ') - Rai, Ra2, Ra3 and Rabi, Rb2, Rb3 identical or different, represent linear or branched alkyl radicals having from 1 to 10 carbon atoms, cyclohexyl, phenyl or naphthyl radicals optionally substituted, Ral , Ra2, Ra3 and / or Rbl, Rb2, Rb3 can form together and with the carbon atom which carries them an optionally substituted benzene or naphthalene ring; optionally the two groups Ral and Rbl can be linked together by a valential bond or by a group -CH2- thus forming a ketone cycle which can be saturated or unsaturated.

dans ladite formule (lla): - Rc et Rd identiques ou différents représentent un atome d'hydrogène ou un substituant, - n1, n2 identiques ou différents est un nombre égal à 0, 1,2 ou 3, - éventuellement les deux atomes de carbone situés en position a par rapport aux deux atomes de carbone portant le groupe - CO peuvent être liés ensemble par un lien valentiel ou par un groupe - CH2 - formant ainsi un cycle cétonique qui peut être saturé mais aussi insaturé.Among all the ketone compounds corresponding to formula (II), special use is made of ketone compounds corresponding to the following formula (IIa):

in said formula (IIIa): - Rc and Rd identical or different represent a hydrogen atom or a substituent, - n1, n2 identical or different is a number equal to 0, 1,2 or 3, - optionally the two atoms of carbon located in position a with respect to the two carbon atoms carrying the group - CO can be linked together by a valential bond or by a group - CH2 - thus forming a ketone cycle which can be saturated but also unsaturated.

 The substituent is chosen so that it does not react under the acidity conditions of the invention. Among other things, it may be a functional group.

 Examples of substituents which are very suitable for the invention are the following: - linear or branched alkyl radicals having from 1 to 4 carbon atoms, - the phenyl radical, - the alkoxy radicals R10 - O in which R10 represents a linear alkyl radical or branched having from 1 to 4 carbon atoms or the phenyl radical, - the hydroxyl group, - the fluorine atom.

 As examples of ketone compounds which are particularly suitable for the invention, mention may very particularly be made of ketone compounds corresponding to the general formula (IIa) in which Ru and Rd, identical or different, represent a hydrogen atom or a substituent as mentioned above, preferably in position 4,4 ′ and n1, n2 identical or different are equal to 0 or 1.

 Use is preferably made of ketone compounds corresponding to formula (IIa) in which Rc and Rd identical or different represent a hydrogen atom; a methyl, ethyl, tert-butyl, phenyl radical; a methoxy or ethoxy radical; a hydroxyl group, preferably in the 3.3 ′ or 4.4 ′ position.

As specific examples of ketones which can be used in the process of the invention, there may be mentioned more particularly:
- benzophenone
- 2-methyl benzophenone
- 2,4-dimethyl benzophenone
- 4,4 'dimethyl benzophenone
- 2,2-dimethyl benzophenone
- 4,4 'dimethoxy benzophenone
- 4-hydroxy benzophenone
- dihydroxy-4-4 'benzophenone
- 4-benzoyl biphenyl
According to the process of the invention, the phenolic compound of formula (I) is reacted with the ketonic compound of general formula (II), in the presence of an acid catalyst and of a sulfur compound.

 The catalyst suitable for the invention is chosen such that it has an acidity function - Ho of between 5 and 20, preferably between 10 and 15.

 The catalyst involved in the process of the invention is an acid catalyst. It can be a homogeneous or heterogeneous catalysis.

 A strong protonic acid and / or a Lewis acid can be used.

 As nonlimiting examples of such strong acids, there may be mentioned halogenated acids such as hydrochloric acid, hydrobromic acid, hydrofluoric acid, halogenated or non-halogenated oxyacids such as sulfuric acid, pyrosulfuric acid, I perchloric acid, halosulfonic acids such as fluorosulfonic acid, chlorosulfonic acid or trifluoromethanesulfonic acid, methanesulfonic acid, ethanesulfonic acid, ethanedisulfonic acid, benzenesulfonic acid, benzenedisulfonic acids, acids toluenesulfonic, naphthalenesulfonic acids and naphthalenedisulfonic acids.

Among these acids1, hydrofluoric acid, perchloric acid, trifluoromethanesu Ifonic acid, paratoluenesulfonic acid, will preferably be used,
Chlorosulfonic acid, fluorosulfonic acid, methanesulfonic acid,
Benzene sulfonic acid.

 Very particularly, hydrofluoric acid, perchloric acid or trifluoromethanesulfonic acid is chosen.

 As other examples of protonic acid catalysts, there may be mentioned sulfonic resins.

Thus, it is possible to use in the process of the invention, the sulphonic resins existing on the market, resins marketed under different commercial names. Mention may be made, among others, of the following resins
TEMEX 50, AMBERLYST 15, AMBERLYST 35, AMBERLYST 36, DOWEX 50W.

 The aforementioned resins which are well suited to the present invention consist of a polystyrenic backbone which carries functional groups which are sulfonic groups.

 The polystyrene skeleton is obtained by polymerization of styrene and divinylbenzene, under the influence of an activation catalyst, most often an organic peroxide, which leads to a crosslinked polystyrene. The polymerization is most often carried out in suspension and beads or granules of polymer are obtained. These are treated with concentrated sulfuric or sulfochloric acid. A sulfonated styrene-divinylbenzene copolymer is obtained.

 It is also possible to use sulfonic resins which are phenol-formaldehyde copolymers and which carry on the aromatic nucleus a methylene sulfonic group. As examples of said resins, mention may be made, among others, of the resin marketed under the name DUOLITE ARC 9359.

dans ladite formule, q est un nombre entier égal à 1,2,3,---, p est compris entre 5 et 13,5 et y est égal à environ 1000.Other resins are also available on the market and mention may be made of perfluorinated resins carrying sulfonic groups and, more particularly NAFION which has the general structure given below:

in said formula, q is an integer equal to 1,2,3, ---, p is between 5 and 13.5 and y is equal to approximately 1000.

NAFION is prepared from a copolymer of tetrafluoroethylene and perfluoro- (fluornsu lfonylethoxy) -propyl] vinyl ether.

 The resins in question may be of the gel type or of the macroreticulated type.

They are used in the acid form.

 Many resins are products available on the market in dry or wet form. Either form can be used in the process of the invention.

 They are usually in the form of substantially spherical particles having a diameter varying from 0.3 to 1.5 mm, preferably between 0.5 and 1.2 mm.

 The aforementioned resins are preferably used in the process of the invention and more preferably resins having a polystyrenic backbone. However, the invention does not exclude the use of resins having a skeleton of another nature insofar as it carries the appropriate sulphonic groups.

 The proportion of sulfonic groups relative to the polymer mass can be variable and this will be taken into account when determining the amount of polymer to be used.

 The concentration of acid sites of the sulfonic polymer advantageously varies between 1 and 10 milliequivalents of H + ions per gram of dry polymer, and preferably between 2 and 7 milliequivalents of H + ions per gram of dry polymer.

 We will also assimilate in the following to strong protonic acids, the acid forms of mixed oxides, clays and zeolites.

 As examples of catalysts with acidic properties, mention may be made, very particularly of combinations of metal and metalloid oxides such as: silica-alumina, silica-Ga203, if lice-B203.

 Another type of acid mineral catalysts which is entirely suitable for carrying out the process of the invention are acid clays.

 To prepare the acid clays, it is preferable to start with natural clays having a structure called "TOT or tetrahedron-octahedron-tetrahedron.

 TOT clays are in the form of elementary sheets comprising two layers of tetrahedra of oxygen atoms in which are included the silicon atoms separated by a layer of octahedra of oxygen atoms in which is included the metal M of type MO4 (OH) 2 or M is a divalent or trivalent cation.

 When all the tetrahedra are occupied by Si4 + ions, the electrical neutrality of the sheet can be measured in two ways, depending on the charge of the octahedral cation: - if it is divalent (Mg2 +, Fe2 +, ...), all the octahedral cavities are busy; the sheet is then said to be trioctahedral, - if it is trivalent (Al3 +, Fe3 +, ...), two out of three octahedral cavities are occupied and the sheet is dioctahedral.

 However, many substitutions are possible, both in the tetrahedral layer and in the octahedral layer. These can lead to a deficit in charge of the sheet and the neutrality of the crystal is then achieved by inserting compensating cations between the sheets.

 Among the TOT clays are the following three classes: smectites, vermiculites and micas.

 Among clays, the class preferentially used according to the invention is that of smectites.

 Smectites are classified according to the nature of the metal M (aluminum, magnesium, iron, lithium), the nature of the compensating cation (sodium, potassium, calcium) and the nature of the tetrahedral or octahedral substitution.

We can thus cite among the class of smectites:
- the montmorillonites of formula Si4 (AI2 y Mgy) O10 (OH) 2, M + y
- the beidellites of formula (Si4.xAlx) Al2Ol0 (OH) 2, M + x
- the nontronites of formula (Si4.xAIx) Fe2Oi0 (OH) 2, M + x
- hectorites of formula Si4 (Mg3 y Liy) Oio (OH) 21M + y
- stevensites of formula Si4 (Mg3y) Oi0 (OH îM + 2y
- the saponites of formula (Si4,, AI,) M9301 O (OH2), M +,
It is still more particularly preferred in the context of the present invention to use montmorillonites.

Commercial clays which are already acidic can be used, such as in particular: the following clays: KSF, TONSIL OPTIMUM FF and K 10 sold by Sud
Chemie.

 It is also possible to treat commercial clays, already acidic or not, with an aqueous solution of an acid. The concentration of the aqueous acid solution is variable, however it must have a pH greater than or equal to 2 so as not to destroy the clay and it must contain a quantity of H + ions expressed in milliequivalents corresponding to at least the capacity clay exchange. The exchange capacity of a clay is defined as the number of monovalent cations, expressed in milliequivalents that 1 9 of sample can exchange.

 This exchange capacity (or charge per half-mesh) varies for smectites between 0.2 and 0.6 and for vermiculites between 0.6 and 0.9. It is therefore preferable in the context of the present invention to use an acid solution containing as many H + equivalents as there will be cations to be exchanged in the clay, therefore containing at least 0.6 and preferably at least 1 milliequivalent acid for 1 g of clay.

 Optionally, to improve the exchange surface of the clay, then treat it with an alcohol such as methanol, then dry it.

 Also suitable for implementing the method of the invention, bridged type clays.

 Bridged clay is understood to mean clays between the sheets of which bridges or pillars have been introduced which maintain a basal spacing.

The basal spacing (or interfoliar distance) is the sum of the thickness of a clay sheet and the interfoliar spacing.

 As examples of mineral species creating the pillars or bridges, mention may be made of those derived from the following elements: aluminum, nickel, cobalt, vanadium, molybdenum, rhenium, iron, copper, ruthenium, chromium, lanthanum, cerium, titanium, boron, gallium , zirconium, niobium, tantalum, silicon.

 The bridged clays preferably used in the process of the invention are the clays bridged by pillars of aluminum oxide, zirconium, chromium, silicon and cerium.

 Said clays are prepared according to the methods described in the literature.

Reference may be made, inter alia, for the preparation of clay bridged with aluminum, to FR-A 2 563 446 and to FR-A 2 656 298; titanium bridged clays at
FR-A 2 669 016 and clay bridged with cerium at French patent application No. 91/04409.

 Among bridged clays, special use is made of smectite-type clays. Among these smectites, non-limiting examples that may be mentioned include beidellites, in particular synthetic beidellites and montmorillonites.

Bridged clays can be obtained by a process comprising the following stages:
a) the treatment of a natural or synthetic clay, in the form of a
aqueous suspension, with an aqueous solution containing at least one
hydroxide of at least one metal,
b) elimination of the excess of unreacted metal hydroxide on
clay; said elimination and drying of the treated clay,
c) heat treatment of the treated clay; said treatment leading to
obtaining bridged clay.

 For the preparation of bridged clays which can be used in the context of the invention, it is also possible to use only steps a) and b).

 The bridging of the clays can be carried out using the hydroxides of the aforementioned metals.

 Preferably, a catalyst or a montmorillonite bridged with aluminum hydroxide is used as catalyst in the process of the invention, for example according to the process described in FR-A 2,563,446.

 As examples of catalysts which are also suitable for the present invention, mention may be made of natural zeolites such as for example: chabazite, clinoptilolite, erionite, mordenite, phillipsite, offerite.

 Synthetic zeolites such as zeolite ZSM-5, zeolite Y, ferrierite are entirely suitable for implementing the invention. faujasite-type zeolite X, type L zeolite, mordenite, zeolite ZSM-11; mazzite, 'offretite. Whatever the zeolite, we make a treatment which makes it acidic.

We preferentially use synthetic zeolites and more particularly commercial zeolites which are in the following forms:
- zeolites in acid form such as zeolites ZSM-5 or silicalite
aluminum with an Si / AI molar ratio of 10 to 500; zeolites Y in
in particular the zeolites obtained after dealumination treatment (by
example hydrotreating, washing with hydrochloric acid or treatment
by SiC 14) and mention may be made more particularly of the US-Y zeolites of
Si / AI molar ratio greater than 3, preferably between 6 and 60; the
zeolites such as ferrierite with an Si / AI molar ratio of 5 to 10,
- exchangeable zeolites in sodium or potassium form such as
zeolite X of faujasite type with Si / AI molar ratio of 1 to 1.5, the zeolite of
type L with Si / AI molar ratio from 3 to 3.5, mordenite with molar ratio
Si / AI from 5 to 6, the zeolite ZSM-11 of Si / AI molar ratio from 5 to 30,
- zeolites both in acid form or in sodium form or
exchangeable potassium such as the mazzite of Si / AI molar ratio of
3.41 'offretite with an Si / AI molar ratio of 4.

 In accordance with the process of the invention, the zeolite used in the process of the invention is an acidified zeolite.

 To acidify the zeolite if necessary, conventional treatments are used.

 Thus, the alkali cations can be exchanged by subjecting the zeolite to a treatment carried out with ammonia thus leading to an exchange of the alkaline cation with an ammonium ion and then to calcining the exchanged zeolite in order to thermally decompose the ammonium cation and replace it with an H + ion.

 The amount of ammonia to be used is at least equal to the amount necessary to exchange all the alkaline cations into NH4 + ions.

 We therefore put at least 5.10-3 to 10-5 mole of ammonia per gram of zeolite into play.

 The exchange reaction of the cation exchangeable with NH4 + is carried out at a temperature which is between ambient temperature and the reflux temperature of the reaction medium. The operation lasts a few hours and can be repeated.

Zeolites can also be acidified by subjecting them to conventional acid treatment. This treatment can be carried out by adding an acid such as in particular hydrochloric acid, sulfuric acid, nitric acid,
Perchloric acid, phosphoric acid and trifluoromethanesulfonic acid.

 According to a preferred embodiment, the zeolite is acidified by passing a volume of acid having a normality of between 0.1 and 2 N per gram of zeolite between 10 ml / g and 100ml / g. This passage can be carried out in a single step or preferably in several successive steps.

It will not depart from the scope of the present invention to use a modified acid zeolite for example by using type zeolites
ZSM-5 and ZSM-11 in which part of the aluminum is filled literature and one can refer among others to the work of ALBERTI et al - J. of
Inorg. Nucl. Chem. p. 1113 (1978).

 It can also be implemented. lamellar phosphonates of tetravalent metals and very particularly lamellar zirconium phosphonates (US-A 4,436,899).

 Also suitable for the invention are the oxides made acidic by treatment. Mention may be made of sulfated, chlorinated or fluorinated oxides. Those which are preferably used are the sulfated oxides of titanium, zirconium or iron. These oxides are described in the literature and reference may be made, inter alia, to EP-A 0 397 553.

 It is also possible to use, in the process of the invention, a catalyst of Lewis acid type.

 By Lewis acid is meant in the present text, according to the usual definition, compounds that accept electronic doublets.

 One can use in particular the Lewis acids cited in the work published by G.A. OLAH "Friedel-Crafts and related Reactions", volume I, pages 191 to 197 (1963).

 The Lewis acids which can be used in the process are more particularly the halides of elements from groups 3a, 4a, 5a lb, 2b, 3b, 4b, 5b, 6b, 7b and 8 of the periodic table of elements such as chlorides , bromides, fluorides and iodides of aluminum, tin, phosphorus, antimony, arsenic, bismuth, titanium, tantalum, tellurium, selenium, zirconium, vanadium, samarium, niobium, tungsten, platinum, molybdenum, iron, colbalt, nickel, zinc and cadmium.

 As specific examples of such halides, there can be mentioned aluminum chloride, titanium tetrachloride, zirconium tetrachloride, vanadium trichloride, samarium chloride, antimony pentafluoride, bismuth trichloride, stannous chloride .

 The preferred embodiments of the invention consist in using the following acid catalysts: hydrofluoric acid, perchloric acid, trifluoromethanesulfonic acid, trifluromethanesu Ifonic acid, hydrofluoric acid, perchloric acid and sulfonic resins of the NAFION type.

As regards the sulfur compound involved in the process of the invention, use may more particularly be made of the following compounds:
sulfur-containing mineral compounds:
- sulfur halides, preferably sulfur monochloride or
sulfur bichloride,
- ammonium thiosulphates, of alkali or alkaline-earth metal, of
preferably ammonium, sodium or potassium thiosulfate,
- hydrogen sulfide or its precursors such as, for example, sulfide
calcium or potassium which, added to the acid reaction medium,
lead to the formation of hydrogen sulfide, sulfur-containing organic compounds:
- the mercaptans, in particular the alkylmercarptans, phenylmercaptans and
phenylalkylmercaptans such as, for example, ethylmercaptan,
butylmercaptan, 1 -nonylmercaptan, benzylmercaptan,
- thioalcohols such as, for example, 2-mercaptoethanol, 3-mercapto
2-butanol,
- thiophenols such as in particular, thiophenol, o-thiocresol, m
thiocresol, p-thiocresol, thioxylenol, p-methylthiophenol, I'o-
ethylthiophenol, thiohydroquinone, thionaphthol,
- thioorganic acids, their salts or their esters such as acid
thioacetic, thiopropionic acid, thiolactic acid, thio acid
salicylic, 2-mercaptoethanesulfonic acid, 3-mercapto acid
propanesulfonic, mercaptosuccinic acid, thioglycolic acid,
methyl, ethyl thioglycolate,
- cation exchange resins modified by reaction with an alkyl
mercaptoamine, preferably polystyrene skeleton resins
carriers of sulfonic groups as defined above, having
reacted with an alkyl mercaptoamine, preferably one with a group
primary amine and even more preferably that having from 1 to 4
carbon atoms, and in particular, 2-mercaptoethylamine, 2
mercaptoisopropylam ine, 3-mercaptobutylam ine.

 In accordance with the process of the invention, the preparation of fuchsone is carried out by reaction of the phenolic compound of formula (I) and of the ketonic compound of formula (II), in the presence of the acid catalyst and of a sulfur compound.

 The amount of phenolic compound of formula (I) used and expressed relative to the ketone compound of formula (II) is generally at least equal to the stoichiometric amount. A molar ratio between the phenolic compound of formula (I) and the ketone compound of formula (II) of between 1 and 20, preferably between 1 and 10, is advantageously chosen.

 As regards the acid catalyst, the amount of acid expressed by the ratio of proton equivalents to the number of moles of ketone compound of formula (II) can vary between 1.10-3 and 1.0, preferably between 5.10- 3 and 0.5.

 It is also possible to use the acid as a reaction medium. Mention may in particular be made of the case of hydrofluoric acid and trifluoromethanesulfonic acid. Thus, the abovementioned ratio can be greater than 1.0 and be very high and exceed 20. Preferably, it is between 5.0 and 10.

 Being a solid heterogeneous catalyst, the quantity to be used is determined so that the catalyst represents, by weight relative to the phenolic compound of formula (I) used, from 0.1 to 20%, preferably of 0.5 to 10%. However, if the process is carried out continuously, for example by reacting a mixture of phenolic compound of formula (I) and of ketone compound of formula (II), on a fixed catalyst bed, these catalyst / ketone compound ratios formula (II) do not make sense and at a given time, there may be an excess weight of catalyst compared to the ketone compound of formula (II).

 The quantity of sulfur compound used expressed relative to the ketone compound of formula (II) is advantageously chosen such that the molar ratio between the sulfur compound and the ketone compound of formula (II) is between 0.001 and 1.0 , preferably between 0.005 and 0.20.

 The preparation of fuchsone according to the process of the invention is carried out at a temperature which can be between 45 "C and 200" C.

 A preferred variant of the process of the invention consists in choosing the temperature between 60 "C and 150" C.

 The reaction is advantageously carried out at atmospheric pressure.

 From a practical point of view, the method according to the invention is simple to implement continuously or discontinuously.

 The different reagents can be introduced in any order.

Preferably, the order of the following reactants is chosen: the phenolic compound of formula (I), the ketonic compound of formula (II), the acid catalyst and the sulfur compound are introduced.

 The reaction medium is brought to the desired temperature, while maintaining the reaction medium with stirring.

 During the reaction, water forms in the reaction medium.

A preferred variant of the invention consists in limiting the concentration of water in the reaction medium, by eliminating it as it is formed, by any known means, in particular by azeotropic distillation.

 At the end of the reaction, the fuchsone formed is recovered from the reaction medium.

 We start by separating the catalyst. If it is a homogeneous catalysis, the reaction mass is washed with water and an organic solvent suitable for extracting the unreacted reagents and the fuchsone formed is added. As examples of organic solvents, mention may in particular be made of ethyl acetate, dichloromethane, p-xylene, toluene, isopropyl ether. The acid catalyst passes into the aqueous phase and the fuchsone formed and optionally the reactants which have not been transformed are recovered in the organic phase.

 In the case of a heterogeneous acid catalyst, the solid acid catalyst is separated according to conventional solid-liquid separation techniques, preferably by filtration and then the reaction medium treated with an organic solvent as mentioned above.

 The fuchsone can be recovered from the organic phase, by preparative liquid chromatography on a silica column.

 It is also possible to separate the fuchsone from the unprocessed phenolic compound and the ketone compound of formula (II), by the usual means, in particular, by crystallization.

 As regards the sulfur-containing compound, the latter may, depending on its nature, be found either in the aqueous phase or in the organic phase. It can be recovered according to the usual separation methods, in particular by distillation.

dans ladite formule (III), les différents symboles R1, R2, R3, R4, Ra et Rb ont la signification donnée précédemment.The process of the invention makes it possible to obtain a fuchsone which can be symbolized by the following general formula (III):

in said formula (III), the different symbols R1, R2, R3, R4, Ra and Rb have the meaning given above.

 The present process is particularly suitable for the preparation of fuchsone from phenol and benzophenone.

 The improvement provided by the present invention makes it possible to increase the reaction rate of formation of fuchsone, appreciably.

 The examples which follow illustrate the invention without however limiting it.

In the examples, the following abbreviations mean
number of moles of ketone processed
TTBENZOPHENONE = ---------------------------------%
number of moles of benzophenone introduced
number of moles of fuchsone formed
RRFuCHsoNE = --------------------------------------%
number of moles of benzophenone introduced
number of moles of fuchsone formed
RTFUCHSONE = --------------------------------------%
number of moles of benzophenone transformed
Example 1
In a 50 ml glass flask, fitted with a central shaker, a
refrigerant, thermometer, we charge:
- 23.5 g (0.25 mol) of phenol
- 4.55 g (0.025 mol) of benzophenone
- 7.9 g (0.05 mol) benzenesulfonic acid
- 0.621 g (0.005 mol) of benzylmercaptan
The reaction mixture is brought to the chosen reaction temperature, 110 ° C., while maintaining the stirring at 1200 rpm.

After 4 hours, the reaction mixture is cooled and the
determination of the reaction products: fuchsone and residual benzophenone
are determined by gas chromatography.

The results obtained are as follows:
RR FUCHSONE = 57.6 49
TT BENZOPHENONE = 62%
RT FUCHSONE = 92.9%
The same test carried out without benzylmercaptan, conducted after 4 hours of reaction at 110 "C, with the following results:
RR FUCHSONE = 14%
TT BENZOPHENONE = 15.2%
RT FUCHSONE = 92.1%
FIG. 1 represents a graph on which are plotted two yield variation curves (RR expressed in%) as a function of the reaction time (expressed in hours), one in the presence of benzylmercaptan (B) and the other in the absence of thiol (A).

 It is noted that the presence of a thiol makes it possible to considerably increase the rate of formation of fuchsone.

Example 2
In a 50 ml glass flask, fitted with a central stirring, a condenser, a thermometer, we load:
- 23.5 g (0.25 mol) of phenol
- 4.55 g (0.025 mol) of benzophenone
- 7.5 g (0.05 mol) of trifluoromethanesulfonic acid
- 0.621 g (0.005 mol) of benzylmercaptan
The reaction mixture is brought to the chosen reaction temperature, 80 ° C. while maintaining the stirring at 1200 rpm.

 After 4 hours, the reaction mixture is cooled and the reaction products are assayed: the fuchsone and the residual benzophenone are determined by gas chromatography.

The results obtained are as follows:
RR FUCHSONE = 94.8%
TT BENZOPHENONE = 99.2%
RT FUCHSONE = 95.6%
The same test carried out without benzylemercaptan, carried out after 4 hours of reaction at 80 "C, with the following results:
RR FUCHSONE = 63.2%
TT BENZOPHENONE = 64.8%
RT FUCHSONE = 97X5%
Example3
In a 50 ml glass flask, fitted with a central stirring, a condenser, a thermometer, we load:
- 23.5 g (0.25 mol) of phenol
- 4.55 g (0.025 mol) of benzophenone
- 7.9 g (0.05 mol) benzenesulfonic acid
- 0.801 g (0.005 mol) of 1-nonylmercaptan
The reaction mixture is brought to the chosen reaction temperature, it 00C while maintaining the stirring at 1200 rpm.

 After 4 hours, the reaction mixture is cooled and the reaction products are assayed: the fuchsone and the residual benzophenone are determined by gas chromatography.

The results obtained are as follows:
RR FUCHSONE = 62%
TT BENZOPHENONE = 67.6%
RT FUCHSONE = 91.7%
The same test carried out without 1-nonyl mercaptan, carried out after 4 hours of reaction at 110 ° C., with the following results:
RR FUCHSONE = 14%
TT BENZOPHENONE = 15.2%
RT FUCHSONE = 92.1%
Example 4
In a 250 ml glass flask, fitted with a central stirring, a condenser, a thermometer, we load:
- 94 g (1 mol) of phenol
- 18.2 g (0.1 mol) of benzophenone
- 76.8 g (0.8 mol) of methanesulfonic acid
- 1.8 g (0.02 mol) of 1 -butanethiol
The reaction mixture is brought to the chosen reaction temperature, 80 ° C. while maintaining the stirring at 1200 rpm.

 After 7 hours, the reaction mixture is cooled and the reaction products are assayed: the fuchsone and the residual benzophenone are assayed by gas chromatography.

The results obtained are as follows:
RR FUCHSONE = 96.5%
TT BENZOPHENONE = 9794%
RT FUCHSONE = 99.1%
Example 5
In a 100 ml glass flask, provided with a central stirring, a condenser, a thermometer, we load:
- 28.2 g (0.3 mol) of phenol
- 5.46 g (0.03 mol) of benzophenone
- 23.04 g (0.24 mol) of methanesulfonic acid
- 0.984 g (0.006 mol) of sodium 2 - mercaptoethanesulfonate
The reaction mixture is brought to the chosen reaction temperature, it 00C while maintaining stirring at 1200 rpm.

 After 4 hours, the reaction mixture is cooled and the reaction products are assayed: the fuchsone and the residual benzophenone are determined by gas chromatography.

The results obtained are as follows:
RR FUCHSONE = 83.7%
TT BENZOPHENONE = 99%
RT FUCHSONE = 84s5%
The same test is carried out without thiol. The results obtained are as follows:
RR FUCHSONE = 46.3%
TT BENZOPHENONE = 47%
RT FUCHSONE = 98.5%
Example 6
Example 5 is repeated except that 0.246 g (0.0015 mol) of sodium 2-mercaptoethanesulfonate is used instead of 0.984 g (0.006 mol).

After 4 hours at 110 "C, the results obtained are as follows:
RR FUCHSONE = 86.3%
TT BENZOPHENONE = 91%
RT FUCHSONE = 94s8%
Example 7
Example 5 is reproduced except that 0.025 g (0.00015 mol) of sodium 2-mercaptoethanesulfonate is used instead of 0.984 g (0.006 mol).

After 4 hours at 110 "C, the results obtained are as follows:
RR FUCHSONE = 65%
TT BENZOPHENONE = 65.7%
RT FUCHSONE = 98.9%
Example 8
In a reactor fitted with a central agitation, a condenser and a thermometer, the following are charged:
8.049 (0.085 mol) phenol
1.559 (0.0085 mol) benzophenone
1.67g (0.0085 H + equivalent) of BAYER K2431 resin
0.2129 (0.0017 mol) of benzylmercaptan
BAYER K2431 resin is a macroporous resin with a polystyrene skeleton carrying sulfonic groups, with a concentration of acid sites of 5.1 milliequivalents of H + per gram of dry polymer.

 The reaction mixture is brought to the selected temperature, 145 "C, while maintaining stirring at 1200 rpm.

 After 4 hours of reaction, the resin is separated from the reaction mixture by filtration on sintered glass, washed with 20 ml of phenol at 80 ° C. The filtrate and the washing are combined.

 The resin is stirred for 1 hour at room temperature with a mixture of water and ethyl acetate 50/50, then filtered. The organic phase is separated by decantation.

 The fuchsone and the residual benzophenone contained in the phenolic phase and in the ethyl acetate phase are assayed by gas phase chromatography.

The results obtained are as follows:
RR FUCHSONE = 11.8%
TT BENZOPHENONE = 14%
RT FUCHSONE = 84.3%
The same test carried out without benzylmercaptan, after 4 hours of reaction at 145 "C, leads to the following results:
RR FUCHSONE = 6.2%
TT BENZOPHENONE = 6.2%
RT FUCHSONE = 100%
Example 9
In a reactor fitted with a central agitation, a condenser and a thermometer, the following are charged:
8.049 (0.085 mol) phenol
1.55 g (0.0085 mol) of benzophenone
1.67g (0.0085 H + equivalent) of BAYER K2431 resin
0.2749 (0.0017 mol) of 1-nonylmercaptan
The reaction mixture is brought to the selected temperature 145 "C while maintaining stirring at 1200 rpm.

 After 4 hours of reaction, the resin is separated from the reaction mixture by filtration on sintered glass, washed with 20 ml of phenol at 80 ° C. The filtrate and the washing are combined.

 The resin is stirred for 1 hour at room temperature with a mixture of water and ethyl acetate 50/50, then filtered. The organic phase is separated by decantation.

 The fuchsone and the residual benzophenone contained in the phenolic phase and in the ethyl acetate phase are assayed by gas phase chromatography.

The results obtained are as follows:
RR FUCHSONE = 11.6%
TT BENZOPHENONE = 17.8%
RT FUCHSONE = 65s17%
The same test carried out without 1-nonylmercaptan, after 4 hours of reaction at 145 "C, leads to the following results:
RR FUCHSONE = 6.2%
TT BENZOPHENONE = 6.2%
RT FUCHSONE = 100%
Example 10
In a 50 ml reactor equipped with a central agitation, a thermometer, and a refrigerant, the following are charged:
0.47 g (0.005 mol) phenol
0.91g (0.005 mol) of benzophenone
8.9 g (0.05 mol) orthophosphoric acid
0.164 g (0.001 me) sodium 2-mercaptoethanesufonate
The reaction medium is brought to the chosen temperature, 80 ° C. while maintaining stirring at 1200 rpm.

 After 5 hours of reaction, the reaction mixture is cooled and the reaction products are assayed. The fuchsone and the residual benzophenone are assayed by high performance liquid chromatography.

The results obtained are as follows:
RR FUCHSONE = 29.6%
TT BENZOPHENONE = 35.6%
RT FUCHSONE = 83s1%
The same test carried out without 2-mercaptoethanethiol, leads after 5 hours of reaction at 80 "C to the following results:
RR FUCHSONE = 4%
TT BENZOPHENONE = 4%
RT FUCHSONE = 100%
Example 1 1
In a 50 ml reactor fitted with a central agitation1 of a thermometer, and of a refrigerant, the following are charged:
- 0.47 g (0.005 mol) of phenol
0.91g (0.005 mol) of benzophenone
- 8.9 g (0.05 mol) of orthophosphoric acid
- 0.164 g (0.001 mol) of sodium 2-mercaptoethanesufonate
The reaction medium is brought to the chosen temperature, 110 ° C. while stirring is maintained at 1200 rpm.

 After 5 hours of reaction, the reaction mixture is cooled and the reaction products are assayed. The fuchsone and the residual benzophenone are assayed by high performance liquid chromatography.

The results obtained are as follows:
RR FUCHSONE = 30.4%
TT BENZOPHENONE = 49s6%
RT FUCHSONE = 61.3
The same test carried out without 2-mercaptoethanethiol, leads after 5 hours of reaction at 110 "C to the following results:
RR FUCHSONE = 3%
TT BENZOPHENONE = 10%
RT FUCHSONE = 30%

Claims (13)

CLAIMS 1- Process for the preparation of a fuchsone which consists in reacting a phenolic compound having at least one hydrogen atom in the para position and a non-insoluble ketone compound, in the presence of an acid catalyst characterized in that the reaction is carried out in the presence of an effective amount of an ionizable sulfur compound. 2- A method according to claim 1 characterized in that the phenolic compound having at least one hydrogen atom in para position is a phenolic compound corresponding to the general formula (I)

 in said formula (I) - the position in para is free, - R1, R21 R3 and R4, identical or different, represent a hydrogen atom or any substituent, - two groups R1 and R2 and / or R3 and R4 placed on two vicinal carbon atoms can form together and with the carbon atoms which carry them a saturated, unsaturated or aromatic carbocycle having from 4 to 7 carbon atoms, - R 'represents a hydrogen atom, a linear or branched alkyl radical having from 1 to 12 carbon atoms, an optionally substituted carbocyclic radical which may be a cycloalkyl radical having from 5 to 12 carbon atoms, an aryl radical having from 6 to 12 carbon atoms, an aralkyl radical having from 7 to 14 carbon atoms carbon. 3 - Method according to one of claims 1 and 2 characterized in that the phenolic compound corresponds to the general formula (I) in which: - the radical R 'represents one of the following groups:  a hydrogen atom  a linear or branched alkyl radical having from 1 to 6 carbon atoms,  a cyclohexyl radical,  a phenyl radical,  a benzyl radical, - R1, R21 R3 and R41 identical or different represent Rg, one of the following groups:  a hydrogen atom,  an alkyl radical, linear or branched, having from 1 to 6 carbon atoms, of  preferably from 1 to 4 carbon atoms, such as methyl, ethyl, propyl,  isopropyl, butyl, isobutyl, sec-butyl, tert-butyl,  a linear or branched alkenyl radical having from 2 to 6 carbon atoms,  preferably from 2 to 4 carbon atoms, such as vinyl, allyl,  a linear or branched alkoxy radical having from 1 to 6 carbon atoms, of  preferably from 1 to 4 carbon atoms such as methoxy radicals,  ethoxy, propoxy, isopropoxy, butoxy,  an acyl group having from 2 to 6 carbon atoms,  a radical of formula -Rs-OH  -R5-COOR6  -R5-X -R5-CF3  in said formulas, R5 represents a valential bond or a radical  divalent hydrocarbon, linear or branched, saturated or unsaturated, having from 1 to  6 carbon atoms such as, for example, methylene, ethylene, propylene,  isopropylene, isopropylidene; R6 represents a linear alkyl radical or  branched having from 1 to 6 carbon atoms; X symbolizes an atom  halogen, preferably a chlorine, bromine or fluorine atom.  - R1, R2, R3 and R4, identical or different, represent R71 one of the following more complex radicals  a cyclohexyl radical,  a radical of formula

 in which R5 represents a valential bond or a divalent, linear or branched, saturated or unsaturated hydrocarbon radical having from 1 to 6 carbon atoms such as, for example, methylene, ethylene, propylene, isopropylene, isopropylidene and Rg having the meaning given above and m is an integer from O to 4, a radical - R5 - A - R8 in which R5 has the meaning given above, R8 represents a linear or branched alkyl radical having from 1 to 6 carbon atoms or a radical

  and A symbolizes one of the following groups:

 in these formulas, Rg represents a hydrogen atom or a radical  alkyl having from 1 to 4 carbon atoms, a cyclohexyl radical or  phenyl. - two groups R1 and R2 and / or R3 and R4 placed on two vicinal carbon atoms can form together and with the carbon atoms which carry them a saturated, unsaturated or aromatic carbocycle having 6 carbon atoms, 4- Process according to one of claims 1 to 3 characterized in that the phenolic compound corresponds to the general formula (I) in which:  - the radical R 'represents one of the following groups:  a hydrogen atom  a linear or branched alkyl radical having from 1 to 4 carbon atoms,  a cyclohexyl radical,  a phenyl radical, - R1, R21 R3 and R4, identical or different, represent one of the following groups:  a hydrogen atom,  an alkyl radical, linear or branched having from 1 to 4 carbon atoms ,.  a linear or branched alkoxy radical having from 1 to 4 carbon atoms,  a hydroxyl group,  a halogen atom,  a group -CF3  a cyclohexyl radical,  a phenyl radical, - two groups R1 and R2 and / or R3 and R4 placed on two vicinal carbon atoms can form together and with the carbon atoms which carry them a benzene ring. 5 - Method according to one of claims 1 to 4 characterized in that the phenolic compound corresponds to the general formula (I) in which R 'represents a hydrogen atom and R1 represents a hydrogen atom, a hydroxyl group , a methyl radical, a methoxy radical and R2, R3 and R4 represent a hydrogen atom. 6 - Method according to one of claims 1 to 5 characterized in that the phenolic compound is phenol, anisole, ortho-cresol, metacresol, 2-methoxyphenol, 2-ethylphenol, Ethyl 3-phenol, propyl-2 phenol, sec-butyl-2 phenol, tert-butyl-2 phenol, tert-butyl-3 phenol, methoxy-2 phenol, methoxy-3 phenol, methyl salicylate, 2-chloro-phenol, 3-chloro-phenol, 2,3-dimethylphenol, 2,5-dimethylphenol, 2,6-dimethylphenol, 3,5-dimethylphenol, dichloro -2.3 phenol, 2,5-dichloro-phenol, 2,6-dichloro-phenol, 3,5-dichloro-phenol, 2,3,5-trimethylphenol, 2,3,6-trimethylphenol, ditert-butyl-2,6 phenol, ditert-butyl-3,5 phenol, trichloro-2,3,5 phenol, trichloro-2,3,6 phenol, hydroxy-naphthalene, phenoxy- 2 phenol, 3-phenoxyphenol. 7 - Method according to one of claims 1 to 6 characterized in that the non-insoluble ketone compound is a ketone compound corresponding to the general formula (II) in which:

 in said formula (II) - Ra and Rb, identical or different are hydrocarbon radicals each having from 3 to 30 carbon atoms; the carbon atoms of each radical Ra and Rb in position a with respect to the carbonyl group being tertiary carbons. 8 - Method according to one of claims 1 to 7 characterized in that the ketone compound corresponds to the general formula (II ') in which:

 in said formula (II ') - Ral, Ra2, Ra3 and Rbl, Rb2, Rb3 identical or different, represent linear or branched alkyl radicals having from 1 to 10 carbon atoms, cyclohexyl, phenyl or naphthyl radicals optionally substituted, Ral , Ra2, Ra3 and / or Rbl, Rb2, Rb3 can form together and with the carbon atom which carries them an optionally substituted benzene or naphthalene ring; optionally the two groups Rai and Rbl can be linked together by a valential bond or by a group -CH2- thus forming a ketone cycle which can be saturated or unsaturated. 9 - Method according to one of claims 1 to 8 characterized in that the ketone compound corresponds to the general formula (Ia) in which:

 in said formula (IIIa): - Rc and Rd identical or different represent a hydrogen atom or a substituent, - n1, n2 identical or different is a number equal to 0, 1,2 or 3, - optionally the two atoms of carbon located in position a with respect to the two carbon atoms carrying the group - CO can be linked together by a valential bond or by a group - CH2 - thus forming a ketone cycle which can be saturated but also unsaturated. 10 - Method according to one of claims 1 to 9 characterized in that the ketone compound corresponds to the general formula (IIIa) in which Rc and Rd, identical or different represent: - linear or branched alkyl radicals having from 1 to 4 carbon atoms, - a phenyl radical, - alkoxy radicals R10 - O in which R10 represents a linear or branched alkyl radical having from 1 to 4 carbon atoms or the phenyl radical, - a hydroxyl group, - a fluorine atom . 11 - Method according to one of claims 1 to 10 characterized in that the ketone compound corresponds to the general formula (IIIa) in which Rc and Rd, identical or different, represent a hydrogen atom or a substituent as defined in claim 10, preferably in position 4,4 'and n1, n2 identical or different are equal to 0 or 1. 12 - Method according to one of claims 1 to 1 1 characterized in that the ketone compound corresponds to the general formula (IIIa) in which R0 and Rd, identical or different represent a hydrogen atom; a methyl, ethyl, tert-butyl, phenyl radical; a methoxy or ethoxy radical; a hydroxyl group, preferably in the 3.3 ′ or 4.4 ′ position. 13 - Method according to one of claims 1 to 12 characterized in that the ketone compound of general formula (lla) is:  - benzophenone  - 2-methyl benzophenone  - 2,4-dimethyl benzophenone  - 4,4 'dimethyl benzophenone  - 2,2-dimethyl benzophenone  - 4,4 'dimethoxy benzophenone  - 4-hydroxy benzophenone  - dihydroxy-4-4 'benzophenone  - 4-benzoyl biphenyl 14 - Method according to one of claims 1 to 13 characterized in that the sulfur compound is a sulfur mineral compound or an organic sulfur compound. 15 - Method according to one of claims 1 to 14 characterized in that the sulfur compound is chosen from: - sulfur halides, - ammonium thiosulfates, of alkali or alkaline earth metal, - hydrogen sulfide or its precursors, - mercaptans preferably alkylmercarptans, phenylmercaptans and phenylalkylmercaptans, - thioalcohols, - thiophenols, - thioorganic acids, their salts or their esters, - cation exchange resins modified by reaction with an alkyl mercaptoamine, preferably the polystyrenic skeleton resins carrying sulfonic groups which have reacted with an alkyl mercaptoamine, preferably that with a primary amine group and even more preferably that having from 1 to 4 carbon atoms. 16 - Method according to one of claims 1 to 15 characterized in that the sulfur compound is chosen from: - sulfur monochloride or sulfur bichloride, - ammonium, sodium or potassium thiosulfate, - l hydrogen sulfide or calcium or potassium sulfide, - ethylmercaptan, butylmercaptan, 1 -nonylmercaptan, benzylmercaptan, - 2-mercaptoethanol, 3-mercapto-2-butanol, - thiophenol, o -thiocresol, m-thiocresol, p-thiocresol, thioxylenol, pmethylthiophenol, o-ethylthiophenol, thiohydroquinone, thionaphthol, - thioacetic acid, thiopropionic acid, thiolactic acid, acid thiosalicylic acid, 2-mercaptoethanesu Ifonic acid, 3-mercaptopropanesulfonic acid, mercaptosuccinic acid, thioglycolic acid, methyl thioglycolate, ethyl, - polystyrenic skeleton resins carrying sulfonic groups which have reacted with the 2-mercaptoethylamine, 2-mer captoisopropylamine, 3mercaptobutylamine. 17 - Method according to one of claims 1 to 16 characterized in that the amount of sulfur compound used expressed relative to the ketone compound of formula (II) is such that the molar ratio between the sulfur compound and the ketone compound of formula (II) is between 0.001 and 1.0, preferably between 0.005 and 0.20.