IL33178A - Process for the production of dihydroxyarylsulphonium salts - Google Patents

Description

Qi » j vs'no 'TR'oaiin'T'n'T ο'π^» npan - nn Process for the production of dihydroxyaryl- sulphonium salts CIBA GEIGY A.G. 395 6 29ΐ Process for the production of dihydroxyarylsulphonium salts The present invention concerns a new process for the production of dihydroxyarylsulphonium salts.

For the synthesis of aromatic sulphonium salts, various processes are known which in general, besides the aromatic compound, employ sulphoxides as starting materials. Hitherto, however, there has been no generally applicable method for producing dihydroxyarylsulphonium salts of greatly varied types.

A process has. now been found which enables these compounds to be obtained in a simple manner with high yields. It is characterized by ad I or to- 1,2-quinones in which formulae X, Y and Z independentl of each other represent hydrogen, hydroxyl group, an alkoxycarbonyl group having from 1 to 4 carbon atoms in the alkoxy radical, a halogen atom, a phenyl, halogenphenyl, nitrophenyl or alkylphenyl group having from 1 to carbon atoms in the alkyl radical or a group -SR or -OR wherein--R represents an alkyl group having from 1 to l8 carbon atoms or a carboxyalkyl, car- boxylic acid ester-alkyl, cyanoalkyl or alkoxyalkyl group havin f-erm 1 to carbon atoms in the alkyl or alkoxy radical, a phenyl, hydroxyphenyl, halogenphenyl, nitrophenyl, . alkylphenyl or alkoxyphenyl group having from 1 to .4 carbon atoms in the alkyl or alkoxy radical, or X and Y together f#em a fused homo- or heterocyclic, saturated . . or unsaturated rin which can be substituted by hydroxyl groups, halogen atoms, nitro, alkoxy and/or alkyl groups .. having from 1 to 4 carbon atoms and which ring, in case it is aromatic, can be condensed with other aromatic r. rings, organic sulphides of the general Formula III 1 - 5 - 2 (HI) wherein represents a propenyl group, an alkyl group having from 1 to 12 carbon atoms in the main chain which alkyl group may 'be substituted by. phenyl groups, halogen atoms, hydroxyl groups, alkoxy groups having from 1 to 12 carbon atoms, ■ phenoxy groups, chlorophenoxy, bromphenoxy, hydroxy- alkoxy, alkoxyalkoxy or alkylthio groups having each from 1 to 4 carbon atoms in the alkoxy or alkyl radical, or a phenyl group which may be substituted by halogen atoms, and Rg represents an alkyl group having from 1 to 12 carbon atoms in the main chain which alkyl group may be substituted by phenyl groups, halogen atoms, hydroxyl groups, alkoxy groups having frortT 1 to 12 carbon atoms, phenoxy, chlorophenoxy, bromophenoxy, hydroxyalkoxy, . alkoxyalkoxy or alkylthio groups having each from 1 to 4 carbon atoms in the alkoxy or alkyl radical, or' ^ and Rg together represent from 4 to 6 methylene groups which may be substituted by alkyl groups having from 1 to 4 carbon atoms and which may include a sulphur or oxygen atom, in a strongly acid medium. .. . ■_■· · When X, Y or Z represent an alkyl group of from 1 to 18 carbon atoms, it is an unbranched or branched hydrocarbon chain, e.g. methyl, ethyl, propyl, isopropyl, butyl, pentyl, isopentyl, heptyl, octyl, decyl, dodecyl, hexadecyl or octadecyl.

When X, Y or Z represents a halogen atom, it is for example fluorine, chlorine or bromine.

In the meaning of a fused ring, X and Y preferably together form a benzo radical which may be unsubstituted or substituted as defined. above .

Especiall suited for the process according to the invention are quinones of the general Formula I in which X, Y and Z, independent of one another, represent hydrogen, an alkyl group having from 1 to 4 carbon atoms or a halogen atom.

Examples of such quinones which can be used as starting materials are: 1, 2-benzoquinone, 1, 4-benzoquinone, 5-wethyl-l, 2- ■ benzoquinone , 2-methyl-1 , 4-benzoquinone , 2-butyl-l , 4-benzoquinone, 2-dodecyi-l , 4-benzoquinone , 5-hexadecyl-l , 2-benzo- quinone, 2-octadecyl-l , 4-benzoquinone, 2 , 5-dimethyl-l , 4-benzoquinone, 3 , 5-di- er . butyl-l , 4-benzoquinone , 2- isopropy1-5-methy1-1 , 4-benzoquinone , 3-chloro-l , 2-benzoquinone , 2-chloro- 1, 4~benzoquinone ,. 2 , 5-dichlor.o-l , 4-benzoquinone , 2, 6-dibromo- 1 , 4-benzoquinone , 2-chloro-3-methyl-l , -benzoquinone , 2-bromo- 6-methyl-l , 4-benzoquinone , 2-phenyl-l, 4-benzoquinone , 2,5-di-phenyl-1 , 4-benzoquinone , 2- (4' -bromo) -phenyl-1 , 4-benzoquinone , 2- (2 ' -chloro) -phenyl-1 , 4-benzoquinone , 2- (4' -methy1) -phenyl- 1. -benzoquinone , 2-(3'- or 4 V-nitro) -phenyl-1 , 4-benzoquinone , 2.5-dimethylthio- , 2 , 5-diethylthio- or 2 , 5-dibutylthio-l , 4-benzoquinone , 2-octylthio-l , 4-benzoquinone , 2-dodecylthio-l , 4-benzoquinone , 2-octadecylthio-l, 4-benzoquinone , 2-butoxy-l , 4-benzoquinone , 2 , 5-dimethoxy-l, 4-rbenzoquinone , 3- or 5-hydroxy-1 , 2-benzoquinone , 2-carboxymethylthio-l , 4-benzoquinone , 3-hydroxy-5-ethoxycarbonyl-l , 2-benzoquinone , 2-cyclohexyloxy-carbo.nylmethyl hio-l , 4-benzoquinone , 2-butoxycarbonylmethylthio- 1.4-benzoquinone , 2-octadecyloxycarbonylmethylthio-l , 4-benzoquinone, 2-cyanoethylthio-l , 4-benzoquinone, 2 , 5-diethoxyethyl-thio-1 , 4-benzoquinone , 2 , 5-diphenoxy-l', 4-benzoquinone , 2-phenyl-thio-l , 4-benzoquinone , 2 ,6-diphenylthio-1 , -benzoquinone , 2.5-dipheriylthio-l , 4-benzoquinone , 2 , 5-di- (4' -chloro) -phenyl-thio-1 , 4-benzoquinone , 2- (2 ' -nitro) -phenylthio-1 , 4-benzoquinone , 2- (4' -methoxy) -phenylthio-1 , 4-benzoquinone , 2- (41 -butyl) -phenylthio-1 , 4-benzoquinone , 2- (4' -chloro) -phenylthio-1 , 4-benzoquinone 2, 5-di- (4' -bromo) -phenoxy-1, 4-benzoquinone, 2- (2 ' -methoxy) - henox -1 , 4-benzo uinone , 2- 4 ' -butox - henox -1 , 4-benzo- quinone , 2 , 5-di- (4' -methyl) -phenoxy-1 , -benzoquinone ; furthermore 1 , 2-naphthoquinone , 1 , 4-naphthoquinone, 2-phenyl-l , 4-naphthoquinone , 3-methyl-l , 2-naphthoquinone , 2-hydroxy-l , 4-naphthoquinone , 3-hydroxy-l , 2-naphthoquinone , 2-chloro-l , 4-naphthoquinone , 2-methyl-l , 4-naphthoquinone , 2-ethyl-l,4-naphthoquinone , 6-hydroxy—l , 2-naphthoquinone, 6-hydroxy-l , 4-naphthoquinone , 5 , 8-dihydroxy-l , 4-naphthoquinone , 5- or 6-chloro-1 , 4-naphthoquinone , 3 , 6-dibromo-l , 4-naphthoquinone , 8-nitro-l , 4-naphthoquinone , 2 , 5-dimethyl-l , 4-naphthoquinone , 2-methyl-5-hydroxy-l , 4-naphthoquinone , quinolinequinone-5 , 8 or 1 , 4-anthraquinone .

Examples of R^ and Rg as unsubstituted alkyl groups having at most 12 carbon atoms ;are: methyl, ethyl, propyl, isopropyl, butyl, pentyl, isopentyl, heptyl, octyl, decyl or deodecyl groups. When R.^ or R2 are substituted by alkylthio groups, these groups must be separated by at least 3 carbon atoms from the. sulphur atom in th general Formula III.

Especially advantageous for the process according to the invention are organic sulphides of the general Formula III in which, of R^ or Rg, at least one R represents an alkyl group having from 1 to 4 carbon atoms or in which R^ and R≥ together represent from k to 6 methylene' roups .

Examples of organic sulphides which are suitable as starting materials are: dimethyl sulphide, diethyl sulphide, dipropyl sulphide, diisopropyl sulphide, dibutyl sulphide, diisobutyl sulphide, dipentyl sulphide, diisopentyl sulphide, diheptyl sulphide, dioctyl sulphide, didecyl sulphide, didodecyl sulphide, methyl dodecyl sulphide, dibenzyl sulphide, methyl benzyl sulphide, (3 ' -methyl) -benzyl- ( ' -methoxy) -benzyl sulphide, ethyl phenethyl sulphide, 3 , 3 ' -dichlorodipropy1 sulphide, di- c -hydrox ethyl sulphide, di- co -hydroxybutyl sulphide, di- -hydroxyhexyl sulphide, methyl- cj -hydroxyethyl sulphide, methyl- ) -hydroxybutyl sulphide, dimethoxy methyl or dibutoxy methyl sulphide, dimethoxy-, diethoxy-, dipropoxy-, diisopropoxy- , dibutoxy- or didodecyloxy-ethyl sulphide, 3-chloropropyl methyl sulphide, dimethoxybutyl . sulphide , methyl- Cj -methoxyethyl sulphide, rnethyl-&j-ethoxybutyl sulphide, di- dodecyloxypropy1 sulphide, diphenoxyethyl sulphide, di-4-bromo- phenoxyethyl sulphide, methyl- (4-methylthio) -butyl sulphide, methyl- (6-methylthio) -hexyl sulphide, ethyl- (6-ethylthio) -hexyl-sulphide, butyl- (6-butylthio) -hexyl sulphide, methyl allyl sulphide, methyl prop-l-en sulphide and methyl hex-1-en sulphide; in addition phenylmethyl sulphide, phenylethyl sulphide, phenyl-butyl sulphide, phenyl isobutyl sulphide, phenylpentyl sulphide, (2-, 3- or 4-methylphenyl-l) -methyl or ethyl sulphide, 4-ethoxy-phenyl-1 methyl sulphide, 2-chlorophenyl-l-methyl sulphide, 2-or 4-bromophenyl-l-methyl sulphide and 2-chlorophenyl-l-methyl sulphide as well as tetrahydrothiophene ,.2-methyl-, 3-methyl-or 3-ethyl- tetrahydrothiophene , 3 , 4-dimethyl etrahydrothiophene , 2 , 3-dimethyltetrahydrothiophene , tetrahydrothiapyran, hexahydro- 1,3- or / thiepine, /I , 4-dithiane and 1 , -oxathiane , methyl cyclopropyl sulphide, methyl cyclopentyl sulphide, methyl cyclohexyl sulphide, methyl cyclooctyl sulphide and dicyclohexyl sulphide.

The compounds which are employed according to the inventa ma a o The reaction of the starting materials in a strongly acid medium is advantageously performed at temperatures of about -40 to 50°C, preferably at -15 to 25CC and the acids used can be Br<z>nsted-Lowry acids or Lewis acids.

. Examples of Bro'nsted-Lowry acids, which can give up a proton to a base and therefore serve as proton donator, usable in the process according to the invention are the following: sulphuric acid, pyrosulphuric acid, phosphoric acid, poly-phosphoric acid, hydrofluoric acid, tetrafluoroboric acid, formic acid, acetic acid, trifluoroacetic acid, oxalic acid, perchloric acid or p-toluene sulphonic acid.

Examples of Lewis acids, which can take up an electron pair and therefore serve as electron acceptor, usable in the process according to the invention are the following: aluminum chloride, aluminum bromide, boron fluoride, phosphorus trichloride, phosphorus oxychloride, antimony pentafluoride or pentachloride , iron(III) chloride or tin (IV) chloride.

Preferably as strongly acid medium an aqueous or aqueous-organic solution is employed having a pH value below 1.0, or an inorganic or organic acid is employed having a pK value in water of less than 4.8, or an organic solvent is employed which is inert under the reaction conditions, e.g. acetic acid, propionic acid, acetic acid anhydride, sulpholane, nitromethane , nitrobenzene or nitrotoluene j or a mixture of such solvents is employed, containing a Br^nsted-Lowry acid having a pK value in water of less than 4.8, or containing a Lewis acid. Examples of suitable solvent mixtures to produce in combination with a nsted-Lowr acid a stron l acid a ueous- organic solution having a pH value below 1, are the following: ■ mixtures of water with acetic acid, propionic acid, sulpholane, methanol, ethanol, acetone or methyl ethyl ketone.

Particularly preferred as strongly acid medium is aqueous sulphuric acid, especially 60 to 857» aqueous sulphuric acid; aqueous perchloric acid/ furthermore aqueous phosphoric acid/ or aqueous hydrofluoric acid as well as polyphosphoric acid can also often be used advantageously.

For the reaction, equivalent amounts of the starting materials are used, or a 5 to 10% excess of an organic sulphide is used. Organic sulphides having a second thio function, where¬ by these two thio functions must be separated by at least 3 carbon atoms from each other, can react with both sulphur atoms of a quinone, i.e. 1 mol of such a bis hio compound reacts with 2 moles of an appropriate quinone.

The acid must also be present in a least an equimolar amount; preferably, however, an excess of acid is employed, especially when the reaction is performed in the presence of water or solvents containing water.

In practice, the reaction can be performed so that the quinone is mixed with the organic sulphide and introduced into the acid medium; the quinone can, however, also be present in the acid medium and the organic sulphide then added; or, finally, the organic sulphide can be present in the acid medium and then the quinone added thereto.

To isolate the end products, various methods can be used, depending on the reaction medium and the solubility properties -of the compounds. For example, the dihydroxyaryl sulphonium salts can be precipitated directly from the acidic aqueous solution by the addition of anions with which they form poorly soluble salts, such as reineckates, thiocyanates or picrates. When the reaction is performed in aqueous sulphuric acid or phosphoric acid, the reaction medium can, after dilution with ice water, be neutralized with calcium hydroxide; after separation of the calcium sulphate or calcium phosphate which precipitates, the solution is acidified with a volatile acid, for example hydrochloric acid or hydrobromic acid, whereupon, after removal of the solvent by distillation, the sulphonium compound is obtained as the corresponding salt, e.g. as the chloride or bromide. In case the reaction is performed in a non-water-miscible solvent containing acid, water can be added to the reaction mixture, thus obtaining transfer of the sulphonium compound formed into the aqueous phase which can be appropriately further processed. Frequently, when the sulphuric or phosphoric acid solution is diluted with ice water, the dihydroxysulphonium salts precipitate directly as the sulphates or phosphates. Preferably, when using aqueous acids, these are neutralized with an. alkali hydroxide, e.g. sodium or potassium hydroxide and then reacidified with an excess of a hydrohalic acid such as hydrochloric or hydrobromic acid, whereby the corresponding halide precipitates.

The addition at 0 to 5°C of an equimolar amount of the sulphide to a suspension of the quinone in the eightfold amount by weight of 60-707o aqueous sulphuric acid has proved to be an especially suitable process for the production of the dihydroxy-aryl sulphonium salts. Depending upon the reactivity of the The sulphonium salts produced according to the new process are, conforming to the nature of salts, solid substances, which, however, in many cases cannot be crystallized. At high temperatures they melt usually at an indefinite melting point with decomposition. If possible, it is advantageous to characterize them as halide, thiocyanate, perchlorate, picrate or reineckate. Most of the sulphonium salts, in particular, e.g. the halides or sulphates are very readily water-soluble; frequently, however, they are also soluble in ethanol, acetone or chloroform. As reactive compounds, dihydroxyary1 sulphonium salts are valuable intermediate products, for example in the dyestuff industry,- in some cases they exhibit fungicidal or bactericidal effects.

The advantages of the new process for the production of dihydroxyaryl sulphonium salts lie in its wide range of application, by which compounds which were hitherto inaccessible or only difficultly accessible can be synthesized in a simple manner. Moreover, it is surprising that in spite of the strongly acid conditions, practically no byproducts are formed and the yields are therefore usually very high.

The following examples illustrate the invention. The temperatures are given in degrees centigrade. ■ r■ Example 1 .8 g of finely pulverized 1 , 4-benzoquinone are suspended at -5 to 0° in 40 ml of 70% aqueous sulphuric acid, a part of which dissolves, and then while stirring well 9.4 g of diethyl sulphide are added. The reaction is allowed to continue with stirring until the originally dark solution becomes light and a sample dissolves clear and colourless in water. 100 ml of water are then added dropwise to the reaction mixture , continuing to keep the temperature at 0°. The solution is then neutralized, while cooling, with 30% aqueous sodium hydroxide solution, treated with 100 ml of concentrated hydrochloric acid and kept for several hours at 0° with stirring. The crystalline precipitate is then removed by filtration and dried in vacuum. 22.0 g : (93%- of theory) of an almost colourless sulphonium salt of the formula are obtained. After from 2%, aqueous or alcoholic hydrochloric acid, it exhibits a melting point of 143° (decomposition).

The corresponding bromide is obtained in an analogous manner when the hydrochloric. acid in the above example is replaced by an equivalent amount of hydrobromic acid. By using instead of 40 ml of 70% aqueous sulphuric acid equal volumes of 85% phosphoric acid, 85% formic acid, 70% perchloric acid or 66% hydrofluoric acid and otherwise repeating the procedure as given in the above example, the same compound of the corresponding salt is obtained in similar yield.

When the starting materials given in Example 1 are replaced by the equivalent amounts of the quinones given in Column 2 of Table 1 and of the sulphides given in Column 3, and the procedure of the example is followed, the temperatures of the reactions lying between -15 and +20°, the corresponding dihydroxy sulphonium salts given in Column 4 are obtained, the melting points of those which can be determined being given in Column 5.

In case the sulphates which form in the reaction in sulphuric acid are poorly soluble, they can, after dilution of the reaction solution with ice water, be removed directly by filtration.

T A B L E 1 Continuation Table 1 Continuation Table 1 Continuation Table 1 Continuation Table 1 Example 63 21.6 g of pulverized 1 , 4-benzoquinone are suspended at -5° in 60 ml of 70% aqueous sulphuric acid, a part of which dissolves, and then 12.8 g of dimethyl sulphide are added dropwise during 30 minutes. The originally yellow-brown reaction mass becomes light in colour after stirring for 2 hours at 0°, and 200 ml of water is slowly added with cooling. This solution is adjusted with cooling to a pH value of about 7 with 307» aqueous sodium hydroxide solution, and then 200 ml of concentrated hydrochloric acid are added. After the addition of 40 g of NaCl, the product is allowed to crystallize while cooling and stirring for several hours ; the product is then removed by filtration and dried in vacuum. 38 g (92% of theory) of a sulphonium salt of the formula having a melting point of 137-138° (decomposition) , are obtained.

The melting point of the product, recrystallized from a little 3% hydrochloric acid at 60°, is 142-143° (decomposition).

Example 64 .8 g of finely pulverized 1 , 4-naphthoquinone are suspended at 0 to 5° in 40 ml of 80% aqueous sulphuric acid, a part of which dissolves, and then, while stirring well, 14.6 g of dibutyl sulphide are added. While stirring at 0 to 5°, the reaction is allowed to continue to completion for 5 more hours. 100 ml of water are then added dropwise to the reaction mixture, continuing to keep the temperature between 0 and 5°. The solution is then neutralized with 30% aqueous sodium hydroxide solution while cooling and then 100 ml of concentrated hydro-chloric acid are added. The temperature is kept at 0° with stirring for about 12 hours, the precipitated product is removed by filtration and dissolved in 120 ml of methanol /water (4:1). To this warm, filtered solution, 50 ml of 4% aqueous hydrochloric acid are added and allowed. to crystallized with cooling. The sulphonium salt is removed by filtration and dried in vacuum. As end product, a compound of the formula having a melting point of 132° (decomposition), is obtained.

When in the procedure described, the neutralized reaction sol-ution is not reacidified with hydrochloric acid, but is diluted to its double volume with water and treated with a saturated aqueous solution of Reinecke's salt (NH^[Cr ( H3)2 (SCN)^] ) , then 50.8 g (89% of theory) of the reineckate of the above sulphonium compound (m.p. 77-80°) are obtained.

The corresponding bromide is obtained analogously when the procedure of the above example is followed, but the hydrochloric acid is replaced by the equivalent amount of hydro-bromic acid.

When the starting materials given in Example 64 are replaced by the equivalent amounts of the quinones given in Column 2 of Table 2 and of the sulphides given in Column 3, and the procedure of the example is followed, the temperatures of the reactions lying between -5 and +25°, the corresponding dihydroxy sulphonium salts given in Column 4 are obtained, the melting points of those which can be determined being given in Column 5.

In case the sulphates which form in the reaction in sulphuric acid are poorly soluble, they can, after dilution of the reaction solution with ice water, be removed directly by filtration.

Continuation Table 2 V.

( Example 82 To a suspension of 6 g AlCl^ in 50 ml dry methylene chlori is added, while stirring well, dropwise at -15° a solution of . 4,2 g of 3-methoxy-o-benzoquinone and 3,5 ml of diethyl sulphide in 100 ml dry methylene chloride. The reaction mixture is kept for 30 minutes at room temperature and then poured into 200 ml of ice water. After :evaporating the aqueous solution the sulphonium . salt may be isolated as reineckate by adding a saturated aqueous solution of Reinecke's salt. 11.5 g (69% of theory) of a sulphonium salt of the formula twice from 30% aqueous ethanol, is 163-165°. If in the above example instead of the Reinecke's salt an aqueous solution of picric acid is used, the corresponding picrate is obtained which melts at 16-9-170°.

Using instead of 6 g AlCl^ equimolar amounts of AlBr^, BF^. or FeCl^ and otherwise proceeding as indicated in the example, the corresponding sulphonium salts are obtained in good yields.

Instead of methylene chloride also the same amounts of dioctyl ether, nitrobenzene, benzene or carbon tetrachloride may be used as solvent. .

When the starting materials given in Example 82 are replaced by the equivalent amounts of the quinones given in the procedure of the example is followed, the corresponding dihydroxy sulphonium salts given in Column 4 are obtained.

T A B L E 3

Claims (5)

What we claim is: .

1. . . Process for the production of dihydroxyaryl-sulphonium salts, characterized hy adding to l,4~quinones of the general Fo or to 1,2-quinones of the general Formula II in which fo X,Y and Z i rogen, an alkyl group having from 1 to 18 carbon atoms, a hydroxyl group, an alkoxycarbonyl group having from 1 to 4 carbon atoms in the alkoxy radical, a halogen atom, a phenyl, halogenphenyl, nitrophenyl or alkylphenyl group having from 1 to 4 carbon atoms in the alkyl radical' or a group -SR or -OR wherein R represents an alkyl group having from 1 to- l8 carbon atoms or a carboxyalkyl, carboxylic acid ester-alkyl, cyanoalkyl . or alkoxyalkyl group having from 1 to 4 carbon atoms in the alkyl or alkox radical, a phenyl, hydroxyphenyl, halogenphenyl, nitrophenyl, alkylphenyl or alkoxyphenyl group havin from 1 to 4 carbon atoms in the alkyl or alkoxy radical, or X and Υ together form a fused homo- or heterocyclic, saturated or unsaturated ring which can be substituted by hydroxyl groups, halogen 'atoms, nitro, alkoxy and/or alkyl groups having from 1 to carbon atoms and which ring, in case it is aromatic, can be condensed with other aromatic rings, organic sulphides of the general Formula III ' ' wherein R.^ represents a propenyl group, an alkyl group having from 1 to 12 carbon atoms in the main chain which alkyl group may be substituted by phenyl • groups, halogen atoms, hydroxyl groups, alkoxy groups . having from 1 to -12 carbon atoms, . henoxy groups, chloro- phenoxy, bromophenoxy, hydroxyalkoxy, alkoxyalkoxy or alkylthio groups having each from 1 to 4 carbon atoms in the alkoxy or alkyl radical, or a phenyl group which may be substituted by halogen atoms, alkyl and/or alkoxy groups having from 1 to 4 carbon atoms, and ^ represents an alkyl group having from 1 to 12 carbon atoms in the main chain which alkyl group may be substituted by phenyl groups, halogen atoms, hydroxyl groups, alkoxy groups having from 1 to 12 carbon atoms, phenoxy groups, chlorophenoxy, bromophenoxy, hydroxyalkoxy, alkoxyalkoxy or alkylthio groups having each from 1 to 4 carbon atoms in the alkoxy or alkyl radical, or ^ and ^ together represent from 4 to 6 methylene groups which may be substituted by alkyl groups having from 1 to 4 carbon atoms and which may include a sulphur or oxygen atom, . . in a strongly acid medium.

2. Process according to claim 1, characterized by employing a compound of the general Formula I or II in which X and Y together represent a benzo radical which is unsubstituted or substituted as defined in claim 1.

J. Process according to claim 1, characterized by employing as strongly acid medium an aqueous-organic solution having a pH value below 1.0.

4. Process according to claim 1, characterized by employing as strongly acid medium, an inorganic or organic acid having a pK value in water of less than 4.8.

5. Process according to claim 1, characterized by employing as strongly acid medium an organic solvent which is inert under the reaction conditions, containing a Brjzfnsted-Lowry acid having a pK value in water of less than 4.8, or containing a Lewis acid. F0 3.25 (Ho)Ho/sg 13.6.72