DE2653446C2 - Process for the preparation of pyrogallol compounds - Google Patents

Description

where all the substituents X are the same and are chlorine or bromine and R ¹ , R ² and R ^{3 have} the above meanings - optionally in the presence of a catalyst - hydrolyzed.

2. The method according to claim 1, characterized in that the reaction is carried out in the presence of Sodium acetate, disodium hydrogen citrate, sodium hydrogen phthalate or sodium hydrogen adiput as cata-

30 lysator performs

3. The method according to claim 2, characterized in that the pH value during the hydrolysis at 2.8 to 6.0 holds.

The invention relates to a process for the preparation of pyrogallol, (1,23-trihydroxybenzene) and certain Ji

Derivatives thereof. ψ

Pyrogallol and its derivatives have various uses, for example as photographi-40 see developers, when dyeing leather and wool, when analyzing heavy metals and as intermediate products, for example in the production of the insecticide 2,2-Dimethy! -l, 3-benzodioxoI-4-yimethylcarbamate. Currently, all commercially available pyrogallol is made by the decarboxylation of gallic acid, which is obtained from relatively rare plant sources. This makes pyrogallol expensive and difficult to use procure. The same applies to pyrogallol derivatives. There has now been a much improved method for 55 Manufacture of pyrogallol and certain derivatives thereof found, in which such rare plant sources can be avoided and the product is easily synthesized.

Accordingly, the present invention relates to a process for the preparation of pyrogallol compounds general formula

HO I OH

wherein R ¹ , R ² and R ^{3 are} identical or different and each represent hydrogen or an alkyl group with 1 to b carbon atoms, or their salts, which is characterized in that a 2,2,6,6-tetrahalogen -6o cyclohexanone compound of the general formula

I 1

HR ^J

where R ¹ , R ² and R ^{3 have} the above meanings and all substituents X are the same and mean chlorine or bromine - optionally in the presence of a catalyst - hydrolyzed.

By this process, the pyrogalloi compounds and their salts can be in very high yields and in can be synthesized in a state of high purity.

The pyrogalloi compounds form salts due to their phenolic OH groups. According to the invention Pyrogalloi compounds produced by processes can be in the form of salts. the Salts are especially alkali salts, for example sodium or potassium salts, especially the sodium salt, and can be made from the pyrogalloi compounds themselves in a manner known per se, for example by reaction be made with alkali oxides. The pyrogallol compound itself can be obtained from the salts in a manner known per se Manner can be obtained, for example by reaction with an acid, for example hydrochloric acid.

Usually, in the hydrolysis of the present invention, the pyrogallol compound is formed rather than a salt hereof, and this can be salted if desired, although this is not preferred.

X is preferably chlorine. The alkyl group R ¹ . R ³ or R ¹ can, for example, be methyl. Be ethyl or, preferably, tertiary butyl. The hydrolysis is of particular interest when at least two of the groups R ¹ . R ² and R ', preferably at least R ^! and R ^J , each represent hydrogen. Thus, according to a particular embodiment, R ¹ and R ² each represent hydrogen and R ^{2 represent} tertiary butyl. Most preferably , R ¹ . R ² and R ¹ each represent hydrogen, so that the pyrogallol compound or the Sa '' / thereof ^ is pyrogallol itself or a salt thereof. The hydrolysis can be represented as follows:

OH

HO

+ 2H ₂ O

OH

+ 4HX

It can be effected directly or indirectly.

The direct hydrolysis takes place in a reaction of the tetrahalocyclohexanone compound itself with water. The indirect hydrolysis best!,! η the reaction of the tetrahalocyclohexanone compound to form a derivative which is reacted with water in a separate step. The indirect hydrolysis can be carried out, for example, by reacting the tetrahalocyclohexanone compound with a metal alkoxide (for example sodium, potassium, calcium or aluminum alkoxide, for example derived from an alkanol with 1 to 4 carbon atoms), preferably sodium methoxide, and subsequent acid hydrolysis, for example with hydrochloric acid . However, direct hydrolysis enables the overall reaction to be carried out in a fewer number of steps and is preferred.

The yield of the direct hydrolysis can be considerably improved by using a catalyst. A wide variety of compounds have been found to act as catalysts in this regard A base or an anion can be used as the catalyst. An anion falls under some definitions of a Base, however, in the present case, it is preferred to distinguish between these. The base can, for example Morpholine, triethanolamine, cyclohexylamine, di-n-butylamine or 2- (diethylamino) -ethanol or an anion exchange resin be.

However, the catalyst is preferably an anion. Suitable anions are

A) the anionic part of a cation exchange resin (for example a carbene acid cation exchange resin) in the hydrogen or salt form (for example, the sodium, potassium, calcium or ammonium form), z. B. Aberlite® IRC 50 in the hydrogen or sodium form, or preferably

B) an anion of another salt (hereinafter referred to as simple salt to distinguish it from the ion exchange resin salt), for example citrate, dihydrogen citrate, hydrogen citrate, acetate, monochloroacetate, hydrogen malate, malate, hydrogen phthalate, hydrogen isophthalate, hydrogen tartrate, tartrate, oxalate (-00CC0O -), o-nitrobenzoate, benzoate, lactate, propionate, glycolate, malonate (-0OCCH ₂ COO-), formate, salicylate (HOC6H4COO-), hydrogen adipate, adipate, hydrogen phosphate, dihydrogen phosphate, picolinate, furoate, dihydrogen pyrophosphate, furoate, dihydrogen pyrophosphate Hydrogen phosphite, gluconate, borate (H ₂ BO ₃ -) or fluoride.

The simple salt anion is preferably in the form of a simple salt rather than the form of Acid used. The anion catalyst can be in the form of a water-soluble metal, ammonium · or Amine salt or a mixture thereof are present. The amine salt can be that of a primary, secondary or be tertiary amine. The amine can be aliphatic, aromatic or heterocyclic or an amine which is a Contains mixture of such substituents on the amine nitrogen atom. It is generally preferred to use the sodium, Use potassium, ammonium or morpholine salt. The salt may or may not be mixed as such generated in situ, for example by reacting the acid from which the salt is derived with alkali. For example The cation exchange resin in the salt form can be generated in situ by putting the resin in hydrogen form is used and an alkali is present. On the other hand, the salt can by using an ester, such as melhyloxalate, in the presence of an alkali, can be formed in situ.

40 45

Specific simple salts that are catalysts are

Trisodium citrate, monomorpholine citrate, dimorphoun citrate, sodium dihydrogen citrate,
Disodium hydrogen citrate, sodium acetate, sodium chloroacetate, sodium hydrogen malate, disodium malate, sodium hydrogen phthalate, potassium hydrogen phthalate, ammonium hydrogen phthalate,

Sodium hydrogen isophthalate, sodium hydrogen trate, disodium tartrate, disodium oxalate
Sodium o-nitrobenzoate, sodium benzoate, sodium lactate, sodium propionate, sodium glycolate,
Disodium malonate, sodium formate, monosodium salicylate, sodium hydrogen adipate
Disodium adipate, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium picolinate,
ίο sodium furoate, disodium dihydrogen pyrophosphate, sodium hydrogen succinate, sodium sulfamal,

Sodium hydrogen phosphite, sodium gluconate, monosodium borate and potassium fluoride.

In the case of a salt of a polybasic acid, a mixed salt, for example a sodium-potassium salt, uses wp ^ den.

The anion catalyst is preferably an anion of a carboxylic acid. The carboxylic acid can be an aliphalic, be aromatic, heterocyclic or alicyclic carboxylic acid. The carboxylic acid can be one or more Contain carboxyl groups. If there is more than one carboxyl group, one is preferably neutralized, and the others may be too. If there is more than one carboxyl group, a mixed salt such as sodium-potassium salt can be used. The carboxylic acid contains preferably only carbon, hydrogen and oxygen atoms. In terms of expediency, availability and high yield is a) a straight-chain alkanoic acid with 1 to 6 carbon atoms, the optionally is substituted by one or more carboxyl and hydroxyl groups, or b) benzoic acid substituted by one or more carboxyl and hydroxyl groups is substituted, preferred

The pK _{a of} the acid whose anion can be used is usually 2.0 to 6.5, preferably 2.5 to

Particularly preferred specific salts are sodium acetate, disodium hydrogen citrate, sodium hydrogen phthalate or sodium hydrogen adipate.
A mixture of catalysts can be used.
The direct hydrolysis takes place at a pH value of at least 2. For a maximum yield this is

pH preferably 2.8 to 6.0. The hydrolysis gives hydrohalic acid HX which has the pH below can lower these lower limits. For an optimal yield it is preferred during the hydrolysis to keep the pH above these lower limits. This can be done in that the catalyst in Salt form is used, for example as the sodium salt, to raise the pH above the value it otherwise, or that alkali is added. The alkali can be any convenient alkali, bcispiclswci-

J5 se alkali hydroxide, carbonate or bicarbonate, e.g. B. sodium carbonate, but preferably sodium hydroxide. According to the invention, the pH is preferably kept at 2.8 to 6.0 during the hydrolysis.

Without being bound by this theory, it appears. that when an anion is used as a catalyst, the hydrolysis is carried out in such a way that a catalyst ion is added to each halogen atom X on the 2,2,6,6-tetrahalogen cyclohexanone compound of formula (II) and then each catalyst anion itself by an HO ion of

«Water ν is displaced, d. H. a rearrangement takes place which leads to the pyrogallol compound of the formula (!). It can be seen that this is analogous to the indirect hydrolysis mentioned above using the tetrahalocyclohexanone compound reacted with a metal alkoxide and the product is acid hydrolyzed; there is a Alkoxide ion is the anion that displaces every X atom and the displacement of the alkoxide ion takes place in one separate stage.

If an anion is used as catalyst and the anion is that of a simple Saiz ^ s, ⁵ rägt be the amount of Ka'alysator preferably at least four anions per molecule Tetrahalogencyclohexanon. In general, better yields are obtained by using 6 to 10 catalyst anions instead of 4 catalyst anions per molecule of tetrahalocyclohexanone. Generally, there is no better yield by using 16 catalyst anions instead of 8 catalyst anions per molecule of Tctrahalogency-

Obtain clohexanone.

When an anion is used as a catalyst and the anion is that of a cation exchange resin. The amount of catalyst is preferably at least 4 equivalents, in particular 6 to 10 equivalents of anion per mole of tetrahalocyclohexanone. generally no better yield by using Ib instead of 8 equivalents of anion per mole of Tetrahalogencyolohex & non is achieved.

■ 55 If a nozzle is used as a catalyst, it is believed, without being bound by this theory;: u

be that one equivalent of base with one equivalent of hydrohalic acid formed during hydrolysis

will respond. When a base is used as the catalyst, the amount of the catalyst is preferably

at least four equivalents of base per mole of tetrahalocyclohexanone.

When direct hydrolysis is used, an organic liquid, e.g. B. methanol or ethanol.

can be used in the reaction mixture to obtain a system that is initially more of a phase than consists of two phases

The hydrolysis according to the invention is preferably carried out in solution. At least the theoretical one must Amount of water used to effect hydrolysis and when direct hydrolysis is applied the solvent is preferably water in excess of the amount required for hydrolysis

is. When direct hydrolysis is used, preferably all of the catalysts are in solution. When the above-mentioned indirect hydrolysis is employed, the reaction with the alkoxide in generally carried out in the presence of the alkanol, from which the alkoxide originates, as solvent, and the subsequent acid hydrolysis can be carried out in the presence of water as a solvent.

which is in excess of the amount required for hydrolysis.

In the hydrolysis, 0.3 ml to 1 l of water per g of tetrahalocyclohexanone compound are preferred used.

The hydrolysis can, for example, at a temperature of 0 to 250 ³ C, z. B. 0 to 120 ⁰ C, are carried out. The reaction mixture is usually heated. According to a preferred embodiment, especially when direct hydrolysis is used, the temperature is 60 to 140 ° C. The direct hydrolysis is preferably carried out under reflux.

The hydrolysis can take place under pressure which is above, at or below atmospheric pressure. Of the Pressure can be, for example, 0.1 to 14.7 bar and is expediently atmospheric pressure.

The pyrogallol compound and its salts absorb oxygen in the heat, and the salts absorb Oxygen even at ambient temperature.

Accordingly, excessive heating thereof should be avoided, and in some cases it can it may be desirable to carry out the hydrolysis under an inert atmosphere, for example in an atmosphere of Nitrogen or carbon dioxide.

The product can be isolated and purified in a manner known per se.

The basic formula (II) of the process according to the invention can be prepared in a manner known per se or by methods which are known for the preparation of analogous compounds. If the starting maicriai 2.2.6.ö-Tcirucrriorc: yt; iunex <ifiufi or 2.2, &, & - Teirabrorrtcyc! OhcxanGic, it can be prepared by Ch'o ricrcn or bromicrcn of cyclohexanone. On the other hand, 2,2,6,6-tetrachlorocyclohexanone can be produced by chlorinating cyclohexanol. However, 2,2,6,6-tetrachlorocyclohexanone or 2,2,6,6-tetrabromocyclohexanone is preferably produced by a process in which, in the case of producing α 2,2,6,6-tetrachlorocyclohexanone, chlorine or in the case of production of 2,2,6,6-tetrabromocyclohexanone bromine in

® of the liquid phase with a cyclohexanone compound of the general formula

O

Il

YCY

Y-C C-H

HC CS ^m "

H ^/ \

wherein the Substitucntcn Y are the same or different and in the case of the preparation of 2.2,6,6-tetrachlorocyclohexanone a hydrogen or chlorine atom and in the case of using 2,2,6,6-tetrabromocyclohexanone represent a hydrogen or bromine atom, in the presence of thionyl chloride, selenium oxychloride, potassium fluoride, Sulfuryl chloride or tributylphosphine is implemented as a catalyst.

The starting compounds of the formula (III) used in the above process are either known Compounds or may be made by methods known to those skilled in the art organic chemical synthesis for the preparation of analogous compounds are known.

The catalysts mentioned for the production of 2,2,6,6-tetrachlorocyclohexanone or 2,2,6,6-tetrabromocyclohexanone enable the reaction to be carried out conveniently and in high yield. The catalysts are particularly useful when the desired product is then hydrolyzed to pyrogallol shall be. Thionyl chloride, potassium fluoride and sulfuryl chloride are advantageous because they are relatively easily available and therefore are relatively cheap. Thionyl chloride is the most preferred catalyst.

In general, the weight of the catalyst is at least 0.1%, preferably the weight of the Catalyst at least 0.1%, preferably 0.5 to 12%, based on the weight of the cyclohexanone compound.

The process is of particular interest for the production of 2,2,6,6-tetrachlorocyclohexanone, so that the halogen employed is chlorine, rather than bromine, and Y is a hydrogen or chlorine atom, rather than a Represents hydrogen or bromine atom.

The cyclohexanone compound is preferably cyclohexanone itself, although it is a halogenated intermediate can be used. For example, you can for the production of 2,2,6,6-tetrachlorocyclohexanone start from 2.2,6-trichlorocyclohexanone.

The reaction is preferably carried out in the presence of a solvent. Suitable solvents are saturated chlorinated hydrocarbons (e.g. aliphatic hydrocarbons with 1 or 2 carbon atoms and 2 to 4 chlorine atoms, such as carbon tetrachloride, methylene dichloride or tetrachloroethane), saturated Hydrocarbons (e.g. those with 5 to 10 carbon atoms, such as pentane, hexane, cyclohexane, octane or Decane) or saturated aliphatic carboxylic acids (e.g. saturated aliphatic carboxylic acids with 2 to 5 carbon atoms, such as acetic acid, propionic acid or butanoic acid). In the manufacture of 2 ^, 6,6-tetrachlorocyclohexanone 2 ^, 6-TrichIorcydohexanon can be used as a solvent. This is the preferred way of solving the problem! however, the melted desired product (e.g. 2,2,6,6-tetrachlorocyclohexanone) itself. It can be a Mixture of solvents can be used, but this is not preferred.

According to a preferred procedure, the halogen and the cyclohexanone compound of a react

tion zone, which contains a solvent and the catalyst, fed. The reaction is usually preferably from 75 to 11O ⁰ C, for example up to 11O ⁰ C, carried out at a temperature in the range of 60 to 160 ⁰ C, 80th The reaction temperature is preferably below the boiling point of the solvent, if one is used. When molten 2,2,6,6-tetrachlorocyclohexanone is used as the solvent, the reaction temperature is its melting point as changed by the other materials present. The melting point of pure 2,2,6,6-tetrachlorocyclohexanone is 82 to 83 ° C.

Preferably the reaction is carried out under essentially anhydrous conditions; H. that less than 1% by weight, preferably less than 0.5% by weight of water, based on the weight of the cyclohexanone compound, available.

The total amount of chlorine or bromine used is usually sufficient. all of the cyclohexanone compound to be converted into the desired product. When the reaction occurs by the halogen and the cyclohexanone compound are fed to a reaction zone, which contains a solvent and the catalyst contains, it is preferred to reduce side reactions to a minimum that that with the cyclohexanone The amount of halogen in contact in the reaction zone is at least stoichiometric at all times The amount that is required. to convert the cyclohexanone compound into the desired product convict. For example, starting from cyclohexanone, preferably at least 4 moles of halogen added per mole of cyclohexanone; expediently 4 to 6 moles of halogen are added per chlorohydroxanone fed.

When the reaction is carried out by having the halogen and the cyclohexanone compound in one reaction zone containing a solvent and a catalyst is the hourly feed rate of the cyclohexanone compound to the zone generally never more than half, for example more than one third of the weight of the respective solvent. If one of a certain weight W des Runs out of solvent, therefore, the initial hourly feed rate of the cyclohexanone compound W / 2. As the reaction proceeds and the desired product formed as an additional solvent acts, the total weight of the solvent is increased, and thus the hourly feed rate the cyclohexanone compound can be increased, while still not more than half the Weight of the solvent. However, a constant feed rate is expedient applied.

In order to achieve maximum conversion into the desired product (in particular 2,2,6,6-tetrachlorocyclohexanone) ensure, it is preferred to continue the supply of halogen at the end of the cyclohexanone compound supply. The supply of halogen is preferably continued until the weight of the 2,2,6-trihalocyclohexanone (in particular of the 2,2,6-trichlorocyclohexanone) less than 5%, in particular less than 1% of the total weight of 2,2,6-trihalocyclohexanone and 2,2,6,6-tetrahalocyclohexanone. Preferably the halogen supply is at least a quarter of an hour, for example 1/4 to 3 hours, z. B. 1/2 to 3 hours. continued after the addition of the cyclohexanone compound was stopped.

The desired product can be separated off in a manner known per se.

The following examples are intended to explain the present invention in more detail. Relate all parts and percentages focus on the weight.

B e i s ρ i e I 1

A mixture of 100 parts of 2,2,6,6-Tetrachlorcyclohexanon and 532 parts of water was heated to 60 ⁰ C. |

and 149 parts of morpholine were added dropwise over a 14 minute period. The mixture was ^{kept at 60 °} C. for a further 4 minutes, then cooled and filtered. The filtrate was acidified by adding 21 parts of concentrated hydrochloric acid solution and then continuously extracted with ether. p

After drying over MgSCu, the extract was evaporated to give 21 parts of tar which, as Gas-liquid chromatography after acetylation showed it contained 6 parts (11.2% yield) pyrogallol.

Example 2

100 parts of 2,2,6,6-tetrachlorocyclohexanone, 424 parts of sodium acetate and 1059 parts of water were mixed under nitrogen and the mixture was refluxed for 10 minutes. Then it was cooled to 5O ⁰ C, and the addition of 318 parts of sodium bicarbonate strong foaming occurred. The mixture was then extracted continuously with ether and the extract dried over magnesium sulfate and evaporated to give 39 parts of residue. This residue was triturated with 39 parts of chloroform, and after filtration and drying in air, 15.2 parts (28.5% yield) of pyrogallol were obtained as a yellow-brown dye. M.p. 130-133.5 ° C.

Example 3
eo

Under nitrogen, 100 parts of 2 ^, 6,6-trachlorocyclohexanone, 456 parts of dinalrium oxalal and 1064 parts

• Mixed water and refluxed the mixture for 2 hours. Then it became continuous with ether extracted and dried over sodium sulfate. After filtering, the extract was evaporated, leaving 52.2 parts

of a residue which, as gas-liquid chromatography showed, after being converted into the Triacetate contained 243 parts (46% yield) pyrogallol.

Example 4

! I 2.36 g (0.01 mol) 2,2,6,6-tetrachlorocyclohexanone were added to 35 ml (0.17 MoH of a stirred 27% sodium

ί Oxide solution added under nitrogen at 24 ° C. The temperature of the mixture rose and became through

External cooling kept at 45 ° C. When the exotherm ceased, the mixture was on ice

cooled and 17 ml of concentrated hydrochloric acid and 28 ml of water were added. The methanol was distilled off from the reaction mixture under nitrogen and the resulting aqueous solution was continuously extracted with ether. The ether extract was _{dried over MgSO 4} and the ether removed in vacuo to give 0.85 g of a residue which, when analyzed, consisted of 18% pyrogallol. This corresponds to a pyrogallol yield of 12.2%.

Example 5

4.72 g (0.02 mol) of 2,2,6,6-tetrachlorocyclohexanone were added to a solution of 0.16 mol of disodium hydrogen citrate added by decomposing 12.8 g of sodium hydroxide to a solution of 33.6 g of citric acid monohydrate in 50 ml of water with cooling. The mixture was stirred and refluxed heated. The reaction mixture was sampled at intervals and analyzed for free chloride, until the samples showed that the reaction was complete. The total time under reflux was 4 hours. the The reaction mixture was continuously extracted with ether. The ether extract was dried over MgSC> 4, filtered and the ether removed to give 2.74 g of a residue which, upon analysis, was 77.5% off Pyrogallol bcscnd. The pyrogallol yield is 84.4%.

Example 6

4.72 g (0.02 mol) of 2,2,6,6-tetrachlorocydohexanone were added to a mixture of 26.5 g (0.16 mol) of phthalic acid in 75 ml of water, to which 6.4 g (0.16 mol) of sodium hydroxide were added had been. The mixture was refluxed for t 1/2 hours. 5 ml of 5N sodium hydroxide solution was added over 5 minutes and the mixture was refluxed for a further 2½ hours. A sample was analyzed for free chloride and it was found that the reaction was complete. 13 ml of concentrated hydrochloric acid was added at 90 ° C. The reaction mixture was cooled to 5 ° C, and the phthalic acid is filtered off, the pH of the Fiitrats was adjusted to 3.5, and was continuously extracted with ether The ether extract was dried over _{Na2 SO4,} fütrtiert and the ether removed to give 3 .04 g of a crude product were obtained which contained 2.02 g of pyrogallol. This corresponds to a pyrogallol yield of 80%.

B e i s ρ i e 1 7

9.6 g (0.16 mol) of glacial acetic acid were dissolved in distilled water and the pH was adjusted to 4.7 with 10 N sodium hydroxide solution. The volume of the solution was adjusted to 55 ml by dilution with distilled water. 4.72 g (0.02 mol) of 2,2,6,6-tetrachlorocyclohexanone was added and the mixture was heated to reflux. The pH of the reaction mixture was maintained at 4.7 by adding 5N sodium hydroxide solution. Samples were taken intermittently and analyzed for free chloride to determine the end of the reaction / u. The aqueous solution obtained was extracted continuously with ether. The ether extract was _{dried over Na 2} SO 4, filtered and the ether removed, 3.5 g of a crude product which contained 1.46 g of pyrogallol being obtained. The pyrogallol yield is 58%.

45 Example 8

16.8 g (dry) Amberlite® IRC50 ion exchange resin in the sodium form was distilled in 50 ml Suspended in water. 4.72 g (0.02 mole) of 2,2,6,6-tetrachlorocyclohexanone was added and the mixture Heated under reflux for 1½ hours, during which time the pH had dropped from 62 to 1.7. Of the pH was adjusted to 3.8 and refluxing continued for an additional 4 hours during which time during which time the pH was maintained between 2 and 4 by adding 5N sodium hydroxide solution. Chloride analysis indicated 92% hydrolysis. The resin was filtered off and the reaction mixture extracted continuously with ether The ether extract was dried, filtered and the ether removed, whereby 1.2 g of a brown oil were obtained. This contained 19.6% pyrogallol on analysis, which corresponds to a yield of Corresponds to 93% pyrogallol

Example 9

4.72 g (0.02 mol) of 22,6,6-tetrachlorocyclohexanone was added to 50 ml of distilled water and the pH adjusted to 5.0 with 5N sodium hydroxide solution. The mixture was stirred and refluxed and the pH adjusted -Value held at 5.0 by adding sodium hydroxide solution. The mixture was sampled at intervals and analyzed for free chloride until the reaction was complete. The reaction mixture was extracted with ether and the ether extract was dried over Na ₂ SO ₄ , filtered and the ether was dissolved out to give 13 g of a brown oil. This contained 0.03 g of pyrogallol, which corresponds to a yield of 1.2%

Example 10

As in Example 9, but keeping the pH at 3.0, a yield of 3.7% was obtained. Pyrogallol scored.

Example! 11th

As in Example 5, but using 0.02 mol of 2,2,6,6-tetrabromocyclohexanone instead of Tetrachlorocyclohexanone, a yield of 44% pyrogallol was achieved.

Example 12 to 52

A suspension of 4.72 g (0.02 mol) of 2,2,6,6-tetrachlorocyclohexanone was refluxed with an aqueous Solution / suspension of the catalyst compound given below (0.16 mol; in the case of Amberlite * iRC 50, 16.0 g of dry resin were used) heated in 50 ml of water. The mixture was in Samples are taken at intervals and analyzed for free chloride to determine the end point of the reaction. The aqueous reaction mixture was then filtered, if necessary, and continuously extracted with ether. The ether extract was dried over NajSO-i, filtered and the ether removed, with the crude pyrogallol was obtained. This was ansiysicrl to determine the yield.

Example catalyst compound yield pyrogallol%

12 trisodium citrate 25.5

13 Sodium Dihydrogen Citrate 31.0

14 sodium chloroacetate 31.0

15 sodium hydrogen malate 71.0

16 disodium malate 52.0

17 potassium hy. ^J rogenphthalat 75.0 18 52.0 Ammoniumhvdrogenphthalat

19 sodium hydrogen isophthalate 59.8

20 sodium hydrogen tartrate 58.0

21 disodium tartrate 60.5

22 disodium oxalate 44.0 23 sodium o-nitrobenzoate 35.1

24 sodium benzoate 49.5

25 sodium lactate 68.5

26 sodium propionate 42.9

27 Sodium Glycolate 5 ^, 0 28 disodium malonate 27.0

29 sodium formate 20.8

30 sodium salicylate 29.0

31 Sodium hydrogen adipate 82.0

32 Disodium Adipate 46.0 33 Amberlite®IRC50H - Form 17.0

34 disodium hydrogen phosphate 22.6

35 Sodium Dihydrogen Phosphate 32.5

36 monosodium boral 7.0

37 Potassium fluoride 16.0 so 38 Ethylenediamine tetraacetic acid disodium salt 49.0

39 Sodium hydrogen fumarate 53

40 disodium fumarate 58

41 Sodium hydrogen 1,23,6-tetrahydrophthalate 62

42 Sodium hydrogen maleate 34 43 Sodium pivalate 11

44 dipotassium oxalate 71

45 sodium picolinate 6

46 sodium furoate 19

47 Disodium Dihydrogen Pyrophosphate 47 48 Sodium Hydrogen Succinate 76

49 sodium sulfamate 13

50 sodium hydrogen phosphite 18

51 dimethyl oxalate 25

52 sodium gluconate 67

Example 53

4.72 g (0.02 mol) of 2,2,6,6-tetrachlorocyclohexanone were added to a solution of morpholine citrate which was prepared by adding 24.6 ml (0.283 mol) of morpholine to a solution of 33.6 g (0 , 15 mol) zilronic acid monohydrate in 50 ml of water with cooling. The mixture was stirred and heated to reflux. The reaction mixture was sampled at intervals and analyzed for free chloride until the samples indicated that the reaction was complete. The total time under reflux was 3 hours. The reaction mixture was continuously extracted with ether. The ether extract was dissolved over MgSO4, the fillerol and the ether removed, giving 5.4 g of a residue which, on analysis, contained 33.6% pyrogallol. The pyrogallol yield is 71.9%. ₁₀

Example 54

5 g (0.02 mol) of 2J2,6,6-tetrachloro-4-methylcyclohexanone were added to a solution of 30.1 g (0.16 mol) of sodium hydrogen phthalate added in 50 ml of water. The mixture was heated to reflux, and at 15 intervals Samples were taken to determine free chloride. When the reaction finished, the mixture became cooled, filtered, extracted with ether and the ether removed, 3.8 g of a crude product being obtained were, the 1.26 g of 1,2,3-trihydroxymethylbenzoI (methyl pyrogenic oil) contained This corresponds to a yield of 45%.

ι ⁵⁵

Claims (1)

Patent claims: 1. Process for the preparation of pyrogallol compounds of the general formula 5 OH HO I OH wherein R ¹ , R ² and R ^{3 are} identical or different and each represent hydrogen or an alkyl group with 1 to 6 carbon atoms, or their salts, characterized in that a 2 ^, 6,6-tetrahalo-15 gencyclohexanone compound the general formula