GB2031887A - Trichlorophloroglucinol tri-n- or -i- propyl ether, preparation thereof and conversion thereof to trichlorophloroglucinol or phloroglucinol - Google Patents

Abstract

Trichlorophloroglucinol tri-n- or -i- propyl ether is disclosed. A process for the preparation of trichlorophloroglucinol tri-n- or -i-propyl ether comprises reacting hexachlorobenzene with from 3 to 20 times the molar quantity of sodium n- or -i- propylate in an aprotic solvent at from 50 to 250 DEG C is also disclosed. Trichlorophloroglucinol tri-n- or -i- propyl ether may be converted to trichlorophloroglucinol or phloroglucinol by hydrolysis and, optionally, dechlorination.

Description

SPECIFICATION Trichlorophloroglucinol tri-n- or -i-propyl ether, preparation thereof and conversion thereof to trichloroph loroglucinol or phloroglucinol This invention relates to trichlorophloroglucinol tri-n- ori-propyl ether, preparation thereof and conversion thereof to trichlorophloroglucinol or phloroglucinol.

Several processes for the synthesis of phloroglucinol are known. Technically important processes include, in particular, the reduction of 1,3,5-trinitrobenzeneto 1,3,5-triaminobenzene and its subsequent hydrolysis.

In earlier processes, reduction may be carried out using tin in hydrochloroic acid solution (Weidel and Pollak, Monatsh 12, (1900); Hepp, Ann. 215,348; Organic Synthesis Coll. Vol. 1,444(1932); US Patent No.

2,461,498) or using hydrogen and Raney nickel in an organic solvent, particularly ethyl acetate, (German Patent No.813,709; Gill petal, J. Chem. Soc. (1949); British Patent No. 1,106,088). One suitable reducing agent for the reduction oftrinitrobenzene on a large scale is iron/hydrochloric acid (US Patent No.2,614,126; Kastens, Ind. and Engin. Chem. 42,402(1950); British Patent No. 1,022,733). Platinum, palladium and rhodium catalysts have also been proposed for the reduction of trinitrobenzene (French Patent No.

1,289,647; Desseigne, Mem. Poudres 44, 325 (1962). Instead of starting with 1 ,3,5-trinitrobenzene, it is even possible in this synthesis to start with 2,4,6-trinitrobenzoic acid, which may be obtained on a large scale by the oxidation of trinitrotoluene using sodium dichromate in sulphuric acid (Kastens, 1. c. ), because the 2,4,6-triaminobenzoic acid which is formed during reduction is either immediately decarboxylated to form triaminobenzene or is converted into phloroglucinol during the subsequent hydrolysis reaction (British Patent Nos. 1,022,733; 1,106,088 and 1,274,551). It is also known that 5-nitro-1, 3-diamino-benzene may be used as the starting material, instead of the trinitrobenzene (British Patent No. 1,012,782).Hydrolysis of the triamine to form phloroglucinol is normally carried out in mineral acid solution (Flesch, Monatsh. 18, 755 (1897); German Patent No. 102,358). In a more recent process, it is carried out in the presence of copper and/or salts thereof as catalyst (German Patent No. 1,195,327).

In another technically important process, phloroglucinol is obtained by oxidising 1,3,5-tri4-propylbenzene, separating off the trihydroperoxide from the thus-obtained mixture of the mono-, di- and tri-hydroperoxide and subsequently subjecting it to splitting with ketone (British Patent No. 751,598; East German Patent No.

12,239; Seidel petal, Journ. prakt. Chemise275, 278(1956)). It is also possible directly to convert tri-i-propylbenzene into phloroglucinol triacetate by oxidation using oxygen in acetic acid anhydride and to hydrolyse the thus-obtained phloroglucinol triacetate using alcoholic sodium hydroxide to form phloroglucinol (US Patent No. 2,799,698). It is also possible to use m-i-propylresorcinol as starting material. In this case, the m-i-propylresorcinol is esterified using acetic acid anhydride, the thus-obtained m-i-propylresorcinol diacetate is oxidised to form the hydroperoxide and, finally the thus-obtained hydroperoxide is converted into phloroglucinol using acid (US Patent No. 3,028,410).

In addition, phloroglucinol may be obtained by melting resorcinol (Barth und Schreder, Ber. 12,503(1879), resorcinol substituted by chlorine or bromine in the 2-4-, 5-, 3,5-or 2,4-position (German Offenlegungsshcrift No. 2,231,005) or 1,3,5-benzene trisulphonic acid (US Patent No.2,773,908) with excess alkali metal hydroxide.

In addition to the benzene derivatives mentioned above, hexaoxybenzene, picryl chloride, tetrachloro- and tetrabromobenzene and tribromobenzene have also been mentioned as starting materials for the synthesis of phloroglucinol. Hexaoxybenzene is hydrogenated using platinum oxide in aqueous medium (Kuhn petal, Ann. 565, (1949). Picryl chloride is reduced using tin and hydrochloric acid or electrolytically and the 1,3,5-triaminobenzene or 2,4,6-triamino-1 -chloro-benzene obtained is subsequently hydrolysed (Heertjes, Receuil 78,452 (1959). The tetrahalobenzenes mentioned above are subjected to ammonolysis in the presence of a copper catalyst and the intermediate triamine is hydrolysed in the reaction mixture, i.e. without being separated off, (U.S. Patent No. 3,230,266).Tribromobenzene may be converted using sodium methanolate and catalytic quantities of copper iodide in methanol/dimethyl formamide as solvent into 1,3,5-trimethoxy benzene which, finally, is also subjected to hydrolysis (McKillop etna!, Synthetic Communications 4(1)35(1974). Reference is also made to the process according to German Offenlegungsschrift No. 2,362,694, in which 2,6-, 2,4-, or 3,5-dihalo-phenols dissolved in pseudocumene are heated in the presence of a strong alkali.

It is also known that phloroglucinol may be synthesised from malonic acid diethyl ester. On treatment with metallic sodium, the malonic acid diethyl ester condenses by itself to form the trisodium salt of phloroglucinol dicarboxylic acid diethyl ester, which is then subjected to alkaline hydrolyss and decarboxylation (V. Baeyer, Ber. 18,3454(1885); Willstatter, Ber. 32, 1272 (1899); Leuchs, Ber. 41,3172 (1908); Komninos, Bull. Soc. Chim. France 23,449 (1918). This synthesis may be improved by carrying out formation of the sodium malonic acid diethyl ester and the trisodium salt of phloroglucinol dicarboxylic acid diethyl ester in a single operation by boiling in an inert, high-boiling solvent, preferably decalin (German Patent No. 24,998).

Of the above-mentioned processes, it is only the process which starts from 2,4,6-trinitrobenzoic acid that has hitherto been adopted for use on a commercial scale. However, this process is attended by many serious disadvantages. The 2,4,6-trinitrobenzoic acid is prepared by oxidation of the explosive trinitrotoluene so that the process is dangerous. In addition, the total yield, as measured on the basis of 2,4,6-trinitrobenzene via the stages trinitrobenzene, triaminobenzene to the phloroglucinol, is poor. The process is also disadvantageous on acount of the effluent problems involved. The effluents accumulating during oxidation and reduction are strongly acid, contain the heavy metals chromium and iron and for this reason have to be worked-up.

Another two processes for synthesising phloroglucinol on a commercial scale have recently become known. In the process according to German Offenlegungsschrift No. 2,502,429, benzenetricarboxylic acid-(1,3,5)-triamide is chlorinated in an aqueous mineral acid medium, the benzene tricarboxylic acid (1 ,3,5)-tri-N-chloramide obtained is converted, by treatment with ammonia, into 1 ,3,5-trireido-benzene and the thus-obtained 1 ,3,5-triureido-benzene is subsequently hydrolysed in mineral acid solution. In the process according to German Offenlegungsschrift No. 2,621,431, s-triacetyl benzene is converted into benzene-1,3,5tris-acetoxime which is subjected to a Becimann rearrangement and the mixture obtained is hydrolysed in acid medium.In both cases, the starting materials are readily obtainable, the yields achieved are high and, in addition, pure products are obtained.

The present invention provides trichlorophloroglucinol tri-n- or -i-propyl ether.

The present invention also provides a process for the preparation of trichlorophloroglucinol tri-n- or -i-propyl ether which comprises reacting hexachlorobenzene with from 3 to 20 times the molar quantity of sodium n-or -i-propylate in an aprotic solvent at from 50 to 250"C.

The present further provides a process for the preparation of trichlorophloroglucinol which comprises hydrolysing trichlorophloroglucinol tri-n- or-i- propyl ether.

The present invention further provides a process for the preparation of phloroglucinol which comprises dechlorinating trichlorophloroglucinol tri-n- or-i- propyl ether and hydrolysing the resulting phloroglucinol tri-n- or -i-propyl ether.

Hexachlorobenzene is commercially available in large quantities. For example, it accumulates as a waste product in the chlorination of propylene. On account of its toxicity, hexachlorobenzene is an extremely problematical compound which has hitherto proved to be very difficult to utilise and eliminate. Small quantities may be utilised by oxidation to form chloranil. Furthermore, equally small quantities are currently being processed to form pentachlorophenol and used in wood preservatives, although this particular application is likely to come to an end in the near future for ecological reasons. However, most of the hexachlorobenzene cannot be utilised, nor may it be burnt or buried. For this reason, it has hitherto had to be chemically eliminated. Thus, there are today chemical utilisation undertakings which charge considerable sums for the removal of hexachlorobenzene.Accordingly, it is a considerable advantage that the process according to the present invention provides a practical way of utilising hexachlorobenzene.

Instead of using pure hexachlorobenzene, it is also possible to use the hexachlorobenzene-containing waste mixtures of chlorinated hydrocarbons which accumulate in the chemical industry. One example of these mixtures are the mixtures of approximately 65 %, by weight, of hexachlorobenzene, approximately 25 %, by weight, of hexchlorobutadiene and approximately 10 %, by weight, of hexachloroethane which accumulate in the chlorination of propylene. The secondary products may readily be separated from the hexachlorobenzene, for example, by extraction using methanol.

The reaction of the hexachlorobenzene with the alcoholate is carried out at temperatures from 50 to 250"C.

Lower or higher temperatures may also be applied, although they are less advantageous for economic reasons. The preferred reaction temperature s from 100 to 200"C.

Sodium n-propylate or sodium i-propylate is obtained in the conventional way from sodium and n-propyl alcohol or i-propyl alcohol. It is used in quantities of from 3 to 20 moles per mole of hexachlorobenzene. In order to guarantee a complete reaction of the hexachlorobenzene, the alcoholate should not be used in smaller quantities. Larger quantities of alcoholate should be avoided on economic grounds. The sodium n-propylate of sodium i-propylate is preferably used in from 5 to 6 times the molar quantity.

According to the present invention, aprotic solvents are used for the synthesis of the ether. Suitable aprotic solvents are the conventional aprotic solvents, such as the N-dialkylated amides of short-chain carboxylic acids, for example dimethyl formamide, diethyl formamide an dimethyl acetamide, dimethyl sulphone, tetramethyl sulphone and dimethyl tetramethylene sulphone. It is preferred to use hexamethyl phosphoric acid triamide, methyl phosphonic acid tetramethyl diamide, dimethyl sulphoxide, N-methyi pyrrolidone, pyridine or N,N,N',N'-tetramethyl ethylene diamine. The quantity in which the solvent is used is not critical. The ratio, by weight, of hexachlorobenzene:solvent preferably amounts to from 1:1 to 1:50, more particularly from 1 :5to 1:10.

The reaction of the hexachlorobenzene with the alcoholate is carried out in a similar way to conventional alkoxylation reactions by heating the mixture of hexachlorobenzene, alcoholate and solvent, for example under reflux, until the reaction is over, subsequently distilling 6ff the solvent and distilling the residue generally after separation of the inorganic salts.

Providing the process conditions according to the present invention are applied, the alkoxylation reaction gives the required triether with a high degree of selectivity. This is surprising because, when sodium methylate is used, this nucleophilic substitution of the hexachlorobenzene results predominantty in the formation of a mixture of the isomeric disubstitution products. For example, the mixture obtained consists of from 63 to 65 mole percent of tetrachlororesorcinol dimethyl ether, from 23 to 26 mole percent of tetrachloropyrocatechol dimethyl ether and from 2 to 10 mole percent of tetrachlorohydroquinone dimethyl ether. in addition, trichlorophloroglucinol trimethyl ether is formed in a yield of only from 4 to 7 mole percent (G.G. Yakobson eft at Zh. Obshch. Khim, 35(1), 137 (1965); C.A. 62, 073 (1965).Similar results are obtained when sodium ethylate is used. Naturally such reaction mixtures are unsuitable.

Even where the homologous alcoholates of higher molecular weight, such as sodium butylate, are used, the alkoxylation reaction is less selective than in the process according to the present invention.

By contrast, in the process according to the present invention, the nucleophilic substitution surprisingly leads in predominantly the 1,3,5-positions to the trichlorophloroglucinol trialkyl ether. It is surprising that, when sodium-n-propylate or sodium i-propylate is used, the trichlorophloroglucinol tri-n- propyl ether and trichlorophloroglucinal tri-i-propyl ether according to the present invention are obtained in high yields and with high selectivity. The selectivity levels which may be reached are in the region of from 85 to 95 % and the ,yeilds in the region of from 80 to 90 % of the theoretical yield.Accordingly, these two compounds are valuable intermediate products, on the one hand, because they may readily be obtained from hexachlor obenzene which is available substantially gratuitously and which has to be destroyed on ecological grounds, and, on the other hand, because they may be further processed by virtue of the reactivity thereof into important end products.

The two compounds have the following properties: Trichlorophloroglucinol tri-n-propyl ether: colourless oil, B.p. (2 mbars) 145 - 150"C. Trichlorophloroglucinol tri-i-propyl ether: colourless crystals, M.p: 55"C.

As mentioned above, the compounds according to the present invention may be converted to trichlorophloroglucinol or phloroglucinol. If it is desired to obtain trichlorophloroglucinol, the ethers are hydrolysed in known manner, If it is desired to obtain phloroglucinol, the ethers are dechlorinated and hydrolysed in known manner.

The dechlorination of the trichlorophloroglucinol tri-n-propyl and tri-i-propyl ether obtained in the manner described above is carried out using metallic sodium in the conventional way for the dechlorination of aromatic halogenated hydrocarbons. To this end, the trichlorophloroglucinol ether is dissolved in a suitable solvent, for example in an alcohol, such as ethanol, n-propanol or i-propanol, an excess of metallic sodium is added to the resulting solution which is then heated until the sodium has completely dissolved. The reaction mixture is then diluted with water and the dechlorinated product is extracted using a suitable solvent, such as ethyl ether, methylene chloride, chloroform or hexane. Distillation of this extract gives the phloroglucinol trialkyl ether in pure form. The yield in this stage of the process is substantially quantitative.

Hydrolysis may be carried out in the conventional way for phenol ethers, for example using a mineral acid (cf. A Luttringhaus, Angew. Chem. 51,915-953 (1938). Suitable mineral acids are, for example, hydrochloric acid, sulphuric acid, hydrogen bromide and hydrogen iodide. Hydrochloric acid, to which glacial acetic acid or acetanhydride may optionally be added, is generally used for economic reasons. Hydrolysis is preferably carried out using concentrated hydrochloric acid at room temperature, e.g. at a temperature of from 15 to 25"C. This reaction stage is also substantially quantitative.

There is no need to produce the trichlorophloroglucinol tri-n-propyl or tri-i-propyl ethers in pure form and subsequently to use them as such for hydrolysis. Instead, it is equally possible and, in addition, of greater advantage, to free the reaction mixture obtained during alkoxylation from the solvent and to subject the crude product obtained to hydrolysis and optionally dechlorination. The trichlorophloroglucinol accumu lates in highly pure form and may be further purified by recrystallisation. It may be commercially used, for example, as a starting material for the production of oxidation inhibitors and flame proofing agents.

The process according to the present invention is eminently suitable for the production of phloroglucinol on a commercial scale. Apart from its simplicity and the high yield which it gives, a particular advantage of the process according to the present invention lies in the fact that it is possible to use a gratuitously obtainable starting material and, in addition, to make a contribution towards protection of the environment.

Phloroglucinol is used as a developer in the diazotype process, as a cross-linking agent, vulcanising agent, stabiliser and corrosion inhibitor and as a coupling component in the production of numerous dyes. In analytical chemistry, it is used as a reagent for aldehydes, pentoses, lignin, galactoses and other substances.

It is also used in the production of coumarins, flavonols and pharmaceuticals.

The following Examples illustrate the present invention.

Example 1 7.13 g (0.25 mole) of hexachlorobenzene and 12.3 g (0.15 mole) of sodium n-propylate were heated under reflux for 2 hours in 50 ml of pyridine. The cooled reaction mixture was diluted with 200 ml of water and acidified to pH 5 using 10 %, by weight, hydrochloric acid. The reaction mixture was then extracted twice with 100 ml of chloroform. The extractant was removed in vacuo and the residue distilled in a bulb tube under a pressure of from 2 to 3 mbar and at an ai r tem peratu repf from 150 to 200"C. A total of 8.35 g (94 % of the theoretical yield) of the isomeric tri-n-propoxytrichlorobenzenes was obtained. 85 % of the mixture consisted of the required trichlorophloroglucinol trin-propyl ether.This corresponds to a yield of 80 %, based on hexachlorobenzene.

Boiling point: 145-150"C/2 mbar.

Analysis: Calculated Observed C 50.63 50.5 H 5.91 5.9 O 13.5 13.6 Cl 29.96 30.0 Example 2 28.5 g (0.1 mole) of hexachlorobenzene and 49.2 g (0.6 mole) of sodium i-propylate were heated under reflux for 2 hours in 200 ml of pyridine. Most of the pyridine was then distilled off and 150 ml of 10%, by weight, hydrochloric acid was added to the residue with cooling. The organic phase was taken up in 100 ml of carbon tetrachloride and dried over sodium sulphate. After the solvent had been distilled off, the residue was distilled in a bulb tube (2 mbar, air temperature from 180 to 2000C).

33.5 g of distillate containing 90 % of the required trichlorophloroglucinol tri-i-propyl ether were obtained.

This corresponds to a yield of 84.4 %, of the theoretical yield. Recrystallisation from 50 ml of methanol gave 27.5 g of the pure product having a melting point of 55"C.

Analysis: Calculated Observed C 50.63 50.4 H 5.91 5.9 O 13.5 13.6 Cl 29.96 30.1 Example 3 100 ml of methanol were added to 50 g of a waste mixture of chlorinated hydrocarbons, consisting of 65 % of hexachlorobenzene, 25 % of hexachlorobutadiene and 10 % of hexachloroethane, followed by stirring for 1 hour at 20"C. 32 g of insoluble fractions consisting of pure hexachlorobenzene were separated off. The residue (0.112 mole of hexachlorobenzene) was dissolved in 400 ml of dimethyl formamide and stirred overnight at 140"C in the presence of 50 g (0.61 mole) of sodium i-propylate. The solvent was distilled off and the trichlorophloroglucinol tri-i-propyl ether left in the residue was recovered as described in Example 2.The yield amounted to 35.8 g (87 % of the theoretical yield, based on the hexachlorobenzene content of the waste mixture).

Example 4 35.5 g (0.1 mole) of trichlorophloroglucinol tri-n-propyl ether was dissolved in 200 ml of 90 % acetic acid and the resulting solution heated to 100"C in a glass autoclave. Gaseous hydrogen chloride was then introduced into this solution until the pressure had risen to about 5 bars. The reaction mixture was maintained under these conditions for 3 hours, subsequently cooled and, after venting of the autoclave, was diluted with 1 litre of water. The trichlorophloroglucinol was filtered off under suction. The yield amounted to 22.1 g (96.3 % of the theoretical yield).

Example 5 35.5 g (0.1 mole) of trichlorophloroglucinol tri-i-propyl ether were hydrolysed as in Example 4. The yield amounted to 22.3 g (97.2 % of the theoretical yield).

Example 6 28.5 g (0.1 mole) of hexachlorobenzene and 49.2 g (0.6 mole) of sodium i-propylate were heated overnight in 400 ml of dimethyl formamide (from 140 to 150"C). The solvent was almost completely distilled off (approximately 350 ml) and the residue refluxed for 6 hours with 600 ml of hydrochloric acid and 450 ml of acetanhydride. After cooling, the mixture was diluted with from 1 to 2 litres of water and the trichlorophloroglucinol filtered off under suction. The yield amounted to 18.19 g (79 % of the theoretical yield).

Example 7 5 g of sodium were added to 3.55 g (0.01 mole) of trichlorophloroglucinol tri-i-propyl ether in 100 ml of i-propanol, followed by heating under reflux until all the sodium had dissolved. The reaction mixture was then diluted with 100 ml of water and neutralised with 15%, by weight, hydrochloric acid. The organic phase was taken up in ethyl ether, the ethyl ether was removed and the residue distilled in a bulb tube (from 2 to 3 mbar, air temperature from 130 to 150"C). 2.47 g of phloroglucinol tri-i-propyl ether were obtained, corresponding to a yield of 98 % of the theoretical yield).

Example 8 Trichlorophloroglucinol tri-n-propyl ether was dechlorinated as described in Example 7.2.45 g of phloroglucinol tri-n-propyl ether were obtained, corresponding to a yield of 97.2 g of the theoretical yield.

Example 9 2.52 g (10 mMoles) of phloroglucinol tri-i-propyl ether and 150 ml of concentrated hydrochloric acid were stirred overnight at room temperature. Traces of phloroglycidol precipitated were filtered off under suction and sodium carbonated added to the filtrate until it showed a pH value of from 2 to 3. The product was then continuously extracted with ethyl ether and the ether extract concentrated. The residue consisting of phloroglucinol and a little phloroglucidol was recrystallised from water. The yield amounted to 1.38 g = 85.2 % of the theoretical yield (phloroglucinol dehydrate).

Claims (16)

1. Trichlorophloroglucinol tri-n- or -i-propyl ether.

2. A process for the preparation of trichlorophloroglucinol tri-n- or -i-propyl ether which comprises reacting hexachlorobenzene with from 3 to 20 times the molar quantity of sodium n-or -i-propyllate in an aprotic solvent at from 50 to 2500C.

3. A process as claimed in claim 2 in which from 5 to 6 times the molar quantity of sodium n- or -ipropylate is used.

4. A process as claimed in claim 2 or claim 3 in which a temperature of from 100 to 200"C is used.

5. A process as claimed in any of claims 2 to 4 in which an aprotic solvent selected from hexamethyl phosphoric acid triamide, methyl phosphoric acid tetramethyl diamide, dimethyl sulphoxide, N-methyl pyrrolidone, pyridine, dimelthyl formamide and N,N,N',N'-tetramethyl ethylene diamine is used.

6. A process as claimed in claim 2 substantially as herein described.

7. A process as claimed in claim 2 substantially as herein described with reference to any one of Examples 1 to 3.

8. Trichlorophloroglucinol tri-n- or 4-propyl ether when prepared by a process as claimed in any of claims 2 to 7.

9. A process for the preparation of trichlorophloroglucinol which comprises hydrolysing trichlorophloroglucinol tri-n- or -i-propyl ether as claimed in claim 1 or claim 8.

10. A process as claimed in claim 9 substantially as herein described.

11. A process as claimed in claim 9 substantially as herein described with reference to any one of Example 4 to 6.

12. Trichlorophloroglucinol when prepared by a process as claimed in any of claims 9 to 11.

13. A process for the preparation of phloroglucinol which comprises dechlorinating trichlorophlorogluci- nol tri-n- or -i-propyl ether as claimed in claim 1 or claim 8 using metallic sodium and hydrolysing the resulting phloroglucinol tri-n- or-i-propyl ether.

14. A process as claimed in claim 13 substantially as herein described.

15. A process as claimed in claim 13 substantially as herein described with reference to any one of Examples 7 to 9.

16. Phloroglucinol when prepared by a process as claimed in any of claims 13 to 15.