SU1731768A1 - Method for m-phenoxytolyene preparation - Google Patents

Abstract

The invention relates to the preparation of diaryl esters, in particular the preparation of m-phenoxytoluene, which can be used. used as an intermediate in the synthesis of pyrethroid insecticides. The goal is to increase the yield of the target product. For this, potassium phenol t in the presence of 92–98% KOH is reacted with o-chlorotoluene at a molar ratio of reagents of 1: 2: (3-4) in search of a salt or Cu (II) oxide or (I) at 240-250 ° C. In these conditions, the yield of the target product is increased to 69.3% with the ratio of m- and o-isomers of 1: 2.6. 5 tab. VI SA O 00

Description

The invention relates to organic chemistry, in particular, to a process for the preparation of diaryl ethers, which can be used as intermediates for the synthesis of pyrethroid insecticides, in the manufacture of pharmaceuticals and high boiling organic heat transfer agents.

A known method for producing substituted diaryl ethers by the reaction of chlorotoluene and cresol in the presence of an aqueous solution of alkali at 230-400 ° C and a pressure of 100-300 atm.

The disadvantages of this method include the high temperature and pressure created by alkaline aqueous solutions, which makes it difficult to implement in industry. The processes carried out under the above stated stringent conditions are not selective, and the final product m-phenoxytoluene is isolated from the mixture of diaryl ethers with an insignificant yield — about 15–20%.

A known method for the preparation of m-phenoxy-toluene from m-cresol and bromine or chlorobenzene, potassium hydroxide in the liquid phase at 200 ° C in solvent is dimethyl sulfoxide. The yield of m-phenoxytoluene is 47.5%.

The disadvantages of the above method include the use of an inaccessible and highly toxic solvent dimethyl sulfoxide. In addition, under the conditions of this process, dimethyl sulfoxide is not an inert product, and by 30 wt.% It is disproportionated to dimethyl sulphide and dimethyl sulphone. Dimethyl sulfide has a boiling point of 36 ° C, and this significantly complicates the conduct of the main process at 200 ° C, and it also has a very unpleasant odor.

Dimethyl sulfone under the process conditions (in an alkaline medium) is converted into the potassium salt of methylsulfinic acid, which passes into the aqueous layer upon subsequent treatment of the reaction mixture and makes it difficult to further process the wastewater of this process, which is important from an environmental point of view.

In the above methods for the preparation of m-phenoxytoluene from m-cresol and halo-aromatic compounds, most commonly bromobeneol, copper catalysts are sometimes used, which somewhat increase the yield of the target product. In general, these so-called cresolate methods are difficult to implement on an industrial scale, since m-cresol, bromobenzene and bromotoluene are difficult to access products.

The closest in technical essence and the achieved result to the invention is the method of obtaining m-substituted diaryl ethers by the interaction of halogen-substituted aromatic compounds with phenol in the presence of caustic alkali at 110-400 ° C,

The preparation of m-phenoxytoluene by this method is carried out by reacting the o-haloaromatic compound chlorotoluene with potassium phenol 1 in the presence of potassium hydroxide (85% concentration) in an autoclave at 110-400 ° C and the ratio potassium hydroxide potassium hydroxide: o -chlorotoluene, equal to 1: 0.3-3: 3. The content of phenoxytoluene isomers is 13-80% with a ratio of w / v isomers of 0.64-2.14: 1, and conversion to orthometho-phenoxytoluene is 12-80%. The output of m-phenoxytoluene 5,2-52,02%.

The disadvantage of this method is the low yield of m-phenoxytoluene.

The purpose of the invention is to increase the yield of m-phenoxytoluene.

This goal is achieved by the interaction of ortho-chlorotoluene with potassium phenol at 240-250 ° C in the presence of potassium hydroxide 92-98% concentration and catalytic amounts of salt or copper oxide (I or II) according to the scheme

CH3

C1 © KOH

Si

+ w

when the ratio of potassium phenol: KOH: o-chlorotoluene is 1: 2: 3-4, and 240-250 ° C.

Conversion of potassium phenol to the mixture of phenoxytoluene isomers using potassium hydroxide 92-98% concentration is 86-96% with a ratio of isomers m: about 2.6: 1, i.e. the output of m-phenoxytoluene, respectively, from 62.1 to 69.3%,

When using sodium hydroxide or lithium hydroxide, the yield of m-phenoxytoluene is reduced to 10-25%.

The proposed technical solution differs from the well-known one in that to obtain m-phenoxytoluene by the interaction of potassium phenol and o-chlorotoluene in the presence of potassium hydroxide at 240-250 ° C with a ratio of potassium phenol and potassium hydroxide 1: 2, in order to increase the yield , the process is carried out in the presence of a salt or copper oxide (I or I), using 92-98% potassium hydroxide with a ratio of potassium phenol t: o-chlorotoluene equal to 1: 3-4.

The proposed method is characterized by an increased yield of the raw product. The process uses available raw materials: phenol, a large-tonnage product, o-chlorotoluene - a by-product in the production of p-chlorotoluene. O-chlorotoluene does not find a qualified application at present, and is partially used as a cheap solvent.

The great advantage of the proposed method of obtaining m-phenoxytoluene is the ease of processing the reaction mass: after water is added to it and the aqueous and organic layers are separated from the organic layer by distillation, the commercial m-phenoxyto alcohol is separated by the method of rectification.

and from aqueous (after neutralization with hydrochloric acid and purification from organic impurities) - pure crystalline potassium chloride.

Example 1. A stainless steel autoclave with a capacity of 70 ml was charged with 6.61 g (0.05 M) potassium phenol, 5.91 g (0.1 M) of 95.0% potassium hydroxide. 18.98 g (0.15 M) o-chlorotoluene and 0.37 g (0.0038 M) copper chloride (). The reaction mixture is heated with shaking and 235 ° C for 4 hours. Cool, the contents of the autoclave are treated with 50 ml of water. The organic part of the reaction mixture is extracted 3 times with 25 ml of o-chloropoluene, dried with magnesium sulfate, the extractant is distilled off to 165 ° C in pairs, the residue is weighed, analyzed by GLC.

Similarly, syntheses were carried out at boundary temperatures of 240, 245, 250, and 260 ° C. The results are presented in table 1 (examples 1-5).

Example 6. In a stainless steel autoclave with a capacity of 70 ml, 12.65 g (0.1 M) phenol ta lithium, 9.6 (0.4 M) lithium hydroxide, 12.65 g (0.1 M) o-chlorotoluo are placed a and 0.4 g of copper (I) chloride. Heat with shaking and 250 ° C for 4 hours. Cool and treat as in Example 1. The content of m-phenoxytoluene in the raw product is 10%.

Example 7. In a 70 ml autoclave with a capacity of 70 ml, 5.81 g (0.05 M} sodium phenol, 6 g (0.15 M) sodium hydroxide, 18.93 g (0.15 M) o-chlorotoluene, are placed and 0.4 g of copper (I) chloride. The autoclave is heated with shaking and 250 ° C for 4 hours. It is cooled, treated and analyzed as in Example 1.

The content of m-phenoxytoluene in the raw product is 25%.

Similar data were obtained in the presence of copper (II) oxide, copper acetate, basic copper carbonate.

In an alkaline medium, the copper compounds are reduced to metallic copper, which at the time of separation forms a finely dispersed slurry with a large contact surface. In this state, copper has a selective effect on the condensation process, directing it towards the preferred formation of the m-isomer.

There are known examples of the use of copper compounds as a catalyst for the Ulman reaction. However, it was found that only in the presence of a strong base of potassium hydroxide at a molar ratio of reagents potassium phenate: potassium hydroxide: ortho-chlorotoluene 1: 2: 3–4 copper at the time of separation has a directional effect. phenoxytoluene.

Preliminarily, the boundary values of the amount of hydroxide of potassium 5 different from the selected 2 moles were investigated. A decrease in the concentration of potassium hydroxide to 1 mol per 1 mol of potassium phenol sharply reduces the yield of m-phenoxytoluene by almost 2 times. Under such conditions, the intermediate active gasoline intermediate is not sufficiently generated and therefore the process is not effective.

Increasing the concentration of potassium hydroxide to more than 2 moles is not economically beneficial, 5 because potassium hydroxide is expensive, and the use of potassium chloride, selected as a by-product, is problematic. In addition, the use of excess (more than 2 moles) potassium hydroxide leads to an increase in the yield of by-products such as isomeric ditolyl ethers, which are difficult to separate from m-phenoxytoluene due to the proximity of boiling points. As can be seen from Table 1, a decrease in temperature to 235 ° C with equal heating time leads to a decrease in the content of m-phenoxytoluene in the reaction mixture to 40-41% (example 1, table 1).

Raising the temperature up to 260 ° C directs the process towards the formation of significant amounts of condensation products, tarring to an average of 30%. Therefore, the optimum temperature for this process is 250 ° C.

5 In addition, studies were carried out to determine the effect of o-chlorotoluene concentration on the content of m-phenoxytoluene in condensation products. The number of moles of o-chlorotoluene varied from 1 to 4.

О The obtained data are presented in table 2 (examples 6-10).

As can be seen from table 2, the use of 1 mol o-chlorotoluene, ceteris paribus, reduces the content of m-phenoxytoluene in

5 reaction mixture to 29% (example 6). Increasing the concentration of o-chlorotoluene to 2 to 2.5 moles markedly increases the content of m-phenoxytoluene in the reaction mixture to 44-49%. At o-chlorotoluene concentration,

0 equal to 3-4 mol per 1 mol of potassium phenol and metaphenoxytoluene yield is 62.1- 69.3% (example E and 10). Therefore, the optimal concentration of o-chlorotoluene was chosen to be 3-4 mol of o-chlorotoluene per

5 1 mole phenol and potassium.

Thus, the described conditions for carrying out the process of phenol condensation, o-chlorotoluene in the presence of potassium hydroxide of 98% concentration and compounds

copper allows to obtain m-phenoxytoluene with a yield of 62-69%.

It is known that alkali metal phenols are thermally unstable at 350-450 ° C; decomposition products are methane, carbon monoxide, hydrogen, which, obviously, create pressure in the autoclave by a known method. In addition, for the alkali metal phenols under severe conditions, due to their chemical structure, arylating reactions are possible along with the formation of ethers. Therefore, the yield of m-phenoxytoluene in a known method is less, and the amount of by-products is greater.

The concentration of potassium hydroxide is essential for the passage of the process of phenol potassium condensation and o-chlorotoluene.

A number of studies have been carried out to study the effect of potassium hydroxide concentration on the conversion of potassium phenol and the yield of m-phenoxytoluene. The obtained data are presented in table 3.

From Table 3, it follows that the best yield of m-phenoxytoluene was obtained on 92-98% potassium hydroxide. Therefore, the optimum concentration for obtaining m-phenoxytoluene is potassium hydroxide concentration of 92-98%.

As shown by studies in the presence of potassium hydroxide (85% purity) and mature boundary parameters of the known method (example 5 and 6), m-phenoxytoluene was isolated with a yield of 50-52% at a ratio of isomers of m / o equal to 1.86 (by analogy with example 5 of the known method), and a mixture of ortho-, meta-phenoxytoluene 43-45% with a ratio w / o equal to 2.14 (by analogy with example b of the known method).

Reproducing a known process at 240-250 ° C without an activator of the compound copper + potassium hydroxide (95%) allowed obtaining meta-phenoxytoluene with a yield of 15-20% and only the introduction of a copper compound in the presence of potassium hydroxide (95%) allows creating such an activator reaction which directs the reaction towards the preferred formation of meta-phenoxytoluene. The data obtained are given in table 4.

As can be seen from Table 4, lowering the temperature by 10 ° C 40 ° C and carrying out the process in the presence of a reaction activator can improve the process and increase the yield of the target product.

Conducting the condensation process in the presence of copper chips, copper plates, copper powder and bronze copper (copper bronze) in the boundary parameters

temperature and composition did not lead to a positive result. Therefore, the use of such a technique as a joint compound of copper and potassium hydroxide (95% concentration) allows increasing the yield of meta-phenoxytoluene to 70%, and by a known method does not exceed 50%, while part of the product is in the order of 15-20% at 350- 400 ° C resinified (known method).

0 Such a combination of copper and hydroxide kg and at 240-250 ° C provides highly efficient catalysis,

The mechanism of action of the catalyst-activator is based on the formation of fine copper by copper at the time of the reduction of the last of its compounds. In this state, copper has a large contact surface and develops a total surface of up to 5-6 m2.

0 To confirm this mechanism of the activation process, a series of syntheses was conducted to obtain meta-phenoxytoluene in the presence of activators of different nature (Table 5),

6 As can be seen from the data of Table 5, only colloidal copper particles formed from copper compounds in an alkaline medium activate the condensation process and allow significantly (4–5 times) to increase the yield of meta-phenoxytoluene compared to other activators, As is well known, one of the two methods for the preparation of dispersion systems is condensation, based on a chemical reaction leading to the formation of insoluble substances of dispersed order. At the same time, the catalyst surface, and therefore the contact surface, rises 500-1000 times.

Copper shavings and other forms of copper in

0 alkaline medium does not have such a catalytic effect.

The process in the presence of copper metal is not intensified, the yield of the target product does not reach 15-18%.

5 As for other alkali metal hydroxides (sodium and lithium), the condensation process at 240-250 ° C practically does not take place (Table 2, examples 6.7).

0 Potassium hydroxide (95% concentration) as a strong base generates the intermediate dehydrotoluene, which in the presence of colloidal copper reacts with potassium phenol to form

5 m-phenoxytoluene. The lithium and sodium hydroxides are inferior in strength to potassium hydroxide, therefore the yield in the presence of these hydroxides does not exceed 10-25%.

Claims (1)

The proposed method simplifies the organization of the industrial production of mphenoxytoluene, an intermediate in the synthesis of third-generation pyrethroids. The invention of the method for producing m-phenoxytoluses by reacting potassium phenol and o-chloro-toluene in the presence of KOH at 240-250 ° C and a molar ratio of phenol t KS or gCON equal to 1: 2, in order to increase the yield, The process is carried out in the presence of a salt or oxide of Cu (II) and (I). using 92-98% KOH, with a 1: 3-4 ratio of potassium phenol t-yl-chlorotoluene ratio. Determination of temperature boundary values method of producing m-phenoxytoluene (time 4 h KOH 95% concentration) The effect of the concentration of o-chlorotoluene (0-HT) on the content m-phenoxytoluene in the reaction mixture (t 250 ° C, time -4h, pressure b atmJON 98% concentration) ten Table 1 Table 2 eleven The effect of potassium hydroxide concentration on the conversion of potassium phenol and the yield of m-phenoxytoluene (t-250 ° C. P-6 atm, g-4h) Comparative performance characteristic meta-phenoxytoluene by the known and proposed methods Synthesis of meta-phenoxytoluene by the reaction of ortho-chlorotoluene (OXT) and potassium phenol (FC) in the presence of activators of different nature (t - 240-250 ° С, Р-6 atm, g 4 h, the molar ratio of FC: KOH: OHT - 1: 2: 3) 1731768 12 Table3 Table4 Table