SU1643532A1 - Method for obtaining 2, 3, 5-trifluoro-4, 6-bis (trifluoromethyl) thiophenol - Google Patents

Description

one

(21) 4662146/04

(22) 03/15/89

(46) 23.04.91. Bul fr 15

(71) Novosibirsk State University. Leninsky Komsomol and Novosibirsk Institute of Organic Chemistry, Siberian Branch of the USSR Academy of Sciences

(72) II, P, Rodionov, V.E. Platonov, A.M. Maksimov, V.V. Kn zev and T.I.Serdo-Ointseva

(53) 547.269.07 (088.8)

(56) 1, Aroskar E.V., J Chem. Soc ,, 1965, No. c, p. 2658-2661.

(54) METHOD FOR PRODUCING 2,3,5-TRIFTOR-4,6-BIS (TRIFTOSHETYL) TIOPHENOL

(57) The invention relates to substituted thiophenols, in particular the preparation of 2,3,5-trifluoro-4,6-bis (trifluoromethyl) thiophenol, an intermediate for the synthesis of a dielectric fluid. The goal is to increase the yield of the target product at - | reducing its cost. Synthesis of ve-4 is carried out by hydrosulfidation of pentafluoromexylene - a technical mixture of perfluoromethan and perfluoroparaxylols with a 1.5-2 fold excess (from stoichiometry) alkali metal hydrosulfide at (-1) - (- 8) ° С in the presence of ethylene glycol in pyridine, followed by precipitation of the target product with an acid in the cold, washing the precipitate with ether at (-15) - (-20) ° C and decomposing the salt with acid. As the alkali metal hydrosulfide, it is better to use potassium hydrosulfide and introduce it gradually during re-molding. These conditions increase the yield of the target product from 30% to 45% while reducing its cost price by using a technical mixture of perfluoromethanes and perfluoroparaxylols. 1 hp f-ly.

(L

The invention relates to the chemistry of polyfluoroaromatic compounds, namely to an improved process for the preparation of 2,3,5-trifluoro-4,6-bis (trifluoromethyl) thiophenol of the formula

CF,

which can be used as an intermediate product for the synthesis of perfluorocycloalkyl sulfur pentafluoride derivative - an effective dielectric liquid and the synthesis of biologically active compounds of the fluorophenothiazines series.

A method is known for producing a compound by hydrosulphiding perfluorometha-xylene with sodium hydrosulfide solution (ethylene glycol in pyridine pyri ovS, followed by precipitation of the desired product with hydrochloric acid, extraction with ether and distilling off the residue under vacuum Јl J.

The disadvantage of the known method is the relatively low yield of the target product, which is only 30% of the theoretical one, for the synthesis, perfluoromethacylol is used as the starting material. (5

The purpose of the invention is to increase the yield of the target product, reduce its cost, and use a technical product, decafluoroxylol, which is a mixture of 67% per-fluorome- and 33% para-xylene.

This goal is achieved by taking the technical mixture of perfluoromethanes and perfluoroparaxylene (technical name J5 decafluoroxylene) as the initial mixture and hydrodiving with potassium hydrosulfide solution in ethylene glycol and conducting the process in pyridine. Potassium hydrosulfide solution is taken in excess of 1.5-20 ice and to the resulting suspension of honey.

2 times against stoichiometric. It is preferable to use potassium hydrosulfide instead of sodium, since the former is better dissolved in ethylene glycol and is in solution at a temperature of less than 0 ° C, unlike sodium hydrosulride, which can precipitate in these conditions, making the process difficult. The process of hydrosulfiding is carried out at (-10) - (-8) ° ".

Upon completion of the potassium hydrosulfide loading, a 2-stage separation of the target product is carried out, for which at the first stage the target product is precipitated in the form of pyri-1 dinium salt insoluble in cold water by gradually acidifying the mass with hydrochloric acid and precipitated. At the same time, the precipitated pyridinium salt of the target thiophenol adsorbs by-products, as well as unplaced perfluorparaxylene.

These impurities are easily removed three times with thiophenol, free of impurities, and the main washing of the precipitate is pyridinium carefully mixed with 500 ml of concentrated ether with cold, preferably at (-15) - (-20) ° C. Rinsing at room temperature is undesirable due to increasing losses from the product due to leaching of the pyridinium salt with ether.

In the second stage, the pyridinium salt of the desired thiophenol is subjected to acid decomposition, bonding with pyridine. or any other mineral acid to a stronger salt and thereby release the desired product, which is then recovered by extraction and distillation.

Example 1. In a stirred reactor cooled to (-5) (- 8) bc, 200 g, 117 ml (g 1.707) of technical decafluoro-xylene (a mixture of isomeric meta- and para-xylene, of which 0.524 moles are perfluoromethacilol and 0.174 moles) are placed. to perfluorparaxyl), 800 ml of pyridine and slowly, drop by drop, with vigorous stirring, load 0.8 mol (initial ratio 1: 1.6) of potassium hydrosulfide in the form (480 ml) of a 15% solution in ethylene glycol. Upon completion of loading, the mass is maintained at the same temperature for 40-60 minutes, after which it is mixed with 2 kg of finely divided

0

five

0

400 ml of concentrated hydrochloric acid are added dropwise while stirring. In this case, the potassium salt of the thiol anion enters the thiol, which is immediately bound to the pyridine salt, insoluble in cold water and precipitated, while the pyridinium salt of the desired thiophenol absorbs the remaining organic part of the reaction mass: perfluorparaxylene that does not react as well as the pyridinium salt of this thiol, which under these conditions is an oily liquid. The precipitated pyridinium salt of the desired thiol is decanted from the remaining water, and then purified from the absorbed impurities by washing the salt with cold (-20 ° C) ether.

Use for washing the ether having a room temperature can lead to partial destruction of the pyridinium salt of the desired thiol.

The resulting mass of pyridinium salt

To complete the process, the mass is heated to an inert atmosphere with reflux for 30 minutes, then cooled to room temperature and extracted with ether (500x5). The combined ether extracts are dried over MgSOjj. Then the solvent is distilled off from the latter in a water bath, and the oily dark liquid (residue) is distilled under vacuum in a stream of inert gas, the desired product is taken at -70-73 ° C (18 -

20 mm Hg). The compound obtained is a colorless transparent liquid with a characteristic smell of 4 thiols, which is stored in sealed Glass ampoules purged with inert times, wrapped in black paper.

71 g (0.235 mol) of compound are obtained with a yield of 45% of the theoretical, calculated on the perfluoromethaxyl contained in the loaded decafluoroxylene

According to GLC analysis, the purity of the substance obtained is 96%.

Example 2. If the conditions of example 1 are observed, the reactor is cooled to -1 ° C, and the pyridine salt is washed at -15 ° C.

The purity of the target product is 96%. Yield 35%.

NimerZ. Under the conditions of example 1, the reactor is cooled to 0 ° C, and the washing of the precipitate is carried out at -5 ° C.

The yield of the target product is 30%, purity 90.5%.

II p and me R 4. With the introduction of potassium hydrosulfide by pouring at one time ejection occurs part of the reaction mass.

PRI me R 5. When carrying out the process using smaller amounts of hydrosulfide, the yield is reduced to 26%.

The proposed method allows to increase the yield of the target product up to 45%, against 30%, and also to reduce the price

this is due to the elimination of the expensive imported starting material and the use of the technical product, decafluoroxyl.

Claims (2)

Invention Formula 1. A method of producing 2,3,5-trifluoro-tO-4,6, -bis (trifluoromethyl) thiophenol by hydroxy-sulfonating the perfluoromeaxyl hydrosulfide with an alkali metal in the presence of ethylene glycol in pyridine with cooling followed by separation of the target product, precipitation with acid, extraction with ether and distillation, characterized in that, in order to increase the yield and reduce the cost of the target product, a technical mixture of perfluorometha and perfluoroparaxylene is used as a source of perfluoromethaciline performed 1.5-2-fold excess of 25 stoichiometric alkali metal hydrosulfide at (-1) ... (- 8) ° C, and the precipitation is carried out by precipitation of the pyridinium salt of thiophenol with acid in the cold, washing the precipitate with ether 30 at (-15) ... (- 20) ° C, followed by decomposition of the salt by acid. 2. A method according to claim 1, characterized in that potassium hydrosulfide is used as an alkali metal hydrosulfide, and its introduction is carried out gradually with stirring.