CS267193B1 - A method for producing O, O-dimethyl-O- (3-methyl-4-nitrophenyl) phosphorothioate - Google Patents

Abstract

Preparation of fenitrothion in a mixed inert solvent. The solvent consists of a combination of a polar ketone-type solvent and a non-polar aromatic solvent. 3-methyl-4-nitrophenol reacts with 0,0-dimethylchlorophosphorothioate.

Description

The present invention relates to a process for the preparation of 0,0-dimethyl-O- (3-methyl-4-nitrophenyl) phosphorothiate. Said compound has insecticidal effects. *

O, O-dimethyl-O- (3-methyl-4-nitrophenyl) phosphorothioate is characterized by relatively low toxicity to warm-blooded animals, while having excellent activity against various species of pests. Although it was first described 30 years ago (Chem, Industry 6, 293 (1956)), it is still widely used under various trademarks, such as Metation Chemické závody J. Dimitrova, n. p., Sumithion by Sumitomo Chern. Corp. Ltd., or Folithion by Bayer AG. Its use in agriculture, fruit growing, vegetables and the communal sector to combat undesirable insect species is constantly expanding, especially in developing countries.

Methods for its preparation are based on the reaction of 3-methyl-4-nitrophenol with O, O-dimethylchlorophosphorothioate in an inert, most often aromatic solvent e.g. in toluene, xylene, chlorobenzene and the like. at temperatures around 100 ° C in the presence of hydrogen chloride scavengers (^ 2 ^ 3, K 2 CO 3, KOH, etc.), as described in MS. pat. no. 89,124, or U.S. Pat. no. 3,091,565; or on the reaction of the same starting materials in a ketone environment such as e.g. methyl ethyl ketone, methyl isobutyl ketone and the like. in the presence of anhydrous soda or potash at temperatures of 60 to 80 ° C for 2 to 8 hours as described in U.S. Pat. pat. No. 3,091,565; possibly G. Schrader in the book: Die Entwicklung neuer Insektizider PhosphorsSure Ester, Verlag Chemie GmbH, Weinheim (1963) p. 293; optionally by reacting an alkaline salt of 3-methyl-4-nitrophenol, or free 3-methyl-4-nitrophenol with O, O-dimethylchlorophosphorothioate in the presence of acid-binding agents at a temperature of 85 to 100 ° C, as described in U.S. Pat. AO no. 211 804.

Processes for the preparation of 0,0-dimethyl-O- (3-methyl-4-nitrophenyl) phosphophothioate using an inert aromatic solvent, e.g. toluene (U.S. Pat. No. 89,124, U.S. Pat. No. 3,091,565 and U.S. Pat. No. 3,080,804) are carried out at temperatures of 85 to 100 ° C for 2 to 5 hours, most often in an anhydrous environment provided prior azeotropic distillation of the water present. Relatively long reaction times and especially high temperatures around 100 ° C support the course of side reactions to the formation of undesired by-products, which by their presence negatively affect the performance of the final product. An example is O-methyl-S-methyl-O- (3-methyl-4-nitrophenyl) phosphorothioate, which can normally be present in fenitrotione in amounts of up to several percent. Due to its high toxicity to warm-blooded animals, it significantly impairs the quality of the preparation (J, Kovačičová et al .: Pěstíc. Sci 1973, 759-63) and is in conflict with the ever-increasing requirements for high purity of applied active substances. . .

According to the requirements of the World Health Organization, for technical fenitrotion, a minimum active substance content of 93%, determined by the gas chromatographic method (WHO Specification / SIT / 17.R2, dated 1983), is required.

Other disadvantages of these processes resulting from high temperatures, long reaction times and large amounts of solvents used are the high energy costs required to ensure operation and solvent regeneration, as well as the low specific performance of the production plant, reflected negatively in the resulting product performance.

The disadvantage of the prior art, which uses various ketones as the polar medium, is the anhydrous nature of the medium, the relatively long reaction times of up to 8 hours (see U.S. Pat. No. 3,091,565) and the need to add a further solvent (see G, Schrader: Die Entwicklung neuer Insectizider PhosphorsSure Ester, Verlag Chemie GmbH, Weinheim (1963) p. 293) for subsequent washing of the active substance solution with water.

The unsatisfactory course of this type of reaction is evidenced by the procedures using the catalytic effect of the medium or its combination with potassium bromide to achieve better results.

CS 267 193 Bl 3 n (France, U.S. Pat. Nos. 1,272,685 and 1,282,891 and U.S. Pat. Nos. 2,784,207 and 2,701,259).

The weight yields of the technical product in the existing processes for the preparation of O, O-dimethyl-O- (3-methyl-4-nitrophenyl) phosphorothioate are in the range from 86 to 94% of theory, based on the starting 3-methyl-4-nitrophenol, the purity of the phenothrotione obtained is either not given or is determined by the analytical method used.

We have now found a new process for the preparation of 0,0 "dimethyl-O- (3-methyl-4-nitrophenyl) phosphorothioate by the reaction of the alkaline salt of 3-methyl-4-nitrophenol with 0,0-dimethylchlorophosphorothioate, characterized in that the reaction is carried out in a mixed medium. an inert solvent consisting of at least one polar solvent from the group of ketones and at least one non-polar aromatic solvent, wherein the weight ratio of polar solvent to non-polar aromatic solvent is 1: 9 to 9: 1.

The combination of a polar and a non-polar solvent, which are fundamentally different in their properties, makes it possible to obtain a higher effect which cannot be achieved using a polar or non-polar solvent alone. The mixed solvent used accelerates the reaction, increases the purity, yields and lowers the reaction temperature, thus achieving a similar effect as in catalyzed reactions. This effect is a new phenomenon, not yet described in the literature, which is not yet used in production practice.

The combination of polar and non-polar solvent makes it possible to maintain the homogeneity of the liquid phase even in the presence of water, without the negative consequences of reducing the yields due to possible hydrolysis of fenitrotion, which is a new and unexpected aspect of the proposed process and is of considerable practical importance.

The ratio of the two selected types of solvents can be chosen in a wide range, from 1:99 to 99: 1. It allows a precise choice of the reaction temperature, provided by the reflux of the used mixed solvent, it can influence the reaction time, the fenitrotion content and the formation of secondary reaction conditions, it is reliable and easy to implement in operation. .

The new procedure substantially eliminates the shortcomings of the previous procedures described above. Suppresses to a minimum the formation of undesirable concomitant substances, especially O-methyl-S-methyl-O- / 3-methyl-4-nitrophenyl / phosphorothioate, increases the content of pure fenitrotion in the final product, reduces its toxicity, increases safety at work in agriculture, essential reduces the technical and economic standards of raw materials and increases the specific performance of production equipment.

The proposed process makes it possible to use O, O-dimethylchlorophosphorothioate in the reaction also in the form of a toluene solution, which is important from the point of view of production practice.

The solvents used can be regenerated in a conventional manner, small amounts of the accompanying impurities in the aromatic solvent used can optionally be decomposed by alkaline hydrolysis at elevated temperature, the advantage being that they do not have to be anhydrous when re-used after regeneration.

The above advantages of the new procedure illustrate but do not limit the following examples:

Example 1

158 ml (125 g) of acetone were poured into a 1 liter three-necked round bottom flask equipped with a thermometer, stirrer, reflux condenser and dropping funnel, and 107.6 g of a wet filter cake of pure 3-methyl-4-nitrophenol sodium salt containing 81 ml of acetone were added with stirring. , 7 g of pure sodium salt of 3-methyl-4-nitrophenol and 16 g of water, 6.9 g of K 2 CO 2 and a solution of 83.5 g of 98% N, N-dimethylchlorophosphorothioate in 224 ml (195 g) of toluene. The contents of the flask were heated to about 35 ° C with heat of reaction and then heated to reflux at 66-68 ° C where it was stirred for 1.5 hours. 150 ml of water were added to the contents of the flask and the mixture was stirred for a further 10 minutes.

CS 267 193 Bl

After stirring was allowed, the layers were allowed to settle for 15 minutes and the aqueous layer was discarded. The organic layer containing fenitrotion was washed with mlβ ml of 8-aqueous aqueous NaOH and 100 ml of 7-aqueous aqueous NaCl.

From the organic layer, pddegtilqval at teplpfe yodP ^ hP k ^ ppl ^ 8f | The acetone used at 0 DEG C. and the toluene solution of fepitrotion were dissipated with aisepropice with steam.

Wet fenitrotion was dried on water at a temperature of 55 Rp. 120.5 g of O, O-dimethyl-O- (3-methyl-n-nitrile-phenyl) -propylthiothioate were obtained by gas chromatography, which represents a yield of 8.9% of theory. N, O-methyl-8-methyl-Q- (3-methyl-4-nitrophenyl) phosphotrothioate.

Example 2

107.8 g of a wet filter cake of pure 3-methyl-4-nitrophenol sodium containing 82 g of 3-methyl-4-nitrophenol sodium salt were weighed into a 1 liter three-necked round bottom flask fitted with a thermometer, a stirrer, an overhead condenser and a dropping funnel. , 9 g of K ₂ CO ₃ and 224 ml (195 g) of toluene. The flask was fitted with an epitopic flask and the wet plug of 3-methyl-4-nitrophenol bottom was dried at reflux until water was partitioned. The contents of the flask were cooled to 50 ° C, 158 mL (125 g) of acetone was added, and 83.5 g of 98% N, N-dimethylchlorophosphorothioate was added dropwise with stirring. The contents of the flask were heated to reflux at 66-68 ° C where it was stirred for 1.5 hours.

Following the procedure of Example 1, 119 DEG-3-O, O-dimethyl-O- (3-methyl-4-nitrophenyl) phosphorothioate was obtained with a purity of 94.0% as determined by gas chromatography, yielding 87.1%. The product contained 0.9% of O-methyl-S-methyl-O- (3-methyl-4-nitrophenyl) phosphorothioate.

Example 3

Using the method described in Example 1, using methyl ketone as the polar solvent, an experiment was carried out at a reflux temperature of 81 to 82 ° C, in which, after working up the organic layer, 121.6 g of 0,0-dimethyl-O- / 3-methyl-4 -nitrophenyl / phosphorothioate with a purity of 93.18 determined by gas chromatography, which represents a yield of 87.4% of theory.

Example 4 The procedure in Example 1 was used with the wet cake of technical sodium 3-methyl-4 ^_ n ^itro f? Nolu and 279 g of a toluene solution of a 0,0-dimetylchlórfosforotioátu containing 30.0% pure material and 0, An experiment was carried out in O, O-dimethylchlorophosphorothioate, in which, after working up the organic layer, 128 g of 0,0-dimethyl-O- (3-methyl-4-nitrophenyl) phosphorothioate were obtained with a purity of $ 7.0 and a determined gas chromatography, representing a yield of 86.0% of theory. The product contained 1.4% of O-methyl-S-methyl-O- (3-methyl-4-nitrophenyl) phosphorothioate.

Example 5

To demonstrate the resulting effect of using a combination of solvents, two comparative experiments were prepared to prepare fenitrotion using the procedure and raw materials of Example 1, one in pure toluene at a reaction temperature of 66-68 ° C (acetone was replaced by toluene) and the second was performed in a pure acetone environment, at a reflux temperature of 56 to 58 Rc, (tolgen was replaced by acetone). The reaction time in both experiments was the same - 1.5 h. The obtained results are summarized in the table.

Claims (1)

Solvent used Reaction temperature ° C Fenitrotion obtained___ g% purity yield in% (gas, chromate) theory acetone toluene 56 to 58 ^X 41.2 91.3 29.0 66 to 68 47.9 90.8 33.6 ^x Experiment was performed at reflux. OBJECT OF THE INVENTION Process for the preparation of 0,0-dimethyl-O- (3-methyl-4-nitrophenyl) phosphorothioate by reaction of an alkaline salt of 3-methyl-4-nitrophenol with 0,0-dimethylchlorophosphorothioate, characterized in that the reaction is carried out in a mixed inert solvent consisting of at least one polar solvent from the group of ketones and at least one non-polar aromatic solvent, wherein the weight ratio of polar solvent to non-polar aromatic solvent is 1: 9 to 9: 1.