FR2487825A1 - PROCESS FOR THE PREPARATION OF ACYLAZO-3 PROPIONIC ACID ESTERS - Google Patents

Abstract

PROCESS FOR THE PREPARATION OF ACYLAZO-3 PROPIONIC ACID ESTERS RESPONDING TO THE FORMULA: (CF DRAWING IN BOPI) IN WHICH R DESIGNATES A RADICAL ALKYL AND R A RADICAL ALCOXY OR AN AMINO GROUP. AN ACRYLIC ESTER IS REACTED WITH AN ACYLHYDRAZINE, AN ALCOXYCARBONYL-HYDRAZINE OR SEMI-CARBAZIDE SO AS TO OBTAIN ESTERS OF ACYLHYDRAZINO-3-PROPIONIC ACID OR 3-CARBAMOYPIONIC ACID OXYPIONIC ACID-3-CARBAMOYPIONIC ACID-3-CARBAMOYDELAENIC 'OXIDIZING AGENTS. THE COMPOUNDS SO OBTAINED ARE IMPORTANT STARTING BODIES FOR THE PREPARATION OF THIADIAZOLE-1,2,3-CARBOXYLIC-5 DERIVATIVES, FROM WHICH PREPARED PHYTOSANITARY PRODUCTS AND PHARMACEUTICAL PRODUCTS CAN BE PREPARED.

Description

The invention relates to a process for the preparation of acylazo

  3 propionics as well as acylhydrazones

  formyl - acetic esters, isomers of the foregoing.

  Methods for preparing semicarbazone of ethyl formylacetate are already known (W. Wislicenus, H.W.

  Bywaters, Liebigs Ann. Chem. 356, 50 (1907) and ethoxycarbo

  nyl hydrazone of ethyl formylacetate (R. Raap, R.G.

  Micetich, Can. J. of Chem. 46, 1057 (1968)). These compounds are prepared by reaction of the sodium derivative of the formylacetic ester with the corresponding hydrazine derivatives, which supposes the synthesis and the isolation of the sodium derivative of the formylacetic ester. However, the latter can be prepared only by long and complicated operations and also with returns that are not satisfactory.

  (DE 708513, GB 568,512).

  It was therefore necessary to find - this was the technical problem which was at the basis of the present invention - a process for preparing, in a technically simple and

  with a high yield, esters of acylazo-3 acids.

  propionics as well as their isomers.

  This technical problem is solved in accordance with the

  by a process for the preparation of 3-acylacpropionic acid esters having the general formula I

CH2 - CH2 - COOR1

1 (I)

N = N - CO - R2

  in which R 1 represents an alkyl radical containing

  1 to 6 carbon atoms and R 2 an alkoxy radical, preferably

  An alkoxy radical containing from 1 to 4 carbon atoms, or an amino group, characterized in that acrylic esters of general formula II are reacted.

H H

C = C - COOR1 (II)

  H with hydrazine derivatives of the general formula III

H2N -NH - CO - R2 (III)

  optionally in an inert solvent and / or in the presence of catalysts, so as to obtain 3-acylhydrazinopropionic acid esters of general formula II ')

CH2- CHI - COOR

I '-t (Iv)

NH - NH - CO - R2

  and these compounds are oxidized in an inert solvent by means of oxidizing agents, which reaction leads to the desired products in which R 1 and R 2 have the previously given meanings. The alkyl radicals are, for example, methyl, ethyl, propyl, isopropyl and n-butyl, sec-butyl, n-pentyl and n-hexyl radicals. The alkoxy radicals are, for example, methoxy radicals,

ethoxy, propoxy and butoxy.

  The process according to the invention thus starts from compounds which are easy to obtain and it makes it possible to prepare the compounds sought with high yields, in a technically way.

simple and safe.

  According to a particular embodiment of the process of the invention, the acrylic esters of formula II are reacted with the hydrazine derivatives of formula III at temperatures of -20 to 150 ° C., preferably 0 to 50 ° C. and at a pressure of 0.1 to 1 MPa, preferably 0.1 MPa, optionally catalyzed by bases or acids, and equimolar amounts of the acrylic esters of formula II and

  hydrazine derivatives of formula III.

  According to another embodiment of the present process, the oxidation of the 3-acylhydrazinopropionic acid esters of general formula IV with oxidation agents is carried out at temperatures of from -20 to 100.degree. C., preferably from -20.degree. 5 to 50 ° C., and a 3-acylhydrazino-3-propionic acid ester of formula IV, which has not been isolated from the reaction mixture which originated and which can be converted by an operating procedure, is used.

continuously.

  The execution of the process according to the invention is technically

simple and elegant.

  The synthesis of the acylhydrazino-3-propionic acid esters of formula IV is carried out, according to the invention, starting from acrylic esters of formula II by reaction with approximately equimolar amounts of hydrazine derivatives of formula III, in an aqueous medium, in inert organic solvents, preferably in an aqueous medium or in an alcoholic medium, but possibly also without any solvent. It is good to add the acrylic ester in portions or diluted with a solvent, such as a C1-C4 alcohol, to the solution of the hydrazine component diluted with water or a C1-C4 alcohol. The ratio of alcohol to water in the

  mixture can then vary over extended intervals,

  we can use both the alcohol alone and the water alone.

  The weight ratio of alcohol to water is preferably 1: 1. The addition of the reaction partners can also

be done in the reverse order.

  The reaction is carried out at temperatures of -20 to C, preferably 0 to 50 C. The pressure can range from

  0.1 to 1 MPa but it is preferably 0.1 ltPa (1 atmosphere).

  Inert solvents for the reactants include, for example, C1-C4 alcohols, such as methanol, ethanol, propanol, isopropanol, butanol, secondary butanol and the like. tertiary butanol; halogenated hydrocarbons, such as methylene chloride, chloroform and carbon tetrachloride, aliphatic and aromatic hydrocarbons, such as petroleum ether, pentane, cyclohexane, benzene, toluene and xylenes, ethers such as diethyl ether, tetrahydrofuran, dioxane and diethyl ether of ethylene glycol, carbonitriles such as acetonitrile, and carboxamides, such as

than dimethylformamide.

  It may be advantageous to catalyze the reaction with bases or also with acids. Alkali metal hydroxides, alkali metal alkoxides, tertiary amines, such as triethylamine and N, N-dimethylaniline, hydroxides, are generally used as basic catalysts.

  benzyl trialkyl ammonium compounds, such as benzyl

  trimethylammonium and dialkyl carboxamides, such as dimethylformamide and dimethylacetamide. For the acid catalysis, it is possible to use sulfuric acid, phosphoric acid, acetic acid, lactic acid and boron trifluoride. When the reaction is complete, the reaction mixture is optionally subjected to a complementary treatment carried out in a known manner. After removal of the solvent, or the residue is distilled off under reduced pressure, or recrystallized in suitable solvents, such as ketones, alcohols, nitriles, esters, ethers or chlorinated hydrocarbons, for example in acetone, methanol, ethanol, acetonitrile, ethyl acetate, di-isopropyl ether or chloroform.The reaction products are obtained in the form of colorless crystals or in the form of liquids colorless, which are stable at

ambient temperature.

  If, however, a continuous procedure is adopted then there is no need to isolate the reaction product of the general formula IV and can be subjected directly to the subsequent reaction. The 3-acylazo-propionic acid esters of general formula I are then prepared, according to the invention, by reacting the 3-acylhydrazinopropionic acid esters of formula IV with common oxidation agents in an aqueous medium and or in inert organic solvents with regard to the bodies taking part in the reaction, the agents

  oxidation is involved in stoichiometric quantities.

in excess.

  It is good to add the oxidation agent in portions, under

  the form of an aqueous solution or in the diluted state

  with a solvent, to the solution of the acylhydrate acid ester.

  zino-3 propionic diluted with water or with a solvent.

  The addition can also be carried out in the opposite direction. This reaction step takes place at a temperature of from -20 to 1000 ° C., preferably from -5 ° to 50 ° C. The reaction time can go

  from 0.5 to 5 hours, depending on the temperature applied.

  Inert solvents for the reactants include aliphatic or aromatic hydrocarbons, such as cyclohexane, heptane, ligroin, benzene, chlorobenzene, toluene and xylenes, and halogenated hydrocarbons. such as methylene chloride, chloroform, carbon tetrachloride and 1,2-dichloroethane. In the presence of these solvents it is also possible to carry out subsequent operations on the raw solutions, because these solvents also show inertia in the subsequent steps. Suitable oxidizing agents which guide the choice of the solvent are, for example, nitric acid, potassium dichromate, potassium permanganate, mercury oxide, ammonium or sodium nitrate, sodium chlorate, chlorine, alkali metal or alkaline earth metal hypochlorites, ammonia hydrogen peroxide, ferric chloride, nitrous

lead oxide (IV).

  When the reaction is complete, the reaction mixture is subjected to a further treatment carried out in a known manner, for example by removal of the solvent used by distillation under reduced pressure or under normal pressure or by extraction, the organic solvents used during the course of the reaction. of the reaction that can be used at the same time

  extraction agents for the acylazo-3 propionic acid esters.

  The extracts are then processed in known manner, for example, after being dried, by removing the solvent used by distillation under normal pressure or under reduced pressure. In this way, the 3-acylazo-propionic acid esters are obtained in the form of slightly colored crystals or in the form of oils, in an extremely pure state and with very good yields, to the extent that they can be used for subsequent reactions

without further purification.

  The oxidation of the acylhydrazino-3-propionic acid esters

  The compounds of formula IV first give rise, as the examination of nuclear magnetic resonance spectra shows, to compounds having the structure of formula I. These compounds tend, in solution, to be converted into acylhydrazones of esters of acetic acid corresponding to the general formula V

CH - CH - COOR

2i i (v)

N - NH - CO - R2

  which are therefore isomers of the compounds of formula I.

  The preparation of the compounds of general formula V, that is to say

  say acylhydrazones of formylacetic esters, so does

  also part of the present invention.

  The compounds of the general formula V are also in a state of isomeric equilibrium with the compounds of general formula VI

CH = CH - COOR1 (VI)

NH - NH - CO - RI

  therefore, the preparation is also part of the present invention. If desired, irreversible transposition of the compounds having the structure (I) into isomeric compounds having the structure (V) or the structure (VI) can be carried out,

  which is also part of the present invention.

  For this purpose, according to the invention, the 3-acylazo-propionic acid esters of general formula I are treated with catalysts, optionally using an inert solvent (R 1 and R 2 have the meanings which have been given

upper).

  A special embodiment of this feature of the process consists in transposing a 3-acylazo-propionic acid ester of formula I at temperatures of from -20 to 50 ° C., preferably from 0 ° to 30 ° C., to the acylhydrazone of ester

  formylacetic of formula V and the enhydrazine of formula VI.

  This reaction can be catalyzed both by

  acids, including Lewis acids, only by bases.

  Examples of acidic catalysts are hydrochloric acid, sulfuric acid and nitric acid, HgCl2, (NH4) 2SO4, NH4Cl, NH4Br, HgBr2, (CH3) 3SiOSO2CF3, SnCl4, BF3, acid hydrate. p-toluenesulfonic acid, acetic acid and trifluoroacetic acid. The basic catalysts can be oxides, hydroxides, alkoxides or carbonates of alkali metals or alkaline earth metals, ammonia, tertiary amines, such as triethylamine,

  amine and N, N-dimethylaniline, and pyridine bases.

  The isomerization reaction is advantageously carried out

  in an aqueous medium and / or in organic solvents.

  Inert solvents may in particular be hydrofluoric

  halogenated carbons, such as methylene chloride, chloroform, 1,2-dichloroethane and carbon tetrachloride, aliphatic or aromatic hydrocarbons, such as petroleum ether, pentane, heptane, cyclohexane, benzene, toluene, laxylenes and chlorobenzene, ethers, such as diethyl ether, tetrahydrofuran, dioxane and di-isopropyl ether, and alcohols, such as

than methanol and ethanol.

  The reaction is carried out at temperatures between -20 and 500C, preferably between 0 and 30'C, in particular

at room temperature.

  In practice, the following procedure is followed: a corresponding catalyst is added to the crude solution of the 3-acylazopropionic acid ester, and then the reaction products, which are generally solid, are isolated by filtration, by freezing or by removal of the solvent, in the form of colorless crystals. These can be recrystallized easily in suitable organic solvents, such as ketones, alcohols, nitriles, esters, ethers and chlorinated hydrocarbons, for example in acetone, methanol, ethanol, amine acetonitrile, ethyl acetate, di-isopropyl ether or chloroform, and they are stable at room temperature. But the compounds are generally obtained in a state of purity so great that they can be subjected to subsequent reactions without having

need to be recrystallized.

  The products prepared according to the invention are important starting materials for the preparation of 1,2,3-thiadiazole carboxylic acid derivatives, from which

  valuable pesticides and phyto-

  as well as pharmaceutical products.

  This preparation of derivatives is 1,2-thiadiazole carboxylic acid of general formula VI. N2 ii (VII)

N C- 00R1

N C -COOR1

  S can be carried out in a known manner: the compounds of the general formula V are, for example, reacted with thionyl chloride (the symbol R1 has the meaning given to it).

upper).

  The process of the invention also opens a new and very interesting route for the preparation of compounds of formula VII by reacting the products of general formula I which have first formed, which can be reacted directly. with thionyl chloride SOC12, so as to obtain the desired compounds (VII), which saves a process step. This particularity of the process

  is also part of the present invention.

  The synthesis of esters of 1,2,3-carboxylic acidethiadiazole

  xyl-5 of formula VII is then made from acylazo-3-propionic acid esters of formula I by reaction with thionyl chloride. The reaction is carried out at temperatures between 20 and 100 C, preferably between -5 and 50 C. The reaction time may vary, depending on

  the applied temperature, from 1 to 20 hours.

  For the synthesis of thiadiazole-1,2,3-carboxylic acid esters, the reaction partners can be used in approximately equimolar amounts. But thionyl chloride can also be used in a large excess, almost as a solvent. However, it is advisable to use the 3-acylazopropionic acid ester and

  thionyl chloride in a molar ratio of 1: 3.

  The reaction can also be carried out in the presence of inert solvents with respect to the bodies which take part in the reaction. These solvents will be, for example, halogenated hydrocarbons, such as methylene chloride, chloroform and carbon tetrachloride, aliphatic or aromatic hydrocarbons, such as petroleum ether, pentane, cyclohexane, benzene, toluene and xylenes, ethers, such as diethyl ether, tetrahydrofuran, dioxane, ethylene glycol diethyl ether and diethylene glycol diethyl ether, and esters, such as

as ethyl acetate.

  In general, the acylazo-3-propionic acid ester, possibly

  also dissolved or suspended in a suitable solvent, is added portionwise to thionyl chloride and optionally diluted with organic solvents, but the addition of reaction partners can optionally

be done in the reverse order.

  The hydrogen chloride which is formed during the reaction can be continuously removed from the reaction vessel by a stream of inert gas or by application of a vacuum. When the reaction is complete, the reaction mixture is subjected to

  to a complementary treatment carried out in a known manner.

  After removing the solvent and the excess of thionyl chloride by distillation, the residue can be subjected to fractional distillation; or the excess thionyl chloride is destroyed with a saturated solution of sodium carbonate or with a solution of sodium or potassium hydrogen carbonate, a solution of sodium acetate or a solution of caustic soda or potassium hydroxide caustic or

  directly by water, and the reaction solution is

  It can be used for steam distillation or extraction, since the solvents used in the course of the reaction can be used as extraction agents at the same time. The extracts are then processed in a known manner; for example, after drying and distilling off the solvent, the residue is subjected to fractional distillation under reduced pressure or is simply macerated with a suitable solvent, for example with an aliphatic hydrocarbon such as pentane, hexane, cyclohexane or petroleum ether. The esters of 1-thiadiazole-2,3-carboxylic acid are thus obtained in extremely pure form and with very high yields, so that they can be used without purification in the reactions leading to the desired end products.

  The following examples illustrate the present invention.

Example 1

  a) Preparation of the methyl 3-methylcarbazido propionate.

  In a two-liter, four-necked, round-bottomed flask equipped with a stirrer, a thermometer, and a reflux-tube reflux condenser, 173.0 grams were added. (1.5 mole) sprayed semicarbazide hydrochloride suspended in 300 ml of methanol; a solution of sodium methylate which has been freshly prepared from 34.4 g (1.5 mol) of sodium and 500 ml of methanol is added dropwise to the suspension over a period of 10 minutes, while maintaining the internal temperature between 15 and 20 C. The reaction mixture is stirred for a further 15 minutes.

  at 20 C, then the sodium chloride is separated by spinning.

  The filtrate is collected in a three-neck round-bottomed flask with a capacity of 2 liters and 90 ml (1.0 mole) of methyl acrylate are added thereto over 1 hour while stirring at 200 ° C. The mixture is allowed to stand for 3 days at room temperature, then filtered again and then the filtrate is concentrated at 40 ° C. under reduced pressure. 205 g of a yellow oily product are collected and stirred for a further 1 hour at room temperature with 1 liter of ethyl acetate. The undissolved material is removed by filtration, and the filtrate is then concentrated to 500 ml at a temperature of 40 ° C. By triturating white crystals are obtained which are separated by spinning and dried at room temperature under reduced pressure, up to constant weight. Quantity collected: 134.4 g, 83.4% of the quantity

theoretical.

Melting point: F = 67-69C.

  b) Preparation of methyl carbamoylazo-3-propionate.

  In a 3-liter balloon equipped with a thermometer

  and a stirrer 16.1 g (0.1 mole) of semicarbonate were dissolved

  bazido-3 methyl propionate in 100 ml of water and 246.0 g (0.3 mole) of a solution freshly prepared at approximately 10% hypochlorite are added over 20 minutes while cooling with ice of sodium, while maintaining the internal temperature between 5 and 7 C. The yellow reaction solution thus obtained is stirred for a further 10 minutes in the ice bath, 85 g of sodium chloride are added thereto and the mixture is carefully extracted 5 times with each time 400 ml of chloroform. The extracts dried over magnesium sulphate are concentrated at 40 ° C. under pressure

  scaled down. A yellow crystalline product is obtained.

  Quantity collected: 12.9 g, 81.1% of the theoretical amount.

F: 85 - 87 C with decomposition.

  b2) Preparation of methyl carbamoylazo-3 propionate.

  In a three-necked flask with a capacity of 1 liter equipped with a stirrer and a thermometer 16.1 g (0.1 mole) of 3-methyl-3-propionate are dissolved in a mixture of 1 ml of water and 10 ml of water. 3 g of about 95% sulfuric acid. While cooling with ice, a solution of 9.79 g (0.0333 mol) of potassium dichromate in 70 ml of water and 13.8 g of sulfuric acid at about 95 is added dropwise over 10 minutes. %, at a reaction temperature of 7 to 10 C. The reaction is allowed to continue for a further minute, then 20.0 g of solid potassium hydrogen carbonate is added. Yellow crystals are formed. The reaction solution is extracted vigorously five times with 300 ml of chloroform each time. The chloroform extracts are dried over magnesium sulphate and concentrated

  at 40 C under reduced pressure. Yellow crystals are obtained.

  Amount collected: 9.0 g, or 56.5% of the quantity

theoretical.

  F = 85-87 C (with decomposition).

  c) Preparation of the 3-methyl-3-propoionate.

  In a 250-ml three-necked flask, covered with a thermometer and stirrer, 15.9 g (0.1 cc of methyl carbamoylazo-3-propionate) are dissolved in 500 ml of chloroform and 0 is added. , 5 ml of trnhy! Arnm-e, all -n

  maintaining the indoor temperature at 30C by a cooler

  ment. It is then stirred for a further hour at room temperature, after which it is evaporated to dryness at room temperature.

  crystal.line porridge formed at 40oC under reduced pressure.

  The residue is macerated with 150 μl of diisopropylene oxide.

  The mixture is filtered off and dried to constant weight under reduced pressure. The amount collected is 14.5 g and corresponds to a yield of 9%. F = 159 ° C (with decomposition). Example 2 a) Preparation of the 3-ethoxycarbonylhydrazinopropionate methyl. In a one-liter three-necked flask equipped with a stirrer, a thermometer and a reflux condenser, 114.4 g (l, mole) of ethyl hydrazino-formate are dissolved. in 600 ml of ethanol and 90 ml (0.1 mole) of methyl acrylate are added over 1 hour at 200 ° C. The mixture is left standing for 4 days at room temperature in the closed flask, and then the reaction solution is concentrated at 40 ° C. under reduced pressure. The liquid thus obtained is distilled under reduced pressure. The quantity collected is

  111.1 g, or 58.4 of the theoretical amount.

  Boiling point: 110-111 ° C at 0.13 hPa.

  b) Preparation of methyl ethoxycarbonylazo-3-propionate.

  In a 250 ml three-necked flask equipped with a stirrer and a thermometer, 9.5 g (0.05 mol) of methyl ethoxycarbonylhydrazinopropionate are dissolved in 50 ml of water and added. in 20 minutes 82 g (0.1 mole) of a solution of sodium hypochlorite at about 10% which has been freshly prepared, while maintaining the internal temperature between 5 and 7 C. A yellow oil is deposited. The mixture is stirred for a further 10 mls of ice-cream.

  extracted three times with 75 ml

  form and, after drying over magnesium sulphate and evaporation of the chloroform phases at 40 C under pressure

  reduced, a thick yellow oil is obtained.

  Amount collected: 8.7 g, ie 92.4% of the theoretical quantity nd = 1, 4424 c) Preparation of the ethoxycarbonylhydrazono-3 propionate

of methyl.

  In a 3-necked flask equipped with an agitator and a

  thermometer, 18.8 g (0.1 mol) of ethoxycarbonyl were dissolved

  3-azo-methyl propionate in 100 ml of chloroform and 0.5 ml of triethylamine is added at 30 ° C. because of the exothermicity of the reaction it is then necessary to cool. It is then stirred for another hour at

  room temperature, then concentrate the reaction solution

  at 40 ° C under reduced pressure. The remaining oil is macerated with 50 ml of di-isopropyl ether, the crystals thus obtained are filtered off and dried. 17.9 g of product are collected, which corresponds to a

yield of 95.2%. Mp = 60-61C.

Example 3

  Preparation of the 3-methyl-3-proparbenzoate (continuously) In a 1-liter flask having 3 tubes and equipped with a thermometer and stirrer, 16.1 g (0.1 mole) was dissolved. of methyl semicarbazido-3-propionate in 100 ml of water and, while cooling with ice, 141.6 g (0.2 mol) of a solution of sodium hypochlorite at about 10 are added over 20 minutes. % which has been freshly prepared, while maintaining the internal temperature between 5 and 7 C. The yellow reaction solution is stirred for a further 20 minutes in the ice bath, 66 g of sodium chloride are added thereto, then Carefully extract 5 times with 400 ml of chloroform each time. The chloroform phases, dried over magnesium sulphate, are concentrated at 40 ° C. under reduced pressure to a volume of 100 ml., Each of 0.5 ml of triethylamine is added to the 100 ml. Temperature is reduced by cooling. After acting for! he-re at room temperature is concentrated to dryness; the bouilie

  crystalline thus obtained, at 40 C under reduced pressure.

  The residue is macerated with diisopropyl ether, filtered off with suction and dried under reduced pressure until its weight remains constant. 12.0 g of product are collected, which corresponds to a yield

  75.5%. F = 158.5 - 159.5 ° C (with decomposition).

  EXAMPLE 4 Preparation of Methyl 3-Methoxycarbonylhydrazono propionate (Continuous) In a 500 ml three-necked flask equipped with a stirrer and a thermometer, 19.0 g (0.1 mole) 3-methoxycarbonylhydrazino-3-propionate in 1 ml of water and 141.6 g (0.2 mole) of a 10% sodium hypochlorite solution are added over 20 minutes while maintaining the internal and 7 C. A yellow oil precipitates. Stirring is continued for 10 minutes, extracted three times with 150 ml of chloroform each time and, after drying the chloroform phase on

  magnesium sulfate, concentrated to 100 ml.

  To the concentrated chloroform solution at 100 ml, add 0.5 ml of triethylamine, while ensuring that the temperature does not rise above 30 ° C. After stirring for 1 hour at room temperature, the mixture is evaporated. reaction solution at 40 ° C. under reduced pressure; The oily residue is then macerated with 50 ml of di-isopropyl ether and the crystals are filtered off with suction.

  colorless that formed and dried.

  Amount collected: 12.9 g; yield: 68.5% -

M.p. 59 - 61 C.

  EXAMPLE 5 Preparation of 3-ethoxycarbonylhydrazono-3-propionate In a 500 ml three-necked flask equipped with a stirrer and a thermometer, 19.0 g (0.1 mole) of ethoxycarbonylhydrazin-3 are dissolved. methyl propionate in 150 ml of water and added in 15 minutes a solution of 9.79 g (0.0333 mol) of potassium dichromate in 70 ml of water and 17.2 g (0.167 mol) of acid. 95% sulfuric. We keep

  the indoor temperature between -2 and 0 C for 30 minutes.

  It is then extracted twice with 40 ml of chloroform each time. After drying over magnesium sulfate, the chloroform solution is evaporated at 40 ° C. under reduced pressure. The remaining oil is macerated with di-isopropyl ether and the obtained crystals are filtered off. Amount collected: 12.4 g, corresponding to a yield

65.9%.

Mp = 57-61C.

Example 6

  Preparation of methyl 1,2,3-thiadiazole-5-carboxylate

  In a 250 ml round bottom flask with three tubes and equipped with a stirrer, a thermometer and a condenser with venting in the fume hood, the mixture is cooled to -10.degree. ) of thionyl chloride and 15.91 g (0.1 mol) of methyl carbamoylazo-3-propionate are added portionwise, while maintaining the internal temperature between -5 to 0 C. The addition is complete, the yellow reaction solution is stirred for a further 2 hours, at the same time the internal temperature is slowly allowed to rise to + 2 ° C. Then 60 ml of chloroform is diluted and 60 ml of a solution are carefully added. saturated with potassium hydrogencarbonate, while maintaining the internal temperature between 10 and 20 C. The chloroform phase is separated, washed neutral with ml of a solution of potassium hydrogen carbonate, dried over magnesium sulphate and it is concentrated at 40 ° C. under reduced pressure. The liquid thus obtained is distilled

under the vacuum of the water pump.

  Quantity collected: 11.6 g, or 80.5% of the quantity

  theoretical. F =] 10-111 C under 19 hPa.

Claims (10)

  1. Process for preparing 3-acylazo-propionic acid esters corresponding to general formula I CH - CH - COOP 2 2- t N = N- CO- R_   in which R 1 represents a C 1 -C 6 alkyl radical and R 2 an alkoxy radical, preferably an alkoxy radical containing from 1 to 4 carbon atoms, or an amino group, characterized in that it denotes is acidic acrylqcaue corresponding to the general formula II H H C = C - COOR (II)   H with hydrazine derivatives corresponding to the general formula III H N - NH - CO - R (III)   optionally using an inert solvent and / or operating in the presence of a catalyst, so as to obtain 3-acylhydrazino-propionic acid esters of general formula IV CH - CH - COOR 12 2 1 (IV) NH - NH - CO - R2   and these compounds are oxidized in an inert solvent, by means of oxidizing agents, in order to convert them into the desired products (in the formulas II to IV the symbols R1 and R2   have the meanings given above).   2. Method according to claim 1, characterized in that the acrylic esters of formula II are reacted with the hydrazine derivatives of formula III at temperatures of -20 to 150 ° C., preferably 0 to 50 ° C., and at a pressure of 0.1 to 1.0 MPa, preferably at a pressure of 0.1 MPa, optionally in the presence of a basic or acidic catalyst, and equimolar amounts of the acrylic esters of formula II and derived from hydrazine of formula III.   3. Process according to claim 1, characterized in that the oxidation of the acylhydrazin-3-propionic acid esters of general formula IV with oxidation agents is carried out at temperatures of 20 to 100 ° C., preferably from -5 to 50 ° C., and a 3-acylhydrazinopropionic acid ester of formula IV which has not been isolated from the reaction mixture and which is reacted is used. by a continuous procedure.   4. Method according to one of claims 1 to 3, for   the preparation of compounds corresponding to one of the general formulas V and VI: CH - CH - COOR u 2 COOR He (V) N - NH - CO - R2 CH = CH - COOR1 1 (VI) NH - NH - CO - R2   5. Process according to claim 4, characterized in that catalysts are treated with compounds corresponding to the general formula I CH2 - CH2-COOR1 (I) N = N - CO - R2   in which R and R2 have the meanings given to the   Claim 1, optionally using a solvent.   6. Process according to claim 5, characterized in that a 3-acylazo-propionic acid ester of formula I is transferred at temperatures of 20 to 50 ° C., preferably from 0 ° to 30 ° C., to the acylhydrazone of formylacetic ester   of formula V and the enhydrazine of formula VI.   7.Procédé according to claim 1 for the preparation of derivatives of thiadiazole-1,2,3-carboxylic acid-5 corresponding to the general formula VII N C - H I II (VII) N C - COOR   Wherein R 1 has the meaning given in claim 1. 8. Process according to Claim 7, characterized in that the compounds corresponding to the general formula CH 2 - CH 2 - COORt are reacted. N = N - CO - P   in which R1 and R2 have the meanings given to the   Claim 1 with SCI2I thionyl chloride.   9. Process according to claim 7, characterized in that compounds of the general formula V are reacted. CH2 - CH2 - COOR he (V) N - NH - CO - R2   in which R1 and R3 have the meanings given to the   Claim 1 with thionyl chloride.   10. Method according to any one of claims 1 J   9 for the preparation of pesticides and phyto-   as well as pharmaceutical products.