DD151187A1 - PROCESS FOR THE PREPARATION OF DIHALOGEN VINYL SODIUM ACIDS OR ESTERS - Google Patents

Abstract

The invention relates to a novel process for the preparation of DihalogenvinylessigsÄururen or their esters, in which a beta-trihalogenomethyl-beta-propiolactone is reduced cathodically. If these lactones are catodically reduced in organic acids with one of their salts as conductive salt, the corresponding dihalo-vinylacetic acids are obtained. If the reduction is carried out in an alcohol with an alkali halide or perchlorate, the corresponding esters of dihalovinylacetic acids are obtained. Dihalovinylacetic acids or their esters are valuable chemical intermediates.

Description

-4- 22 14

Title of the invention

Process for the preparation of dihalovinylacetic acids or their esters,

Field of application of the invention

The invention relates to a novel process for the preparation of Dihalogenvinylessigsäuren or their esters, which are valuable chemical intermediates. Their high reactivity enables versatile use, i.a. can be used to produce pyrethroid intermediates under technical conditions.

Characteristic of the known technical solutions

Dichlorovinylacetic acids are generally prepared by reacting saturated carboxylic acids with polychloroolefins. The reaction is initiated by organic peroxides, requires special autoclave and must be carried out in an inert gas atmosphere at 4O3K. (US Pat. No. 3,558,660) Dichlorovinylacetic acid esters are obtainable by Grignard reactions from ethyl 4,4,4-trichlorocrotonate in tetrahydrofuran at 195K. (CRAcad. Sci., Ser. C 266 , 146 (1968)) However, when implemented in the art, the major drawbacks of a Grignard reaction are of great importance. In addition ,, the reaction must be carried out at low temperatures and in relatively expensive solvents. Hur the oC-unsubstituted dichlorovinylacetic acid can be represented in a relatively simple manner, as by saponification of 1, 1-dichloro-3-cyan ~ -propene-1, which by reaction of

_ ₂ _ 2 2 1 4 5 L,

1,1,3-Trichloropropene-i can be obtained with CuCIT. (Bull.Soc.Chim.Fr. 1967 , '269-73) However, one is forced to start from expensive products.

The reduction of 4,4,4-trihalo-3-hydroxy-butyric acid or its lactone in the presence of formic, acetic or propionic acid with zinc, iron or tin powder has also been proposed. (DE 136 834) The disadvantage here is the use of expensive reducing agents and · the forced attack of their reaction products.

Object of the invention

The aim of the invention is a new, technically simple and selective process for the preparation of Dihalogenvinylessigsäuren or their esters, starting from readily available starting materials.

Explanation of the essence of the invention

The invention has for its object to develop a process by which it is possible to produce Dihalogenvinylessigsäuren or their esters without the use of chemical reducing agents, without pressure and without interfering byproducts. According to the invention, dihalovinylacetic acids or their esters are obtained by cathodic reduction of β-trihalomethyl / 3-propiolactones of the general formula:

CCl ₃

R ¹ -

1 p

where R, R- are the same or different and are hydrogen,

Alkyl, aryl, halogen, alkoxy, phenoxy and X-chloro, bromine,

or produced their hydrolysis or Alkoholyseprodukte, wherein depending on the choice of the electrolyte system, the acid or its esters formed.

As the electrolyte for the preparation of Dihalogenvinylessigsäuren are preferably organic acids, in particular

, - 3 - 2 2 1 4 5 ¹ A.

Acetic acid, with one of its salts as conductive salt. For the preparation of Dihalogenvinylessigsäureester are as electrolysis alcohols, preferably having 1 to 4 carbon atoms, with alkali halides:! or perchlorates suitable as conductive salts, and alcoholic solutions of mineral acids, preferably hydrochloric and sulfuric acid. The conductive salts are suitably used in concentrations of less than 10 -.% Is used. However, it is also possible to use higher concentrations, since the conducting salts serve only for charge transport and can be returned to the electrolysis process after working up.

The temperature of the cathodic reduction is limited only by the boiling or pest point of the alcohol or organic acid used. Expediently, the electrolysis is carried out at room temperature or with slight cooling. To avoid concentration polarization, the electrolysis solution should be stirred or pumped. Examples of suitable anodes are graphite or platinum. Suitable cathodes are electrode materials with a high hydrogen overvoltage, preferably mercury and lead.

The current density can be varied without substantial influence on current efficiency and type of product and within wide limits. The cathode potential is selectable from -1.1 to -1.8V against the saturated calomel electrode.

The electrolysis product is obtained by the catholyte is concentrated in vacuo after completion of the electrolysis, then treated with V / asser and with an organic solvent, this is particularly suitable ethers, hydrocarbons and chlorinated hydrocarbons, extracted several times. After drying the combined extracts, the extractant is distilled off and the remaining residue subjected to a vacuum distillation.

The lactones are readily accessible in a known manner by reaction of chloral or Bromal with a carboxylic acid chioMd, which has at least one hydrogen atom in the el position, and a tertiary Amiη or with an o ^ -halogen substituted carboxylic acid chloride by reaction with zinc accessible.

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Exemplary embodiments .

EXAMPLE 1

In 150 ml of 0.4 M Ammoniunacetat / acetic acid is dissolved 10 g / 3-trichloromethyl- fb- propiolactone. Mercury is used as working electrode and graphite as anode. Cathode and anode compartment are separated by a G5 frit diaphragm. It is electrolysed at 293K. The working potential is -1, TV against the saturated calomel electrode. The catholyte

is stirred. The current density is at the beginning of ΕΙβΙίΐΓΟ-ρ

lysis 5mA / cm. After completion of the electrolysis of the catholyte is poured into water and extracted several times with methylene chloride. The combined, neutral / ash extracts are dried and then the extractant is distilled off in vacuo. As electrolysis product dichloro-dichloroacetic acid is obtained. The structure of the electrolysis product is confirmed by IR, H-NMR spectroscopy and elemental analysis.

Pp = 313K Yield: 49 %

Kp ₃ = · 383-386K

EXAMPLE 2

In 150 ml of 1 M LiCl / methanol is dissolved 15 g /?> - Tri chloro thy 1-ß-propiolactone. Mercury is used as working electrode and graphite as anode. Cathode and anode compartment are separated by a G5 prittendiaphragm. The anolyte used is 30 ml of 3 M methanolic HCl. The working potential is -1 »5V against the saturated calomel electrode. It is electrolyzed at 288K in a pot cell. The catholyte is stirred. The electrolysis is stopped when the current has dropped to the value of the basic current. The catholyte is separated from the mercury and the solvent evaporated in vacuo. The electrolysis product is separated from the precipitated Leitsälz. To increase the yield V / asser is added to the electrolyte salt and extracted several times with ether. After drying, the extractant is distilled off and the electrolysis. product subjected to vacuum distillation. Dichlorovinylacetic acid methyl ester is obtained.

Kp ₁ 2 - 343K Yield: 81 %

The structure of the electrolysis product is confirmed by IR, H-NMR spectroscopy and elemental analysis.

- 5 - 2 2 1 4 5 Λ

EXAMPLE 3

In 100 ml of 1 in LiCl / methanol is dissolved 8 g of cC-methyl- / 3-trichloromethyl-ß-propiolactone. It electrolyzed at -1.5V against the saturated calomel electrode. All other conditions are analogous to Example Working up gives methyl c1-methyldichlorovinylacetate.

Kp ₉ = 344K Yield: 77 %

EXAMPLE 4

In 100 ml of 1 M LiCl / methanol is dissolved 7 g of q-ethyl-.beta.-trichloro-ethyl / 2> -propiolactone. One electrolyzes at -1.45 V against the saturated calomel electrode. All other conditions are analogous to Example Working up gives c.sub.2 -ethyldichlorovinylacetic acid methyl ester.

Kp ₁₁ = 355K * Yield: 78 %

EXAMPLE 5

8 g of oil- chloro- / 3-trichloromethyl-P-propiolactone are dissolved in 100 ml of 1 M LiCl / methanol. It is electrolyzed at -1.2V against the saturated calomel electrode. All other conditions analogously to Example Working up gives dichloro vinylacetic acid methyl ester.

Kp ₁₂ "= 343K Yield: 72 %

EXAMPLE 6

10 g of A-trichloromethyl (h- propiolactone are dissolved in 100 ml of 1 M LiCl / ethanol All other conditions are analogous to Example 2.

After working up Dichlorvinylessigsäureäthylester.

K ₁ = 363K Yield: 75 %

EXAMPLE I

9.0 g of 4,4,4-trichloro-3-hydroxybutyric acid are dissolved in 10 ml of 5 M HCl / ethanol. Mercury is used as working electrode, platinum as anode. Cathode and anode compartment are through

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a G5 ~ F'rittendiaphragma separated. The electrolysis is carried out in a pot cell. The catholyte is stirred. It works galvanostatically at a current density of 5mA / cm It is electro-lysed up to 1.5 times the theoretical amount of electricity. The work-up is carried out analogously to Example 2. As an electrolysis product Dichlorvinylessigsäureäthylester. ,

Kp ₁₂ = 359K. Yield: 60 %

EXAMPLE 8

8 g of 4,4,4-trichloro-3-hydroxy-butyric acid are dissolved in 100 ml of 5M HCl / methanol. The working electrode is lead, while the anode is graphite. One electrolyzed in a circulation cell. The cathode and anode compartments are separated by an ion exchange membrane. It works potentiostatisch.bei -1,8V against the saturated calomel electrode. Katolyte and anolyte are pumped. The work-up is analogous to Example Dichlorvinylessigsäuremethylester is obtained as the electrolysis product.

Kp ₁₁ = 343K Yield: 62 %

Claims (5)

· - 7 - 2 Invention Claims 1. A process for the preparation of Dihalogenvinylessigsäuren or their esters, characterized in that / 3-trihalomethyl-p-propiolactones of the general formula: CCl ₃ 0
1 1 2 in which R, R - are identical or different and are hydrogen, alkyl, aryl, halogen, alkoxy, phenoxy and X is chlorine or bromine, or their hydrolysis or Alkoholyseprodukte, cathodically reduced v / earth, depending on the choice of the electrolyte sy stems the acids or their esters formed. 2. The method according to item 1, characterized in that are used as electrolytes for the preparation of Dihalogenvinylessigsäuren organic acids, in particular acetic acid, with one of its salts as conductive salt * '... 3. The method according to item 1, characterized in that are used as electrolytes for the preparation of the · Dihalogenvinylessigsäureester alcohols, preferably having 1 to 4 carbon atoms, with Älkalihalogeniden or Alkaliperchloraten as conductive salt. 4. The method according to item 1 to 3, characterized in that materials with high hydrogen overvoltage, preferably mercury or lead, are used as cathode materials. 5. Method. According to item 1 to 4, characterized in that the cathode potential between -1.1 and -1.8V, measured • against the saturated calomel electrode.