CH617166A5 - Process for the preparation of novel 3-substituted 1-(2,2-dihalovinyloxy)benzene compounds - Google Patents

Description

617 166

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PATENT CLAIMS 1. Process for the preparation of a compound of the formula

XCH.

(I)

OCH = CR1R2

wherein R 1 and R 2 are halogen and X is halogen, characterized in that a compound of the formula

(II)

-CH (OH) CR1R2Z

where Z is halogen,

subjected to reductive dehydrohalogenation to form a compound of the formula

CH,

(III)

0-CH ~ CR R

The invention relates to a process for the preparation of a compound of the formula

XCH.

(I)

wherein R] and R2 are halogen and X is halogen.

The process according to the invention is characterized in that a compound of the formula

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and that in this compound (III) the methyl group is then halogenated.

2. The method according to claim 1, characterized in that a reaction with a metallic reducing agent is carried out as reductive dehydrohalogenation.

3. The method according to claim 2, characterized in that zinc dust is used as the metallic reducing agent.

4. The method according to claim 1, characterized in that the compound (III) is implemented with a supply source for positive halogen.

5. The method according to claim 4, characterized in that is reacted with an N-haloimide.

6. Use of the compounds of the formula (I) obtained by the process according to claim 1 for the preparation of compounds of the formula (IV)

(IV)

OCH = CR1R2

characterized in that a compound of formula (I) obtained is converted into the corresponding aldehyde by reaction with hexamethylenetetramine and this is then reacted with hydrogen cyanide or with a cyanide via the bisulfite compound into the cyanohydrin compound.

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CH,

(II)

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0-CH (0H) CR1R2Z

wherein Z is halogen, is subjected to reductive dehydrohalogenation to form a compound of the formula

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CH.

(III)

b-CH ^ CRjRg

OCH = CR1R2

and that in this compound (III) then the methyl group is halogenated, is converted into (I). Z is preferably the same halogen as Ri and R2.

The halogen atoms mentioned above are preferably to be understood as fluorine, chlorine and bromine.

Compounds of the formula (II) can be obtained by an analogous process, as described by Hesse and Moll in J. Prakt. Chemie, 1974, 316 (2), 304, wherein anhydrous chloral and bromal are reacted with m-cresol in the presence of an acyl halide.

British Patent No. 1 221 205 describes the preparation of 2,2-dichlorovinyl esters of carboxylic and carbamic acid by reducing the corresponding 1-sulfonyl-2,2,2-trichloroethyl ester with zinc. In this reductive elimination process, it is advantageous that the sulfonyl group is an effective cleavable group. It has now surprisingly been found that the process can also be used for the preparation of dichlorovinyl aryl ethers, which are valuable intermediates for insecticides from the corresponding l-hydroxy-2,2,2-trichloroethyl aryl ethers, although the hydroxyl group is not as such effective cleavable group can be considered as the sulfonyl group of the known method.

The reductive dehydrohalogenation carried out in the process according to the invention is a reaction known per se to the person skilled in the art, which can be carried out, for example, using a metallic reducing agent or by means of electrochemical reduction.

The electrochemical reduction can be carried out in an organic solvent, for example a lower alcohol, such as methanol or ethanol, a cyclic ether, such as dioxane or tetrahydrofuran, an aliphatic ketone, such as acetone or cyclohexanone, or a mixture of such solvents with strong mineral acids containing water or water such as sulfuric, hydrochloric or phosphoric acid.

It is assumed that the reduction takes place mainly on the cathode with a high hydrogen overvoltage, for example on a mercury, lead mangalgam or lead cathode. The reaction can expediently be carried out in a cell which is equipped with a ceramic or glass frit membrane, a stirrer, a working and a reference electrode. This procedure can be set up for the continuous production of the required end product by using a solvent with which the reaction product can be extracted, for example methylene chloride.

The chemical reducing dehydrohalogenation can be carried out with a suitable metallic reducing agent, for example zinc dust and acetic acid.

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The halogenation of compounds of the formula (III) can expediently be carried out using a supply source for positive halogen, for example an N-haloimide, such as N-bromosuccinimide or N-chlorosuccinimide.

After application of the process according to the invention as claimed in claim 1, a compound of the formula (I) in which R3 is hydrogen and X is a halogen atom can be converted into a compound of the formula (I) in which R3 is a cyano group and X is a hydroxyl group by reaction with hexamethylenetetramine to give a compound of the formula

OHC

0

which is then reacted with hydrogen cyanide or via the bisulfite compound with a cyanide to form the cyanohydrin compound. The reaction via the bisulfite compound is preferred. Sodium cyanide, for example, is used as the cyanide.

example 1

Preparation of 3- (2,2-dichlorovinyloxy) benzyl bromide

A. The production of 3-tolyl-2,2-dichlorovinyl ether was carried out in two different ways:

a) By metallic reducing dehydrohalogenation. 14.2 g of l- (3-tolyloxy) -2,2,2-trichloroethyl acetate are added in

40 ml of glacial acetic acid dissolved and 3.6 g of zinc dust slowly added to the solution with stirring at room temperature. Due to the exothermic reaction occurring, the temperature rose to 60 ° C, after which the mixture was kept at 50 to 60 ° C for 4 h. Then the mixture was filtered and the filtrate was poured into an excess of water and extracted with chloroform. The extracts were washed twice with water, then with a saturated aqueous solution of sodium bicarbonate and finally with water. After drying the chloroform extracts over anhydrous magnesium sulfate, the solvent was evaporated under reduced pressure and the residual oil was distilled to give crude 3-tolyl-2,2-dichlorovinyl ether as a fraction with a boiling point of 92 to 95 ° C at 0.3 mm Hg was taken up, distilled again and taken up as a fraction with a boiling point of 84 ° C. at 0.2 mm Hg.

b) By electrochemically reducing dehydrohalogenation. 15.8 g of l- (3-tolyloxy) -2,2,2-trichloroethyl acetate, 9.8 g of sulfuric acid (conc. 98% by weight), based on the total volume, and 220 ml of methanol are introduced into an electrolytic cell, the purpose of which Compliance with an operating temperature of approximately 15 ° C was provided with a cooling jacket and equipped with a cylindrical membrane, a stirrer, a reference electrode (SCE) and a working electrode. The cathode was a rotating plate with a surface area of approximately 40 cm 2. Using a current density in the range of 5 to 10 mA / cm 2, the reaction was carried out in a voltage range of-1.1 to +1.7 V, based on the reference electrode. After complete reduction, the cathodic electrolyte was neutralized with sodium hydroxide solution and extracted with methylene chloride. The extracts were dried over anhydrous sodium sulfate and evaporated to give crude 3-tolyl-2,2-dichlorovinyl ether as a residue.

B. For the preparation of 3- (2,2-dichlorovinyloxy) -benzyl bromide, 12.2 g of the 3-tolyl-2,2-dichlorovinyl ether obtained were dissolved in 75 ml of carbon tetrachloride, 12 g of N-bromo-succinimide and added a trace of aqueous benzoyl peroxide,

after which the mixture was heated to reflux temperature for 3 hours. After filtration, the solvent was evaporated from the filtrate, the residue was dissolved in ether and extracted with an aqueous solution containing 1% by weight of sodium hydroxide, based on the total volume. The ethereal solution was dried over anhydrous magnesium sulfate, the solvent was evaporated under reduced pressure and the residual oil was distilled, a fraction having a boiling point of 150 ° C. at 0.5 mm Hg being obtained, which according to NMR spectroscopy was 65% by weight of required final product, together with approximately 30% by weight of unchanged starting material, the remainder containing a small proportion of the dibromomethyl compound.

C. The l- (3-tolyloxy) -2,2,2-trichloroethyl acetate used as the starting product was prepared as follows. 27 g of m-cresol were added to a solution of 37 g of anhydrous chloral in 125 ml of anhydrous ether, and the resulting mixture was stirred for 20 min at room temperature, then cooled to 10 ° C. and then slowly with a solution of 25.25 g of triethylamine in 100 ml of anhydrous ether added. Then, 20 g of acetyl chloride was carefully added to the mixture with stirring, and stirring was continued for 1 hour. Insoluble matters were then filtered off and the filtrate was dried over anhydrous magnesium sulfate. After evaporation of the ether under reduced pressure, the residual oil was distilled under high vacuum and the fraction was taken up with a boiling point of 132 to 134 ° C at 0.5 mm Hg. The required end product was identified by IR and NMR spectroscopy.

Example 2

Preparation of 3- (2,2-dichlorovinyloxy) benzyl alcohol A mixture of 2.8 g of 3- (2,2-dichlorovinyloxy) benzyl bromide, 2 g of sodium p-toluenesulfonate and 20 ml of methanol was stirred for 1 hour Heated to 50 ° C and then mixed with stirring with 20 ml of water and toluene. The toluene layer was separated, washed with water and concentrated by evaporation of the solvent under reduced pressure. The concentrate obtained was then added dropwise to 100 ml of an aqueous solution containing 15% by weight of potassium hydroxide, based on the total volume, and the mixture was heated to 60 ° C. for 1 h, then cooled to room temperature and with a mixture of 10 ml each Toluene and methyl isobutyl ketone extracted. The extracts were dried over anhydrous magnesium sulfate and from the extracts the solvent was evaporated under reduced pressure to give the required end product as a residue in the form of a light yellow oil.

Example 3

In this example, the conversion of 3- (2,2-di-chlorovinyloxy) benzaldehyde to its cyanohydrin compound is explained via the bisulfite compound.

2 g of 3- (2,2-dichlorovinyloxy) benzaldehyde were added to a solution of 3.2 g of sodium metabisulfite in a mixture of 5.2 ml of water and methanol at room temperature while stirring. After 30 minutes, the white precipitate formed was filtered off, washed with cold methanol and dried to give 2.5 g of the bisulfite compound of 3- (2,2-di-chlorovinyloxy) benzaldehyde, which was suspended in 5 ml of water and at room temperature a solution of 0.4 g of sodium cyanide in 5 ml of water was added. The mixture was stirred for 2 h and then washed with 2 X 10 ml of water, dried over anhydrous magnesium sulfate and evaporated under reduced pressure to give the cyanohydrin compound of 3- (2,2-dichlorovinyloxy) benzaldehyde in the form of a yellow oil has been.

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Example 4

The 3- (2,2-dichloro-vinyloxy) benzaldehyde used in the above example can be prepared, for example, as follows. 2.5 g of 3- (2,2-dichlorovinyloxy) -benzylbromide are carefully added to a solution of 2.1 g of hexamethylenetetramine in 20 ml of carbon tetrachloride while stirring at room temperature. After 5 min the precipitate was filtered off and washed with acetone. The solid obtained in this way was mixed with 16 ml of a 50% by weight aqueous acetic acid solution and heated to reflux temperature for 1 h. Then a mixture of 16 ml of water and 4.5 ml of hydrochloric acid was concentrated. added and the mixture heated to reflux temperature for a further 15 min. After cooling, the mixture was extracted with chloroform. The extracts were washed twice with water, dried over anhydrous magnesium sulfate and the solvent was evaporated under reduced pressure to give practically pure 3- (2,2-dichlorovinyloxy) benzaldehyde, identified by IR and NMR spectroscopy.

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