IE45374B1 - A procress for preparing [-cyano-3-pehnoxylbenzyl alcohol - Google Patents

Abstract

alpha -Cyano-3-phenoxybenzyl alcohol is prepared by reacting the bisulphite compound of formula: in a solvent, with a compound which generates CN ions, for example hydrocyanic acid or the alkali metal, alkaline-earth metal or ammonium cyanides. The alcohol obtained can be used, especially, for preparing, with certain cyclopropanecarboxylic acids, esters possessing a high insecticidal activity. The bisulphite compound, which is prepared from meta-phenoxybenzaldehyde, has the advantage over the latter of being more stable and of being able to be purified by crystallisation in an organic solvent.

Description

The invention relates to a process for preparing a-cyano3-phenoxybenzyl alcohol.

In the past·a-cyano~3”Phenoxybenzyl alcohol has been prepared by directly treating metaphenoxy benzaldehyde with cyanide ions. But since metaphenoxy benzaldehyde is itself not easily purified, some difficulty has been experienced in obtaining a-cyano-J-phsnoxybenzyl alcohol in a sufficiently pure fora.

We have now found, however, that a bisulphite adduct of metaphenoxy benzaldehyde is more stable than the aldehyde alone , aP& Ha7 easily be purified by crystallisation from organic solvents. A purified bisulphite adduct may then be treated with cyanide ions to give the desired a-cyano-J™ phenoxybenzyl alcohol in good yield and of high purity.

IS Thus, this invention provides a process for preparing α-cyano-J-phenoxybenzyl alcohol in which process an alkali metal bisulphite adduct of metaphenoxy benzaldehyde, of general formula: (1) (wherein A represents an alkali metal atom) is reacted, in & liquid reaction medium, with a compound capable of liberating Gif’ ions.

Amongst' compounds capable of liberating CN- ions, it is convenient to employ hydro-cyanic acid, ammonium cyanide OP alkaline-egrth metal cyanides, although alkali metal cyanides, especially the sodium salt, are preferably employed.

The alkali metal A is most conveniently sodium.

The reaction may he performed in an aqueous reaction medium, in which case the medium is preferably a mixture of water with an aprotie dipolar solvent, such as dimethoxy ethane, dimethyl sulphoxide or acetonitrile, and most preferably dimethyl formamide.

When the reaction is performed in an aqueous medium the presence of an acid is advantageous. This may be a strong acid such as sulphuric acid or hydrochloric acid, but weak carboxylic acids, especially acetic acid, are preferred.

It is advantageous to perform the reaction either by first forming a suspension of She bisulphite adduct of general formula I in an aprotie dipolar solvent, and then introducing this into an aqueous solution of alkali metal cyanide, or by introducing the aqueous solution into the adduct suspension, in which case it is preferred to add some acid to the formed reaction mixture.

We have, evensore unexpectedly discovered that the reaction may also be performed in an anhydrous medium, which preferably consists of the seme aprotie dipolar solvents as are used in the preferred aoueous media described above, although of course in an anhydrous condition.

As before, it is preferred to use alkali metal cyanides as the source of CN” ions, especially the sodium salt.

The reaction in an anhydrous medium may be performed advantageously without the addition of an acid, a preferred method being to introduce an anhydrous alkali metal cyanide into a suspension of a bisulphite adduct of general formula I formed in an anhydrous aprotic dipolar solvent.

The bisulphite adducts of general formula 1 may be prepared from metaphenoxy benzaldehyde by treatment thereof with an alkali metal bisulphites in a solvent.

The solvent is preferably a mixture of water, isopropyl 10 ether and methanol, or a mixture of water and isopropanol.

After crystallisation from an organic solvent such as ethyl acetate, the bisulphite adduct obtained is of excellent purity, of the order of 93%, and may be converted into a=cyanc-5“phenoxybenzyl alcohol using one of the . processes described hereinbefore, in a yield approaching that expected from theory. a-Cyano-3“phenoxyben-3yl alcohol is used industrially to prepare cyclopropane carboxylic acid esters with a dihalogenovinyl chain, which are used as insecticides. 5374 The following Examples are given, though only by way of illustration, to show preferred aspects of the process of the invention.

Example 1: · Preparation of a bisulphite adduct of metaphenoxy benzaldehyde 200 g of metaphenoxy benzaldehyde were dissolved in 800 cnr of isopropyl ether, and 200 g of sodium metabisulphite in 800 cm^ of water w»re added to the solution, followed by 25Ο cm- of methanol, The solution was then agitated for 3 hours, after which the precipitated product was isolated by vacuum-filtration, washed with a mixture of methanol and water (50:50), then with isopropyl ether, ar.d dried to obtain 295 B of the desired bisulphite adduct (labile hydrogen titre 95-5%).

The product was purified by crystallisation from 4 volumes of ethyl acetate and gave a total yield of 97.($>· Tbe labile hydrogen titre of the purified product was a minimum of 98%.

Preparation of a-cyano-3“-phenoxybenzyl alcohol in an aqueous medium Under an atmosphere of nitrogen and over a period of one minute, 20 g of bisulphite adduct were added to 40 cm^ of dimethyl formamide, and the suspension formed was agitated for 15 minutes at 20°C, then cooled to +5°C· Then, over 20 minutes and without exceeding +10°C, a solution of 5.4 g of potassium cyanide in 20 cnr' of water was added. The mixture was agitated for 2 hours at +5°0, after which the precipitate was eliminated by filtration. 100 cnr of water and 100 cnr 4537 4 of ethyl acetate were added to the filtrate and, after more agitation, the aqueous phase was decanted and product was extracted therefrom with ICO cur’ of ethyl acetate. The organic phases were reunited, then washed with water, dried and concentrated to dryness under reduced pressure, to give a residue which was dissolved in ether. The ethereal solution was washed vzith vzater, dried and concentrated to dryness to give 14.46 g of a-oyano-3-phenoxybenzyl alcohol.

Example 2; Preparation of g-eyano-3-phenoxybenzyl alcohol in an aqueous medium vtje above , indicating a purity 3.700 kg of/bisulphite adduct (labile hydrogen titre/ of 98%) t-zere introduced into 7.4 litres of dimethyl formamide, snd, over a period of about 10 minutes at 5°C, a solution of 0.765 kg of sodium cyanide in 3.8 litres of vzater was added.

Then, over about 30 minutes and at +5°0, 3.8 litres of acetic acid were further added and the mixture was again agitated for 30 minutes at +10°0, before being poured into a mixture of water and ethyl acetate and there agitated. The aqueous phase was separated by decanting and product was twice extracted therefrom with ethyl acetate. The organic phases were then reunited, washed vzith vzater and dried. Next 0.37 kg of active charcoal and Ο.37 kg of sodium sulphate were added to the mixture, agitated and separated again by filtration.

Finally the filtrate was concentrated to dryness by distillation under reduced pressure to give 2.770 kg of g-eyano-3-phenoxybenzyl alcohol, which contained about 1% of dimethyl formamide.

The compound obtained had the following characteristics: nitrogen titre 6.3 g per 100 g (theory 6.20); labile hydrogen titre: 100%. - 6 45374 13.5 cur of acetic acid were added to the product for storage. z Example 3? Preparation of a-cyano-3-phenoxybenzyl alcohol in an anhydrous medium g of anhydrous bisulphite adduct were introduced into 80 cm^ of anhydrous dimethyl formamide. Then, under an inert atmosphere and at 0°C, 3.3 S of anhydrous sodium cyanide were added and the mixture was agitated for 45 minutes at 0°C. A sample from the reaction mixture was separated and subjected to chromatographic analysis so as to verify that the conversion of the bisulphite adduct into a-cyano-3-phenoxybenzyl alcohol had completed, after which the reaction mixture was poured incc a mixture of water, ice, acetic acid, and isopropyl ether and there agitated. Next, the organic phase was separated by decanting, the product was extracted with isopropyx other, and the organic extracts were washed with water, dried and concentrated to dryness to give 13.8 g of a-cyanc-3~phenoxybenzyl alcohol.

Claims (15)

1. A process for preparing a-cyano-3-*phenoxybenzyl alcohol, in which process an alkali metal bisulphite adduct of mgtaphenoxy benzaldehyde, of general formula: (wherein A represents an alkali metal atom) is reacted, in a liquid reaction medium, with a compound capable of liberating CS“ ions.

2. A process as claimed in claim 1, in which the compound capable of liberating CN - ions is an alkali metal cyanide.

3. A process as claimed in claim 1 or claim 2 in which the reaction is performed in an aqueous medium containing an aprotic dipolar solvent.

4. -. A process as claimed, in claim 1, in which the reaction is performed by first forming a suspension of a bisulphite adduct of general formula I in an aprotic dipolar solvent, and then introducing this into an aqueous solution of an alkali metal cyanide.

5. A process as claimed in claim 3, in which the aqueous medium contains an acid. S. A process as claimed in claim 1, in which the reaction is performed by introducing an aqueous solution of an alkali metal cyanide into a suspension of a bisulphite adduct of general formula I formed in an aprotic dipolar solvent, - 8 45374 and then adding acid to the mixture.

6. 7. A process as claimed in claim 5 or claim 6, in which the acid is a carboxylic acid.

7. 8. A process as claimed in any of claims β to 7, in which the acid is acetic acid.

8. 9. A process as claimed in claim 1 or claim 2, in which the reaction is performed in an anhydrous medium comprising an aprotic dipolar solvent.

9. 10. A process as claimed in claim 1, in which the reaction is performed by introducing an anhydrous alkali metal cyanide into a suspension of a bisulphite adduct of general formula I formed in an anhydrous aprotic dipolar solvent.

10. 11. A process according to any of claims 3 to 10, in which the aprotic dipolar solvent is dimethyl formamide.

11. 12. A process as claimed in any of the claims 2 to 11, in which the alkali metal cyanide is sodium cyanide. IJ. A process as claimed in any of the preceding claims, in which the alkali metal A is sodium.

12. 14. A process as claimed in any of the preceding claims, in which the bisulphite adduct of general formula I is prepared by treating metaphenoxy benzaldehyde with an appropriate alkali metal bisulphite, in a solvent.

13. 15. A process as claimed in claim 14 in which the solvent is a mixture of water, isopropyl ether and methanol, or a mixture of water and isopropanol.

14. 16. A process for preparing a-cyano-J-phenoxybenzyl alcohol - 9 >45374 as descibed herein, with reference to any one of the examples.

15. 17. a-Cyano-3“phenoxybenzyl ^lcohol when prepared by a process claimed in any of the claims 1 to 16. Dated this 25th day of August, 1977.