US2394280A - Dihydroisophoryl thiocyano esters and compositions containing same - Google Patents

Description

-=OSlITIONS CONTKNG S Paul E. Williams, Berkeley, Calif., assignor to Shell Development Company, San Francisco, Calif., corporation of Delaware No Drawing. Application April 6, 1943,

Serial No. 482,032

s on (or. 167-30) This invention relates to new and novel compoundswhich are particularly suitable for killing noxious insects. More specifically, the invention is concerned with the thiocyano esters, particularly the thiocyano lower fatty acid esters, of dihydroisophorol, and with insecticidal com-. positions containing the same.

Among the best known toxicants used in insecticidal compositions, particularly in household insecticides, are pyrethrum and rotenone. These are both derived from plants grown in foreign countries and are therefore expensive and not always obtainable in desired quantities. Thus, many organic compounds which'are more read- 113; available in this country have been proposed as toxicants for insecticidal compositions. However, although many of these proposed compounds are relatively eiilcient for momentarily incapacitating insects, they are relatively inefilcient for killing insects. In addition to the desirability of high toxic action, for use in insecticides, particularly for use in household insectiold-es, the compounds must be light-stable, compatible with light paraffinic mineral oils, such as kerosene, and freedom from injurious effect and offensive odor to human beings and tendency to stain walls, fabrics, etc.

it is an object of the present invention to provide new compounds which are particularly suited as insecticidal toxicants because of their high toxicity to insects but low toxicity to man and other warm-blooded animals, Another object is to provide new insecticidal compositions containing these compounds as the active toxic ingredient.

We have found that the thiocyano fatty acid estersof dihydroisophorol are particularly eiiective and highly active insecticidal toxicants. These compounds contain a saturated hydrocarbon cyclohexane ring directly attached to a fatty acid residue through an ester linkage and have two of the three methyl groups on the ring attached to the same carbon atom of the I ring. The particular applicability of these substances as insecticidal toxicants may be due to the direct linkage of the ester group to the ring and to the arrangement and nature of the three methyl groups attached to the ring. These compounds are not ofiensive in odor, do not stain fabrics, painted walls, wallpaper, etc., are lightstable, and are compatible with or soluble in light parafiinic mineral oils, such as kerosene.

Included within the scope of the present invention are the monoor polythiocyano aliphatis, both saturated and unsaturated as well as straight and branched chain, fatty acid esters of dihydroisophorol, which may be represented by the general formula:

CH3 CH1 where A represents a monoor poly-thiocyano substituted aliphatic group. Particularly efiective ion use as insecticidal toxicants are the dihydroisophoryl thiocyano esters of the lower aliphatic acids having from 2 to 6 carbon atoms. However, for other purposes, such as for example, wetting agents, or depositing agents in insecticides, the thiocyano esters of the higher acids up to 20 carbon atoms with dihydroisophorol are desirable. Representative acids, which may be used in forming the thiocyano ester of dihydroisophorol, include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, capric acid undecylic acid, lauric acid, myristic acid, palmitic acid, oleic acid, stearic acid, arachidic acid, and their homologues and analogues together with suitably substituted compounds thereof, such as hydroxyacetic acid, lactic acid, d-hydroxy-n-butyric acid, cl-hydroxyisovaleric acid, ricinoleic acid, etc.

The compounds of the invention may be pre pared in a variety of ways. However, a, preferred method of preparation generally comprises reacting dihydroisophorol with a. suitable halogen substituted acylating agent, and the ester so produced reacted with a suitable metal thiocyanate to obtain the desired thlocyano ester of dihydro isophorol of the present invention.

Poth steps and especially the second, may be carried out in the presence of an inert solvent, such as methanol, ethanol, isopropanol, butancl, isobutanol, acetone, ethyl acetate, benzene, toluene, xylene, hexanes, octanes, isopropyl ether, hydrocarbon fractions, such as gasoline, etc. Each step may be carried out at any temperature within the range between-0 C. and about 250 C., and preferably in the range between about 50 C. and about C. It may be desirable to carry out the reactions of each step in the absence of oxygen, such as under a blanket of C02. The products of each stage are preferably vacuum distilled, although if only a crude prodnot is desired, no distillation is needed.-

As suitable halogen substituted acylating agents which may be used, there may be mentioned: the halogen substituted aliphatic carboxylic acids, such as monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, alphachloropropionic acid, beta-chloropropionic acid, dichloropropionic acid, dichlorobutyric acid, chloroisovaleric acid, chlorolauric acid, chloromyristie acid, chlorostearic acid, chloroleic acid, chlororicinoleic acid, chloromalonic acid, etc., or the corresponding bromine, iodine, and fluorine substituted acids. Mixtures may be utilized if desired and also the anhydrides of halogen substituted carboxylic acids, or the acyl halides of these halogen substituted carboxylic acids may be used.

Suitable metal thiocyanates include, for example, sodium thiocyanate, potassium thiocyanate, lithium thiocyanate, ammonium thiocyanate, calcium thiocyanatc, etc.

As examples of preferred methods of forming the desired compounds of the present invention the following may be given:

In a 250 ml. flask equipped with a reflux condenser-was placed 142 g. (1.0 mol) of dihyd isophorol and while maintaining the temperature of the reaction mixture at 80 C., 124 g. (1.1 mols) of chloroacetyl chloride was added dropwise. Afterreaction had ceased, the mixture was cooled, nd washed with water and 5% aqueous sodium carbonate and then distilled. Dihydroisophoryl chloroac'etate, having a boiling point of log-110 C. at 5 mm. pressure and by anaylsis 16.25% chlorine content (16.25% theoretical chlorine content) was obtained. Into a one liter flask was placed 164 g. (0.75 mol) of the resultant dihydroisophoryl chloroacetate, 76 g. (1.0 mol) of ammonium thiocyanate, and 400 cc. of ethanol (95%). .The mixture was refluxed for about one hour and then the ammonium chloride formed was filtered off. The ethanol was removed by distillation and the remaining material was distilled through a Claisenflask at reduced pressure to obtain dihydroisophoryl thiocyanoacetat-e havin a boiling point mainly 134-138" C. at ca. 3 mm. pressure, which material gave on analysis a sulphur content of 13.27% (13.1% sulphur-theoretical for Ci2Hi902SN) In anothercase the dihydroisophorol was first separated into its cis and trans forms. One isomer had a boiling point of 108.1-108.4 C. at 50' mm. pressure, and the other isomer had a boiling point of 117.2-118.0 C. at 50 mm. pressure. Since the evidence is not conclusive which is the cis or trans forms, these forms will be referred to as the low boiling and the high boiling types. The thiccyanoacetates of both of these isomers Were prepared as in the above example. The isomer of dihydroisophoryl thiocyanoacetate prepared from low boiling dihydroisophorol had a boiling point of 134.0- 142.0 C. at 3 mm. pressure and a sulphur content by analysis of 13.6% (13.27% sulphurtheoretical), and the dihydroisophoryl thiocyanoacetate isomer prepared from the high boiling-form of dihydroisophorol had a boiling point of 130.0-l31.0 C. at 3 mm. pressure and a sulphur content by analysis of 13.6%.

In a like manner dihyd roisophoryl thiocyanoacetate was prepared from a mixture of the cis and trans forms of dihydroisophorol by reacting the latter with chloroacetic acid in the presence of toluene as an entraining agent for water and then reacting the resulting product with ammonium thiocyanate. This product had a boiling point of 137.5 C. at 3.0 mm. pressure and a sulphur content by analysis of 13.5%.

' cyano propionate was prepared by ester-flying dihydroisophorol with e-chloropropionic acid and reacting the product thus obtained with ammonium thiocyanate. The dihydroisophoryl thiocyano propionate thus obtained had a boiling point of 149-151" C. at 4.7 mm. and a sulphur content by analysis of 12.6% (l2.55%-theo retical).

In addition to the above preferred method of preparation, the thiocyano esters of dihydroisophorol may be formed by the reaction of metal thiocyanates with the sulfated esters of dihydroisophorol. Likewise, any other suitable method may be used.

The thiocyano esters of dihydroisophorol according to this invention and particularly the lower esters, such as the acetate and propionate, are useful in insecticidal compositions. The compounds, either alone or in combination with other active or inactive substances, may be applied to plants, animals, fabrics and the like, by spraying, dusting, pouring, dipping, etc., in the form of concentrated liquids, solutions, aqueous emulsions, suspensions, dusting powders, and the like, containing such concentration of the active principle asis most suited for the particular purpose at hand. They may be applied, for example, in the form of dilute solutions, in a. suitable solvent or mixture of solvents, containing, for instance, water, acetone, petroleum distillate, lignite tar oils, hydrogenated hydrocarbons, parafiin oils, naphthenes, chlorinated hydrocarbons, chlorinated others, fenchyl and bornyl alcohols, monoand poly-hydric alcohols, glycol others, or the like or mixtures thereof.

The present compounds may b advantageously used in combination with other insecticides or fungicides such as pyrethrum, derris resins, rotenone, nicotine, lime-sulphur, Bordeaux mixture, copper sulfate, copper carbonates, sulphur. mercury compounds, sodium, calcium and lead arsenates, iron sulfate, phenol, paradichlorobem zene, unsaturated chlorides, alkene sulfides, thiuram sulfides, thiocyanates, isothiocyanates, unsaturated cyclic ketols, such as diisophorone and its homologues, obtained by condensation of lower ketones, such as acetone, methyl ethyl ketone. etc., according to U. S. Patent 2,307,482, and the like.

As will be readily apparent, the most desirable thiocyano ester of dihydroisophorol and solvent. or solvent mixture, or combination with other active and inactive ingredients, will depend considerably upon the particular use for which the material is intended.

For use in household insecticides, the dihydrolsophoryl thiocyano esters are preferably dissolved in a light hydrocarbon oil, such as highly refined, odorless kerosene or kerosene distillate with or without the addition of other insecticides and sprays. Ordinarily from about 1% to 25% and preferably from 2 to 6% of the present toxicants are used in such sprays. Particularly effective for this purpose is the combination of dihydroisophoryl thiocyano lower esters, such. as the acetate, with the unsaturated cyclic ketols of the above-mentioned U. S. Patent 2,307,482. Especially effective is the combination of about 2%-4% dihydroisophoryl thiocyanoacetate and 2%-4% diisophorone. When more than 2% of dihydroisophoryl thiocyanoacetate is used with diisophorone, a decided synergistic effect of increased insecticidal toxicity is obtained.

When solutions of the dihydroisophoryl thiocyano esters in odorless base are placed on filter paper and exposed to air, the liquid evaporates leaving substantially no stain behind, which feature is of particular advantage in household insecticides. I

For use on plants, the dihydroisophoryl thiocyano esters may be dissolved in plant spray oils and emulsified in water to produce sprayable emulsions. The common emulsifying agents such as glyceryl mono-oleate, amine salts, sulfated and sulfonated fatty and mineral oils, soaps and the like may be used in combination with such sprays. In the same manner, the dihydroisophoryl thiocyano esters themselves, without the addition of oil, may be emulsified and used as plant spray insecticides. The present compounds may also be absorbed by finely divided solid materials, such as wood flour, talc, clay, bentonite, sulphur and carbon black and used as dusting insecticides.

The dihydroisophoryl thiocyano esters are more pronounced insecticidal toxicants than th seemingly closely related cyclohexyl thiocyano esters. This greater toxic action of the present agents makes them particularly suited for use in household insecticidal compositions,

Modified Feet-Grady test were made with the dihydroisophoryl thiocyano esters of the present invention. The general test is fully described in the 1940 Blue Book published by the publisher of Soap and Sanitary Chemicals" periodical on pages 193 to 197, as the large group method. Briefly the test as practiced consists of releasmg 100 to v15G flies in an air-conditioned cage 6 x 6 x 6 feet and spraying them with 6 ml. of insecticide. After 10 minutes exposure the number of flies which are incapacitated or knocked down is noted and all flies transferred to a cage and allowed to recuperate in fresh air fo 24 hours. when the dead flies are counted. For the purpose of this study the omcial Feet-Grady procedure was not followed in calculating the results, but only the percentages knocked down at 10 minutes and killed at 24 and 48 hours were recorded. The results obtained by testing in the above manner dihydroisophoryl thiocyanoacetate and cyclohexyl thiocyanoacetate in highly refined, odorless kerosene are given in the following table:

I claim as my invention:

1. An insecticidal composition comprising a carrier and dihydroisophoryl thiocyanoacetate.

2. An insecticidal composition comprising a carrier and a dihydroisophoryl thiocyano ester of an aliphatic acid having from 2 to 20 carbon atoms in the acid portion.

3. A household insecticidal composition comprising a carrier and a dihydroisophoryl thiocyano ester oi a lower aliphatic acid. I

4. An insecticidal composition comprising a mineral oil and a dihydroisophoryl thiocyano ester of an aliphatic acid having from 2 to 20 carbon atoms in the acid portion.

5. A household insecticidal composition comprising odorless kerosene and dihydroisophoryl thiocyano ester of a lower aliphatic acid.

6. An insecticidal composition comprising a mineral oil and a dihydroisophoryl thiocyano ester of a lower aliphatic acid.