1,4-Benzodioxan Derivatives and Pesticidal Use Thereof

The present invention provides 2-phenoxymethylene-1,4-benzodioxan derivatives, a process for their manufacture and a method of using them in pest control.

The 2-phenoxymethylene-1,4-benzodioxan derivatives have the formula ##STR2## wherein R.sub.1 represents alkyl of 1 to 3 carbon atoms or chlorine, R.sub.2 represents hydrogen, alkyl of 1 to 3 carbon atoms and Y represents --O--, --CH.sub.2 --, --S-- or >C=O.

Preferred compounds on account of their action are those of the formula (I) wherein R.sub.1 represents hydrogen, methyl or chlorine, R.sub.2 represents hydrogen and Y represents --O--, --CH.sub.2 -- or --S--.

The most preferred compounds are those of the formula (I) wherein R.sub.1 and R.sub.2 represents hydrogen and Y represents --O--, --CH.sub.2 -- or --S--.

The compounds according to the invention are manufactured by methods which are known per se, for example in the following manner: ##STR3## R.sub.1, R.sub.2 and Y in the formulae II to V have the meanings previously assigned to them for formula (I), X represents a halogen atom, especially chlorine, bromine or iodine, and M represents a metal of the 1st. or 2nd. main group of the Periodic Table, in particular sodium or potassium.

Suitable dehydrating agents are, for example, N,N-substituted carbodiimides, in particular N,N-dicyclohexyl-carbodiimide, and a suitable catalyst is e.g. copper (I) chloride. Processes 1 and 2 are carried out at a reaction temperature between +10.degree. and 150.degree. C, preferably at +50.degree. to 130.degree. C, at normal pressure and, if appropriate, in the presence of inert solvents or diluents.

Examples of suitable solvents or diluents for method 1) are ethers, e.g. 1,2-dimethoxyethane, dioxan, tetrahydrofuran; N,N-dialkylated carboxy amides, e.g. dimethyl formamide; ketones, e.g. acetone, methyl ethyl ketone or cyclohexanone; also hexamethylphosphoric triamide, dimethyl sulphoxide. The starting materials of the formulae II to V are known compounds or compounds which can be manufactured in analogous manner to known methods which are described in the literature.

Compounds of the formula I are suitable for combating a variety of animal and plant pests. They are therefore suitable for combating acarides, but are used especially for combating insects of the following families: acrididae, blattidae, gryllidae, gryllotalpidae, tettigoniidae, cimicidae, pyrrhocoridae, reduviidae, aphidae, delphacidae, dispididae, pseudococcidae chrysomelidae, coccinellidae, bruchidae, scarabaeidae, dermestidae, tenebrionidae, bostrichidae, cucujidae, curculionidae, tineidae, noctuidae, lymantridae, pyralidae, galleridae, culicidae, tipulidae, stomoxydae, muscidae, calliphoridae, trypetidae and pulicidae.

The insecticidal or acaricidal action can be substantially broadened and adapted to given circumstances by addition of other insecticides and/or acaricides. Examples of suitable additives are: organic phosphorus compounds, nitrophenols and derivatives, ureas, carbamates, chlorinated hydrocarbons, or pyethroids.

The compounds of the formula I may be used as pure active substance or together with suitable carriers and/or additives. Suitable carriers and additives can be solid or liquid and correspond to the substances conventionally used in formulation technology, for example natural or regenerated substances, solvents, dispersants, wetting agents, stickers, thickeners, binders and/or fertilisers.

For application, the compounds of the formula I may be processed to dusts, emulsion concentrates, granules, dispersions, sprays, to solutions, or suspensions, in the conventional formulation which is commonly employed in application technology.

The compositions according to the invention are manufactured in known manner by intimately mixing and/or grinding active substances of the formula I with the suitable carriers, optionally with the addition of dispersants or solvents which are inert to the active substances.

The active substances may take, and be used in, the following forms: Solid forms:

Dusts, tracking agents, granules, coated granules, impregnated granules and homogeneous granules. Liquid forms:

a. active substances which are dispersible in water: wettable powders, pastes, emulsions;

b. solutions.

The content of active substance in the above described compositions is between 0.1 to 95%.

The active substances of the formula I can, for example, be formulated as follows:

The following substances are used to manufacture a) a 5% and b) a 2% dust:

The active substances are mixed with the carriers and ground.

The following substances are used to produce 5% granules:

The active substance is mixed with epichlorohydrin and dissolved with 6 parts of acetone; the polyethylene glycol and cetyl polyglycol ether are then added. The resultant solution is sprayed on kaolin, and the acetone is subsequently evaporated in vacuo.

The following constituents are used for the preparation of a) a 40%, b) and c) a 25%, and d) a 10% wettable powder:

The active substances are intimately mixed, in suitable mixers, with the additives, the mixture being then ground in the appropriate mills and rollers. Wettable powders are obtained which can be diluted with water to give suspensions of any desired concentration.

The following substances are used to produce a) a 10%, b) a 25% and c) a 50% emulsifiable concentrate:

From these concentrates it is possible to produce by dilution with water, emulsions of any desired concentration.

The following constituents are used to prepared a) a 5% and b) a 95% spray:

A mixture of 18.6 g of 4-phenoxyphenol, 20.7 g of 2-hydroxymethyl-1,4-benzodioxan, 22.9 g of N,N'-dicyclohexylcarbodiimide and 0.03 g of copper (I) chloride is heated for 48 hours to 105.degree.-110.degree. C in the process of which a melt forms. The reaction mixture is then cooled to room temperature and treated with 300 ml of diethyl ether. The copper (I) chloride and precipitated N,N'-dicyclohexyl urea are filtered off and the filtrate is washed repeatedly with 10% potassium hydroxide solution and then with water and saturated saline solution. The ethereal solution is dried over sodium sulphate and the ether distilled off. The residue is further purified by chromatography on silica gel (eluant: diethyl ether/hexane 1:4) to yield pure 2-(4-phenoxy)-phenoxymethylene-1,4-benzodioxan of melting point 73.degree.-74.degree. C (compound 1).

The following compounds can also be manufactured in analogous manner:

A. contact action on dysdercus fasciatus larvae

A given amount of a 0.1% solution of active substance in acetone (corresponding to 10 mg of active substance/m.sup.2) was pipetted into an aluminium dish and evenly distributed. After the acetone had evaporated, 10 dysdercus fasciatus larvae in the 5th. stage were put into the treated dish which contained feed and moist cotton wool. The dish was then covered with a screen top. After about 10 days, i.e. as soon as the controls had fully shed and emerged to the adult stage, the test subjects were examined for the number of adults.

Compounds according to Example 1 acted well in this test.

B. contact action on aedes aegypti larvae

Approximately 20 two-day old larvae of the yellow fever fly (aedes aegypti) are put into a beaker containing a solution of the active substance (concentration 5 ppm). After the controls had shed and emerged to the adult stage, the test subjects were examined and the percentage of normal adults in comparison to the controls was determined.

Compounds according to Example 1 acted well in this test.

C. contact action on Tenebrio molitor pupae

A given amount of a 0.1% solution of active substance in acetone (corresponding to 10 mg of active substance/m.sup.2) was pipetted into an aluminium dish and evenly distributed. After the acetone had evaporated, 10 freshly shed pupae were laid on the treated surface. The dish was covered with a screen top. After the controls had emerged from the cocoon as imagines, the test subjects were examined for the number of normal adults.

Compounds according to Example 1 acted well in this test.

50 g of wheat flour were mixed in two beakers with a given amount of active substance formulated as a 5% dust to give a concentration of 0.05%. Then 10 Ephestia kuhniella larvae were added per beaker (25 g of flour). The development of the population was recorded over the course of 8 weeks and the number of moths determined.

Compounds according to Example 1 acted well in this test against Ephestia kuhniella.

Wheat was treated with the active substance (10 ppm) and populated with 25 adult beetles at a time. After an exposure time of 3 months, the number of test subjects compared with the untreated controls was determined.

The compounds according to Example I acted very well against Trogoderma granarium, Sitophilus granarius, Rhyzoptera dominica, Tribolium castaneum and Oryzaephilus surinamensis.