Benzodioxane Herbicides

The most closely related ether to applicant's novel compounds of which applicant is aware are those disclosed in U.S. Pat. No. 3,119,682 which discloses 3-[p-(p-chlorophenoxy)phenyl]-1,1-dimethylurea. It would be readily apparent that the compound of the above cited U.S. patent is only remotely related to applicants' novel compounds due to the lack of the presence of the dioxane radical.

This invention relates to novel benzodioxanes having the formula ##STR3## in which R is selected from the group consisting of alkoxy having from 1 to 6 carbon atoms, preferably having from 1 to 3 carbon atoms and more preferably --OCH.sub.3, cycloalkyl having from 3 to 6 carbon atoms, preferably cyclopropyl, alkyl having from 1 to 6 carbon atoms, preferably having from 2 to 4 carbon atoms and more preferably ethyl, thioalkyl having from 1 to 6 carbon atoms, preferably having from 1 to 3 carbon atoms and more preferably thiomethyl, chloroalkyl having from 1 to 6 carbon atoms, preferably having from 2 to 4 carbon atoms and more preferably chloroethyl, alkynyl having from 2 to 6 carbon atoms, preferably having from 2 to 4 carbon atoms and more preferably vinyl ##STR4## wherein R.sub.2 is alkyl having from 1 to 6 carbon atoms, preferably from 1 to 3 carbon atoms and more preferably methyl, or alkoxy having from 1 to 6 carbon atoms, preferably from 1 to 3 carbon atoms and more preferably methoxy and R.sub.3 is hydrogen or alkyl having from 1 to 6 carbon atoms, preferably from 1 to 3 carbon atoms and more preferably is methyl. The compounds are useful as herbicides when used in a herbicidally effective amount.

The term "herbicides" as used herein means a compound which control or modifies growth of plants. By the term "herbicidally effective amount" is meant an amount of compound which causes a modifying effect upon the growth of plants. By "plants" is meant germinant seeds, emerging seedlings and established vegetation, including roots and above-ground portions. Such modifying effects include all deviations from natural development; for example, killing, retardation, defoliation, desiccation, regulation, stunting, tillering, stimulation, leaf burn, dwarfing and the like.

The compounds of the present invention, as will be seen from the data which follows, have utility as post-emergence herbicides, against a wide range of plant species.

Novel intermediate compounds having the formulas ##STR5## which are useful in preparing the novel herbicidal compounds of the present invention are prepared in the following general manner:

The condensation of 3,4-dichloronitrobenzene is conducted in a polar solvent (non-reacting solvent) such as dimethylsulfoxide or water with the sodium or potassium salt of the hydroxymethyl 1,4-benzodioxane. The salt can be prepared from the alcohol and NaH or potassium t-butoxide or under certain conditions with NaOH or KOH.

The reduction of the nitro group of the above compound is effected by several means such as catalytically with H.sub.2 and a nobel metal catalyst or with iron in ethanol-water (50:50 by weight) using hydrochloric acid.

The novel compounds of the present invention which are defined by the formula ##STR6## in which R is selected from the group consisting of alkoxy having from 1 to 6 carbon atoms, preferably having from 1 to 3 carbon atoms and more preferably --OCH.sub.3, cycloalkyl having from 3 to 6 carbon atoms, preferably cyclopropyl, alkyl having from 1 to 6 carbon atoms, preferably having from 2 to 4 carbon atoms and more preferably ethyl, thioalkyl having from 1 to 6 carbon atoms, preferably having from 1 to 3 carbon atoms and more preferably thiomethyl, chloroalkyl having from 1 to 6 carbon atoms, preferably having from 2 to 4 carbon atoms and more preferably chloroethyl, alkynyl having from 2 to 6 carbon atoms, preferably having from 2 to 4 carbon atoms and more preferably vinyl ##STR7## wherein R.sub.2 is alkyl having from 1 to 6 carbon atoms, preferably from 1 to 3 carbon atoms and more preferably methyl, or alkoxy having from 1 to 6 carbon atoms, preferably from 1 to 3 carbon atoms and more preferably methoxy and R.sub.3 is hydrogen or alkyl having from 1 to 6 carbon atoms, preferably from 1 to 3 carbon atoms and more preferably is methyl exhibit herbicidal activity and are prepared (from the intermediate 2-benzpyranylmethyl-2-chloro-4-aminophenyl ether) by reacting an appropriately substituted acid chloride with the aniline type intermediate compound 2-benzpyranylmethyl-2-chloro-4-aminophenyl ether in an inert solvent such as acetone, ether, methylene chloride, chloroform, toluene or benzene. The reaction is preferably conducted at a temperature of from about -50.degree. C. to about 100.degree. C. Acid binding agents such as pyridine triethylamine, sodium hydroxide and dimethyl aniline may be employed.

Although the above reactions will proceed at any temperature, side reactions become more prominent at higher temperatures raising the level of impurities in the final product. For this reason, it is preferred to run the reaction at from about -40.degree. C. to about 0.degree. C., and most preferably at about -30.degree. C.

The examples shown herein are illustrative of the method of preparation of both intermediates and compounds of the invention.

Specific compound preparation and herbicidal activity of the compounds of this invention are shown in the following examples.

To a mixture of 25 grams (g.) (0.15 mole) 2-hydroxymethyl-1,4-benzodioxane in 200 milliliters (ml.) dimethyl sulfoxide was added 4.6 g. (0.196 mole) sodium hydride. Then 29 g. (0.15 mole) 3,4-dichloronitrobenzene was added. The reaction was exothermic to 60.degree. C. After the exotherm ceased, the mixture was heated to 70.degree. C. for 5 minutes and then cooled to 0.degree. C. Fifty g. of ice and 400 ml. methylene chloride were then added. The reaction mixture was then washed with ice water (200 ml.), 10 ml. 10% NaOH, 200 ml. 1 N hydrochloric acid and 100 ml. saturated sodium carbonate solution. The washed solution was dried over magnesium sulfate and evaporated in vacuo to give 44.1 g. of product having a melting point of 113.degree.-114.degree. C. The product was identified as the title product by infrared (IR) and nuclear magnetic resonance (NMR) spectra analyses.

Under an argon atmosphere, 22.3 g. electrolyte iron, 64 ml. ethanol and 53.4 ml. water were mixed together. To the resultant stirred mixture was added in one portion 1.88 ml. concentrated hydrochloric acid and the resulting mixture heated to reflux. 4.1 g. of the nitro ether prepared in Example I was added to this hot stirred mixture. The addition was made in portions of near reflux temperatures. The mixture was then refluxed for 30 minutes and 1.26 ml. of 50% sodium hydroxide solution was added. This mixture was filtered while hot through dicalite. The filtrate was concentrated in vacuo and then taken up in 200 ml. of methylene chloride, washed with two 500 ml. portions of water and four 100 ml. portions of saturated sodium carbonate solution. The washed mixture was dried over magnesium sulfate and evaporated in vacuo to yield 34 g. of product having a m.p. of 90.degree.-91.degree. C. The product was identified as the title product by IR and NMR analyses.

Five g. (0.017 mole) of the intermediate product of Example II, 1.65 ml. (0.020 mole) pyridine and 50 ml. acetone were added to a 300 ml. stirred round bottom flask and cooled to a -30.degree. C. in a dry ice acetone bath. 1.45 ml. (0.019 mole) of methyl chloroformate was added with stirring and solution was allowed to reach ambient temperature. About 50 ml. of chloroform was added to the mixture which was then washed sequentially with approximately 100 ml. of water and 100 ml. of sodium bicarbonate. The organic layer was dried over MgSO.sub.4, filtered and rotary evaporated to obtain an oil. The oil was triturated with pentane to crystallize product, yielding 5.3 g. of product having a melting point of from 100.degree. to 104.degree. C. The structure was confirmed by IR and NMR analyses as the title compound. The compound of this example will be referred to as Compound 1.

The equipment and procedure as in Example III above were followed with the exceptions that the round bottom flask was originally cooled to -40.degree. C. and that 1.70 ml. (0.019 mole) of cyclopropane carboxylic acid chloride was added to the cooled round bottom flask instead of methylchloroformate. The crystals were formed in the mixture which were filtered off in vacuum and the filter was washed sequentially with water and sodium bicarbonate solution. The organic layer was dried over MgSO.sub.4 and rotary evaporated to obtain crystals which were added to those previously obtained. 5.3 g. of a product having a m.p. of from 144.degree. to 148.degree. C. were produced for a yield of 86.5%. The structure was confirmed by analyses of IR and NMR of the title compound. The compound of this example will be referred to as Compound 2.

The equipment and procedure were the same as Example III with the exceptions that 3.0 g. (0.010 mole) of the intermediate of Example II, 1.67 ml. (0.012 mole) of triethylamine and 50 ml. of dichloromethane were added to the round bottom flask which was then cooled to -40.degree. C. 0.96 ml. (0.011 mole) of propionyl chloride were then added. The reaction mixture was worked up as in Example III and the filtrate was readily evaporated to remove solvent and obtain 3.4 g. of crystalline product having a m.p. of 111.degree.-113.degree. C. in a yield of 97.8%. The structure was confirmed by analyses of IR and NMR as the title compound. The compound of this example will be referred to as Compound 3.

The procedure and reagents were the same as in Example III with the exception that 1.62 ml. (0.019 mole) of methylchlorothioformate was added to the cooled flask instead of the methylchloroformate. The round bottom flask was originally cooled to -35.degree. C. The product was worked up in the same manner with the exception that triturate with pentane was not required. 6.4 g. of crystalline product having a m.p. of 112.degree.-116.degree. C. and at a yield of 102.9% was obtained. The structure was confirmed by analyses of IR and NMR as the title compound. The compound of this example will be referred to as Compound 4.

Ten g. (0.035 mole) of the intermediate prepared in Example II and 100 ml. of toluene were combined in a 250 ml. round bottom 4-neck flask and heated to 70.degree. C. with stirring. The stirred solution was saturated with hydrogen chloride gas to give a thick slurry. Phosgene was then added until excess refluxing occurred and the mixture became much more fluid. The mixture was filtered and the filtrate evaporated in vacuo to form an oil that crystallized to give 10 g. of the crystalline isocyanate intermediate having a m.p. of 79.degree.-80.degree. C. The structure was confirmed by analysis of the mass spectra.

Five g. (0.0157 mole) of the above isocyanate intermediate was dissolved in 100 ml. of dry toluene. Into this stirred solution excess dimethylamine was bubbled. The reaction was exothermic to 40.degree. C. The reaction was allowed to cool to room temperature and evaporated in vacuo to yield 4.6 g. of a product having a m.p. of 130.degree.-132.degree. C. The structure was confirmed by analysis of the NMR as the title compound. The compound of this example will be referred to as Compound 7.

Five g. (0.0157 mole) of the isocyanate intermediate prepared in Example VII was dissolved in 50 ml. of methylene chloride. A mixture of 1.69 g. (0.0173 mole) of O,N-dimethylhydroxylamine hydrochloride and 2.41 ml. (0.0173 mole) of triethylamine in 50 ml. of methylene chloride was added to this solution. The resulting mixture was allowed to stand overnight and was then washed with 100 ml. of water, 50 ml. of 1 N hydrochloric acid and 100 ml. of saturated sodium bicarbonate solution. The mixture was then dried over magnesium sulfate and evaporated in vacuo to yield 4.3 g. of an oil that crystallized on standing. The crystalline product had a m.p. of 91.degree.-92.degree. C. The structure was confirmed by analysis of the NMR. The compound of this example will be referred to as Compound 8.

As previously mentioned, the novel benzodioxanes herein described are phytotoxic compounds which are useful and valuable in controlling various plant species. Compounds of this invention are tested as herbicides in the following manner.

On the day preceding treatment, seeds of six plant species, including hairy crabgrass [Digitaria sanguinalis (L.) Scop] (CG), watergrass [Echinochloa crusgalli (L.) Beauv.] (WG), red oat [Avena sativa (L.)] (RO), mustard [Brassica juncea (L.) Coss.] (MD), curly dock [Rumex crispus (L.)] (CD) and Pinto beans [Phaseolus vulgaris (L).] (Bean) are planted in individual rows using one species per row across the width of the flat. The flats are placed in the greenhouse at 70.degree. to 85.degree. F. and watered daily with a sprinkler. About 10 to 14 days after planting when the primary leaves of the bean plants are almost fully expanded and the first trifoliate leaves are just starting to form, the plants are sprayed. The spray is prepared by weighing out 20 ml. of the test compound, dissolving it in 5 ml. of acetone containing 1% Tween 20.RTM. (an emulsifying agent defined as a polyoxyethylene sorbitan monolaurate) and then adding 5 ml. of water. The solution is sprayed on the foliage using a No. 152 DeVilbiss atomizer at an air pressure of 5 lb/sq. inch. The spray concentration is 0.2 and the rate is 8 lb/acre. The spray volume is 476 gallons/acre. Injury ratings are recorded 14 days after treatment. The injury rating from 1 to 100% is recorded for each species as percent control with 0% representing no injury and 100% representing complete injury.

The results of these tests are shown in Table II.

The compounds of the present invention are useful as herbicides in controlling the growth of undesirable vegetation by post-emergence application to the locus where control is desired. The compounds are generally embodied in formulations suitable for convenient application. In general, such formulations will contain inert or occasionally active ingredients or diluent carriers in addition to the active compound. Examples of such ingredients or carriers are water, organic solvents, dust carriers, granular carriers, surface active agents, oil and water, water in oil emulsions, wetting agents, dispersing agents and emulsifying agents. The herbicidal formulations generally take the form of dusts, wettable powders, granules, solutions or emulsifiable concentrates.

Dusts are free-flowing powder compositions containing the herbicidal compound impregnated on a particulate carrier. The particle size of the carriers is usually in the range of from about 30 to 50 microns. Examples of suitable carriers are talc, bentonite, diatomaceous earth and pyrophyllite. Anticaking and antistatic agents can be added, if desired. The composition generally contains up to 50% of active ingredient.

Wettable powders are finely divided compositions comprising a particulate carrier impregnated with the herbicidal compound and additionally contain one or more surface active agents. The surface active agent promotes rapid dispersion of the powder in aqueous medium to form stable, sprayable suspensions. A wide variety of surface active agents can be used, for example, long chain fatty alcohols and alkali metal salts of the sulfated fatty alcohols; salts of sulfonic acid; esters of long chain fatty acids; and polyhydric alcohols, in which the alcohol groups are free, omega-substituted polyethylene glycols of relatively long chain length. A list of surface active agents suitable for use in agriculture formulations can be found in Pesticide Formulations by Wade Van Valkenburg, Marcel Dekker, Inc., N.Y. 1973 at pages 79-84.

Granules comprise the herbicidal compound impregnated on a particulate inert carrier having a particle size of about 1 to 2 millimeters (mm.) in diameter. The granules can be made by spraying a solution of the active ingredient in a volatile solvent onto the granular carrier. Suitable carriers in preparation of granules include clay, vermiculite, sawdust, granular carbon, and the like.

The herbicidal compounds can also be applied to the soil in the form of a solution in a suitable solvent. Solvents frequently used in herbicidal formulations include kerosene, fuel oil, xylene, petroleum fractions with boiling ranges above xylene, and aromatic petroleum fractions rich in methylated naphthalenes.

Emulsifiable concentrates consist of an oil solution of the herbicide along with an emulsifying agent. Prior to use the concentrate is diluted with water to form a suspended emulsion of oil droplets. The emulsifiers used are usually a mixture of anionic and nonionic surfactants. Other additives such as spreading agents and stickers can be included in the emulsifiable concentrate.

The formulations described above, employing phytotoxic or herbicidally effective amounts of the compounds described herein, are applied to the loci where control is desired in any conventional manner. The loci referred to above include soil, seeds, seedlings and the actual plants. Dusts and liquid compositions can be applied by the use of power dusters, boom and hand sprayers and spray dusters. The compositions can also be applied from airplanes as dusts or sprays because they are effective in very low dosages.

The phytotoxic compositions of this invention can also contain other additaments, for example, fertilizers, pesticides, and the like, used as adjuvants or in combination with any of the above-described adjuvants. Other phytotoxic compounds useful in combination with the above-described compounds include, for example, 2,4-dichlorophenoxyacetic acids, 2,4,5-trichlorophenoxyacetic acid, 2-methyl-4-chlorophenoxyacetic acid, and the salts, esters and amides thereof; triazine derivatives, such as 2,4-bis(3-methoxypropylamino)-6-methyl-thio-s-triazine, 2-chloro-4-ethylamino-6-isopropylamino-3-triazine, and 2-ethylamino-4-isopropylamino-6-methylmercapto-s-triazine; urea derivatives such as 3-(3,4-di-chlorophenyl)-1,1-dimethyl urea; and acetamides such as N,N-diallyl-.alpha.-chloroacetamide, N-(.alpha.-chloroacetyl)hexamethyleneamine, and N,N-diethyl-.alpha.-bromoacetamide, and the like; benzoic acids such as 3-amino-2,5-dichlorobenzoic; S-ethyldipropylthiocarbamate; S-ethyl hexahydro-1H-azepine-1-carbothioate and the like. Fertilizers useful in combination with the active ingredients include, for example, ammonium nitrate, urea and superphosphate. Other useful addditaments include materials in which plant organisms take root and grow, such as compost, manure, humus, sand and the like.

The amount of a compound of the present invention which constitutes a phytotoxic or herbicidally effective amount depends upon the nature of the seeds or plants to be controlled. The rate of application of active ingredient varies from about 0.1 to about 50 pounds per acre, with the actual amount used depending on the overall cost and the desired results. It will be readily apparent to one skilled in the art that compounds exhibiting lower herbicidal activity will require a higher dosage rate for the same degree of control than more active compounds.