2,6-Dialkyl-N-Dialkylphosphonomethyl Chloroacetanilides as Herbicides

This invention relates to certain novel 2,6-dialkyl-N-dialkylphosphonomethyl chloroacetanilides which are useful as herbicides.

The compounds of this invention have the following structural formula ##STR2## WHEREIN R and R.sup.1 are both methyl or both ethyl, preferably both methyl; R.sup.2 is alkyl having 1 to 4 carbon atoms, preferably methyl and ethyl; and R.sup.3 is alkyl having 1 to 4 carbon atoms, preferably methyl and ethyl.

In the above description of the compounds of this invention, alkyl includes both straight chain and branched chain configurations, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl or tert. butyl.

The compounds of this invention are active herbicides of a general type. That is, they are herbicidally effective against a wide range of plant species. The method of controlling undesired vegetation of the present invention comprises applying a herbicidally effective amount of the above-described compounds to the area where control is desired.

A herbicide is used herein to mean a compound which controls or modifies the growth of plants. By a "growth controlling amount" is meant an amount of compound which causes a modifying effect upon the growth of plants. Such modifying effects include all deviations from natural development, for example, killing, retardation, defoliation, desiccation, regulation, stunting, tillering, stimulation, dwarfing and the like. By "plants" it is meant germinating seeds, emerging seedlings, and established vegetation including the roots and above-ground portions.

The compounds of the present invention are prepared by the following general method.

Generally, a mole amount of the 2,6-dialkylphenylazomethine reactant is combined with about mole excess of dimethylphosphite or diethylphosphite at about 80.degree. C. for 30 minutes. Thereafter, the mixture is cooled and the excess dimethylphosphite or diethylphosphite is removed by vacuum stripping yielding the desired product at high yields.

Generally, a mole amount of the aniline reaction product of Reaction No. 1, a mole amount of chloroacetyl chloride and a mole amount of an acid acceptor such as pyridine is dissolved in a solvent such as methylene chloride in a reaction vessel fitted with a reflux condenser. The reaction mixture is heated to reflux with stirring for 30 minutes.

The reaction mixture is then cooled to room temperature and washed with dilute hydrochloric acid and water. The final organic solution is dried over magnesium sulfate and the volatiles removed to yield the desired reaction product.

Preparation of the compounds of this invention is illustrated by the following examples.

This example teaches a method of preparation for the aniline reactant.

7.8 grams (g.) 2,6-diethylphenylazomethine (0.05 mole) is combined with diethylphosphite (13.8 g., 0.1 mole) in an open vessel and gently heated to 80.degree. C. for 30 minutes. The reaction mixture is allowed to cool and the excess phosphite is stripped off under reduced pressure to yield 11.8 g. of the desired product, clear liquid, n.sub.D.sup.30 1.5096.

This example teaches the preparation of a representative compound of this invention.

A solution of 2,6-diethyl-N-dimethylphosphonomethyl aniline (6.5 g., 0.024 mole) and chloroacetyl chloride (2.7 g., 0.025 mole) in 100 milliliter methylene chloride is added to a reaction flask equipped with a reflux condenser. Next, pyridine (2.0 g., 0.025 mole) is added at 10.degree. C. The mixture is refluxed at 40.degree. C. for 30 minutes and allowed to cool. The solution is washed with dilute HCl solution, water and then dried over anhydrous magnesium sulfate. The solution is roto-evaporated under reduced pressure to yield 8.2 g. of the desired product, clear liquid, n.sub.D.sup.30 1.5340.

The following is a table of certain selected compounds that are preparable according to the procedure described hereto. Compound numbers are assigned to each compound and are used through the remainder of the application.

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

Pre-emergence herbicide test

On the day preceding treatment, seeds of seven different weed species are planted in individual rows using one species per row across the width of the flat. The seeds used are hairy crabgrass (Digitaris sanguinalis), yellow foxtail (Setaria glauca), watergrass (Echinochloa crusgalli), California red oat (Avena sativa), redroot pigweed (Amaranthus retroflexus), Indian mustard (Brassica juncea) and curly dock (Rumex crispus). Ample seeds are planted to give about 20 to 50 seedlings per row, after emergence, depending upon the size of the plants. The flats are watered after planting. Using an analytical balance, 20 ml. of the compound to be tested was weighed out on a piece of glassine weighing paper. The paper and compound were placed in a 30 ml. wide-mouth bottle and 3 ml. of acetone containing 1% polyoxyethylene sorbitan monolaurate emulsifier was added to dissolve the compound. If the material was not soluble in acetone, another solvent such as water, alcohol or dimethylformamide (DMF) was used instead. When DMF was used, only 0.5 ml. or less was used to dissolve the compound and then another solvent was used to make the volume up to 3 ml. The 3 ml. solution was sprayed uniformly on the soil contained in a small flat 7 inches long, 5 inches wide and 2.75 inches deep, one day after planting weed seeds in the flat of soil. A No. 152 DeVilbiss atomizer was used to apply the spray using compressed air at a pressure of 5 lb/sq. inch. The rate of application was 8 lb/acre and the spray volume was 143 gallon/acre.

After treatment, the flats were placed in the greenhouse at a temperature of 70.degree. to 85.degree. F. and watered by sprinkling. Two weeks after treatment the degree of injury or control was determined by comparison with untreated check plants of the same age. The injury rating from 0 to 100% was recorded for each species as percent control with 0% representing no injury and 100% representing complete control.

Post-emergence herbicide test

Seeds of six plant species, including hairy crabgrass, watergrass, red oat, mustard, curly dock and pinto beans (Phaseolus vulgaris) were planted in the flats as described above for pre-emergence screening. The flats were 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 were almost fully expanded and the first trifoliate leaves were just starting to form, the plants were sprayed. The spray was prepared by weighing out 20 ml. of the test compound, dissolving it in 2.5 ml. of acetone containing 1% polyoxyethylene sorbitan monolaurate and then adding 2.5 ml. of water. The solution was sprayed on the foliage using a No. 152 DeVilbiss atomizer at an air pressure of 5 lb/sq. inch. The spray concentration was 0.2% and the rate is 8 lb/acre. The spray volume was 238 gallon/acre.

The injury rating is from 0 to 100% as described above for the pre-emergence herbicide screening test.

The results of these tests are shown in the following Table 2.

The compounds of the present invention are used as pre-emergence or post-emergence herbicides and are applied in a variety of ways at various concentrations. In practice, the compounds herein defined are formulated into herbicidal compositions, by admixture, in herbicidally effective amounts, with the adjuvants and carriers normally employed for facilitating the dispersion of active ingredients for agricultural applications, recognizing the fact that the formulation and mode of application of a toxicant may affect the activity of the materials in a given application. Thus, these active herbicidal compounds may be formulated as granules of relatively large particle size, as wettable powders, as emulsifiable concentrates, as powdery dusts, as solutions or as any of several other known types of formulations, depending upon the desired mode of application. Preferred formulations for both pre- and post-emergence herbicidal applications are wettable powders, emulsifiable concentrates and granules. These formulations may contain as little as about 0.5% to as much as about 95% or more by weight of active ingredient. A herbicidally effective amount depends upon the nature of the seeds or plants to be controlled and the rate of application varies from about 0.05 to approximately 25 pounds per acre, preferably from about 0.1 to 10 pounds per acre.

Wettable powders are in the form of finely divided particles which disperse readily in water or other dispersant. The wettable powder is ultimately applied to the soil either as a dry dust or as a dispersion in water or other liquid. Typical carriers for wettable powders include fuller's earth, kaolin clays, silicas and other readily wet organic or inorganic diluents. Wettable powders normally are prepared to contain about 5% to about 95% of the active ingredient by weight and usually also contain a small amount of wetting, dispersing or emulsifying agent to facilitate wetting and dispersion.

Emulsifiable concentrates are homogeneous liquid compositions which are dispersible in water or other dispersant, and may consist entirely of the active compound with a liquid or solid emulsifying agent, or may also contain a liquid carrier, such as xylene, heavy aromatic naphtha, isophorone and other non-volatile organic solvents. For herbicidal application, these concentrates are dispersed in water or other liquid carrier and normally applied as a spray to the area to be treated. The percentage by weight of the essential active ingredient may vary according to the manner in which the composition is to be applied, but in general comprises about 0.5% to 95% of active by weight of the herbicidal composition.

Granular formulations, wherein the toxicant is carried on relatively coarse particles, are usually applied without dilution to the area in which suppression of vegetation is desired. Typical carriers for granular formulations include sand, fuller's earth, bentonite clays, vermiculite, perlite and other organic or inorganic materials which absorb or which may be coated with the toxicant. Granular formulations normally are prepared to contain about 5% to about 25% of active ingredient and may also contain small amounts of other ingredients which may include surface-active agents such as wetting agents, dispersing agents or emulsifiers; oils such as heavy aromatic naphtha, kerosene or other petroleum fractions, or vegetable oils; and/or stickers such as dextrins, glue or synthetic resins.

Typical wetting, dispersing or emulsifying agents used in agricultural formulations include, for example, the alkyl and alkylaryl sulfonates and sulfates and their sodium salts; polyhydric alcohols; and other types of surface-active agents, many of which are available in commerce. The surface-active agent, when used, normally comprises from 0.1% to 15% by weight of the herbicidal composition.

Dusts, which are free-flowing admixtures of the active ingredient with finely divided solids such as talc, clays, flours, and other organic and inorganic solids which act as dispersants and carriers for the toxicant, are useful formulations for soil-incorporating applications.

Pastes, which are homogeneous suspensions of a finely divided solid toxicant in a liquid carrier such as water or oil, are employed for specific purposes. These formulations normally contain about 5% to about 95% of active ingredient by weight, and may also contain small amounts of a wetting, dispersing or emulsifying agent to facilitate dispersion. For application, the pastes are normally diluted and applied as a spray to the area to be affected.

Other useful formulations for herbicidal applications include simple solutions of the active ingredient in a dispersant in which it is completely soluble at the desired concentration, such as acetone, alkylated naphthalenes, xylene or other organic solvents. Pressurized sprays, typically aerosols, wherein the active ingredient is dispersed in finely-divided form as a result of vaporization of a low boiling dispersant solvent carrier, such as the Freons, may also be used.

The phytotoxic compositions of this invention are applied to the plants in the conventional manner. Thus, the dust and liquid compositions can be applied to the plant by the use of power-dusters, boom and hand sprayers and spray dusters. The compositions can also be applied from airplanes as a dust or a spray because they are effective in very low dosages. In order to modify or control growth of germinating seeds or emerging seedlings, as a typical example, the dust and liquid compositions are applied to the soil according to convention methods and are distributed in the soil to a depth of at least 1/2 inch below the soil surface. It is not necessary that the phytotoxic compositions be admixed with the soil particles since these compositions can also be applied merely by spraying or sprinkling the surface of the soil. The phytotoxic compositions of this invention can also be applied by addition to irrigation water supplied to the field to be treated. This method of application permits the penetration of the compositions into the soil as the water is absorbed therein. Dust compositions, granular compositions or liquid formulations applied to the surface of the soil can be distributed below the surface of the soil by conventional means such as discing, dragging or mixing operations.

The phytotoxic compositions of this invention can also contain other additaments, for example, fertilizers, pesticides and the like, used as adjuvant 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 acid, 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-methylthio-s-triazine, 2-chloro-4-ethylamino-6-isopropylamino-s-triazine, and 2-ethylamino-4-isopropylamino-6-methylmercapto-s-triazine; urea derivatives, such as 3-(3,4-dichlorophenyl)-1,1-dimethyl urea and 3-(p-chlorophenyl)-1,1-dimethyl urea; and acetamides such as N,N-diallyl-.alpha.-chloroacetamide, and the like; benzoic acids such as 3-amino-2,5-dichlorobenzoic; thiocarbamates, such as S-propyl dipropylthiocarbamate, S-ethyl-dipropylthiocarbamate, S-ethyl cyclohexylethyl thiocarbamate, S-ethyl hexahydro-1H-azepine-1-carbothioate and the like; 4-(methylsulfonyl)-2,6-dinitro-N,N-substituted anilines, such as 4-(methylsulfonyl)-2,6-dinitro-N,N-substituted anilines, such as 4-trifluoromethyl-2,6-dinitro-N,N-di-n-propyl aniline and 4-trifluoromethyl-2,6-dinitro-N-ethyl-N-n-butyl aniline. Fertilizers useful in combination with the active ingredients include, for example, ammonium nitrate, urea and superphosphate. Other useful additaments include materials in which plant organisms take root and grow such as compost, manure, humus, sand and the like.