Certain 1-phenyl-3-alkyl-1,3-propanediones

Abstract

Compounds of the formula ##STR1## wherein R is halogen; C.sub.1 -C.sub.2 alkyl; C.sub.1 -C.sub.2 alkoxy; nitro; cyano; C.sub.1 -C.sub.2 haloalkyl; or R.sup.a SO.sub.n -- wherein n is 0 or 2 and R.sup.a is C.sub.1 -C.sub.2 alkyl; R.sup.1 is C.sub.1 -C.sub.4 alkyl; R.sup.2 is C.sub.1 -C.sub.4 alkyl or C.sub.1 -C.sub.4 alkoxy; R.sup.3 and R.sup.4 independently are (1) hydrogen; (2) halogen; (3) C.sub.1 -C.sub.4 alkyl; (4) C.sub.1 -C.sub.4 alkoxy; (5) trifluoromethoxy; (6) cyano; (7) nitro; (8) C.sub.1 -C.sub.4 haloalkyl; (9) R.sup.b SO.sub.n -- wherein n is the intger 0, 1 or 2; and R.sup.b is (a) C.sub.1 -C.sub.4 alkyl; (b) C.sub.1 -C.sub.4 alkyl substituted with halogen or cyano; (c) phenyl; or (d) benzyl; (10) --NR.sup.c R.sup.d wherein R.sup.c and R.sup.d independently are hydrogen or C.sub.1 -C.sub.4 alkyl; (11) R.sup.e C(O)-- wherein R.sup.e is C.sub.1 -C.sub.4 alkyl or C.sub.1 -C.sub.4 alkoxy; or (12) --SO.sub.2 NR.sup.c R.sup.d wherein R.sup.c and R.sup.d are as defined; and (13) --N(R.sup.c)C(O)R.sup.d wherein R.sup.e and R.sup.d are as defined and their salts are useful as herbicides.

Description

BACKGROUND OF THE INVENTION

3-(2-Nitro,5-chlorobenzoyl-2,4-pentanedione is taught in J. Chem. Soc., Chem. Commun., 19 782-3 (1975). No use for this compound is taught. 3-(2-Nitrobenzoyl)-2,4-pentanedione is taught in Tetrahedron, 39(19), 2933-8 (1982). No use for this compound is taught.

DESCRIPTION OF THE INVENTION

This invention relates to 1-phenyl-3-alkyl-1,3-propanediones and their use as herbicides.

One embodiment of this invention is an herbicidal composition comprising an herbicidally active 1-phenyl-3-alkyl-1,3-propanediones and an inert carrier therefor. The 2-position of the 1,3-propanedione moiety is substituted, preferably with a C.sub.1 -C.sub.4 alkyl C(O)-- or C.sub.1 -C.sub.4 alkoxy C(O)-- group. The benzoyl moiety can be substituted, preferably with the groups hereinafter recited.

Also embodied within the scope of this invention are novel compounds having the following structural formula ##STR2## wherein

R is halogen; C.sub.1 -C.sub.2 alkyl, preferably methyl; C.sub.1 -C.sub.2 alkoxy, preferably methoxy; nitro; cyano; C.sub.1 -C.sub.2 haloalkyl, preferably trifluoromethyl; or R.sup.a SO.sub.n -- wherein n is 0 or 2, preferably 2 and R.sup.a is C.sub.1 -C.sub.2 alkyl, preferably methyl. Preferably, R is chlorine, bromine, C.sub.1 -C.sub.2 alkyl, C.sub.1 -C.sub.2 alkoxy, trifluoromethyl, cyano, nitro, C.sub.1 -C.sub.2 alkylthio or C.sub.1 -C.sub.2 alkylsulfonyl; more preferably chlorine, nitro, methyl, trifluoromethyl or methylsulfonyl; and

R.sup.1 is C.sub.1 -C.sub.4 alkyl, preferably methyl;

R.sup.2 is C.sub.1 -C.sub.4 alkyl, preferably methyl, or C.sub.1 -C.sub.4 alkoxy, preferably, ethoxy;

R.sup.3 and R.sup.4 independently are (1) hydrogen, (2) halogen, preferably chlorine, fluorine or bromine; (3) C.sub.1 -C.sub.4 alkyl, preferably methyl; (4) C.sub.1 -C.sub.4 alkoxy, preferably methoxy; (5) trifluoromethoxy; (6) cyano; (7) nitro; (8) C.sub.1 -C.sub.4 haloalkyl, more preferably trifluoromethyl; (9) R.sup.b SO.sub.n -- wherein n is the integer 0, 1 or 2, preferably 2; and R.sup.b is (a) C.sub.1 -C.sub.4 alkyl, preferably methyl; (b) C.sub.1 -C.sub.4 alkyl substituted with halogen or cyano, preferably chloromethyl, trifluoromethyl or cyanomethyl; (c) phenyl; or (d) benzyl; (10) --NR.sup.c R.sup.d wherein R.sup.c and R.sup.d independently are hydrogen or C.sub.1 -C.sub.4 alkyl; (11) R.sup.e C(O)-- wherein R.sup.e is C.sub.1 -C.sub.4 alkyl or C.sub.1 -C.sub.4 alkoxy; (12) --SO.sub.2 NR.sup.c R.sup. d wherein R.sup.c and R.sup.d are as defined; or (13) --N(R.sup.c)C(O)R.sup.d wherein R.sup.e and R.sup.d are as defined.

Preferably R.sup.3 is in the 3-position. More preferably R.sup.3 is hydrogen, chlorine, fluorine, trifluoromethyl, cyano, C.sub.1 -C.sub.4 alkoxy or C.sub.1 -C.sub.4 thioalkyl. Most preferably, R.sup.3 is hydrogen. Preferably R.sup.4 is in the 4-position. Most preferably R.sup.4 is halogen, cyano, trifluoromethyl, or R.sup.b SO.sub.2 wherein R.sup.b is C.sub.1 -C.sub.4 alkyl, preferably methyl or C.sub.1 -C.sub.4 haloalkyl, preferably chloromethyl, difluoromethyl or trifluoromethyl.

The term "C.sub.1 -C.sub.4 alkyl" includes methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl and t-butyl. The term "halogen" includes chlorine, bromine, iodine and fluorine. The terms "C.sub.1 -C.sub.4 alkoxy" includes methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, isobutoxy and t-butoxy. The term "C.sub.1 -C.sub.4 haloalkyl" includes the alkyl groups defined above under C.sub.1 -C.sub.4 alkyl in which one or more hydrogen is replaced by chlorine, bromine, iodine or fluorine.

Salts of the above-described compounds (as defined hereinafter) are included within the scope of the instant invention.

The compounds of this invention can have the following four structural formulae because of tautomerism: ##STR3## wherein R, R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are as defined above.

The circled proton on each of the four tautomers is reasonably labile. These protons are acidic and can be removed by reaction with a base to form a salt having an anion of the following four resonance forms: ##STR4## wherein R, R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are as defined above.

Examples of cations of these bases are inorganic cations such as alkali metals, e.g. lithium, sodium and potassium; the alkaline earth metals, e.g. calcium and magnesium or ammonium or organic cations such as substituted ammonium, sulfonium, sulfoxonium or phosphonium wherein the substituents are aliphatic or aromatic groups.

Those skilled in the art will recognize in considering the salts of this invention that varying degrees of association between the anion and cation will exist depending upon the nature of the cation. In some instances with a suitable cation, such as copper, the salt can exist in a chelated form.

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

The compounds of the present invention can be prepared by the following general method. ##STR5##

Generally, mole amounts of the dione, magnesium ethoxide, and substituted benzoyl chloride are used. The dione and magnesium ethoxide are combined in a solvent such as ethyl ether and heated at reflux for 1 hour. The benzoyl chloride is then slowly added, and the reaction mixture is heated at reflux for another 0.5-1 hour. The reaction product is worked up by conventional techniques.

The above described substituted benzoyl chlorides can be prepared from the corresponding substituted benzoic acids according to the teaching of Reagents for Organic Synthesis, Vol. I, L. F. Fieser and M. Fieser, pp. 767-769 (1967). ##STR6## wherein R, R.sup.3 and R.sup.4 are as previously defined.

The substituted benzoic acids can be prepared by a wide variety of general methods according to the teaching of The Chemistry of Carboxylic Acids and Esters, S. Patai, editor, J. Wiley and Sons, New York, N.Y. (1969) and Survey of Organic Synthesis, C. A. Buehler and D. F. Pearson, J. Wiley and Sons, (1970).

The following are three representative examples of the methods described therein. ##STR7## wherein R, R.sup.3 and R.sup.4 are as previously defined.

In reaction (a) the substituted benzonitrile is heated to reflux in aqueous sulfuric acid for several hours. The mixture is cooled and the reaction product is isolated by conventional techniques. ##STR8## wherein R, R.sup.3 and R.sup.4 are as previously defined.

In reaction (b) the substituted acetophenone is heated to reflux for several hours in an aqueous hypochlorite solution. The mixture is cooled and the reaction product is isolated by conventional techniques. ##STR9## wherein R, R.sup.3 and R.sup.4 are as previously defined.

In reaction (c) the substituted toluene is heated to reflux in an aqueous solution of potassium permanganate for several hours. The solution is then filtered and the reaction product is isolated by conventional techniques.

The following example teaches the synthesis of a representative compound of this invention.

EXAMPLE 1

3-(2,4-Dichlorobenzoyl)-2,4-pentanedione ##STR10##

A mixture of magnesium ethoxide (22.9 g, 0.2 moles) 2,4-pentanedione (20.0 g, 0.2 moles), and ether (150 ml) was heated at reflux for 1 hour. 2,4-Dichlorobenzoyl chloride (41.9 g, 0.2 mole) in ether (50 ml) was added to the mixture over a period of 15 minutes, and the resultant mixture was heated at reflux for an additional 0.5 hour. After cooling, the reaction mixture was poured into 200 ml of 10% sulfuric acid. The ether layer was separated and stirred with 250 ml of 5% copper (II) acetate. The resulting copper salt was filtered, washed with ether, and stirred with 6N hydrochloric acid to destroy the salt. The acidic aqueous solution was extracted with ether. The ether extract was washed with saturated sodium chloride, dried over anhydrous magnesium sulfate, and concentrated under vacuum yielding 21 g of the desired product as a yellow oil. It was identified as such by nuclear magnetic resonance spectroscopy, infrared spectroscopy, and mass spectroscopy.

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 throughout the remainder of the application.

TABLE I______________________________________ ##STR11## n.sub.D.sup.30 /Cmpd. No. R R.sup.1 R.sup.2 R.sup.3 R.sup.4 m.p. .degree.C.______________________________________.sup. 1.sup.a Cl CH.sub.3 CH.sub.3 H 4-Cl oil2 NO.sub.2 CH.sub.3 CH.sub.3 H H oil3 NO.sub.2 CH.sub.3 CH.sub.3 H 4-CF.sub.3 79-834 Cl CH.sub.3 CH.sub.3 H 4-SO.sub.2 CH.sub.3 oil5 NO.sub.2 i-C.sub.3 H.sub.7 i-C.sub.3 H.sub.7 H 4-CF.sub.3 semi-solid.sup. 6.sup.b Cl CH.sub.3 C.sub.2 H.sub.5 O H 4-Cl 97-997 Cl CH.sub.3 C.sub.2 H.sub.5 O H 4-Cl oil.sup. 8.sup.b Cl CH.sub.3 C.sub.2 H.sub.5 O H 4-SO.sub.2 CH.sub.3 221 (dec.).sup. 9.sup.c Cl CH.sub.3 C.sub.2 H.sub.5 O H 4-Cl 220 (dec.)10 Cl CH.sub.3 C.sub.2 H.sub.5 O H 4-SO.sub.2 CH.sub.3 oil______________________________________ .sup.a prepared in Example 1. .sup.b sodium salt of compound .sup.c ammonium salt of compound

HERBICIDAL SCREENING TESTS

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 were 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 loamy sand soil in individual rows using one species per row across the width of a flat. The seeds used are green foxtail (FT) (Setaria viridis), watergrass (WG) (Echinochloa crusgalli), wild oat (WO) (Avena fatua), annual morningglory (AMG) (Ipomoea lacunosa), velvetleaf (VL) (Abutilon theophrasti), Indian mustard (MD) (Brassica juncea), and yellow nutsedge (YNG) (Cyperus esculentus). Ample seeds are planted to give about 20 to 40 seedlings per row, after emergence, depending upon the size of the plants.

Using an analytical balance, 600 milligrams (mg) of the compound to be tested are weighed out on a piece of glassine weighing paper. The paper and compound are placed in a 60 milliliter (ml) wide-mouth clear bottle and dissolved in 45 ml of acetone or substituted solvent. Eighteen ml of this solution are transferred to a 60 ml wide-mouth clear bottle and diluted with 22 ml of a water and acetone mixture (19:1) containing enough polyoxyethylene sorbitan monolaurate emulsifier to give a final solution of 0.5% (v/v). The solution is then sprayed on a seeded flat on a linear spray table calibrated to deliver 80 gallons per acre (748 L/ha). The application rate is 4 lb/acre (4.48 Kg/ha).

After treatment, the flats are placed in the greenhouse at a temperature of 70.degree. to 80.degree. F. and watered by sprinkling. Two weeks after treatment, the degree of injury or control is determined by comparison with untreated check plants of the same age. The injury rating from 0 to 100% is recorded for each species as percent control with 0% representing no injury and 100% representing complete control.

The results of the tests are shown in the following Table II.

TABLE II______________________________________Pre-Emergence Herbicidal ActivityApplication Rate - 4.48 kg/haCmpd.No. FT WG WO AMG VL MD YNG______________________________________1 60 -- 0 10 0 20 02 100 70 60 10 20 70 03 100 100 70 50 100 100 804 85 85 20 35 100 100 90 5* 0 5 0 60 100 100 156 60 100 5 0 30 50 07 10 95 5 0 0 10 08 60 100 20 40 100 100 809 40 100 5 10 50 50 3010 80 100 30 10 100 100 80______________________________________ A blank (--) indicates that the weed was not tested. *Tested at 1,12 kg/ha.

Post-Emergence Herbicide Test: This test is conducted in an identical manner to the testing procedure for the pre-emergence herbicide test, except the seeds of the seven different weed species are planted 10-12 days before treatment. Also, watering of the treated flats is confined to the soil surface and not to the foliage of the sprouted plants.

The results of the post-emergence herbicide test are reported in Table III.

TABLE III______________________________________Post-Emergence Herbicidal ActivityApplication Rate - 4.48 kg/haCmpd.No. FT WG WO AMG VL MD YNG______________________________________1 20 20 0 20 100 65 102 20 25 40 20 50 15 153 80 75 50 40 100 100 554 80 70 40 30 100 100 65 5* 30 20 0 45 25 20 106 0 0 0 5 5 5 07 5 10 10 10 100 100 08 90 60 10 80 100 100 309 10 20 10 40 100 100 010 50 60 20 95 95 95 40______________________________________ A blank (--) indicates the weed was not tested. *Tested at 1.12 kg/ha.

The compounds of the present invention and their salts are useful as herbicides and can be applied in a variety of ways at various concentrations. In practice, the compounds or salts 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 or salts can be formulated as granules of relatively large particle size, as wettable powders, as emulsifiable concentrates, as powdery dusts, as flowables, as solutions or as any of several other known types of formulations, depending upon the desired mode of application. 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 0.01 to approximately 10 pounds per acre, preferably from about 0.02 to about 4 pounds per acre.

Wettable powders are in the form of finely divided particles which disperse readily in water or other dispersants. 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 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 or salt with a liquid or solid emulsifying agent, or may also contain a liquid carrier, such as xylene, heavy aromatic naphthal, 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 ingredient 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, attapulgite clay, bentonite clays, montmorillonite clay, 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 ingredients which may include surface-active agents such heavy aromatic naphthas, kerosene or other petroleum fractions, or vegetable oils; and/or stickers such as destrins, 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 salts; polyhydric alcohols; polyethoxylated alcohols; esters and fatty amines; 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 application.

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 and 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 can be 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 or by rope wick applications 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 can be applied to the soil according to conventional methods and can be 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 mechanically 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. In the following examples the herbicidal compound can be substituted with the herbicidal salt of the compound.

______________________________________General Formula with Ranges Specific Formula______________________________________EMULSIFIABLE CONCENTRATE FORMULATIONSHerbicidal compound 5-55 herbicidal compound 24surfactant(s) 5-25 proprietary blend of oil- 10solvent(s) 20-90 soluble sulfonates and 100% polyoxyethylene ethers polar solvent 27 petroleum hydrocarbon 39 100%WETTABLE POWDER FORMULATIONSherbicidal compound 3-90 herbicidal compound 80wetting agent 0.5-2 sodium dialkyl naphthalene 0.5dispersing agent 1-8 sulfonatediluent(s) 8.5-87 sodium lignosulfonate 7 100% attapulgite clay 12.5 100%EXTRUDED GRANULAR FORMULATIONSherbicidal compound 1-20 herbicidal compound 10binding agent 0-10 lignin sulfonate 5diluent(s) 70-99 calcium carbonate 85 100% 100%FLOWABLE FORMULATIONSherbicidal compound 20-70 herbicidal compound 45surfactant(s) 1-10 polyoxyethylene ether 5suspending agent(s) 0.05-1 attagel 0.05antifreeze agent 1-10 propylene glycol 10antimicrobial agent 1-10 1,2-benzisothiazoline-3-one 0.03antifoam agent 0.1-1 silicone defoamer 0.02solvent 7.95- water 39.9 77.85 100% 100%______________________________________

When salts are used as the active ingredient in the herbicidal compositions of this invention it is recommended to use salts that are agriculturally acceptable.

The phytotoxic compositions of this invention can also contain other additives, for example, fertilizers, other herbicides and other pesticides, used as adjuvant or in combination with any of the abovedescribed adjuvants. Fertilizers useful in combination with the active ingredients include, for example, ammonium nitrate, urea and superphosphate.

Claims

1. The method of controlling undesirable vegetation comprising applying to the area where control is desired, an herbicidally effective amount of a compound having the formula ##STR12## wherein R is halogen; C.sub.1 -C.sub.2 alkyl; C.sub.1 -C.sub.2 alkoxy; nitro; C.sub.1 -C.sub.2 haloalkyl; or R.sup.a SO.sub.n -- wherein n is 0 or 2 and R.sup.a is C.sub.1 -C.sub.2 alkyl;

R.sup.1 is C.sub.1 -C.sub.4 alkyl;

R.sup.2 is C.sub.1 -C.sub.4 alkyl or C.sub.1 -C.sub.4 alkoxy;

R.sup.3 and R.sup.4 independently are (1) hydrogen; (2) halogen; (3) C.sub.1 -C.sub.4 alkyl; (4) C.sub.1 -C.sub.4 alkoxy; (5) trifluoromethoxy; (6) nitro; (7) C.sub.1 -C.sub.4 haloalkyl; (8) R.sup.b SO.sub.n -- wherein n is the integer 0, 1 or 2; and R.sup.b is (a) C.sub.1 -C.sub.4 alkyl; (b) C.sub.1 -C.sub.4 alkyl substituted with halogen; (c) phenyl; or (d) benzyl and their salts.

2. The method of claim 1 wherein R is chlorine, bromine, methyl, methoxy, nitro, trifluoromethyl, or methylsulfonyl; R.sup.1 is C.sub.1 -C.sub.4 alkyl; R.sup.2 is C.sub.1 -C.sub.4 alkyl or C.sub.1 -C.sub.4 alkoxy; and R.sup.3 and R.sup.4 independently are (1) hydrogen; (2) halogen; (3) C.sub.1 -C.sub.4 alkyl; (4) C.sub.1 -C.sub.4 alkoxy; (5) trifluoromethoxy; (6) nitro; (7) C.sub.1 -C.sub.4 haloalkyl; (8) R.sup.b SO.sub.n -- wherein n is the integer 0, 1 or 2; and R.sup.b is (a) C.sub.1 -C.sub.4 alkyl; (b) C.sub.1 -C.sub.4 alkyl substituted with halogen; (c) phenyl; or (d) benzyl.

3. The method of claim 1 wherein R.sup.3 and R.sup.4 are independently hydrogen; chlorine; fluorine; bromine; methyl; C.sub.1 -C.sub.4 alkoxy; trifluoromethoxy; nitro; trifluoromethyl; R.sup.b SO.sub.n -- wherein n is the integer 0 or 2 and R.sup.b is methyl, chloromethyl, trifluoromethyl, ethyl, or n-propyl; and R.sup.3 is in the 3-position and R.sup.4 is in the 4-position.

4. The method of claim 1 wherein R.sup.3 is hydrogen and R.sup.4 is hydrogen, chlorine, bromine, fluorine, trifluoromethyl or R.sup.b SO.sub.2 wherein R.sup.b is C.sub.1 -C.sub.4 alkyl or C.sub.1 -C.sub.4 haloalkyl.

5. The method of claim 1 wherein R is nitro, R.sup.1 is methyl; R.sup.2 is methyl; R.sup.3 is methyl; R.sup.3 is hydrogen; and R.sup.4 is 4-trifluoromethyl.

6. The method of claim 1 wherein R is chlorine; R.sup.1 is methyl; R.sup.2 is methyl; R.sup.3 is hydrogen; and R.sup.4 is 4-SO.sub.2 CH.sub.3.

7. The method of claim 1 wherein R is chlorine; R.sup.1 is methyl; R.sup.2 is ethoxy; R.sup.3 is hydrogen and R.sup.4 is 4-SO.sub.2 CH.sub.3.

8. The method of claim 1 wherein R.sup.3 is hydrogen.

9. The method of claim 2 wherein R.sup.3 is hydrogen.

10. The herbicidal composition comprising a herbicidally active 1-phenyl-3-alkyl-1,3-alkanedione compound of the formula ##STR13## wherein R is halogen; C.sub.1 -C.sub.2 alkyl; C.sub.1 -C.sub.2 alkoxy; nitro; C.sub.1 -C.sub.2 haloalkyl; or R.sup.a SO.sub.n -- wherein n is 0 or 2 and R.sup.a is C.sub.1 -C.sub.2 alkyl;

R.sup.1 is C.sub.1 -C.sub.4 alkyl;

R.sup.2 is C.sub.1 -C.sub.4 alkyl or C.sub.1 -C.sub.4 alkoxy;

R.sup.3 and R.sup.4 independently are (1) hydrogen; (2) halogen; (3) C.sub.1 -C.sub.4 alkyl; (4) C.sub.1 -C.sub.4 alkoxy; (5) trifluoromethoxy; (6) nitro; (7) C.sub.1 -C.sub.4 haloalkyl; (8) R.sup.b SO.sub.n -- wherein n is the integer 0, 1 or 2; and R.sup.b is (a) C.sub.1 -C.sub.4 alkyl; (b) C.sub.1 -C.sub.4 alkyl substituted with halogen; (c) phenyl; or (d) benzyl; or their salts and an inert carrier therefor with the proviso that when R is nitro both R3 and R4 can not be hydrogen.

11. The composition of claim 10 wherein R is chlorine, bromine, methyl, methoxy, nitro, trifluoromethyl, or methylsulfonyl; R.sup.1 is C.sub.1 -C.sub.4 alkyl; R.sup.2 is C.sub.1 -C.sub.4 alkyl or C.sub.1 -C.sub.4 alkoxy; and R.sup.3 and R.sup.4 independently are (1) hydrogen; (2) halogen; (3) C.sub.1 -C.sub.4 alkyl; (4) C.sub.1 -C.sub.4 alkoxy; (5) trifluoromethoxy; (6) nitro; (7) C.sub.1 -C.sub.4 haloalkyl; (8) R.sup.b SO.sub.n -- wherein n is the integer 0, 1 or 2; and R.sup.b is (a) C.sub.1 -C.sub.4 alkyl; (b) C.sub.1 -C.sub.4 alkyl substituted with halogen; (c) phenyl; or (d) benzyl.

12. The composition of claim 11 wherein R.sup.3 and R.sup.4 are independently hydrogen; chlorine; fluorine; bromine; methyl; C.sub.1 -C.sub.44 alkoxy; trifluoromethoxy; nitro; trifluoromethyl; R.sup.b SO.sub.n -- wherein n is the integer 0 or 2 and R.sup.b is methyl, chloromethyl, trifluoromethyl, ethyl, or n-propyl; and R.sup.3 is in the 3-position and R.sup.4 is in the 4-position.

13. The composition of claim 11 wherein R.sup.3 is hydrogen and R.sup.4 is hydrogen, chlorine, bromine, fluorine, trifluoromethyl or R.sup.b SO.sub.2 wherein R.sup.b is C.sub.1 -C.sub.4 alkyl or C.sub.1 -C.sub.4 haloalkyl.

14. The composition of claim 10 wherein R is nitro, R.sup.1 is methyl; R.sup.2 is methyl; R.sup.3 is hydrogen; and R.sup.4 is 4-trifluoromethyl.

15. The composition of claim 10 wherein R is chlorine; R.sup.1 is methyl; R.sup.2 is methyl; R.sup.3 is hydrogen; and R.sup.4 is 4-SO.sub.2 CH.sub.3.

16. The composition of claim 10 wherein R is chlorine; R.sup.1 is methyl; R.sup.2 is ethoxy; R.sup.3 is hydrogen and R.sup.4 is 4-SO.sub.2 CH.sub.3.

17. The compositions of claim 10 wherein R.sup.3 is hydrogen.

18. The compositions of claim 10 wherein R.sup.3 is hydrogen.