Substituted diphenyl ethers having herbicidal activity

Abstract

This invention concerns certain substituted diphenyl ethers, their method of preparation, and herbicidal uses thereof.

Description

DESCRIPTION OF THE INVENTION

This invention concerns substituted diphenyl ethers which, in one embodiment, are represented by the formula: ##STR1## wherein: X is hydrogen or halogen;

Y is hydrogen, halogen, trifluoromethyl, cyano, or alkyl containing 1 to 4 carbon atoms;

Z is nitro;

R is alkylidene or monosubstituted alkylidene containing 1 to 3 carbon atoms wherein the substituent is alkyl containing 1 to 4 carbon atoms;

R¹ is hydrogen, alkyl or alkoxy containing 1 to 4 carbon atoms; and

R² is hydrogen, alkyl or alkoxy containing 1 to 4 carbon atoms, phenyl or substituted phenyl wherein the substituent is selected from halogen, cyano, trifluoromethyl or alkyl containing 1 to 4 carbon atoms.

This invention also concerns substituted diphenyl ethers which, in another embodiment, are represented by the above formula, wherein X, Y, R, R¹, and R² are as above defined, but wherein Z is halogen or cyano.

It is believed that the compounds of this invention wherein the `Z` substituent is other than nitro, for example, halogen, exhibit somewhat better herbicidal activity when applied postemergent rather than preemergent. The compounds of this invention wherein the `Z` substituent is nitro have been generally found effective when applied either pre- or postemergent.

Exemplary of halogens represented by X, Y and Z in the above formula are, for example, bromine, chlorine, iodine, or fluorine, preferably bromine or chlorine. Exemplary alkylidene radicals represented by R are, for example, methylidene, ethylidene, or propylidene. Some alkyl groups represented by R¹ and R² or with which the alkylidene radicals represented by R may be substituted are, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or t-butyl. As alkoxy radicals represented by R¹ and R², there may be mentioned methoxy, ethoxy, propoxy, or butoxy. Preferred compounds of this invention are those wherein X is hydrogen; Y is halogen, e.g. chlorine; and Z is nitro.

Compounds embodied by the above general formula are believed to have herbicidal activity in accordance with this invention. Some specific examples of compounds within the scope of said formula that have been found to be especially efficacious are 1'-(aminocarbonyl)ethyl 5-(2-chloro-4-trifluoromethylphenoxy)-2-nitrobenzoate; 1'-(N,N-dimethylaminocarbonyl)ethyl 5-(2-chloro-4-trifluoromethylphenoxy)-2-nitrobenzoate; and 1'-(N-isopropylaminocarbonyl)ethyl 5-(2-chloro-4-trifluoromethylphenoxy)-2-nitrobenzoate.

It is, of course, to be further understood that the stereo and optical isomers of compounds represented by the above formula are within the scope of this invention.

The compounds of this invention are typically synthesized by reacting an appropriately substituted benzoic acid represented by the formula: ##STR2## wherein X, Y, and Z are as defined hereinabove with an at least stoichiometric amount of an appropriately substituted haloalkylamide represented by the formula: ##STR3## wherein R, R¹, and R² are as defined hereinabove and A is halogen, preferably chlorine or bromine, using techniques known to the art. The substituted benzoic acids and haloalkylamide may be obtained from commercial sources or prepared by known techniques.

More particularly, an at least stoichiometric amount of substituted benzoic acid is reacted with the haloalkylamide, preferably in the presence of an azo compound, such as, for example, 1,5-diazobicyclo(5.4.0)-undec-5-ene (DBU). If desired, either or both the substituted benzoic acid and the haloalkylamide may be dissolved in an inert solvent, such as, for example, benzene, methylene chloride, chloroform, ethyl acetate, tetrahydrofuran, or the like. The reaction mixture is heated to reflux and maintained at reflux until the reaction reaches the desired degree of completion. The reaction mixture is then cooled to ambient temperature and washed typically consecutively with dilute mineral acid, dilute caustic and water, and allowed to phase separate. Substituted diphenyl ether is recovered from the organic phase by any known technique, such as, for example, evaporation, crystallization, vacuum drying or the like. If desired, the product, substituted diphenyl ether, may be further purified by, for example, recrystallization.

The following Examples are illustrative of the synthesis of certain specific substituted diphenyl ether compounds of this invention.

EXAMPLE I

PAC Preparation of 1'-(aminocarbonyl)ethyl 5-(2-chloro-4-trifluoromethylphenoxy)-2-nitrobenzoate

A three-necked 100 milliliter flask provided with an addition funnel, a reflux condenser, and a magnetic stirring bar was charged with 3.61 grams (0.01 mole) of 5-(2-chloro-4-trifluoromthylphenoxy)-2-nitrobenzoic acid and a solution of 1.52 grams (0.01 mole) of 2-bromopropionamide in 50 milliliters of benzene. To this stirred solution at ambient temperature was added 1.53 grams (0.01 mole) of 1,5-diazobicyclo(5.4.0)-undec-5-ene (DBU). Upon completion of the addition, the reaction mixture was refluxed for 22.5 hours, cooled and transferred to a separatory funnel. The reaction mixture was then washed with 30 milliliters each of 1 Normal hydrochloric acid, water, 7 percent aqueous ammonium hydroxide solution (bis) and water, respectively. The organic phase was removed, dried over anhydrous magnesium sulfate and concentrated on a rotary evaporator at 55°C, yielding 2.85 grams of a light green oil identified as 1'-(aminocarbonyl)ethyl 5-(2-chloro-4-trifluoromethylphenoxy)-2-nitrobenzoate, having:

NMR (d₆ acetone): 7.0δ (broad singlet, 2H); 7.2-8.3δ (multiplet, 6H); 5.33δ (quartet, 1H); 1.55δ (doublet, 3H).

EXAMPLE II

PAC Preparation of 1'-(N,N-dimethylaminocarbonyl)ethyl 5-(2-chloro-4-trifluoromethylphenoxy)-2-nitrobenzoate

A three-necked 100 milliliter flask provided with an addition funnel, a reflux condenser, and a magnetic stirring bar was charged with 3.61 grams (0.01 mole) of 5-(2-chloro-4-trifluoromethyl)-2-nitrobenzoic acid and a solution of 1.94 grams (0.01 mole) of N,N-dimethyl-2-bromopropionamide in 50 milliliters of benzene. To this stirred solution at ambient temperature was added 1.53 grams (0.01 mole) of DBU. Upon completion of the addition, the reaction mixture was refluxed for 25 hours, cooled and transferred to a separatory funnel. The reaction mixture was then washed with 30 milliliters each of 1 Normal hydrochloric acid, water, 7 percent aqueous ammonium hydroxide solution and water, respectively. The organic phase was removed, dried over anhydrous magnesium sulfate and concentrated on a rotary evaporator at 55°C, yielding 3.2 grams of a light yellow oil identified as 1'-(N,N-dimethylaminocarbonyl)ethyl 5-(2-chloro-4-trifluoromethylphenoxy)-2-nitrobenzoate, having:

NMR (d₆ acetone): 7.15-8.28δ (multiplet, 6H); 5.68δ (quartet, 1H); 3.18δ (singlet, 3H); 2.88δ (singlet, 3H); 1.5δ (doublet, 3H).

EXAMPLE III

PAC Preparation of 1'-(N-isopropylaminocarbonyl)ethyl 5-(2-chloro-4-trifluoromethylphenoxy)-2-nitrobenzoate

A three-necked 100 milliliter flask provided with an addition funnel, a reflux condenser and a magnetic stirring bar was charged with 3.61 grams (0.01 mole) of 5-(2-chloro-4-trifluoromethylphenoxy)-2-nitrobenzoic acid and a solution of 1.94 grams (0.01 mole) of N-isopropyl-2-bromopropionamide in 50 milliliters of benzene. To this stirred solution, at ambient temperature was added 1.53 grams (0.01 mole) of DBU. Upon completion of the addition, the reaction mixture was refluxed for 23.5 hours, cooled and transferred to a separatory funnel. The reaction mixture was then washed with 30 milliliters each of 1 Normal hydrochloric acid, water, 7 percent aqueous ammonium hydroxide solution and water, respectively. The organic phase was removed, dried over magnesium sulfate and concentrated on a rotary evaporator at 55° C., yielding 3.67 grams of a light brown oil identified as 1'-(N-isopropylaminocarbonyl)ethyl 5-(2-chloro-4-trifluoromethylphenoxy)-2-nitrobenzoate, having:

NMR (d₆ acetone): 7.12-8.25δ (multiplet, 7H); 5.3δ (quartet, 1H); 4.05δ (heptet, 1H); 1.5δ (doublet, 3H); 1.1δ (doublet, 6H).

Although the mode of synthesis of the compounds of this invention has been illustrated in some detail by the foregoing Examples, it is to be understood that any compound contemplated to be within the scope of this invention may be prepared by those skilled in the art simply by varying the choice of starting materials and using the illustrated techniques or any other suitable techniques.

The compounds of this invention have been found effective in regulating the growth of a variety of undesirable plants, i.e., weeds, when applied, in an herbicidally effective amount, to the growth medium prior to emergence of the weeds or to the weeds subsequent to emergence from the growth medium. The term "herbicidally effective amount" is that amount of compound or mixture of compounds required to so injure or damage weeds such that the weeds are incapable of recovering following application. The quantity of a particular compound or mixture of compounds applied in order to exhibit a satisfactory herbicidal effect may vary over a wide range and depends on a variety of factors such as, for example, hardiness of a particular weed species, extent of weed infestation, climatic conditions, soil conditions, method of application, and the like. Typically, as little as 0.2 or less pound per acre to 10 or more pounds per acre of compound or mixtures of compounds may be required. Of course, the efficacy of a particular compound against a particular weed species may readily be determined by relatively straightforward laboratory or field testing in a manner well known to the art.

The compounds of this invention may be used as such or in formulation with agronomically acceptable adjuvants, inert carriers, other herbicides, or other commonly used agricultural compounds, for example, pesticides, stabilizers, safeners, fertilizers, and the like. The compounds of this invention, whether or not in formulation with other agronomically acceptable materials, are typically applied in the form of dusts, granules, wettable powders, solutions, suspensions, aerosols, emulsions, dispersions or the like in a manner well known to the art. When formulated with other typically used agronomically acceptable materials, the amount of compound or compounds of this invention present in the formulation may vary over a wide range, for example, from about 0.05 to about 95 percent by weight on weight of formulation. Typically such formulations will contain from about 5 to about 75 percent by weight of compound or compounds of this invention.

Certain of the compounds of this invention have been found effective in controlling a variety of broadleaf and grassy weeds at application rates of one pound per acre or less pre- or postemergence while not significantly damaging desirable crops such as, for example, corn, cotton, and soybeans. Exemplary of weeds that may be effectively controlled by the application of compounds of this invention are wild mustard (Brassica kaber); yellow foxtail (Setaria glauca); crabgrass (Digitaria sanguinalis); coffeeweed (Sesbania spp.); velvetleaf (Abutilon theophrasti); johnsongrass (Sorghum halepense); barnyardgrass (Echinochloa crusgalli); jimsonweed (Datura stramonium); teaweed (Sida spinosa); tall morningglory (Roth); and the like.

The compounds prepared according to Examples I, II, and III were tested for herbicidal activity against certain weed species under controlled laboratory conditions of light, temperature, and humidity. Seeds of selected weeds were planted in flats. For preemergence tests, the flats were treated with the selected compound immediately after planting. For postemergence tests, the flats were treated with the selected compound after a two-week germination period. Each compound was applied to the flats at the rate of 2 pounds per acre by spraying a solvent solution of the compound. The state of growth of the weeds was observed, and the toxic effect of each compound was evaluated periodically after application. The following shows in tabular form the weed species (identified by common name), the compound applied (indicated by an "X" and identified by reference to the Example in which it was prepared) to the weed species, and whether the application was pre- or postemergent.

______________________________________
Compound
Weed         I      I       II   II    III  III
______________________________________
Teaweed      X              X
Jimsonweed   X      X
Wild Mustard X      X       X    X     X    X
Johnsongrass X                         X
Yellow Foxtail
X      X       X          X
Large Crabgrass
X              X          X
Coffeeweed   X      X       X    X          X
Velvetleaf          X       X          X
Tall Morningglory
X
Barnyardgrass
X
emergence    Pre    Post    Pre  Post  Pre  Post
______________________________________

In each of the foregoing tests, it was observed that all of the various weeds were either killed or injured beyond recovery within 21 to 22 days after application of the particular compound. Moreover, it was observed that the tested compounds appear to have somewhat better herbicidal activity when applied preemergent as compared with postemergent application, especially at relatively low rates of application, i.e. 2 or less pounds per acre.

In addition, the compound prepared according to Example I, i.e. 1'-(aminocarbonyl)ethyl 5-(2-chloro-4-trifluoromethylphenoxy)-2-nitrobenzoate, was applied preemergence at the rate of 2.0 pound per acre to the crops, corn, cotton, wheat, and soybeans. No damage to these crops was observed 21 days after application.

Also the compound prepared according to Example III, i.e. 1'-(N-isopropoxylaminocarbonyl)ethyl 5-(2-chloro-4-trifluoromethylphenoxy)-2-nitrobenzoate was applied preemergence at the rate of 1.0 pound per acre to the crops, cotton, tomatoes, corn, wheat, rice, and soybeans. No damage to these crops was observed 21 days after application.

Although the invention has been described in considerable detail with reference to illustrative embodiments thereof, it is to be understood that it is not intended to be so limited since many variations may be made therein by those skilled in the art without departing from the spirit and scope thereof as defined in the appended claims.

Claims

1. A compound represented by the formula: ##STR4## wherein: X is hydrogen or halogen;

Y is hydrogen, halogen, trifluoromethyl, cyano, or alkyl containing 1 to 4 carbon atoms;

Z is nitro, halogen, or cyano;

R is alkylidene or monosubstituted alkylidene containing up to 3 carbon atoms, wherein the substituent is alkyl of up to 4 carbon atoms;

R¹ is hydrogen, alkyl or alkoxy containing 1 to 4 carbon atoms; and

R² is hydrogen, alkyl or alkoxy containing 1 to 4 carbon atoms, phenyl or substituted phenyl wherein the substituent is selected from halogen, cyano, trifluoromethyl or alkyl containing 1 to 4 carbon atoms.

2. The compound of claim 1 wherein Z is nitro.

3. The compound of claim 1 wherein Z is halogen or cyano.

4. The compound of claim 1 wherein X is hydrogen, Y is halogen, and Z is nitro.

5. The compound of claim 4 wherein Y is chlorine.

6. A compound of claim 1 selected from 1'-(aminocarbonyl)ethyl 5-(2-chloro-4-trifluoromethylphenoxy)-2-nitrobenzoate, 1'-(N,N-dimethylaminocarbonyl)ethyl 5-(2-chloro-4-trifluoromethylphenoxy)-2-nitrobenzoate, or 1'-(N-isopropylaminocarbonyl)ethyl 5-(2-chloro-4-trifluoromethylphenoxy)-2-nitrobenzoate.

7. A herbicidal composition containing an inert carrier and a herbicidal effective amount of a compound or mixture of compounds defined in claim 1.

8. In a method of controlling weed growth wherein a herbicidally effective amount of a herbicide is either applied to the growth medium prior to emergence of the weeds or applied to the weeds subsequent to emergence from the growth medium wherein the improvement resides in using as the herbicide a herbicidally effective amount of a compound or mixture of compounds defined in claim 1.