CA1065890A - Substituted-phenoxy benzoic acid anhydrides - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Anhydrides of 2-nitro-5-(subsitituted-phenoxy) benzioc acids comprise a class of compounds that are highly effective pre-and post-emergence herbicides, particularly against broadleaf weeds.

Description

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~ACKGRCUND OF TH~ INVENTION
Field of the Invention ... .
This invention is concerned with certain phenoxy-benzoic acid anhydrides and their use as herbicides.

Descrip~ion of the Prior Art In United States Letters Patent No. 3,652,645, there are disclosed alkyl (Cl C5) esters o~ 2-nitro-~-(halophenoxy) benzoic acids as herbicides. Under some early-season weather conditions, especially when treated soil is splashed onto the i lower leaves, contact injury ma~ be seen. On soybeans~ this may appear as crinkling of the lower lea~es of you~g plants.
On corn, the eifect may be a discolored band on the lower blades.
Occasionally, stunting may be observed. Crop in~ury under high soil moisture le~els may not appear for 2 or 3 weeks and is tem-porary. The crop will grow out of it and yields are not adversel~
affected.
Ihe trans~erse (chlorotic) band on corn blades presents a phytotoxic appearance that is evident on the plant throughout the growing season. Such appearance, although not adversely af-fecting yield, can be offensive to many growers and could dis-suade ~hem from using an otherwise effective herbicide. It is the discovery of this invention that the anhydrides do not appear to give the phytotoxic appearance evidenced by the alkyl esteTs disclosed in U.s.(patent No. 3,652,645.

SUMNARY 0~ THE INVENTION

This invention provides herbic~dal co~pounds having the formula: -?
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o--~ (X)n ~2N~ ~ J 2 wherein X is halogen, nitro~ alkyl (Cl-C4), CF3, or CN~and n is l ~o 3.

DE I TION OF SPECIFIC EMBODIMENTS

The compounds o~ this invention are readily prepared by reacting a 2-nitro-5-substituted-phenoxybenzoyl chloride with the corresponding 2-nitro-5-substituted-phenoxybenzoic acid in the presence of a tertiary amine acceptor ~or EICl, such as tri-ethylamine and pyridine. The benzoyl chloride is prepared, in a first step by the W ~nn ether syntheæis reaction between the alkali metal (Na, K) salt of a substitu~ed phenol and a 5-halo (Cl, Br)-2-nitrobenzolc ac~d, methyl ester, or salt. The 2-nltro-5-substituted-phenoxy benzoic acid can be converted to the acyl chloride by well known methods, such as by reacting it with PCl5, PCl3, or SOCl2. The salt (Na) of the benzoic acid can be converted to the acyl halide by we~l known methods, such as by react~ng it with PCl5, PCl3, POC13, or S02Cl2. I~ the methyl ester is used in Ullm~nn ether synthesls, it is hydrolyzed to the acid, which is converted to the acyl halide as a~oredescribed.
The 5-halo-2-nitrobenzoic acid ~ readily prepared by nitrating a m-halotoluene, ~ollowed by oxidation of the methyl group by well-known procedures.
Non-limiting examples of compounds of this lnvention are:

2-Nitro-5-(2',4',6l-trichlorophenoxy)benzoic acid anhydride.
2-Nitro-5-(2',4',5'-trichlorophenoxy)benzoic acid anhydride.
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~65~90 5-(2'/6'-Dichlorophenoxy)-2-nitrobenzoic acid anhydride.
5-(2'-Chloro-4'-M uorophenoxy)-2-nitrobengoic acid anhydride.
5-(2',4'-Dichloro-6'-fluorophenoxy)-2-nitrobenzoic acid anhydrid~
5-(4'-Chloro-2'-methylphenoxy)-2-nitrobenzoic acid anhydride.
5-(2~,4'-Dichloro-6'-methylphenoxy)-2-nitrobenzoic acid an-hydride.
2-Nitro-5 (2'-nitro-4'~ trifluoromethylphenoxy)-benzoic acid anhydride.
5-(2'-cyano-4'- ~ , ç~ trifluoromethylphenoxy)-2-nitro-0 benzoic acid anhydride.

Example 1 5-(?' ,4~-DichlorophenoxyL-2-nitrobenzoic Acid Anhydride To a stirred suspension of 5-(2'~4'-dichlorophenoxy) -2-nitrobenzoic acid 3.28g, 0.01 mole) and triethylamine (l.lg, 0.011 mole) in toluene (40 ml) was added 5-(2',4'-dichlorophenoxy)-2-nitrobenzoyl chloride (3.47g, 0.01 mole). Following the dissolution of the acid~ a copious precipitate of triethylamine hydrochloride appeared. The reactio~ was heated over~ight at 100C., cooled and the 0 final portion of triethylamine hydrochloride precipitated by the addition of ether. After filtratlon, the solvent was evaporated to give the anhydride product (5.3g) with m.p. 142-144~C. 0 I.R. ("Nujol"*): ~ r// /~ 181~ (s) and 1160 (w) V C-0-C cm~l.

HERBICIDAL EFFECTIVENESS
Method Gf Propagating Test Species Crabgrass Digitaria sanguinalis Johnson grass Sor~um ~ale~ense Barnyard ~rzss Echinochloa crus-galli .. . .... . . . . . . . ..
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colorless, almost odorless,oily liquid.

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Field bindweed Convo v _us arvensis Velvet lea~ Abutilon theophrasti Turnip Brassica sp.
Cotton Gossypium hirsutum var.
DPL-smooth leàf Corn Zea Mays~ var. Golden Ban am Bean Phaseolus vul aris var.
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All crop and weed species are planted individually in 3" plastic pots containing potting soil. Four seeds of each of corn~ cotton, and snapbeans are seeded to a depth equal to the diameter o~ the seed. All other species are sur~ace seedad and sprinkled with screened soil in an a~ount suf~icient to cover the seeds. I~mediately after planting, all pots are watered by sub-irrigation in greenhouse trays. Pots ~or the pre-emergence phase are seeded one day before treatment.
Planting dates for the post-emergence phase are varied so that all the seedlings will reach the desired stage of develop-ment simultaneously. The proper stage o~ seedling development ~or treatment in the post-emergence ph~se is as ~ollows:
CTRASSES: 2 inches in height PIGWEED, BINDWEED~ 1 or 2 true leaves visible VEL~ET LEAF ~ TURNIPS above cot~ledons COTTON: ~irst true lea~ 1 inch in length, expanded cot~ledons C~RN. 3 inches-4 inches in height BE~NS: primary leaves expanded

3 growing point at primary lea~ node.
Method o~ Treatment Spray applications are made in a hood containing a movable belt and fixed spray nozzle. E`or passage through the - spray hood, one pot of each species ~pre-emergence phase) is .. . . . . . . . . . ..

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placed on the forward hal~ of a wooden flat and one pot of established plants (post-emergence phase) is placed on the rear half of the flat. Treatments are moved to the greenhouse a~ter spraying. Waterin~ during the observation period is applied onl~ by sub-irrigation.
Compounds are screened initially at a rate of appli-cation equl~ale~t to four to eight pounds per acre. Two weeks after treatment the pre and post-emergence per cent injury is visually rated. Subsequent testing c~n be carried out at 2,1 lQ and 0.5 pounds per acre.
Herbicidal testing of the compound o~ Example 1 showed the results ~% control) set forth in Table I. A blank (-) indicates not tested. The plants are tabulated using the following abbreviations:
Crabgrass CG
Johnson grass JG
Barnyard grass BG
Bindweed BW
Vel~et leaf V~
Turnip TP
Cotton CT
Corn CN
Bean BN

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CORN LEAF PHYTOTOXICITY COMPARISON TESTS

Under rainfall conditions anything more than a very light drizzle the halophenoxybenzoate ester herbicide can readily be splashed into the whorl of young (l-10 day old) corn seedlings. As the leaves grow out, the phytotoxicity is ob-served as a chlorotic transverse band across the leaf occurring at the previous point of contact in the corn whorl.
In order to demonstrate the considerably less phyto-toxic nature of the anhydrides as compared to C3 and less esters, the following greenhouse corn leaf toxicity tests were conducted.
These tests served as a screening procedure in simulating the phytoxicity which occurs under actual field use conditions.
Comparison is made with the ester because the anhydride is ~n internal ester of itself. Accordingly, its chemical and bio-logical properties (solubility, hydrolysis rate polarity, plant penetration) are most similar to the corresponding alkylester.
Test Method - Test solutions of the candidate compounds were prepared as follows:
30 ppm - 3.0 mg of compound dissolved in lO.O ml. of acetone.
This was then diluted with 90.0 ml. of distilled water to give a cloudy colloidal suspension. 0.3 ppm - l.O ml. o~ the 30 ppm solution was diluted with 99.0 ml. o~ distilled water. (This concentration level is about the average water solubility limit of the test compounds and it more likely represents the actual ~ield condition under which phytotoxicity occurs.) One drop (ca~ 0.05 ml.) o~ the test solution was then placed into the whorl of three (3) corn seedlings in the 2-3 leaf stags. me phytotoxicity ratings shown in the following Table II were taken 2 days after treatment. Examples 2-4 are ~(J165~
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reference comparisons of C3 and lower esters corresponding to the anhydride o~ Example 1.

Example 2 - Methyl 5-(2',4'-DichIorophenoxy)-2-nitrobenzoate mp 83-5C.
Example 3 - n-Propyl 5-~2',4'-Dichlorophenoxy)-2-nitrobenzoate, oil.
Example 4 - Isopro~yl 5-(2~,4'-Dichlorophenoxy)-2-nitrobenzoate, TABLE II
CORN LEAF PHYTOTOXICITY RATINGS
5-Severe, 4-Moderate, 3-Mild, 2-Slight, l-Trace~ 0-None A ueous Solution Concentration Example ~ p~ 0 3 pp,m -~-~~~

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The compounds of this in~entlon can be applied in ~arious ways to achieve herbicidal action. They can be applied per se, as solids or in vaporized form, but are pre~erably ap-plied as the toxic components in pesticidal compositions of the compound and a carrier. These compo~ition~ are pre~erablg applied directly to the soil and incorporated therewith. The compositions can be applied, as granulars or dusts; as liquid sprays, or as gas-propelled sprays and can contain, in addition to a carrier, additives such as emulsi~ying agents, binding agents, gases com-pressed to the liquid state, odorants, stabilizers, and the like.
A wide variety o~ liquid and solid carriers can be used. ~on-limiting examples of solid carriers include talc, bentonite, dia-tomaceous earth, pyrophyllite, ~ullers earth, gypsum, M ours derived from cotton seeds and nut shells, and various natural and ~589~

~y~hetic clays having a pH not exceeding about 9.5. Non-limiting examples of liquid carriers include waker, organic solvents such as alcohols, ketones, amides and esters, mineral oils such as kerosene, light oils, and medium olls and vegetable oils such as cottonseed oil.
In practice, herbicidal application is measured in terms o~ pounds of herbicide applied per acre. The co~pounds o~ this invention are e~fective herbicides when applied in herbi-cidal amounts~ i.e., at rates between about 0.2 pounds and about 10 pounds per acre.
Although the present invention has been described with pre~erred embodiments, it is to be understood that modi-~ications and variations may be resorted to, without departing ~rom the spirit and scope of this invention, as those skilled in the art will readily unders~and. Such modif~cations and variations are considered to be within the purview and scope o~ the appended cla~ms

Claims (5)

WHAT IS CLAIMED IS:

1. A compound having the formula:

wherein X is halogen, nitro, alkyl (C1-C43, CF3, or cyano,and n is 1-3.

2. A compound of Claim 1, wherein said compound is 5-(2',4'-dichlorophenoxy)-2-nitrobenzoic acid anhydride.

3. The method for controlling plant growth that comprises applying an herbicidal amount of an herbicidal com-pound having the formula:

wherein X is halogen, nitro, alkyl (C1-C4), CF3, or cyano and n is 1-3.

4. The method of Claim 3, wherein said compound is

5-(2',4'-dichlorophenoxy)-2-nitrobenzoic acid anhydride.