Control of certain grasses with certain 5-(2-chloro-4-(trifluoromethyl)phenoxy-2-nitrobenzoic acid esters and amides

The present invention provides a method for controlling perennial johnsongrass, purple nutsedge, yellow nutsedge and quackgrass with an application of alkyl esters, alkoxycarbonylalkyl esters or alkylsulfonamide salts of 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid.

BACKGROUND OF THE INVENTION 
Herbicidal 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid and 
salts thereof, and various herbicidal derivatives of these compounds have 
been proposed including alkyl and cycloalkyl esters, alkylthio esters, 
phenyl ester, alkyl and dialkyl amido and benzoyl chlori forms. U.S. 
Patents which describe such compounds and the like include U.S. Pat. Nos. 
3,652,645; 3,784,635; 3,873,302; 3,983,168; 3,907,866; 3,798,276; 
3,928,416; and 4,063,929. The published European Patent Application 3,416 
to ICI describes various alkylsulfonamide derivatives of 
5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-nitrobenzoic acid including, 
inter alia, 5-[2-chloro-4-(trifluoromethyl) 
phenoxy]-2-nitro-N-methanesulfonyl benzamide. The published European 
Patent Application 20,052 to Rohm and Haas and the published UK Patent 
Application 2,058,055A to PPG describe various alkoxycarbonylalkyl esters 
of 5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-nitrobenzoic acid. 
According to a particular herbicidal treatment it has been proposed to 
apply sodium 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoate to 
soybean fields in post-emergence applications to control certain weeds 
such as broadleaf weeds, e.g., velvetleaf, cocklebur and morningglory. 
Accordingly, there is a need in the art to provide methods for controlling 
grass weeds such as johnsongrass. 
SUMMARY OF THE INVENTION 
The present invention provides a method for controlling grass weed selected 
from the group consisting of perennial johnsongrass, purple nutsedge, 
yellow nutsedge and quackgrass in the field under field conditions with an 
application of a herbicidally effective amount of a compound of the 
formula 
##STR1## 
where R is selected from the group consisting of: 
(i) C.sub.1 -C.sub.4 alkoxy (preferably OCH.sub.3); 
(ii) 
##STR2## 
where R.sub.1 is H or C.sub.1 -C.sub.4 alkyl and R.sub.2 is C.sub.1 
-C.sub.4 alkyl; 
(iii) 
##STR3## 
where R.sub.3 is C.sub.1 -C.sub.4 alkyl (preferably CH.sub.3) and M is 
alkali metal (preferably Na) or (substituted or unsubstituted) ammonium; 
and 
(IV) NHSO.sub.2 R.sub.3. 
Examples of such (substituted or unsubstituted) ammonium groups may be 
represented as follows when M is of the formula 
##STR4## 
where R.sub.4, R.sub.5, R.sub.6 and R.sub.7 are the same or different and 
are selected from the group consisting of H and C.sub.1 -C.sub.6 
(substituted or unsubstituted) alkyl. 
Particular R groups according to formula I include OCH.sub.3, OCH.sub.2 
COOC.sub.2 H.sub.5, OCH(CH.sub.3)COOCH.sub.3, OCH.sub.2 COOH.sub.3, 
OCH(CH.sub.3)COOC.sub.2 H.sub.5 and N(Na)SO.sub.2 CH.sub.3. 
The compounds of formula (I) which are alkoxycarbonylalkyl esters of 
5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid may be 
prepared by techniques known by those of ordinary skill in the art (Note 
the aforementioned published European Patent Application 20,052 and the 
published UK Patent Application 2,058,055A). 
For example, the compound, ethoxycarbonyl methyl 
5-[2-chloro-4-(trifluoromethyl)-phenoxy]-2-nitro-benzoate, has been 
prepared as follows: To a stirred solution of ethyl glycolate (83.7 g, 0.8 
mole) and 5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-nitrobenzoyl chloride 
(306 g, 0.8 mole) in toluene (800 ml) cooled in an ice bath was added 
triethylamine (80.8 g, 0.8 mole) dropwise. The exotherm was controlled 
below 35.degree. C. during addition. The reaction temperature was raised 
to 62.degree. C. and held for five hours. After cooling the precipitate 
was filtered. The toluene solution was then washed with 5% sodium 
hydroxide solution followed by saturated sodium chloride solution. The 
dried toluene solution was stripped on a rotary evaporator to give 225 g 
of a brown oil. Vapor phase chromatographic-mass spectral analysis showed 
that in addition to the desired product there was about 1% of ethyl 
5-[2-chloro-4-(trifluoro-methyl)phenoxy]-2-nitrobenzoate and about 9% of 
ethoxycarbonyl-methoxycarbonylmethyl 5-[2 -chloro-4-(trifluoromethyl) 
phenoxy]-2-nitrobenzoate. The product can be further purified by 
crystallization from hexane to give an off-white solid. 
m.p. 58.degree.-59.degree. C. 
I.R. (Neat): C=0, 1745 and 1760 cm.sup.-1 
NMR (CDCl.sub.3): triplet 1.30 ppm (3H, J=7.2 Hz); quartet 4.33 ppm (2H, 
J=7.2 Hz); singlet 4.92 (2H), complex multiplet 7.1-8.1 ppm (5H) and 
doublet 8.21 ppm (1H, J=9.0 Hz). 
A number of compounds of this formula I may alternatively be prepared by 
displacement of an active halogen (e.g. Haloalkyl X) with the salf of an 
acid 
##STR5## 
The following is an example of such a procedure. 
To a stirred solution of 85% potassium hydroxide (0.66 g, 0.01 mole) in 
ethanol (25 ml) was added 5-[2-chloro-4-(trifluoromethyl) 
phenoxy]-2-nitrobenzoic acid. To this mixture was then added ethyl 
bromoacetate (1.67 g, 0.01 mole) at 30.degree. C. The temperature was 
raised to 70.degree. C. and maintained for 18 hours. The cooled solution 
was poured into water and the resulting oil solidified to an off-white 
solid which was filtered and dried to give 3.85 g (86% yield), m.p. 
55.degree.-6.degree. C. 
A still further alternative synthesis is shown by the following reaction 
scheme: 
##STR6## 
The compounds of formula I, which are alkylsulfonamides, may be formed by 
the reaction of the corresponding compound of formula I with an 
appropriate base (e.g., by titration of this free acid with NaOH). This 
free acid form of the compound of formula I may be formed by any suitable 
techniques known by those skilled in the act. For example, the procedures 
discussed in the aforementioned ICI published European Patent Application 
3,416 may be followed. However, when 
EQU H.sub.2 NSO.sub.2 CH.sub.3 
is reacted with 
##STR7## 
this reaction preferably takes place at elevated temperatures (e.g. at 
about 150.degree. C.) in the absence of a free acid acceptor such as 
pyridine. 
The compounds of formula I can be applied in various ways to achieve 
herbicidal action. They can be applied per se, but preferably, may be 
applied as the toxic components in pesticidal compositions of the compound 
and a carrier. These compositions may be applied directly to the soil and 
often 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 emulsifying agents, binding 
agents, gases compressed to the liquid state, odorants, stabilizers, and 
the like. A wide variety of liquid and solid carriers can be used. 
Non-limiting examples of solid carriers include talc, bentonite, 
diatomaceous earth, pyropyllite, fullers earth, gypsum, flours derived 
from cotton seeds and nut shells, and various natural and synthetic clays 
having a pH not exceeding about 9.5. Non-limiting examples of liquid 
carriers include water, organic solvents such as alcohols, ketones, light 
oils, and medium oils and vegetable oils such as cottonseed oil. In 
practice, herbicidal application is measured in terms of pounds of 
herbicide applied per acre. The compounds of this invention are effective 
herbicides when applied in herbicidal amounts, e.g., at rates, depending 
upon climate and soil type, between about 0.03 pound and about 10 pounds 
per acre. More particularly, the sodium salt of 
5-[2-chloro-4-(trifluoromethyl) phenoxy]- 2-nitro-N-methanesulfomyl 
benzomide may preferably be applied at rates of from about 1/4 to about 5 
lbs./acre, more preferably, from about 1/2 to about 2 lbs/acre. 
The compounds of formula I may be particularly advantageous when used to 
control perennial johnsongrass, purple nutsedge, yellow nutsedge and 
quackgrass in fields of crops which are relatively tolerant to these 
compounds. For instance, soybeans are relatively tolerant to these 
compounds, particularly depending upon the manner in which these compounds 
are applied. Accordingly, methyl 
5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrolenzoate is preferably 
applied to soybean fields to control the above-specified weeds in a 
pre-plant incorporation application, and alkoxycarbonylalkyl (e.g., 
ethoxycarbonylmethyl) 5-[2-chloro-4-(trifluoromethyl) 
pheroxy]-2-nitrobenzoate is preferably applied to soybean fields to 
control the above-specified weeds in either a pre-plant incorporation 
application or a pre-emergence application. The salts of 
5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-nitro-N-methanesulfonyl 
benzamide, being highly selective towards soybeans, may be applied to 
soybean fields to control the above-specified weeds in pre-plant 
incorporation applications, pre-emergence applications or post-emergence 
applications. In such pre- and post-emergence applications the salts of 
5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-nitro-N-methanesulfonyl 
benzamide may be applied, e.g., at rates from about 1/2 to about 2 
lb./acre.

EXAMPLE 
To a field test plot containing perennial johnsongrass was applied: 
(1) methyl 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoate at 0.75 
lb/acre in a pre-plant incorporation application; 
(2) ethoxycarbonylmethyl 5-[2-chloro-4-(trifluoromethyl) 
phenoxy]-2-nitrobenzoate at 1.5 lb/acre in a pre-plant incorporation 
application; and 
(3) ethoxycarbonylmethyl 5-[2-chloro-4-(trifluoromethyl) 
phenoxy]-2-nitrobenzoate at 0.75 lb/acre in a pre-emergence application. 
Perennial johnsongrass was controlled in each of these applications. It is 
noted that the johnsongrass had sprouted from the rhizome and was 6-8" 
tall before evidence of a herbicidal effect was noticed. It is further 
noted that these tests indicated that the compounds of this example 
appeared to have a systemic action on johnsongrass.