4-Methylthio-2-trifluoromethylmethane-sulfonanilide and derivatives thereof

2-(Trifluoromethyl)methanesulfonanilides substituted in the para position by methylthio, methylsulfinyl or methylsulfonyl groups and horticulturally acceptable salts thereof and composition containing these compounds are useful herbicides.

This invention relates to 2-(trifluoromethyl)methanesulfonanilides 
substitued in the para position by methylthio, methylsulfinyl or 
methylsulfonyl groups and horticulturally acceptable salts thereof and 
composition containing these compounds. The compounds of the invention are 
active herbicidal agents and, in many cases, are also active plant growth 
modifying agents. Specifically, the invention includes the compounds 
4-methylthio-2-trifluoromethylmethanesulfonanilide, 
4-methylsulfinyl-2-trifluoromethylmethanesulfonanilide and 
4-methylsulfonyl-2-trifluoromethylmethanesulfonanilide and agriculturally 
acceptable salts thereof. The invention also relates to herbicidal 
formulations containing said compounds and to the use of the compounds to 
regulate and control the growth of higher plants. Methods for preparing 
the compounds and intermediates in their preparation are also included. 
BACKGROUND OF THE INVENTION 
Several classes of haloalkylsulfonamido-substituted aromatic compounds have 
been known heretofore, as have certain uses for these compounds. Thus, 
U.S. Pat. No. 3,639,474 discloses trifluoromethanesulfonanilides, 
including such compounds with trifluoromethyl, methylthio, methylsulfinyl 
and methylsulfonyl substituents, to be useful as herbicides. French Pat. 
No. 1,188,591 includes disclosures of two classes of compounds, i.e. 
haloalkylsulfonanilides and haloalkylsulfonamidodiphenyl compounds in 
which the rings are bonded directly or are linked by various groups 
including sulfonyl, sulfinyl and thio groups. The areas of utility 
disclosed by the French patent include activity against textile material 
parasites as well as antibacterial and anti-mildew activity. Herbicidal 
activity is not disclosed in that patent however. British Patent 971,219 
discloses alkanesulfonanilides containing both chlorine and nitro ring 
substituents to have herbicidal activity. 
The present invention provides a limited class of novel compounds which 
contain a non-fluorinated methanesulfonamido group and which have a unique 
and particularly valuable spectrum of activity. They are especially 
effective in controlling established rhizomatous Johnson Grass (Sorghum 
halepense (L. Pers.)). This is of significance since while seedling 
Johnson Grass is susceptible to several commercial herbicides, rhizomatous 
Johnson Grass is not controlled effectively at application rates of such 
materials that are tolerated by crops. It is unexpected to find such 
effective control of established rhizomatous Johnson Grass in the 
compounds of the invention. The compounds of the invention have also been 
found to be particularly effective in controlling nutsedge (for example 
Cyperus esculentus) species. 
DETAILED DESCRIPTION OF THE INVENTION 
This invention relates to compounds of the formula 
##STR1## 
wherein "n" is zero, one or two and agriculturally acceptable salts 
thereof. 
The invention also relates to compositions for killing and modifying the 
growth of higher plants consisting essentially of a compound of the 
invention dispersed in an extending medium. 
The invention also relates to the use of the compounds of the invention to 
modify the growth of higher plants, and to kill higher plants. 
This invention also relates to processes for the preparation of the 
compounds of the invention. 
The acid-form compounds of the invention are acidic, i.e. the amido 
hydrogen is acidic. Consequently, they form salts, i.e. compounds of the 
above formula wherein H is replaced by an agriculturally acceptable 
cation. These are generally metal, ammonium, and organic amine salts and 
can be prepared by treating the acid form compound with a 
stoichiometrically equivalent amount of an appropriate base under mild 
conditions. Among the metal salts of the invention are alkali metal (e.g. 
lithium, sodium and potassium), alkaline earth metal (e.g. barium, calcium 
and magnesium) and heavy metal (e.g. zinc and iron) salts as well as other 
metal salts such as aluminum. Appropriate bases for use in preparing the 
metal salts include metal oxides, hydroxides, carbonates, bicarbonates and 
alkoxides. Some salts are also prepared by cation exchange reaction (by 
reacting a salt of the invention with an organic or inorganic salt in a 
cation exchange reaction). The organic amine salts include the salts of 
aliphatic (e.g. alkyl), aromatic and heterocyclic amines, as well as those 
having a mixture of these types of structures. The amines useful in 
preparing the salts of the invention can be primary, seondary or tertiary 
and preferably contain not more than 20 carbon atoms. Such amines include, 
for example, morpholine, methyl cyclohexylamine, glucosamine, amines 
derived from fatty acids, etc. The amine and ammonium salts can be 
prepared by reacting the acid form with the appropriate organic base or 
ammonium hydroxide. Any of the salts of the types set out above are 
agriculturally acceptable, the one chosen depending upon the particular 
use and upon the economics of the situation. Of particular utility are the 
alkali metal, alkaline earth, ammonium and amine salts. 
The salts of the invention are frequently formed by reacting the precursors 
in aqueous solution. This solution can be evaporated to obtain the salt of 
the compound, usually as a dry powder. In some cases, it may be more 
convenient to use a non-aqueous solvent such as alcohols, acetone, etc. 
The resulting solution is then treated to remove the solvent, for example, 
by evaporation under reduced pressure. Since many of the salts are water 
soluble, they are often used in the form of aqueous solutions. 
The compounds of the invention can be prepared according to the reaction 
sequences outlined below. 
##STR2## 
The reaction of step 1 is carried out by heating 
5-chloro-2-nitrobenzotrifluoride and a slight excess of methanethiol in a 
suitable inert solvent in the presence of the appropriate amount of base. 
The inert solvent is one in which the reactants are soluble such as a 
lower alkanol, e.g. ethanol. The base is a strong organic or inorganic 
base. Suitable organic bases are tertiary amines such as 
N,N-dimethylaniline, triethylamine, pyridine, alkoxides such as sodium 
ethoxide and the like. Suitable inorganic bases are alkali metal 
hydroxides, such as sodium and potassium hydroxides, calcium hydride and 
the like. The product is isolated by conventional methods. 
The reaction of step 2 is a reduction of the nitro-group of the novel 
intermediate 2-nitro-5-methylthiobenzotrifluoride (II). Chemical or 
catalytic methods well known to the art are successful. Raney nickel is 
one suitable catalyst for the reduction. The product is isolated by 
conventional methods. 
The reaction of step 3 is the bis(methylsulfonylation) of the novel 
intermediate 4-methythio-2-trifluoromethylaniline (III) with two or more 
moles of methanesulfonylchloride in the presence of excess base. The 
product obtained is the novel intermediate (IV). Alternatively step 3a is 
the mono(methylsulfonylation) of III with one equivalent of 
methanesulfonylchloride in the presence of one equivalent of base in an 
inert solvent. Suitable bases for the reactions of steps 3 and 3a are 
organic or inorganic bases such as pyridine, triethylamine, 
N,N-dimethylaniline and substituted pyridines, and the like. 
Step 4 is partial hydrolysis of the novel intermediate (IV). This is a high 
yield base hydrolysis reaction using a strong base such as potassium 
hydroxide in methanol. 
Steps 5 and 6 are both carried out using conventional oxidation methods 
such as hydrogen peroxide in acetic acid, sodium metaperiodate and the 
like. Step 5 requires equimolar amounts of peroxide and reactant, while 
step 6 utilizes two moles (or slight excess) of oxidizing agent per mole 
of reactant. 
The herbicidal activity of the compounds of the invention has been 
determined using screening tests against greenhouse plantings. Both pre- 
and post-emergence activity are determined in a direct screen against 
selected weed species. The following weeds are examples of weeds which are 
used for these tests. 
Grasses 
Giant foxtail (Setaria faberii) 
Barnyard grass (Echinochloa crusgalli) 
Crabgrass (Digitaria ischaemum) 
Quackgrass (Agopyron repens) 
Yellow Nutsedge (Cyperus esculentus) 
Broadleaves 
Pigweed (Amaranthus retroflexus) 
Purslane (Portulaca oleracea) 
Wild Mustard (Brassica kaber) 
Wild Morning Glory (Convolvulus arvensis) 
The test chemicals are dissolved in a small amount of acetone or other 
suitable solvent and then diluted with water to give a concentration of 
2000 ppm. From this concentration aliquots are diluted to give a final 
concentration of 500 ppm. Eighty ml. of this solution are added to a 
6-inch pot containing the weed seeds to give a concentration equivalent to 
20 lb./acre. Use of 20 ml. of said solution gives a concentration equal to 
5 lb./acre. All subsequent waterings are made from the bottom. Two pots 
are used per treatment. Data are taken two to three weeks after treatment 
and recorded as percent pre-emergence kill for each species compared to 
the untreated controls. 
To assess post-emergence activity, the same weed mixtures are allowed to 
grow from two to three weeks until the grasses are approximately 1 to 3 
inches and the broadleaves 1 to 11/2 inches tall. They are sprayed for 
approximately 10 seconds or until good wetting of the leaf surfaces occurs 
with a 2000 ppm solution as described above. 
Data are taken two to three weeks after treatment and recorded as percent 
kill for each species compared to the untreated controls. 
The compounds of this invention are broadly active as herbicides. The 
mechanism(s) by which this herbicidal activity is effected is not 
presently known. However, many of the compounds of this invention also 
show various types of plant growth modifying activity. Plant growth 
modification as defined herein consists of all deviations from natural 
development, for example, defoliation, stimulation, stunting, retardation, 
dessication, tillering, dwarfing, regulation and the like. This plant 
growth modifying activity is generally observed as the compounds of the 
invention begin to interfere with certain processes within the plant. If 
these processes are essential, the plant will die if treated with a 
sufficient dose of the compound. However, the type of growth modifying 
activity observed varies among types of plants. 
As noted previously, the compounds of the invention have been found to be 
particularly effective in controlling established rhizomatous Johnson 
Grass (Sorghum halepense (L. Pers.)) and nutsedge (for example Cyperus 
esculentus) species. The control of rhizomatous Johnson Grass especially 
important since it is not controlled effectively at an application rate 
that is tolerant to crops by commercially available herbicides (although 
seedling Johnson Grass is susceptible to several commercial herbicides). 
For application to plants, the compounds can be finely divided and 
suspended in any of the usual aqueous media. In addition, spreading 
agents, wetting agents, sticking agents or other adjuvants can be added as 
desired. Dry powders, as such or diluted with inert materials such as 
diatomaceous earth, can likewise be used as dusts for this purpose. The 
preparations are coated on the plants or the ground is covered when 
pre-emergence control is desired. Application is made with the usual 
sprayers, dust guns and the like. Application rates are at 0.5 to 20 
lbs./acre in general, but may be increased or reduced according to 
individual circumstances of use. 
Since certain compounds of the invention are particularly active against 
Johnson grass, it is particularly advantageous to combine them with other 
known herbicides to broaden or maximize the weed spectrum controlled by 
herbicidal compositions of this invention or to better control a weed not 
well controlled by specific compounds of the invention. Among these other 
known herbicides are phenoxy herbicides, e.g. 2,4-D; 2,4,5-T, Silvex and 
the like, carbamate herbicides, thiocarbamate and dithiocarbamate 
herbicides, substituted urea herbicides, e.g. diuron, monuron, and the 
like, triazine herbicides, e.g. simazine and atrazine, chloroacetamide and 
chlorinated aliphatic acid herbicides, chlorinated benzoic and 
phenylacetic acid herbicides such as chloroamben and other herbicides such 
as trifluralin, paraquat, nitralin and the like. Furthermore, herbicidal 
compositions containing compounds of the invention may contain, in 
addition, nematicides, fungicides, insecticides, fertilizers, trace 
metals, soil conditioners, other plant growth regulators and the like. 
Such combinations are clearly envisioned in this invention. 
The following examples are given for the purpose of further illustrating 
the procedures of the present invention, but are not intended, in any way, 
to be limiting on the scope of the invention.

EXAMPLE 1 
2-Nitro-5-methylthiobenzotrifluoride 
The sodium salt of methanethiol is formed by stirring a solution of 
methanethiol (100 g, 2.0 mole plus a slight excess), sodium hydroxide (80 
g, 2.0 mole) and ethanol (2 l.) under nitrogen at 0.degree.-5.degree. C. 
for one hour. To this solution is rapidly added 
5-chloro-2-nitrobenzotrifluoride (451.2 g, 2.0 mole). The solution is 
allowed to warm to room temperature overnight and then refluxed four 
hours, cooled, filtered and the solvent evaporated off under reduced 
pressure. The resulting oil is poured into cold water (1 l.), extracted 
with methylene chloride, dried over magnesium sulfate and the solvent 
evaporated under reduced pressure to afford a yellow solid. 
Recrystallization from hexane affords a product having a melting point of 
47.degree.-50.degree. C. 
Analysis: %C; %H; %N; Calculated for C.sub.8 H.sub.6 F.sub.3 NO.sub.2 S: 
40.5; 2.5; 5.9; Found: 40.4; 2.5; 5.6. 
EXAMPLE 2 
4-Methylthio-2-trifluoromethylaniline 
2-Nitro-5-methylthiobenzotrifluoride (190 g, 0.85 mole) in ethanol (1 l.) 
is reduced over Raney nickel at about 45 psi of hydrogen gas. After 
hydrogen uptake is complete the catalyst is deactivated with elemental 
sulfur, the mixture is filtered, and the filtrate evaporated under reduced 
pressure to afford the desired product as an oil. IR 2.9.mu. (strong NH 
band). 
EXAMPLE 3 
N-Methylsulfonyl-4-methylthio-2-trifluoromethylmethanesulfonanilide 
Methanesulfonyl chloride (21.8 g, 0.19 mole) is added dropwise to a cold 
(0.degree.-10.degree. C.) stirred solution of 
4-methylthio-2-trifluoromethylaniline prepared according to Example 2 
(15.8 g., 0.076 mole) in pyridine (48 g, 0.61 mole). The solution is 
stirred at room temperature overnight, poured into ice water (80 ml) and 
concentrated hydrochloric acid (20 ml) and the resulting solid dissolved 
in methylene chloride, dried over magnesium sulfate, and the solvent 
evaporated under reduced pressure. The product is recrystallized from a 
hexane-methylene chloride mixture to give a white solid, m.p. 
147.degree.-154.degree. C. 
Analysis: %C; %H; %N; Calculated for C.sub.10 H.sub.12 F.sub.3 NO.sub.4 
S.sub.3 : 33.1; 3.3; 3.9; Found: 32.9; 3.3; 3.8. 
EXAMPLE 4 
4-Methylthio-2-trifluoromethylmethanesulfonanilide 
A mixture of 
N-methylsulfonyl-4-methylthio-2-trifluoromethylmethanesulfonanilide (545 
g, 1.5 mole), 85% potassium hydroxide (297 g., 4.5 mole) and methanol (2 
l.) is stirred overnight at room temperature. The solvent is evaporated 
under reduced pressure and the resulting solid dissolved in hot water. The 
solution is filtered and the filtrate acidified with dilute hydrochloric 
acid. Product is isolated by extraction with methylene chloride, drying 
over magnesium sulfate followed by evaporation of the solvent under 
reduced pressure to yield a beige solid, m.p. 82.degree.-85.degree. C. 
Analysis: %C; %H; %N; Calculated for C.sub.9 H.sub.10 F.sub.3 NO.sub.2 
S.sub.2 : 37.9; 3.5; 4.9; Found: 38.0; 3.7; 4.9. 
EXAMPLE 5 
4-Methylsulfinyl-2-trifluoromethylmethanesulfonanilide 
To a cold (0.degree.-5.degree. C.) stirred mixture of 
4-methylthio-2-trifluoromethylmethanesulfonanilide (118.5 g, 0.42 mole) in 
glacial acetic acid (470 ml) is added 30% hydrogen peroxide (47.3 g, 0.42 
mole). The solution is stirred at 0.degree.-5.degree. C. for six hours, 
allowed to warm to room temperature overnight, diluted with water (1000 
ml) and extracted with methylene chloride. The extract is further washed 
with water, dried over magnesium sulfate and the product precipitated with 
hexane as a white solid, m.p. 123.degree.-125.degree. C. 
Analysis: %C; %H; %N; Calculated for C.sub.9 H.sub.10 F.sub.3 NO.sub.3 
S.sub.2 : 35.9; 3.3; 4.7; Found: 35.9; 3.4; 4.6. 
EXAMPLE 6 
4-Methylsulfonyl-2-trifluoromethylmethanesulfonanilide 
To a warm (60.degree. C.) stirred solution of 
4-methylthio-2-trifluoromethylmethanesulfonanilide (105.6 g, 0.37 mole) in 
glacial acetic acid (350 ml), 30% hydrogen peroxide (170 g, 1.49 mole) is 
added dropwise at such a rate that refluxing is maintained with little or 
no external heating. The solution is heated at reflux for an additional 2 
hours, water (250 ml) is added, and the mixture is cooled. The precipitate 
is collected by filtration, washed with water, and dried to give a white 
solid, m.p. 177.degree.-181.degree. C. 
Analysis: %C; %H; %N; Calculated for C.sub.9 H.sub.10 F.sub.3 NO.sub.4 
S.sub.2 : 34.1; 3.2; 4.4; Found: 34.1; 3.2; 4.4.