GB2041369A - 4-Phenylthioalkanesulfonanilides and Derivatives thereof Useful as Plant Growth Modifiers or Herbicides - Google Patents

Abstract

Compounds of the formula <IMAGE> wherein R is alkyl containing from 1 to 4 carbon atoms or monohalomethyl, A is halogen or CF3, B is hydrogen or halogen and n is 0-2, provided that when A is CF3 and B is hydrogen, R cannot be methyl, or agriculturally acceptable salts thereof are active as plant growth modifiers, e.g. herbicides, and may be obtained by partial hydrolysis of the corresponding bis(sulfonyl) compounds in which n is zero, followed by oxidation when compounds in which n is 1 or 2 are required.

Description

SPECIFICATION 4-PhenylthioalkanesuIfonanilides and Derivatives Thereof This invention relates to alkanesulfonanilides substituted in the para position by a phenylthio, phenylsulfinyl or phenylsulfonyl group, and additionally substituted by halogen and/or trifluoromethyl, and to agriculturally acceptable salts thereof. The compounds of the invention are active herbicidal agents and plant growth modifying agents. 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.

More particularly, the invention relates to compounds of the formula

wherein R is an alkyl group containing from 1 to 4 carbon atoms or monohalomethyl(chloromethyl, bromomethyl, fluoromethyl or iodomethyl), A is halogen or CF3, B is hydrogen or halogen and n is 0--2, provided than when A is CF3 and B is hydrogen, R cannot be methyl, and agriculturally acceptable salts thereof, to compositions for killing and modifying the growth of higher plants consisting essentially of a compound of the invention dispersed in an extending medium, to the use of the compounds of the invention to modify the growth of higher plants and to kill higher plants, and to processes for the preparation of the compounds of the invention.

The compounds of formula /, above, can 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 an appropriate base under mild conditions. Among the metal salts of the invention are alkali 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, secondary 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 nonaqueous solvent such as alcohols, acetone, etc. The resulting solution is then treated to remove the solvent, for example, by evaporation under reduced pressure.

The compounds of the invention can be prepared according to the reaction sequences outlined in Methods 1 and 2 below.

Method 1

Step (1) of Method 1 is carried out by heating equimolar amounts of a substituted 4chloronitrobenzene and benzenethiol in a suitable solvent in the presence of an equimolar amount of base. The solvent is one in which the reactants are soluble such as a lower alkanol (e.g. ethanol or methanol), dimethyl sulfoxide or dimethyl formamide. The base is an 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 hydroxide, 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 intermediate substituted 4phenylthionitrobenzene. Chemicai or catalytic methods well known to the art are successful. Raney nickel is one suitable catalyst for the reduction. Product is isolated by conventional methods.

The reaction of step (3) is the sulfonylation of the intermediate substituted 4-phenylthioaniline with a sulfonyl chloride in the presence of a base. If one to two equivalents of sulfonyl chloride are used, a mixture of mono- and bis-(sulfonylated) product can be obtained which may be used in step (4).

More of the bis(sulfonylated) product can be formed if two or more equivalents of sulfonyl chloride are reacted in the presence of a strong base.

Suitable bases for the reaction of step (3) are organic and inorganic bases such as pyridine, triethylamine, dimethylcyclohexylamine, and substituted pyridines, and the like. Liquid bases in excess can be used to eliminate the need for a solvent. Stronger bases promote the formation of bis(sulfonylated) product over mono(sulfonylation).

Step (4) is partial hydrolysis of the intermediate bis(sulfonyl) compounds. This is a high yield reaction. Basic hydrolysis using a strong base, such as potassium hydroxide in ethanol is used.

Alternatively, the precursor of step (3) can be converted directly to the product of step (4) by means of a mono(sulfonylation) reaction using one or more equivalents of sulfonyl chloride and one or more equivalents of base. This reaction is favored by a base weaker than pyridine, such as 3-bromopyridine.

Step (5) is carried out using conventional oxidation methods such as hydrogen peroxide in acetic acid, sodium metaperiodate and the like. The sulfoxide compound (n=1 ) is produced when equimolar amounts of the oxidizing agent and the reactant are utilized, whereas the sulfone (n=2) is prepared directly utilizing 2 mole (or a slight excess) of the oxidizing agent per mole of the reactant.

Method 2

The reaction of step (1) of Method 2 involves the formation of the substituted 4-thiocyanoaniline from the corresponding aniline, generally by conventional means.

The reaction of step (2) involves the formation of the substituted 4-phenylthioaniline directly from the corresponding 4-thiocyanoaniiine. This reaction involves the formation of a sodium mercaptide from the thiocyano moiety by reacting it with sodium sulfide in aqueous dimethylformamide followed by its arylation (i.e. by heating the aqueous dimethylformamide solution with cuprous oxide and an aryl halide, preferably iodobenzene). This product is identical to the precursor of step (3) of Method 1, and can be converted to the compounds of the invention in identical fashion.

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 facer!) Barnyardgrass {echinochloa crus-gallil Crabgrass (Digitaria ischaemum} Quackgrass (Agropyron repents) Yellow nutsedge (Cyperus esculentus) Broadleaves: Pigweed ZAmaranthus retroflexus) Purslane {Portulaca o/eracea) Wild mustard {Brassica saber) Field bindweed {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 Ib/acre. Use of 20 ml. of said solution gives a concentration equal to 5 Ib/acre. All subsequent waterings are made from the bottom. Two pots are used per treatment. Data are taken 2 to 3 weeks after treatment and recorded as percent preemergence 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 1-1/2 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, the compounds of this invention alsd show various types of plant growth modifying activity. Plant growth modification as defined herein is any deviation from natural development, for example, defoliation, stimulation, stunting, retardation, desiccation, 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.

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 usuai sprayers, dust guns and the like. Application rates are at 0.5 to 20 Ibs/acre in general, but may be increased or reduced according to individual circumstances of use.

The compounds of the invention may be advantageously combined with other known herbicides to broaden or maximize the weed spectrum controlled by herbicides 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. 2,4D, 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, chlorinate benzoic and phenylacetic acid herbicides, 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 of finai products, intermediate compounds, and their preparation are given for the purpose of further illustrating the present invention but are not intended, in any way, to be limiting on the scope thereof. All parts are given by weight unless otherwise specifically noted.

Example 1 2-Nitro-5-phenylthiobenzotrifluoride A solution of 2-nitro-5-chlorobenzotrifluoride (28.8 g., 0.15 mole), benzenethiol (16.6 g., 0.15 mole) and ethanol (1 50 ml.) is heated to its reflux temperature under nitrogen. To this solution is slowly added a solution of sodium hydroxide (6 g., 0.15 mole) and water (7 ml.) at such a rate that refluxing continues with no external heating. The solution is then heated at its reflux temperature for an additional two hours, filtered hot and the filtrate cooled. The resulting precipitate is collected by filtration and recrystallized from hexane to afford a yellow solid, m.p. 65-670C.

Analysis Calculated for C,3H8F3NO2S: C 52.2; H 2.7; N 4.7 Found: C 52.2; H 2.6; N 4.7 The following compound can be prepared utilizing the same general method: 2-chloro-4-phenylthionitrobenzene, a solid.

Example 2 4-Phenylthio-2-trifluoromethylaniline 2-Nitro-5-phenylthiobenzotrifluoride (25.6 g., 0.86 mole) in ethanol (500 ml.) is reduced over Raney nickel at about 45 psi of hydrogen gas. After hydrogen uptake is complete the mixture is deactivated with elemental sulfur, filtered, and the filtrate evaporated under reduced pressure to afford product as an oil. The infrared spectrum shows an absorption at 2.9,u (strong NH band). The product crystallizes on standing to give a solid, m.p. 63--66.50C.

The following compounds can be prepared utilizing the same general method: 2-chloro-4-phenylthioaniline, a solid.

Example 3 2-Bromo-4-phenylthioaniline A solution of 2-bromo-4-thiocyanoaniline (91.6 g., 0.4 mole) and dimethylformamide is added dropwise to a solution of sodium sulfide (0.48 mole) and water, under nitrogen, and the resulting solution is heated at 500C. for one hour. Cuprous oxide (34.33 g., 0.24 mole) and iodobenzene (97.9 g., 0.48 mole) are added and the mixture is heated at a heating bath temperature of 150 C. for 4.5 hours. The reaction is quenched with water, methylene chloride is added and the resulting mixture is filtered through filter aid to remove suspended solids. The aqueous and organic layers are separated, and the aqueous layer is extracted three times with methylene chloride. The methylene chloride extracts are combined, washed with water and dried.Removal of the drying agent and methylene chloride gives the desired product, of which a purified sample melts at 61-630C.

Analysis Calculated for C,2H,OBrNS: C 51.44; H 3.6; N 5.0 Found: C 51.9; H 3.6; N 5.0 The following compounds can be prepared utilizing the same general procedure: 2-chloro-4-phenylthioaniline, a solid.

2-fluoro-4-phenylthioaniline, a solid.

2,3-dichloro-4-phenylthioaniline, a solid.

2,5-dichloro-4-phenylthioaniline, a solid.

Example 4 N-ChlornmethylsulfonylA-phenylthio-2-trifl uoromethylchloromethanesulfonanilide Chloromethanesulfonyl chloride (1 8.6 g., 0.125 mole) is added dropwise to a cold (0--5 0 C.), stirred solution of 4-phenylthio-2-trifluoromethylaniline (13.5 g., 0.05 mole) in pyridine (20 g., 0.25 mole). The solution is stirred at room temperature overnight, poured into ice water and 1 2 N hydrochloric acid with stirring to give N-chloromethylsulfonyl-4-phenylthio-2 trifluoromethylchloromethanesulfonanilide as an oil.

The following compound can be prepared utilizing the same general method: N-methylsulfonyl-2-chloro-4-phenylthiomethanesulfonanilide, a solid.

Example 5 4-Phenylthio-2-trifluoromethylchloromethanesulfonanilide A solution of N-chloromethylsulfonyl-4-phenylthio-2-trifluoromethylchloromethanesulfonanilide and 85 percent potassium hydroxide (0.15 mole) in ethanol (200 ml.) is stirred overnight at room temperature. The solvent is removed by filtration under reduced pressure, and the solid product is taken up in hot water, filtered and then acidified with dilute hydrochloric acid. The product is taken up in methylene chloride and dried. Removal of the drying agent and solvent gives an oil that crystallizes on standing. Recrystallization from methylene chloride-hexane gives a beige solid, m.p. 97-990C.

Analysis: Calculated for C,4H"CIF3N02S2: C 44.0; H 2.9; N 3.7 Found: C 44.0; H 2.9; N 3.7 The following compound can be prepared utilizing the same general method: 2-chloro-4-phenylthiomethanesulfonanilide, a solid.

Example 6 2-Bromo-4-thiocyanoaniline To a cold (0.5"C.), stirred solutio of o-bromo-aniline (20.6 g., 0.12 mole) and sodium thiocyanate (29.2 g., 0.36 mole) in methanol (300 ml.) is added dropwise a solution of bromine (19.5 0.122 mole) in methanol (75 ml.) saturated with sodium bromide. The solution is stirred for one hour following the addition of the bromine and then poured into water (2 liters) and neutralized with sodium carbonate. The resulting solid is collected, washed with water and dried, m.p. 74-790C.

The following compounds are prepared using the same general method: 2-chloro-4-thiocyanoaniline, m.p. 63-650C.

2-fluoro-4-thiocyanoaniline, m.p. 34-350C.

2,5-dichloro-4-thiocyanoaniline, m.p. 111-11 50C.

2,3-dichloro-4-thiocyanoaniline, m.p. 132-1 370C.

Example 7 2-Bromo-4-phenylthiomethanesulfonanilide Methanesulfonyl chloride (26.9 g., 0.23 mole) is added dropwise to a cold (0--50C.) solution of 2-bromo-4-phenylthioaniline (52.5 g., 0.187 mole) in 3-chloropyridine (1 63 g.), and the solution is warmed to room temperature and stirred overnight. An additional quantity of methanesulfonyl chloride (7 g.) is added, and the reaction mixture is heated at 500 C. for 24 hours. The reaction mixture is mixed with dilute hydrochloric acid and then extracted three times with methylene chloride. The methylene chloride is washed three times with water and dried. Removal of the drying agent and methylene chloride leaves the desired product in crude form.This product is leached with hexane, and the residue is chromatographed on silica gel with methylene chloride eiuant. Removal of the methylene chloride eluant by evaporation gives solid product that is recrystallized from hexane-methylene chloride, m.p.

74.5-750C.

Analysis: Calculated for C,3H12BrNO2S2: C 43.58; H 3.38; N 3.91 Found: C 43.7; H 3.4; N 3.9 The following compounds are prepared using the same general method: 2-chloro-4-phenylthiomethanesulfonanilide, m.p. 79.5-81 OC.

2-fl uoro-4-phenylthiomethanesu Ifona nilide, m.p. 1 25-12 5.50C.

The following compounds are also prepared using the same general method except utilizing chloromethanesulfonyl chloride or ethanesulfonyl chloride as appropriate: 2-bromo-4-phenylthiochloromethanesulfonanilide, m.p. 71-72.5 0C.

2-chloro-4-phenylthiochloromethanesulfonanilide, m.p. 73--740C.

2-fluoro-4-phenylthiochloromethanesulfonanilide, m.p. 83-83.50C.

2,3-dichloro-4-phenylthiochloromethanesulfonanilide, m.p. 122-1 23.5 0C.

2,5-dichloro-4-phenylthiochloromethanesulfonanilide, m.p. 144-144.5 0C.

4-phenylthio-2-trifluoromethylethanesulfonanilide, a solid.

Example 8 4-Phenylsulfinyl-2-trifluoromethylchloromethanesulfonanilide To a stirred solution of 4-phenylthio-2-trifluoromethylchloromethanesulfonanilide (2.6 g., 0.0068 mole) in glacial acetic acid (15 ml.) is added 30 percent hydrogen peroxide (0.77 g., 0.0068 mole). The solution is stirred overnight at room temperature, heated just to reflux then treated with water. The aqueous mixture if filtered, and the tan solid is washed with water and dried, m.p. 146-1 500C.

Analysis: Calculated for C,4H"CIF3NO3S2: C 42.2; H 2.8; N 3.5 Found: C 42.3; H 3.0; N 3.6 The following compounds are prepared utilizing the same general formula: 2-chloro-4-phenylsulfinylmethanesulfonanilide, m.p. 129-1 29.50C.

2-fluoro-4-phenylsulfinylmethanesulfonanilide, m.p. 121-1 22.50C.

2-bromo-4-phenylsulfinylmethanesulfonanilide, m.p. 1 38-1 38.5 0C.

2-fluoro-4-phenylsulfinylchloromethanesulfonanilide, m.p. 1 85-1 85.50C.

2-bromo-4-phenylsulfinylchloromethanesulfonanilide, m.p. 1 23.5-1 240 C.

2-chloro-4-phenylsulfinylchloromethanesulfonanilide, m.p. 142-143 0C.

4-phenylsu If inyl-2-trifluoromethylethanesu If onanilide, a solid.

Example 9 4-Phenylsulfonyl-2-trifluoromethylchloromethanesulfonanilide To a stirred solution of 4-phenylthio-2-trifluoromethylchloromethanesulfonanilide (2.6 g., 0.0068 mole) in glacial acetic acid (15 ml.) is added 30 percent hydrogen peroxide (3 g., 0.0272 mole). The solution is heated at reflux for three hours, water is added, and the mixture is cooled. The resulting precipitate is collected by filtration, washed with water and dried to give a white solid, m.p. 93-970C.

Analysis: Calculated for C,4H1,CIF3N04S2: C 40.6: H 2.7; N 3.4 Found: C 40.6; H 2.8: N 3.5 The following compounds are prepared utilizing the same general method: 2-chloro-4-phenylsulfonylmethanesulfonanilide, a solid.

2-bromo-4-phenylsulfonylmethanesulfonanilide, m.p. 1 59-1 600C.

2-bromo-4-phenylsulfonylchloromethanesulfonanilide, m.p. 1 36-1 36.5 0C.

2-fluoro-4-phenylsulfonylmethanesulfonanilide, m.p. 127.5-1 280C.

2-chloro-4-phenylsulfonylmethanesulfonanilide, m.p. 1 52-1 56 0C.

2-chloro-4-phenylsulfonylchloromethanesulfonanilide, m.p. 1 42-142.5 0C.

2-fluoro-4-phenylsulfonylchloromethanesulfonanilide, m.p. 142-1 42.5 0C.

4-phenylsulfonyl-2-trifluoromethylethanesulfonanilide, a solid.

Claims (12)

Claims

1. A compound of the formula

wherein R is alkyl containing from 1 to 4 carbon atoms or monohalomethyl, A is halogen or CF3, B is hydrogen or halogen and n is 0--2, provided that when A is CF3 and B is hydrogen, R cannot be methyl, or an agriculturally acceptable salt thereof.

2. A compound according to claim 1 wherein n is zero.

3. A compound according to claim 1 wherein n is 1.

4. A compound according to claim 1 wherein n is 2.

5. A compound according to claim 1 wherein R is-CH2Cl.

6. A compound according to claim 1 to 5 wherein A is -CF3.

7. A compound according to claim 1 to 5 wherein A is halogen.

8. A compound according to claim 1 substantially as hereinbefore described in Example 5, 7, 8, or9.

9. The use as a plant growth modifying agent of a compound according to any preceding claim.

10. A composition for modifying the growth of higher plants which comprises a compound according to any of claims 1 to 8 dispersed in an agriculturally acceptable extending medium.

11. A method of making a compound according to claim 1 , the method being substantially as hereinbefore described.

12. A method of making a compound according to claim 1, the method being substantially as hereinbefore described in Example 5, 7, 8 or 9.