CH615667A5 - Process for the preparation of new N-oxides of 2-sulphinylpyridine or 2-sulphonylpyridine - Google Patents

Abstract

The compounds corresponding to the formula: <IMAGE> in which the symbols have the meaning given in Claim 1, are prepared by oxidation of the corresponding N-oxides of 2-thiopyridine, in an inert solvent, at between 0 DEG C and the boiling temperature of the solvent. These compounds have a selective herbicidal action and can be used for destroying weeds in various crops, especially flax, lucerne, cotton, soya, ground nut, tomato and tobacco.

Description

The present invention relates to a process for the preparation of new oxides of 2-sulfinylpyridine and 2-sulfonylpyridine and their use for destroying weeds.

W. Walter, "Liebig's Ann.", 695, 77 (1966), reveals a 2- (phenylmethylsulfinyl) pyridine N-oxide (also called 2-benzylsulfinylpyridine N-oxide) and a 2- (phenylmethyl N-oxide) -sulfonyl) pyridine (also known as 2-benzylsulfonyl-pyridine N-oxide), but no usefulness for these chemicals has been found.

U.S. Patent No. 3,107,994 of October 22, 1963 to Rawlings discloses certain 2- (alkenylthio) pyridine N-oxides as herbicides, while U.S. Patent No. 3,155,671 of November 3, 1964 to D'Amico discloses certain N -benzyl-2-thiopyridine oxides as herbicides.

The state of the art is further illustrated by references such as E. Shaw, "JACS", 72.4362 (1950) and U.S. Patent No. 3,772,307 dated November 13, 1973, to Kaminsky.

The N-oxide derivatives of 2-sulfinylpyridine and 2-sulfonylpyridine make it possible to obtain considerably improved results, in particular from the herbicidal point of view, compared to the various compounds according to the prior art.

Weeds compete with crops for light, moisture, nutrients and space.

Thus, weeds interfere with the production of foliage, fruit or seed from agricultural crops. The presence of weeds can also reduce the quality of the crop and reduce the effectiveness of harvesting or harvesting. Weed control is essential for maximum production in many agricultural and horticultural crops, including soybeans (Glycine max L.), peanuts (Arachis hypogaea L.), flax (Unum usitatissimum L.) and cotton (Gossypium sp.).

The compounds which can be prepared according to the invention correspond

C-H

l

[O]

in which n represents the number 1 or 2, Ri represents hydrogen or a methyl and, when Ri is hydrogen, R2 represents a 2,2-dichlorocyclopropyle, 2,2-dichloro-1-methylcyclopropyle, cyano, naphthyl group , methylnaphthyl, phenyl monosubstituted in the ortho position by a C1 or C2 alkyl, a halogen or a nitro, or phenyl substituted by 2 to 5 identical or different substituents, chosen from a C1 or C2 alkyl, a halogen, a nitro, a methoxy, ethoxy and methylenedioxy, or, when R 1 is methyl, R 2 represents a phenyl, naphthyl or phenyl group substituted with 1 to 3 identical or different substituents, chosen from C1 or C2 alkyl, halogen and nitro.

The compounds of the above formula are new.

The compounds of formula above, where R2 is a phenyl group, phenyl substituted by 1 to 3 methyl groups or by 1 to 3 halogens, and 2-naphthyl, are of particular interest.

Particular mention may be made of the compounds defined above where R 1 is hydrogen and R 2 is chosen from the group consisting of phenyl substituted by 1 to 3 methyl groups and phenyl substituted by 2 to 3 chlorine atoms.

Compounds of the class defined above where R 1 is hydrogen and R 2 is 2-methylphenyl, or a di- or trisubstituted phenyl where the substituents are methyl or chlorine,

are particularly interesting.

The compounds of the class defined above where R 1 is methyl and R 2 is chosen from the group consisting of phenyl, phenyl substituted with 1 or 2 methyl groups, monohalophenyl and 2-naphthyl are also particularly valid.

The new preferred derivatives of pyridine N-oxides which can be used as herbicides according to the present invention include the following:

s

10

15

20

25

30

35

40

45

50

55

60

65

3

615,667

2- (2,5-dimethylphenylmethylsulfonyl) pyridine N-oxide, 2- (2,4,6-trimethylphenylmethylsulfonyl) pyridine N-oxide, 2- (2,6-dichlorophenylmethylsulfonyl) pyridine N-oxide,

2- (2,4-dichlorophenylmethylsulfinyl) pyridine N-oxide,

2- (2,6-dichlorophenylmethylsulfinyl) pyridine N-oxide,

2- (1- [4-methylphenyl] ethylsulfonyl) pyridine N-oxide,

2- (2,3,6-trichlorophenylmethylsulfonyl) pyridine N-oxide, 2- (2-methylphenylmethylsulfonyl) pyridine N-oxide,

2- (1- [4-fluorophenyl] ethylsulfonyl) pyridine N-oxide,

2- (1 - [2,5-dimethylphenyl] ethylsulfonyI) pyridine N-oxide, 2- (2,3,6-trichorophenylmethylsulfinyl) pyridine N-oxide, 2- (1-phenylethylsulfonyl) pyridine N-oxide,

2- (1- [2-naphthyl] ethyl sulfonyl) pyridine N-oxide,

2- (1- [4-chlorophenyl] ethylsulfonyl) pyridine N-oxide,

2- (1- [4-bromophenyl] ethylsulfonyl) pyridine N-oxide,

2- (2,3,6-trimethylphenylmethylsulfonyl) pyridine N-oxide, and 2- (2,3,6-trimethylphenylmethylsulfinyl) pyridine N-oxide.

The particularly preferred new compounds are the following:

2- (2,5-dimethylphenylmethylsulfonyl) pyridine N-oxide 2- (2,6-dichlorophenylmethylsulfinyl) pyridine N-oxide,

2- (l- [2,5-dimethylphenyl] ethylsulfonyl) pyridine N-oxide, 2- (2,4,6-trimethylphenylmethylsulfonyl) pyridine N-oxide, 2- (l- [2-naphthyl) N-oxide ] ethylsulfonyl) pyridine,

2- (1- [4-chlorophenyl] ethyl sulfonyl) pyridine N-oxide,

2- (1- [4-methylphenyl] ethylsulfonyl) pyridine N-oxide, and 2- (2,3,6-trimethylphenylmethylsulfinyl) pyridine N-oxide.

The method according to the invention is characterized in that a 2-thiopyridine N-oxide is subjected corresponding to the action of an oxidizing agent in an inert solvent, at a temperature between 0 ° C and the temperature d solvent boiling.

The starting materials involved in the process are known (see AR Katritsky, “J. Chem. Soc.”, 191 [1957], US patents Nos. 3107994 and 3155671 indicated above, and the articles by E Shaw and W. Walter indicated above). The 2-thiopyridine N-oxides can be prepared by one of the following two methods: 1) the reaction of 2-chloropyridine N-oxide with the appropriate mercaptan in the presence of an acid acceptor, such as an alkali hydroxide - earthy; 2) reaction of the sodium salt of 2-mercaptopyridine N-oxide with an appropriate halide, preferably of the benzyl type. The yields of the two processes are comparable.

The conversion of 2-thiopyridine N-oxide into its sulfinyl or sulphonyl derivative is preferably carried out using one or two equivalents of an oxidizing agent chosen in particular from hydrogen peroxide, peracetic acid, and acids. aromatic peroxy. The ratio of peroxide and substrate varies with the desired product. A general diagram of the channels and equivalents involved is given below:

i &]

at

\ N ^ S-X

-N O

The solvents that can be used vary with the oxidant, as described in the literature (Katritsky and Lagowski, "Chemistry of the Heterocyclic N-oxides", Academic Press, 1971). Glacial acetic acid and water are preferred when using hydrogen peroxide, and a non-polar solvent such as chloroform with aromatic peroxy acids. When using water as a solvent, a catalyst consisting generally of a tungsten, vanadium, zirconium or molybdenum salt is generally used (US Pat. Nos. 3005852 of October 24, 1961, to Freyer-io muth, No. 3006962 of October 31, 1961, in Schultz, N ° 3006963 of October 31, 1961, in Bue, and British patent N ° 1335626 of October 31, 1973, in Eastman Kodak). The temperature and the duration of the reaction depend on the sulfide employed; the temperature is usually between 50 ° C and the reflux temperature in i5 cases of water and acetic acid, and between 0 and 60 ° C with chloroform.

The herbicidal efficacy pyridine N-oxide derivatives described herein are useful for both pre-emergence and post-emergence control of weeds, and are further noted for their ability to selectively destroy weeds without harming harvests. We can obtain a perfect destruction of weeds such as quackgrass (Agrópyrum repens (L.) Beauv.), Texas panicum (Panicum texanum Buckl.), Giant vulpin (Setariafaberi Herrm.), Yellow vulpin [Setaria lutescens (Weigel) Hubb.], The green vulpin [Setaria viridis (L.) Beauv.], The cockerel [Echinochloa crus-galli (L.) Beauv.] And the wild oats (Avena fatua L.) , with compounds such as 2- (2,5-dimethylphenylmethyl-sulfonyl) pyridine N-oxide, without harming crops such as flax (Unum usitatissimum L.); alfalfa (Medicago sativa L.), cotton (Gossypium sp.), soybeans [Glycine max (L.) Merr.], peanuts (Arachis hypocaea L.), tomatoes (Lycopersicon esculentum Mill.) and tobacco (Nicotiana tabacum L.).

Surprisingly, the N-oxides of 2-sulfinylpyridine and 2-sulfonylpyridine described herein are more effective as herbicides than the corresponding precursor sulfides.

The compounds can be used for the selective destruction of various broad-leaved herbs and plants including anserine (Amaranthus retroflexus L.) and purslane (Portulaca 40 oleracea L.) in various crops including flax (Iinum usitatissimum L.), alfalfa (Medicago sativa L.), cotton (Gossypium sp.), soybeans [Glycine max (L.) Merr.], peanuts (Arachis hypogaea L.), tomatoes (lycopersicon esculenum Mill.), and tobacco (Nicotiana tabacum L).

Various weeds such as panie \ Digitaria ischaemum (Schreb.) Muhl.] Can be destroyed by postemergence application of the compounds prepared according to the present invention.

The use according to the present invention of N-oxide derivatives of 2-sulfinylpyridine and 2-sulfonylpyridine can be carried out according to current farming practice. The compounds are usually applied in the form of formulations containing a vehicle and / or a surfactant. The formulation may contain more than one of the pyridine N-oxide derivatives described, if desired; other active herbicides may also be included in the formulation.

The compounds can be added, by tank mixing, to other herbicide solutions; thus, the number of different kinds of weeds destroyed in a single application "o can be increased. The formulations of the compounds may also include other herbicides so that the spectrum of weeds destroyed by spray or pellet application can be increased. The application can be made in aqueous solutions or suspensions which can be sprayed on the soil surface before the emergence of weeds and the crop, and before or after sowing the seeds of the crop. The soil can be subjected to shallow plowing (less than 75 mm), after application of the

45

615,667

4

chemical, but this is not necessary as with some preemergence herbicides. The compounds can also be applied by sowing a granular formulation on the fly before weeds and harvesting emerge.

Thus, the compound can be impregnated on inorganic or organic vehicles, finely divided or in granules, such as attapulgite, sand, vermiculite, corn on the cob, activated charcoal or other granular vehicles known in the art. . The impregnated granules can then be distributed over the ground. Furthermore, the compound can be formulated as a wettable powder, grinding it into a fine powder and mixing it with an inactive powder vehicle, to which a surface active dispersing agent has been added. Solid powdered vehicles are the various mineral silicates, for example mica, talc, pyrophyllite and clays. The wettable powder can then be dispersed in water and distributed over the soil surface or over weeds. Likewise, an emulsifiable concentrate can be prepared by dissolving the compound in a solvent such as benzene, toluene, or another aliphatic or aromatic hydrocarbon, to which a surfactant dispersing agent has been added. The emulsifiable concentrate can then be dispersed in water, and applied by spraying. Suitable surfactants are well known to those skilled in the art, and reference may be made to "McCutcheon's Detergents and Emulsifiers", 1970, Allured Publishing Corp., Ridgewood, New Jersey; or U.S. Patent Nos. 2,614,916, columns 2 to 4, and 2,547,724, columns 3 and 4, of Hoffman, for examples of suitable surfactants. The concentration of the active compound in the formulation can vary widely, for example from 1 to 95%. The concentration of the active compound in dispersions applied to the soil or to the foliage is almost invariably between 0.002% and 75%. The compound is frequently applied at 0.11 to 28 kg / ha. If used as a preemergence herbicide, the compound is applied to the soil containing the weeds and the crop (either on the soil surface or incorporated into the top 25 to 75 mm of soil).

The most suitable rate of application will depend, in each case, on factors such as the type of soil, the pH of the soil, the content of organic substances in the soil, the amount and intensity of rainfall before and after the treatment, the air and earth temperature, the light intensity and the duration of illumination per day. All of these factors can influence the effectiveness of the compounds used as herbicides. In the examples, the melting points are not corrected. In Table I, the IR symbols in the analysis column indicate that the infrared data of the compound is shown in Table II. Infrared data was obtained on a Perkin-Elmer Infracord.

Example 1:

2- (2,5-dimethylphenylmethylsulfonyl) pyridine N-oxide

To a stirred solution of 792 g (2.2 moles) of sodium salt of 2-mercaptopyridine N-oxide (40% aqueous solution), in 1400 ml of ethanol, 344 g (2.2 moles) are added. ) 2,5-dimethylbenzyl chloride, over a period of 15 min. The mixture is brought to reflux for 15 min, filtered hot and treated with 5 l of cold water. The product is removed by filtration and dried in the oven to give 533 g of 2- (2,5-dimethyl-phenylmethylthio) pyridine N-oxide. Yield 97%. Melting point: 140-142 ° C.

A. To a vigorously stirred solution of 74 g (0.3 mole) of the thio compound in 250 ml of glacial acetic acid at 45-50 ° C, 75 ml of 30% hydrogen peroxide is added over a period of 15 mins. The temperature is raised to 70 ° C and, after 30 min, it is further increased to 80-90 ° C and maintained for 3 h. The temperature of the reaction mixture is lowered to room temperature, and vigorously stirred cold water is slowly added thereto, to two to three times its volume. The pale yellow solid separates and is removed by filtration. Recrystallization from ethanol gives 74.5 g of fine crystals melting at 156-158 ° C (IR N-O 1275 cm ^ 'SO2 1140.131315 cm "1). Theoretical yield: 89%.

Analysis for Ci4.H15N03S:

Calculated: C 60.63 H 5.45 N 5.05 S 11.54%

Found: C 60.66 H 5.56 N 5.18 S 11.81%

B. To a vigorously stirred heated slurry (80-90 ° C) of 30 g (0.12 mole of the thio compound in 150 ml of water containing

10 g of acetic acid and 0.2 g of sodium tungstate dihydrate), 26 ml of 30% hydrogen peroxide are slowly added. The addition is exothermic and the temperature is maintained at 80-90 ° C for the first 14 ml, then it is allowed to rise to 95-105 ° C for the remaining 12 ml.

The initial porridge becomes fairly fluid in the state of sulfoxide,

then separates again as a sulfone. The total reaction time is of the order of 1 h. The reaction mixture is filtered, washed with water and air dried. The melting point is 150-158 ° C. The melting point when mixed with an authentic sample does not show any reduction. The yield is 32.8 g (quantitative).

Example 2:

2- (2,4,6-trimethylphenylmethylsulfonyl) pyridine N-oxide

A mixture of 17 g (0.05 mole) of sodium salt of 2-mercaptopyridine N-oxide (40% aqueous solution) and 8.5 g (0.05 mole) of a2-chloro-isodurene in 50 ml of ethanol is brought to reflux for 15 min. The volatile products are removed and the residue is extracted with 150 ml of boiling chloroform,

filtered and dried over sodium sulfate. Evaporation and trituration of the residue with a few drops of acetone induce crystallization. 11.5 g of 2- (2,4,6-trimethylphenylmethylthio) pyridine N-oxide are obtained. The melting point is 137-138 ° C. The structure is confirmed by infrared rays and nuclear magnetic resonance.

To a well-cooled solution (0-10 ° C) of 15 g (0.06 mole) of the thio compound in 200 ml of chloroform, 25 g (0.12 mole) of acid are added slowly, with vigorous stirring. meta-chloroperoxybenzoic acid (MCPBA) (85%) in 400 ml of chloroform. At the end of the addition, the temperature is allowed to increase to room temperature, and stirring is continued for 24 h. The reaction mixture is washed thoroughly with 300 ml of a saturated solution of baking soda and water, then

It is dried over magnesium sulfate. Evaporation of the chloroform and crystallization of the solid residue in methanol give 15 g (86% theoretical) of the product. The melting point is del73-175 ° C (IRN-01275cm "1, S021310,1140 cm" 1).

Analysis for C15H17NO3S:

Calculated: C 61.90 H 5.84 N 4.81%

Found: C 61.97 H 6.06 N 4.79%

Example 3:

3- (2,6-dichlorophenylmethylsulfinyl) pyridine N-oxide

A mixture of 37 g (0.1 mole) of sodium salt of 2-mercaptopyridine N-oxide (40% aqueous solution) and 19.5 g (0.1 mole) of 2,6-dichlorobenzyl chloride in 200 ml of ethanol is heated to 65-70 ° C for 30 min, cooled and filtered. The filtering bread is washed thoroughly with water and finally with 40 ml of acetone. The dry bread (25.3 g) represents a 92% yield of 2- (2,6-dichlorophenylmethylthio) pyridine N-oxide. The melting point is 240-241 ° C. The structure is confirmed by infrared and nuclear magnetic resonance.

A solution of 5.8 g (0.02 mole) of the thio compound in 100 ml of chloroform is cooled to 0-10 ° C. 4 g (0.02 mole) of MCPBA

5

10

15

20

25

30

35

40

45

50

55

60

65

5

615,667

(85%) are added with good stirring. After 24 hours at room temperature, the reaction mixture is washed thoroughly with a solution of baking soda, dried and evaporated. Crystallization from hot ethyl acetate gives 4.3 g (71% theoretical) of the product. The melting point is 135-137 ° C (IR N-O 1260 cm-1; SO 1050 cm "1).

Analysis for C12H9CI2NO2S:

Calculated: C 47.65 H 2.98 N 4.64%

Found: C 47.25 H 2.95 N 4.29%

Example 4:

2- (1- \ 4-chlorophenyl] ethylsulfonyl) pyridine N-oxide

The intermediate 2- (1- [4-chlorophenyl] ethylthio) pyridine N-oxide is prepared from 1- (4-chlorophenyl) ethyl chloride and the sodium salt of 2-mercaptopyridine N-oxide by process described in Example 2. The melting point is 106-108 ° C. The structure is confirmed by infrared rays and nuclear magnetic resonance.

The thio compound (0.02 mole) is oxidized with MCPBA (0.04 mole) and is isolated as described above in Example 2. The theoretical yield is 78%. The melting point is 188-191 ° C (IR N-O 1300 cm "1; S02 1340, 1160 cm" 1).

Analysis for C13H12CINO3S:

Calculated: C 52.44 H 4.06 N 4.71%

Found: C 52.09 H 4.11 N 4.61%

Example 5:

2- (1- [4-methylphenyl} ethylsulfonyl) pyridine N-oxide

The intermediate compound N-oxide of 2- (1- [4-methylphenyl] -ethylthio) pyridine is prepared from 1- (4-methyl-phenyl) ethyl chloride and sodium salt of 2- N-oxide mercapto-pyridine, by the process described in Example 2. The melting point is 83-85 ° C. The structure is confirmed by infrared and nuclear magnetic resonance.

The thio compound (0.02 mole) is oxidized with MCPBA (0.04 mole) and isolated as described in Example 2 (IR N — O 1275 cm "1; SOz 1315.1140 cm" 1).

Analysis for C14H15NO3S:

Calculated: C 60.35 H 5.45 N5.02%

Found: C 61.18 H 5.70 N 5.22%

Example 6:

2- (1- [2,5-dimethylphenyQethylsulfonyl) pyridine N-oxide

2- (1- [2,5-dimethylphenyl] ethylthio) pyridine N-oxide is prepared from 1- (2,5-dimethylphenyl) ethyl chloride and 2-mercaptopyridine N-oxide sodium salt by the process described in Example 2. The melting point is 118-120 ° C. The structure is confirmed by infrared and nuclear magnetic resonance.

The thio compound (0.05 mole) is oxidized with MCPBA (0.1 mole) and is isolated as described in Example 2. The theoretical yield is 83%. The melting point is 160-163 ° C. (IR N-O 1275 cm "1; SOz 1315.1145 cm" 1).

Example 7:

2- (1- \ 2-naphthy] ethylsulfonyl) pyridine N-oxide

The intermediate 2- (1- [2-naphthyl] ethylthio) pyridine N-oxide is prepared from 1- (2-naphthyl) ethyl chloride and the sodium salt of 2-mercaptopyridine N-oxide, by process described in Example 2. The melting point is 112-115 ° C. The structure is confirmed by infrared and nuclear magnetic resonance.

The thio compound (0.02 mole) is oxidized with MCPBA (0.04 mole) and is isolated as described in Example 2. Crystallization from ethanol gives 73% of product. The melting point is 144-146 ° C. (IR N-O 1275 cm "1; S02 1310, 1140 cm" 1).

Example 8:

2- (2,3,6-trimethylphenylmethylsulfinyl) pyridine N-oxide

The intermediate 2- (2,3,6-trimethylphenylmethylthio) pyridine N-oxide is prepared from oc2-bromoprehnitene with the sodium salt of 2-mercaptopyridine N-oxide, by the process described in Example 2. The theoretical yield is 50%. The melting point is 108-110 ° C. The structure is confirmed by infrared and nuclear magnetic resonance.

The thio compound (0.03 mole) is oxidized with MCPBA (0.03 mole) and is isolated as described in Example 2. Theoretical yield: 50%. Melting point: 72-75 ° C (IR N-O 1250 cm "1; SO 1050 cm" 1).

Example 9:

2- (1-Phenylethylsulfonyl) pyridine N-oxide

To a cold (0-10 ° C) and well stirred solution of 46.3 g (0.2 mole) of 2- (1-phenylethylthio) pyridine N-oxide in 400 ml of chloroform, a solution of 80 g (0.4 mole) of MCPBA in 11 of chloroform. After 3 h at 0-10 ° C, the temperature is allowed to reach room temperature, and left to stand for 24 h. After washing with saturated sodium bicarbonate to remove all traces of acid, the solution in chloroform is dried and evaporated. The yield is 47 g (90% theoretical). The melting point is 141-143 ° C (IR N-O nóOcm- ^ SOz 1300,1140 cm "1).

Analysis for C13H13NO3S:

Calculated: C 59.40 H 4.95 N 5.32%

Found: C 59.03 H 4.90 N 5.35%

Example 10:

2- (2,4-dichlorophenylmethylsulfinyl) pyridine N-oxide

A well stirred solution of 5.8 g (0.02 mole) of 2- (2,4-dichlorophenylmethylthio) pyridine N-oxide in 50 ml of chloroform is treated at 0-10 ° C with 4 g (0.02 mole) of MCPBA (85%) in 50 ml of chloroform. The temperature of the mixture is allowed to increase to ambient temperature, which is maintained for 16 h. The reaction mixture is washed with saturated sodium bicarbonate, dried and evaporated to give 5.5 g of the product (89% theoretical). Melting point: 138-141 ° C. The structure is confirmed by infrared and nuclear magnetic resonance (IR N — O 1240 cm "1; SO 1050 cm" 1).

Example 11:

2- (2-methylphenylmethylsulfonyl) pyridine N-oxide

The intermediate 2- (2-methylphenylmethylthio) pyridine N-oxide is prepared by the process described in Example 2 from α-chloro o-xylene and the sodium salt of 2-mercaptopyridine N-oxide. The melting point is 134-136 ° C. The theoretical yield is 85%. The structure is confirmed by infrared rays and nuclear magnetic resonance.

A slurry of 14 g (0.06 mole) of the thio compound, 100 ml of water, 0.5 g of sodium tungstate dihydrate and 4 ml of glacial acetic acid is heated to 75 ° C. add, in portions, 12 ml of hydrogen peroxide (30%) (0.12 mole), with a slight exotherm, until 6 ml are consumed. The remaining 6 ml are added at the temperature of the water bath in three parts of 2 ml, at a controlled rate by testing the mixture with a starch-potassium iodide paper, to ensure the consumption of the previous peroxide. The final temperature is 97 ° C after 1 hour. Cool, filter and wash the bread with

5

10

15

20

25

30

35

40

45

50

55

60

65

615,667

6

water and a small amount of cold ethanol. After drying, 15.4 g of product are obtained (99% theoretical). Melting point: 159-160.5 ° C. Structure confirmed by infrared.

Analysis for C13H13NO3S:

Calculated: C 59.31 H 4.98 N 5.32%

Found: C 59.30 H 5.21 N 5.31%

Example 12:

2- (2,2-Dichloro-1-methylcyclopropylmethyl-sulfonyl) pyridine N-oxide

To a well-stirred solution of 62.5 g (0.25 mole) of 2 ^ (2,2-di-chloro-1-methylcyclopropylmethylthio) pyridine in 250 ml of glacial acetic acid, slowly added at room temperature , 90 g (0.8 mole) of 30% hydrogen peroxide. The temperature is increased to 80 ° C over a period of 2 h, and is maintained for 12 h. A further 10 ml of peroxide is added, and the heating is continued for 4 h.

The reaction mixture is reduced to approximately one third of its volume by a rotary evaporator, and the residue is slowly poured into a volume four times equal, vigorously stirred, of cold water. The separated product is removed by filtration and dried under vacuum to give 31.5 g. 42% theoretical yield. Melting point: 93-94 ° C (IR N-O 1280 cm "1; S02 1315.1140 cm" 1).

Analysis for C10H11CI2NO3S:

Calculated: C 40.50 H 3.72 Cl 23.95 N4.72%

Found: C 40.36 H 3.77 Cl 24.15 N 4.63%

Example 13:

2- (2,3,6-trichlorophenylmethylsulfinyl) pyridine N-oxide The intermediate 2- (2,3,6-trichlorophenylmethylthio) pyridine N-oxide is prepared from 2,3,6-trichloro-benzyl chloride and sodium salt of 2-mercaptopyridine N-oxide by the process used in Example 3. The melting point is 232-234 ° C. The yield is quantitative. The structure is confirmed by infrared and nuclear magnetic resonance.

A slurry of 6.4 g (0.02 mole) of the thio compound in 50 ml of chloroform is cooled to 5-10 ° C and a solution of 4 g (0.02 mole) of MCPBA in 100 ml of chloroform. The temperature of the reaction mixture is allowed to rise to room temperature, the mixture is stirred for 16 h, washed with a solution of saturated baking soda and dried over sodium sulfate. The dry solution is evaporated to dryness, and the crude product is refluxed in ethanol, cooled and filtered. The theoretical yield of the product is 65%. The melting point is 168-170 ° C (IR N-O 1350 cm "1; SO 1050 cm" 1).

Analysis for C12H8CI3NO2S:

Calculated: C 42.82 H 2.39 N 4.16 S 9.54%

Found: C 42.01 H 2.32 N4.18 S 9.74%

Example 14:

2- (2,6-dichlorophenylmethylsulfonyl) pyridine N-oxide

A mixture of 37 g (0.1 mole) of sodium salt of 2-mercaptopyridine N-oxide (40% solution) and 19.5 g (0.1 mole) of 2,6-dichlorobenzyl chloride in 200 ml of ethanol is heated to 65 ° C for 30 min, cooled and filtered. The filtering bread is washed completely with water and finally with 40 ml of acetone. Drying the bread under vacuum gives 25.3 g (92% theoretical) of 2- (2,6-dichlorophenylmethylthio) pyridine N-oxide. The melting point is 240-241 ° C. The structure is confirmed by infrared.

A slurry of 29 g (0.1 mole) of the thio compound in 300 ml of chloroform at 10 ° C is treated slowly with 40 g (0.2 mole) of MCPBA (85%) in 450 ml of chloroform. The temperature of the mixture is allowed to rise to ambient temperature, which gives a clear solution which is kept for 16 h. The solution is washed with a saturated baking soda solution, dried over magnesium sulfate and evaporated to dryness. The residue is transformed into a slurry in 400 ml of boiling methanol, cooled and filtered to give 28 g (89% theoretical) of the product. Melting point: 214-215 ° C.

Analysis for C12H9CI2NO3S:

Calculated: C 45.32 H 2.83 N 4.40%

Found: C 45.67 H 2.89 N 4.55%

Example 15:

2- (2,3,6-Trichlorophenylmethylsulfonyl) pyridine N-oxide

2- (2,3,6-trichorophenylmethylthio) pyridine N-oxide is prepared from 2,3,6-trichlorobenzyl chloride and sodium salt of 2-mercaptopyridine N-oxide by the process employed in 'Example 1. The melting point is 232-234 ° C. The yield is quantitative. The structure is confirmed by infrared and nuclear magnetic resonance.

A slurry of 6.4 g (0.02 mole) of the thio compound in 50 ml of chloroform is cooled to 5-10 ° C, and a solution of 8 g (0.04 mole) of MCPBA is slowly added to it in 100 ml of chloroform. The temperature of the mixture is allowed to increase to room temperature, it is stirred for 16 h, it is washed with a solution of saturated baking soda and it is dried over sodium sulfate. The dry solution is evaporated to dryness, and the crude product is refluxed in ethanol, cooled and filtered. The yield of the product is 6.7 g (95% theoretical). The melting point is 194-196 ° C. The structure is confirmed by infrared and nuclear magnetic resonance.

Example 16:

2- (1- [4-fluorophenyl] ethylsulfonyl) pyridine N-oxide

The compound is prepared from the sodium salt of 2-mercaptopyridine N-oxide and from 1- (4-fluorophenyl) ethyl chloride as described in Example 4. 2- (1-) N-oxide [4-fluorophenyl] ethylthio) pyridine is obtained in a yield of 40%. The melting point is 95-97 ° C. The structure is confirmed by infrared and nuclear magnetic resonance.

The oxidation of the thio compound (0.04 mole) with MCPBA (0.08 mole) and the isolation process are the same as that used in Example 7. The yield is 83%. The melting point is 142-144 ° C.

Analysis for C13H12FNO3S:

Calculated: C 55.50 H 4.30 N 4.98%

Found: C 55.47 H 4.61 N 5.07%

Example 17:

2- (1- [4-bromophenyt] ethylsulfonyl) pyridine N-oxide

2- (1- [4-bromophenyl] ethylthio) pyridine N-oxide is prepared from 1- (4-bromophenyl) ethyl chloride and 2-mercaptopyridine N-oxide sodium salt by the process described in Example 1. The melting point is 113-115 ° C. The structure is confirmed by infrared and nuclear magnetic resonance.

The thio compound (0.05 mole) is oxidized with MCPBA (0.1 mole) and is isolated as described above in Example 9. The yield is 85%. The structure is confirmed by infrared and nuclear magnetic resonance.

Analysis for CisH ^ BrNOaS:

Calculated: C 45.63 H 3.45 N 4.09%

Found: C 45.04 H 3.32 N 4.15%

The chemicals shown in Table I can be prepared by the same process. Table I summarizes the previous preparations as well as additional similar preparations. Table II shows the infrared data.

5

10

15

20

25

30

35

40

45

50

55

60

65

7

615,667

The numbers given to the preparations in Table I are used quents. Compound 44 of Table I also contains one to identify the chemicals in the minor examples of the 4-ethylphenyl isomer.

Table 1

Ex.

Herbicide chemicals (name)

P.F.

(° c)

VS (%)

Calculated / Found Analysis

H, N (%) (%)

S (%)

12

2- (2,2-Dichloro-1-methylcyclopropyl-methylsulfonyl) pyridine N-oxide

93-95

40.50 / 40.51

3.72 / 3.87

4.73 / 4.59

10.81 / 10.94

24

2- (l-naphthylmethylsulfonyl) pyridine N-oxide

183-186

IR

21

2- (3,4-dimethylphenylmethylsulfonyl) -pyridine N-oxide

165-167

60.63 / 60.77

5.45 / 5.73

5.05 / 5.03

11.54 / 11.71

1

2- (2,5-dimethylphenylmethylsulfonyl) -pyridine N-oxide

156-158

60.63 / 60.66

5.45 / 5.56

5.05 / 5.18

11.54 / 11.81

11

2- (2-methylphenylmethylsulfonyl) -pyridine N-oxide

159-161

59.31 / 59.30

4.93 / 5.21

5.32 / 5.31

14

2- (2,6-dichlorophenylmethylsulfonyl) -pyridine N-oxide

214-216

45.37 / 45.67

2.83 / 2.89

4.40 / 4.55

2

2- (2,4,6-trimethylphenylmethylsulfonyl) -pyridine N-oxide

173-175

61.90 / 61.97

5.84 / 5.06

4.81 / 4.79

34

2- (2,4-Dichlorophenylmethylsulfonyl) -pyridine N-oxide

154-156

IR

9

2- (1-Phenylethylsulfonyl) pyridine N-oxide

141-143

59.40 / 59.03

4.95 / 4.90

5.32 / 5.35

31

2- (2-chlorophenylmethylsulfonyl) -pyridine N-oxide

151-152

IR

36

2 - ([[2-methoxy-5-nitrophenyl] methyl-sulfonyl) pyridine N-oxide

226-227

IR

42

2- (2-fluorophenylmethylsulfonyl) -pyridine N-oxide

151-153

54.00 / 54.03

3.74 / 3.79

5.24 / 5.31

41

2 - [(3,4-dioxymethylene-6-chlorophenyl) -methylsulfonyl] pyridine N-oxide

179-180

47.60 / 46.87

3.06 / 2.83

4.28 / 4.23

44

2- (2-Ethylphenylmethylsulfonyl) pyridine N-oxide

-

IR

4

2- [1- (4-chlorophenyl) ethylsulfonyl] -pyridine N-oxide

188-191

IR

3

2- (2,6-dichlorophenyimethylsulfinyl) -pyridine N-oxide

135-137

47.65 / 47.25

2.98 / 2.95

4.64 / 4.25

46

2- (2-5-dimethylphenylmethylsulfinyl) -pyridine N-oxide

142-144

64.80 / 64.43

5.64 / 5.67

5.26 / 5.13

10

2- (2,4-Dichlorophenylmethylsulfinyl) -pyridine N-oxide

138-141

IR

56

2- (2,4,6-trimethylphenylmethylsulfinyl) -pyridine N-oxide

164-166

65.50 / 66.11

6.18 / 6.49

5.09 / 5.15

57

2- (2-Chlorophenylmethylsulfinyl) pyridine N-oxide

124-127

53.65 / 53.91

3.73 / 4.11

5.22 / 5.25

58

2- (3,4-dimethylphenylmethylsulfinyl) -pyridine N-oxide

123-126

64.43 / 64.89

5.75 / 6.08

5.36 / 5.40

59

2- (2-methylphenylmethylsulfinyl) pyridine N-oxide

99-102

63.14 / 62.66

5.30 / 5.31

5.66 / 5.45

12.96 / 12.57

32

2-cyanomethylsulfinylpyridine N-oxide

164-165

IR

66

2- (2-fluorophenylmethylsulfinyl) pyridine N-oxide

110-113

57.40 / 57.43

3.98 / 3.95

5.57 / 5.68

68

2- (2-methoxy-5-methylphenylmethyl-sulfonyl) pyridine N-oxide

115-118

IR

69

2- (2-Bromo-5-methoxyphenylmethyl-sulfonyl) pyridine N-oxide

157-158

IR

70

2- (pentachlorophenylmethylsulfonyl) -pyridine N-oxide

235-238

IR

15

7

5

16

6

17

82

71

13

79

77

19

80

83

86

88

18

87

94

8

96

98

: 03

93

92

95

97

99

8

Table 1 (continued)

Herbicide chemicals Analysis Calculated / Found

(name) P.F. C H N S

(° C) (%) (%) (%) (° / i

2- (2,3,6-Trichlorophenylmethylsulfonyl) -pyridine N-oxide

194-196

IR

2- [1- (2-naphthyl) ethylsulfonyl)] pyridine N-oxide

144-146

IR

2- [1- (4-methylphenyl) ethyl sulfonyl] -pyridine N-oxide

158-160

60.35 / 61.18

5.45 / 5.70

5.05 / 5.22

2- [1- (4-fluorophenyl) ethylsulfonyl] -pyridine N-oxide

142-144

55.50 / 55.47

4.30 / 4.61

4.98 / 5.07

2- [1- (2,5-dimethylphenyl) ethylsulfonyl] -pyridine N-oxide

160-163

IR

2- [1- (4-bromophenyl) ethylsulfonyl] -pyridine N-oxide

193-195

45.63 / 45.04

3.45 / 3.32

4.09 / 4.15

2- (3,4-dichlorophenylmethylsulfonyl) -pyridine N-oxide

170-173

45.30 / 45.20

2.85 / 2.41

4.40 / 4.49

2- (pentachlorophenylmethylsulfinyl) -pyridine N-oxide

213-215

IR

2- (2,3,6-Trichlorophenylmethylsulfinyl) -pyridine N-oxide

168-170

IR

2- [1- (4-fluorophenyl) ethylsulfinyl] -pyridine N-oxide

98-101

58.85 / 54.94

4.56 / 5.08

5.28 / 5.34

2- [1- (4-methylphenyl) ethylsulfinyl] pyridine N-oxide

121-123

IR

2- (2,2-Dichlorocyclopropylmethylsulfinyl) -pyridine N-oxide oil

IR

2- [1- (4-bromophenyl) ethylsulfinyl] -pyridine N-oxide

177-180

IR

2- (3,4-dichlorophenylmethylsulfinyl) -pyridine N-oxide

133-135

47.70 / 47.44

3.00 / 2.92

4.64 / 4.71

2- (1- [3,4-dichlorophenyl] ethylsulfonyl) -pyridine N-oxide

129-134

IR

2- (3,4-methylenedioxyphenylmethyl-sulfonyl) pyridine N-oxide

163-165

IR

2- (2,3,6-trimethylphenylmethylsulfonyl) -pyridine N-oxide

155

IR

2- (3,4-methylenedioxyphenylmethyl-sulfinyl) pyridine N-oxide

171-173

IR

2- (2-nitrophenylmethylsulfinyl) pyridine N-oxide

165-167

IR

2- (2,3,6-trimethylphenylmethylsulfinyl) -pyridine N-oxide

72-75

IR

2- (2-methyl-1-naphthylmethylsulfinyl) -pyridine N-oxide

127-130

IR

2- (2-iodophenylmethylsulfinyl) pyridine N-oxide

160-163

IR

2- (1- [l-naphthyl] ethylsuIfinyl) pyridine N-oxide

146-147

IR

2- (2-nitrophenylmethylsulfonyl) pyridine N-oxide

155-158

IR

2- (1- [2,4,6-trimethylphenyl] ethylsulfonyl) -pyridine N-oxide

172-175

IR

2- (2-methyl-1-naphthylmethylsulfonyl) -pyridine N-oxide

195-198

IR

2- (2-iodophenylmethylsulfonyl) pyridine N-oxide

142-146

IR

2- (1- [4-nitrophenyl] ethylsulfonyl) -pyridine N-oxide

167-121

IR

2- (l- [l-naphthyl] ethylsulfonyl) pyridine n-oxide wax

IR

2- (3,4-dimethoxyphenylmethylsulfinyl) -pyridine N-oxide

133-135

IR

9

Table 1 (continued)

i

615,667

Ex.

Herbicide chemicals (name)

P.F. C

(° C) (%)

Calculated / Found Analysis

H N S

(%) (%) (%)

108

2- (3,4-Dimethoxyphenylmethylsulfonyl) -pyridine N-oxide

159-161

IR

109

2- (1- [2,5-diethylphenyl] ethylsulfonyl) -pyridine N-oxide

124-127

IR

111

2- (2,5-dimethoxyphenylmethylsulfonyl) -pyridine N-oxide

129-132

IR

112

2- (2,5-dimethoxyphenylmethylsulfinyl) -pyridine N-oxide

136-138

IR

Claims (7)

615,667 1. Process for the preparation of N-oxides of 2-sulfinylpyridine or 2-sulfonylpyridine of formula: C-H i in which n represents the number 1 or 2, R 1 represents hydrogen or a methyl and, when R 1 is hydrogen, R 2 represents a 2,2-dichlorocyclopropyle, 2,2-dichloro-1-methyl-cyclopropyl group, cyano, naphthyl, methylnaphthyl, phenyl mono-substituted in the ortho position by a C1 or C2 alkyl, a halogen or a nitro, or phenyl substituted by 2 to 5 identical or different substituents, chosen from a C1 or C2 alkyl, a halogen , a nitro, a methoxy, an ethoxy and a methylenedioxy, or, when R 1 is a methyl, R 2 represents a phenyl, naphthyl or phenyl group substituted by 1 to 3 identical or different substituents, chosen from a C1 or C2 alkyl, a halogen and a nitro, characterized in that a 2-thiopyridine N-oxide is subjected corresponding to the action of an oxidizing agent in an inert solvent, at a temperature between 0 ° C and the boiling point solvent. 2. Method according to claim 1, characterized in that the oxidizing agent used is hydrogen peroxide, peracetic acid or an aromatic peracid. 2 3. Method according to claim 1, characterized in that the oxidizing agent used is hydrogen peroxide, the solvent is glacial acetic acid or water and the temperature is between 0 ° C and the temperature of solvent boiling. 4. Method according to claim 3, characterized in that the solvent used is water and that one operates in the presence of a catalyst chosen from tungsten, vanadium, zirconium or molybdenum salts. 5. Method according to claim 1, characterized in that the oxidizing agent used is peracetic acid or an aromatic peracid, the solvent is a non-polar solvent and the temperature is between 0 and 60 ° C. 6. Method according to one of claims 1 to 4, characterized in that the N-oxide of 2- (2,4,6-trimethylphenylmethylsulfonyl) pyridine, de2- (2,6-dichlorphenylmethylsulfonyl) pyridme is prepared, de2- (2,4-dichlorphenylmethylsulfinyl) pyridine, de2- (2,6-dichlorphenylmethylsulfinyl) pyridine, de 2- (l - [4-methylphenyl] ethylsulfonyl) pyridine, de2- (2,3,6-trichlorphenylmethylsulfonyl) pyridine, 2- (2-methylphenylmethylsulfonyl) pyridine, de2- (l- [4-fluorphenyl] ethylsulfonyl) pyridine, 2- (l- [2,5-dimethylphenyl] ethylsulfonyl) pyridine, 2- (2,3,6 -trichlorphenylmethylsulfinyl) pyridine, 2- (1-phenylethylsulfonyl) pyridine, (l- [2-naphthyl] ethylsulfonyl) pyridine, 2- (l- [4-chlorphenyl] ethylsulfonyl) pyridine, 2- (l- [ 4-bromphenyl] ethylsulfonyl) pyridine, 2- (2,3,6-trimethylphenylmethylsulfonyl) pyridine, and 2- (2,3,6-trimethylphenylmethylsulfinyl) pyridine. 7. Use of the N-oxides of 2-sulfinylpyridine or 2-sulfonylpyridine prepared by the process according to claim 1, for destroying weeds.