NO141991B - 1,2,4-TRIAZOLIDIN-3-ON DERIVATIVES WITH HERBICIDE EFFECT - Google Patents

Description

The present invention relates to new 1,2,4-triazolidin-3-one derivatives with herbicidal action. They are characterized by having the formula:

1 2 where R is alkyl, and R is: where X is alkyl, alkoxy, alkylthio, halogen, haloalkyl or nitro, and n is a number from 1 to 3, or R 2 is:

where R 3 is alkyl, trifluoromethyl, alkoxy, alkylthio, alkylsulfonyl, alkylsulfinyl or cycloalkyl with from 3 to 7 carbon atoms optionally substituted with from 1 to 2 alkyl, alkoxy or halogen groups, all alkyl substituents or substituent parts having linear or branched carbon chains with to 6 carbon atoms.

The compounds according to the invention can be prepared by reacting a semicarbazide with the formula:

where R 1 and R 2 are as described above, with formaldehyde. The reaction can be carried out by combining a solution of a molar amount of the semicarbazide of formula II in a water-miscible solvent such as e.g. methanol, with an approx. equimolar or slightly over a molar amount of aqueous

formaldehyde. Inorganic base such as e.g. potassium hydroxide can be added to raise the pH of the reaction medium to from approx. 7 to approx. 9.

This reaction can be carried out at room temperature or at slightly elevated temperatures such as e.g. temperatures in the area up to approx. 50°C. The reaction mixture can then be stirred or allowed to stand for up to approx. 8 hours to ensure that the reaction is complete and precipitate solid products. The solid can then be recovered by filtration and can be dried

to achieve the desired product. This product can be used as such or can be further purified using normal methods such as e.g. recrystallization, washing and the like.

The semicarbazide of formula II where R 2 is a substituted phenyl ring can be prepared by reacting one mole of an isocyanate of the formula: where X and n are as described above, with an approximately equimolar or excess molar amount of a hydrazine of the formula:

where R^" is as described above. This reaction can be carried out by combining a solution of the isocyanate of formula III in an inert aromatic solvent such as benzene or methylene chloride with a solution of the hydrazine of formula IV in an inert organic solvent such as e.g. benzene or methylene chloride. The reaction temperature can be maintained from about -20 to about 30°C with stirring for up to about 1 hour. Then more solvent can be added and the reaction mixture can optionally be heated under reflux for up to about 2 hours to ensure complete reaction. The reaction mixture can then be filtered to recover the solid product that is formed. This desired product can then be used as is or it can be further purified by conventional methods such as recrystallization and the like.

The semicarbazide of formula II where R 2 is a thiadiazol ring can be prepared by reacting one mole of an isocyanate dimer with the formula: where R is as described above, with at least approx. two moles of a hydrazine with the formula:

where R"<*>" is as described above. This reaction can be carried out by adding the isocyanate dimer of formula V to a solution of the hydrazine of formula VI in an inert, organic solvent such as e.g. methylene chloride at room temperature with stirring. After the addition is finished, the reaction mixture can be heated to temperatures up to the reflux temperature for the mixture for a time of up to approx. 2 hours. The solvent can then be evaporated from the mixture and excess hydrazine can be removed by vacuum distillation so that the desired product is obtained.

The isocyanate dimer of formula V can be prepared by reacting a thiadiazole of the formula:

where R^ is as described above, with phosgene. This reaction can be carried out by adding a slurry or a solution of the thiadiazole, in a suitable organic solvent such as e.g. ethyl acetate, to a saturated solution of phosgene in an organic solvent such as e.g. ethyl acetate. The resulting mixture can be stirred at ambient temperature for a time of from approx. 4 to approx. 24 hours. The reaction mixture can then be blown through with nitrogen gas to remove unreacted phosgene. The desired product can then be recovered by filtration if a precipitate has formed or by evaporation of the organic solvent if the product is soluble in it. This product can be used as is or can be further purified if desired.

The method for producing the compounds according to the invention is more particularly illustrated in the following examples.

Example 1 a)

Preparation of 2-methyl-4-(3-chlorophenyl)semicarbazld

A solution of methylhydrazine (8.6 grams) in methylene chloride

(100 mL) was added to a glass reaction vessel equipped with a mechanical stirrer and a thermometer. The solution was cooled to a temperature of approx. 10°C and 3-chlorophenyl isocyanate (30 grams) was added

placed under stirring whereby a solid precipitate was formed.

The precipitate was recovered by filtration and was dried so that the desired product 2-methyl-4-(3-chlorophenyl)semicarbazide was obtained.

bj_

Preparation of 2-methy1-4-(3-chlorophenyl)-1,2,4-triazolidin-3-one

2-Methyl-4-(3-chlorophenyl)semicarbazide (10 grams), aqueous formaldehyde (6 ml, 37% concentration) and methanol (50 ml) were added

transferred to a beaker at room temperature. Dilute aqueous potassium hydroxide was added to adjust the pH of the reaction medium to approx. 8. The mixture was stirred until it was homogeneous and allowed to stand for approx. 6 hours. Then, water and methanol were evaporated from the reaction mixture, leaving a solid residue. The residue was then recrystallized from a water-acetone mixture to give the desired product 2-methyl-4-(3-chlorophenyl)-1,2,4-triazolidin-3-one with a melting point of 62 to 63°C.

Example 2a)

Preparation of 2-methyl-4-(3,4-dichlorophenyl)semicarbazide

A solution of methylhydrazine (12.1 grams) in benzene (100 ml)

and a solution of 3,4-dichlorophenyl isocyanate (50 grams) in benzene

(150 mL) was added to a glass reaction vessel equipped with a mechanical stirrer, a thermometer, and a reflux condenser. The reaction mixture was stirred and the temperature maintained between

about. 20 and 25°C when cooling for half an hour. Then more benzene (500 mL) was added to the reaction mixture and the mixture was heated to reflux. The mixture was then cooled and filtered to recover the solid formed. The solid became so

dried to give the desired product 2-methyl-4-(3,4-dichlorophenyl)-semicarbazide with a melting point of from 134 to 138°C.

p

Preparation of 2-methy1-4-(3,4-dichlorophenyl)-1,2,4-triazolidin-3-one

2-Methyl-4-(3,4-dichlorophenyl)semicarbazide (12 grams), aqueous formaldehyde (5 mL, 37% concentration) and methanol (100 mL) were added

transferred to a glass reaction vessel at room temperature. Diluted aqueous

potassium hydroxide was added to adjust the pH of the reaction mixture to approx. 8. The mixture was stirred and allowed to stand for approx. 2 hours. Then, water and methanol were evaporated from the reaction mixture under vacuum to give a solid. The solid was recrystallized from heptane to give the desired product 2-methyl-4-(3,4-dichlorophenyl)-1,2,4-triazolidin-3-one, mp 77 to 79°C.

Example 3a)

Preparation of 2-methyl-4-(2-methoxyphenyl) semicarbazide

A solution of methylhydrazine (0.2 mol) in benzene (100 mL) was added to a glass reaction vessel equipped with a mechanical stirrer and a thermometer. The solution is cooled to a temperature of approx. 10°C and a solution of 2-methoxyphenyl isocyanate (0.2 mol) in benzene (100 ml) is added with stirring. After the addition is finished, the stirring is continued for approx. 30 minutes. Solvent is then removed from the reaction mixture under reduced pressure to give the desired product 2-methyl-4-(2-methoxyphenyl)-semicarbazide as a residue.

b]_

Preparation of 2-methyl-4-(2-methoxyphenyl)-1,2,4-triazolidin-3-one

2-Methyl-4-(2-methoxyphenyl)semicarbazide (0.1 mol), aqueous formaldehyde (0.1 mol, 37% concentration) and methanol (100 mL) are added to a glass reaction vessel at room temperature. Dilute aqueous potassium hydroxide is added to adjust the pH of the reaction mixture to approx. 8. The mixture is stirred and then allowed to stand for approx. 6 hours. Water and methanol are then removed from the reaction mixture, leaving a solid residue. The residue is then recrystallized and gives the desired product 2-methyl-4-(2-methoxyphenyl)-1,2,4-triazolidin-3-one.

Example 4a^

Preparation of 2-methyl-4-(4-methylthiophenyl) semicarbazide

A solution of methylhydrazine (0.2 mol) in benzene (100 mL) is added to a glass reaction vessel equipped with a mechanical stirrer and a thermometer. The solution is cooled to a temperature of approx. 10°C and a solution of 4-methylthiophenyl isocyanate (0.2 mol) in benzene

(100 ml) is added while stirring. After the addition is finished, the stirring is continued for approx. 30 minutes. The solvent is then evaporated from the reaction mixture under reduced pressure

so that the desired product 2-methyl-4-(4-methylthiophenyl)semicarbazide is obtained as a residue.

b)_

Preparation of 2-methyl-4-(4-methylthiophenyl)-1,2,4-triazolidin-3-one

2-Methyl-4-(4-methylthiophenyl)semicarbazide (0.1 mol), aqueous formaldehyde (0.1 mol, 37% concentration) and methanol (100 mL) are added to a glass reaction vessel at room temperature. Dilute aqueous potassium hydroxide is added to adjust the pH of the reaction mixture to approx. 8. The mixture is stirred and then allowed to stand for approx. 6 hours. Water and methanol are then evaporated from the reaction mixture and a solid residue is left behind. The residue is recrystallized so that the desired product 2-methyl-4-(4-methylthiophenyl)-1,2,4-triazolidin-3-one is obtained.

Example 5 a)

Preparation of 2-ethyl-4-(4-bromophenyl) semicarbazide.

A solution of ethylhydrazine (0.2 mol) in benzene (100 ml) is added to a glass reaction vessel equipped with a mechanical stirrer and a thermometer. The solution is cooled to a temperature of approx. 10°C and a solution of 4-bromophenyl isocyanate (0.2 mol) in benzene (100 ml) is added with stirring. After the addition is finished, the stirring is continued for approx. 30 minutes. The solvent is then evaporated from the reaction mixture under reduced pressure so that the desired product 2-ethyl-4-(4-bromophenyl)semicarbazide is obtained as a residue.

b)_

Preparation of 2-ethyl-4-(4-bromophenyl)-1,2,4-triazolidin-3-one

2-Ethyl-4-(4-bromophenyl)semicarbazide (0.1 mol), aqueous formaldehyde (0.1 mol, 37% concentration) and methanol (100 mL) are added to a glass reaction vessel at room temperature. Dilute aqueous potassium hydroxide is added to adjust the pH of the reaction mixture to approx. 8. The mixture is stirred and then allowed to stand for approx. 6 hours. Water and methanol are then evaporated from the reaction mixture so that a solid residue remains. The residue is recrystallized so that the desired product 2-ethyl-4-(4-bromophenyl)-1,2,4-triazolidin-3-one is obtained.

Example 6 a)

Preparation of 2-methyl-4-(2-methyl-4-chlorophenyl)semicarbazide

A solution of methylhydrazine (0.2 mol) in benzene (100 mL) is added to a glass reaction vessel equipped with a mechanical stirrer and a thermometer. The solution is cooled to a temperature of approx. 10°C and a solution of 2-methyl-4-chlorophenyl isocyanate (0.2 mol) in benzene (100 ml) is added with stirring. After the addition is finished, the stirring is continued for approx. 30 minutes. Then for-

solvent is evaporated from the reaction mixture under reduced pressure so that the desired product 2-methyl-4-(2-methyl-4-chlorophenyl)-semicarbazide is obtained as a residue.

Pl

Preparation of 2- methyl- 4-( 2- methyl- 4- chlorophenyl)- 1, 2, 4- triazolidin- 3- one

2-methyl-4-(2-methyl-4-chlorophenyl)semicarbazide (0.1 mol),

aqueous formaldehyde (0.1 mol, 37% concentration) and methanol (100 ml) are added to a glass reaction vessel at room temperature. Dilute aqueous potassium hydroxide is added to adjust the reaction

the pH of the mixture to approx. 8. The mixture is stirred and allowed to stand for approx.

6 hours. Water and methanol are then evaporated from the reaction mixture, leaving behind a solid residue. The residue is then recrystallized so that the desired product 2-methyl-4-(2-methyl-4-chlorophenyl)-1f 2,4-triazolidin-3-one is obtained.

Example 7 a)

Preparation of 2-methyl-4-(4-trifluoromethylphenyl) semicarbazide

A solution of methylhydrazine (0.2 mol) in benzene (100 mL) is added to a glass reaction vessel equipped with a mechanical stirrer and a thermometer. The solution is cooled to approx. 10°C and a solution of 4-trifluoromethylphenyl isocyanate (0.2 mol) in benzene (100 ml) is added with stirring. After the addition is finished, the stirring is continued for approx. 30 minutes. The solvent is then evaporated from the reaction mixture under reduced pressure whereby the desired product 2-methyl-4-(4-trifluoromethylphenyl)semicarbazide is obtained as a residue.

hl

Preparation of 2-methyl-4-(4-trifluoromethylphenyl)-1,2,4-triazolidin-3-one

2-Methyl-4-(4-trifluoromethylphenyl)semicarbazide (0.1 mol), aqueous formaldehyde (0.1 mol, 37% concentration) and methanol (100 mL) are added to a glass reaction vessel at room temperature. Dilute aqueous potassium hydroxide is added to adjust the pH of the reaction mixture to approx. 8. The mixture is stirred and then allowed to stand for approx. 6 hours.

Water and methanol are then evaporated from the reaction mixture whereby

there will be a fixed residue left. The residue is recrystallized so that the desired product 2-methyl-4-(4-trifluoromethylphenyl)-1,2,4-triazolidin-3-one is obtained.

Example 8 a)

Preparation of 2-methyl-4-(4-nitrophenyl) semicarbazide

A solution of methylhydrazine (0.2 mol) in benzene (100 mL) is added to a glass reaction vessel equipped with a mechanical stirrer and a thermometer. The solution is cooled to a temperature of approx.

10°C and a solution of 4-nitrophenyl isocyanate (0.2 mol) in benzene is added with stirring. After the addition is finished, the stirring is continued for approx. 30 minutes. The solvent is then evaporated from the reaction mixture under reduced pressure whereby the desired product 2-methyl-4-(4-nitrophenyl)semicarbazide is obtained as a residue.

at

Preparation of 2-methyl-4-(4-nitrophenyl)-1,2,4-triazolidin-3-one

2-methyl-4-(4-nitrophenyl)semicarbazide (0.1 mol), aqueous formaldehyde (0.1 mol, 37% concentration) and methanol (100 ml) to

is added to a glass reaction vessel at room temperature. Dilute aqueous potassium hydroxide is added to adjust the pH of the reaction mixture

to approx. 8. The mixture is stirred and then allowed to stand for approx. 6 hours.

Water and methanol are then evaporated from the reaction mixture and that

remains a fixed residue. The residue is then recrystallized so that the desired product 2-methyl-4-(4-nitrophenyl)-1,2,4-triazolidin-3-one is obtained.

Example 9 a) Preparation of 5-trifluoromethyl-1,3,4-triadiazol-2-yl-isocyanate dimer

A saturated solution of phosgene in ethyl acetate (100 mL) was

added to a glass reaction vessel equipped with a mechanical stirrer.

A slurry of 5-trifluoromethyl-2-amino-1,3,4-thiadiazole (45 grams)

in ethyl acetate (300 mL) was added to the reaction vessel and the resulting mixture was stirred for approx. 16 hours, whereby a precipitate was formed. The reaction mixture was then purged with nitrogen gas to remove unreacted phosgene. The purified mixture was filtered to recover 48 grams of a white solid. This solid was recrystallized from dimethylformamide so that the desired product 5-trifluoromethyl-1,3,4-thiadiazol-2-yl-isocyanate dimer was obtained.

b)

Preparation of 2-methyl-4-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-semicarbazide

A solution of methylhydrazine (6.5 grams) in methylene chloride

(100 mL) was added to a glass reaction vessel equipped with a

mechanical stirrer, a thermometer and a reflux condenser. 5-trifluoromethyl-1,3,4-thiadiazol-2-yl-isocyanate dimer (25 grams) was then

added with stirring at a temperature of from 20 to 25°C. Additional methylhydrazine (3.0 grams) was then added and the reaction mixture was heated at reflux for approx. 4 hours. Then solvent and excess hydrazine were evaporated from the reaction mixture so that the desired product 2-methyl-4-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)semicarbazide was obtained as a residual oil.

c)

Preparation of 2-methyl-4-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-1,2,4-triazolidin-3-one

The 2-methyl-4-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-semicarbazide prepared in Example 18 was dissolved in methanol

(100 ml in a glass reaction flask equipped with a mechanical stirrer

and a thermometer. Aqueous formaldehyde (12 ml, 37% concentration)

was then added to the flask with stirring. The reaction mixture warmed to a temperature of about 35°C. Sufficient aqueous potassium hydroxide was then added to adjust the pH of the reaction medium to from about 7 to 8. A solid precipitate formed. The precipitate was then recovered by filtration, was recrystallized

from an ethyl acetate-heptane mixture and was dried under vacuum to give the desired product 2-methyl-4-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-1,2,4-triazolidin-3 -on was obtained and this substance had a melting point of from 187 to 188°C.

Example 10 a)

Preparation of 5-t-butyl-1,3,4-thiadiazol-2-yl isocyanate dimer

A saturated solution of phosgene in ethyl acetate (100 ml) was added

taken to a glass reaction vessel equipped with a mechanical stirrer. A slurry of 5-t-butyl-2-amino-1,3,4-thiadiazole (10 grams) in ethyl acetate (300 mL) was added to the reaction vessel and the resulting mixture was stirred for approx. 16 hours, whereby a precipitate formed. The reaction mixture was then purged with nitrogen gas to remove unreacted phosgene. The purified mixture was then filtered

so that the desired product 5-t-butyl-1,3,4-thiadiazol-2-yl-isocyanate dimer was obtained as a solid with a melting point of

from 261 to 263°C.

b)

Preparation of 2-methyl-4-(5-t-butyl-1,3,4-thiadiazol-2-yl)-semicarbazide

A solution of methylhydrazine (0.3 mol) in methylene chloride

(150 mL) is added to a glass reaction vessel equipped with a mechanical stirrer, a thermometer, and a reflux condenser. 5-t-butyl-1,3,4-thiadiazol-2-yl-isocyanate dimer (0.1 mol) is then added with stirring at room temperature. After the addition is complete, the reaction mixture is heated at reflux for approx. 4 hours. The solvent and excess hydrazine are then evaporated from the reaction mixture so that the desired product 2-methyl-4-(5-t-butyl-1,3,4-thiadiazol-2-yl)semicarbazide is obtained as a residue.

c)

Preparation of 2-methyl-4-(5-t-butyl-1,3,4-thiadiazol-2-yl)-1,2,4-triazolidin-3-one

2-Methyl-4-(5-t-butyl-1,3,4-thiadiazol-2-yl)semicarbazide (0.1 mol) dissolved in methanol (100 ml) is added to a glass reaction vessel equipped with a mechanical stirrer and a thermometer. Aqueous formaldehyde (0.2 mol, 37% concentration) is then added to the reaction vessel with stirring. Dilute aqueous potassium hydroxide is added to the reaction mixture to adjust the pH to between 7 and 8 and stirring is continued for approx. 20 minutes, whereby a solid precipitate is formed. The precipitate is recovered by filtration, recrystallized and dried in vacuo so that the desired product 2-methyl-4-(5-t-butyl-1,3,4-thiadiazol-2-yl)-1,2,4-triazolidin-3 -on is achieved.

Example 11 a)

Preparation of 5-methyl-1,3,4-thiadiazol-2-yl isocyanate dimer.

A saturated solution of phosgene in ethyl acetate (100 mL) is added to a glass reaction vessel equipped with a mechanical stirrer. A slurry of 5-methyl-2-amino-1,3,4-thiadiazole (40 grams) in ethyl acetate (300 ml) is added to the reaction vessel and the resulting mixture is stirred for approx. 16 hours, whereby a precipitate is formed. The reaction mixture is then purified by blowing through with nitrogen gas to remove unreacted phosgene. The purified mixture is then filtered to recover the precipitate. The precipitate is then recrystallized so that the desired product 5-methyl-1,3,4-thiadiazol-2-yl-isocyanate dimer is obtained.

b)

Preparation of 2-ethyl-4-(5-methyl-1,3,4-thiadiazol-2-yl)semicarbazide

A solution of ethylhydrazine (0.3 mol) in methylene chloride

(150 mL) is added to a glass reaction vessel equipped with a mechanical stirrer, a thermometer, and a reflux condenser. 5-methyl-1,3,4-thiadiazol-2-yl-isocyanate dimer (0.1 mol) is then added with stirring at room temperature. After the addition is finished, the reaction mixture is heated at reflux for approx. 4 hours. The solvent and excess hydrazine are then evaporated from the reaction mixture so that the desired product 2-ethyl-4-(5-methyl-1,3,4-thiadiazol-2-yl)semicarbazide is obtained as a residue.

c)

Preparation of 2-ethyl-4-(5-methyl-1,3,4-thiadiazol-2-yl)-1,2,4-triazolidin-3-one

2-ethyl-4-(5-methyl-1,3,4-thiadiazol-2-yl)semicarbazide

(0.1 mol) dissolved in methanol (100 mL) is added to a glass reaction vessel equipped with a mechanical stirrer and a thermometer. Aqueous formaldehyde (0.2 mol, 37% concentration) is then added to the reaction vessel with stirring. Dilute aqueous potassium hydroxide is added to the reaction mixture to adjust the pH to between 7

and 8 and the stirring is continued for approx. 20 minutes, whereby a solid precipitate is formed. The precipitate is recovered by filtration, recrystallized and dried in vacuum so that the desired product 2-ethyl-4-(5-methyl-1,3,4-thiadiazol-2-yl)-1,2,4-triazolidin-3-one is achieved.

Example 12 a)

Preparation of 5-methoxy-1,3,4-thiadiazol-2-yl isocyanate dimer

A saturated solution of phosgene in ethyl acetate (100 mL) is added to a glass reaction vessel equipped with a mechanical stirrer.

A slurry of 5-methoxy-2-amino-1,3,4-thiadiazole (40 grams) in ethyl acetate (300 ml) is added to the reaction vessel and the resulting mixture is stirred for approx. 16 hours, whereby a precipitate occurs. The reaction mixture is then purified by blowing through with nitrogen gas to remove unreacted phosgene. The purified mixture is then filtered to recover the precipitate. The precipitate is then recrystallized so that the desired product 5-methoxy-1,3,4-thiadiazol-2-yl-isocyanate dimer is obtained.

b)

Preparation of 2-propyl-4-(5-methoxy-1,3,4-thiadiazol-2-yl)-semicarbazide

A solution of propylhydrazine (0.3 mol) in methylene chloride

(150 mL) is added to a glass reaction vessel equipped with a mechanical stirrer, a thermometer, and a reflux condenser. 5-methoxy-1,3,4-thiadiazol-2-yl-isocyanate dimer (0.1 mol) is then added with stirring

stirring at room temperature. After the addition is finished, the reaction mixture is heated at reflux for approx. 4 hours. There-

solvent and excess hydrazine are then evaporated from the reaction mixture so that the desired product 2-propyl-4-(5-methoxy-1,3,4-thiadiazol-2-yl)semicarbazide is obtained as a residue.

c)

Preparation of 2-propyl-4-(5-methoxy-1,3,4-thiadiazol-2-yl)-1,2,4-triazolidin-3-one

2-propyl-4-(5-methoxy-1,3,4-thiadiazol-2-yl)semicarbazide

(0.1 mol) dissolved in methanol (100 mL) is added to a glass reaction vessel equipped with a mechanical stirrer and a thermometer.

Aqueous formaldehyde (0.2 mol, 37% concentration) is then added to the reaction vessel with stirring. Dilute aqueous potassium hydroxide is added to the reaction mixture to adjust the pH to between 7 and 8 and stirring is continued for approx. 20 minutes, whereby a solid precipitate is formed. The solid precipitate is recovered by filtration, recrystallized and dried in vacuum so that

desired product 2-propyl-4-(5-methoxy-1,3,4-thiadiazol-2-yl)-1,2,4-triazolidin-3-one is obtained.

Example 13 a)

Preparation of 5-methylthio-1,3,4-thiadiazol-2-yl isocyanate dimer

A saturated solution of phosgene in ethyl acetate (100 ml) to

is added to a glass reaction vessel equipped with a mechanical stirrer.

A slurry of 5-methylthio-2-amino-1,3,4-thiadiazole (45 grams) in ethyl acetate (300 ml) is added to the reaction vessel and the resulting mixture is stirred for approx. 16 hours, whereby a precipitate is formed. The reaction mixture is then purified by blowing through with nitrogen gas to remove unreacted phosgene. The purified mixture is recrystallized so that the desired product 5-methylthio-1,3,4-thiadiazol-2-yl-isocyanate dimer is obtained.

b)

Preparation of 2-methyl-4-(5-methylthio-1,3,4-thiadiazol-2-yl)-semicarbazide

A solution of methylhydrazine (0.3 mol) in methylene chloride (150 ml) is added to a glass reaction vessel equipped with

a mechanical stirrer, a thermometer and a reflux condenser. 5-Methylthio-1,3,4-thiadiazol-2-yl-isocyanate dimer (0.1 mol) is then added with stirring at room temperature. After the addition is finished, the reaction mixture is heated under reflux for approx. 4 hours. The solvent and excess hydrazine are then evaporated from the reaction mixture so that the desired product 2-methyl-4-(5-methylthio-1,3,4-thiadiazol-2-yl)semicarbazide is obtained as a residue.

Preparation of 2-methyl-4-(5-methylthio-1,3,4-thiadiazol-2-yl)-1,2,4-triazolidin-3-one

2-methyl-4-(5-methylthio-1,3,4-thiadiazol-2-yl)semicarbazide

(0.1 mol) dissolved in methanol (100 ml) is added to a glass reaction vessel equipped with a mechanical stirrer and a thermometer.

Aqueous formaldehyde (0.2 mol, 37% concentration) is then added to the reaction vessel with stirring. Dilute aqueous potassium hydroxide is added to the reaction mixture to adjust the pH to between 7 and 8 and stirring is continued for approx. 20 minutes, whereby a solid precipitate is formed. The precipitate is recovered by filtration, recrystallized and dried in vacuum so that the desired product 2-methyl-4-(5-methylthio-1,3,4-thiadiazol-2-yl)-1,2,4-triazolidin-3-one is achieved.

Example 14 a) Preparation of 5-methylsulfonyl-1,3,4-thiadiazol-2-yl isocyanate dimer

A saturated solution of phosgene in ethyl acetate (100 ml) to

is added to a glass reaction vessel equipped with a mechanical stirrer.

A slurry of 5-methylsulfonyl-2-amino-1,3,4-thiadiazole (50 grams)

in ethyl acetate (300 ml) is added to the reaction vessel and the resulting mixture is stirred for approx. 16 hours, whereby a precipitate is formed. The reaction mixture is then purified by blowing through with nitrogen gas to remove unreacted phosgene. The purified mixture is then filtered to recover the precipitate. The precipitate is then recrystallized so that the desired product 5-methylsulfonyl-1,3,4-thiadiazol-2-yl-isocyanate dimer is obtained.

b)

Process for the production of 2-n-butyl-4-(5-methylsulfonyl-1,3,4-thiadiazol-2-yl)semicarbazid

A solution of n-butylhydrazine (0.3 mol) in methylene chloride (150 ml) is added to a glass reaction vessel equipped with a mechanical stirrer, a thermometer and a reflux condenser. 5-methylsulfonyl-1,3,4-thiadiazol-2-yl-isocyanate dimer (0.1 mol) is then added with stirring at room temperature. After the addition is finished, the reaction mixture is heated under reflux for approx. 4 hours. The solvent and excess hydrazine are then evaporated so that the desired product 2-n-butyl-4-(5-methylsulfonyl-1,3,4-thiadiazol-2-yl)semicarbazide is obtained as a residue.

c)

Preparation of 2-n-butyl-4-(5-methylsulfonyl-1,3,4-thiadiazol-2-yl)-1,2,4-triazolidin-3-one

2-n-butyl-4-(5-methylsulfonyl-1,3,4-thiadiazol-2-yl)-semicarbazide (0.1 mol) dissolved in methanol (100 ml) is added to a glass reaction vessel equipped with a mechanical stirrer and a thermometer. Aqueous formaldehyde (0.2 mol, 37% concentration) is then added to the reaction vessel with stirring. Dilute aqueous potassium hydroxide is added to the reaction mixture to adjust the pH to between 7 and 8 and stirring is continued for approx. 20 minutes, whereby a precipitate is formed. The precipitate is recovered by filtration, recrystallized and dried in vacuum so that the desired product 2-n-butyl-4-(5-methylsulfonyl-1,3,4-thiadiazol-2-yl)-1,2,4-triazolidin-3 -on is achieved.

Example 15 a)

Preparation of 5-methylsulfinyl-1,3,4-thiadiazol-2-yl isocyanate dimer A saturated solution of phosgene in ethyl acetate (100 ml) is added to a glass reaction vessel equipped with a mechanical stirrer. A slurry of 5-methylsulfinyl-2-amino-1,3,4-thiadiazole (50 grams) in ethyl acetate (300 ml) is added to the reaction vessel and the resulting mixture is stirred for approx. 16 hours, whereby a precipitate is formed. The reaction mixture is then purified by blowing through with nitrogen gas to remove unreacted phosgene. The purified mixture is then filtered to recover the precipitate. The precipitate is recrystallized so that the desired product 5-methylsulfinyl-1,3,4-thiadiazol-2-yl-isocyanate dimer is obtained.

Preparation of 2-n-hexyl-4-(5-methylsulfinyl-1,3,4-thiadiazol-2-yl)-semicarbazide

A solution of n-hexylhydrazine (0.3 mol) in methylene chloride (150 ml) is added to a glass reaction vessel equipped with a mechanical stirrer, a thermometer and a reflux condenser. 5-methyl-sulfinyl-1,3,4-thiadiazol-2-yl-isocyanate dimer (0.1 mol) is then added with stirring at room temperature. After the addition is finished, the mixture is heated under reflux for approx. 4 hours. The solvent and excess hydrazine are then evaporated so that

the desired product 2-n-hexyl-4-(5-methylsulfinyl-1,3,4-thiadiazol-2-yl)semicarbazide is obtained as a residue.

O

Preparation of 2-n-hexyl-4-(5-methylsulfinyl-1,3,4-thiadiazol-2-yl)-1,2,4-triazolidin-3-one

2-n-hexyl-4-(5-methylsulfinyl-1,3,4-thiadiazol-2-yl)-semicarbazide (0.1 mol) dissolved in methanol (100 ml) is added to a glass reaction vessel equipped with a mechanical stirrer and a thermometer. Aqueous formaldehyde (0.2 mol, 37% concentration) is then added to the reaction vessel with stirring. Dilute aqueous potassium hydroxide is added to the reaction mixture to adjust the pH to between 7 and 8 and stirring is continued for approx. 20 minutes, whereby a solid precipitate is formed. The precipitate is recovered by filtration, recrystallized and dried in vacuum so that the desired product 2-n-hexyl-4-(5-methylsulfinyl-1,3,4-thiadiazol-2-yl)-1,2,4-triazolidine is obtained.

Example 16 a)

Preparation of 5-cyclobutyl-1,3,4-thiadiazol-2-yl-isocyanate dimer

A saturated solution of phosgene in ethyl acetate (100 mL) is added to a glass reaction vessel equipped with a mechanical stirrer. A slurry of 5-cyclobutyl-2-amino-1,3,4-thiadiazole (50 grams) in ethyl acetate (300 ml) is added to the reaction vessel and the resulting mixture is stirred for approx. 16 hours, whereby a precipitate is formed. The reaction mixture is purified by blowing through with nitrogen gas to remove unreacted phosgene. The purified mixture is then filtered to recover the precipitate. The precipitate is then recrystallized so that the desired product 5-cyclobutyl-1,3,4-thiadiazol-2-yl-isocyanate dimer is obtained. 0

b)

Preparation of 2-methyl-4-(5-cyclobutyl-1,3,4-thiadiazol-2-yl)-semicarbazide

A solution of methylhydrazine (0.3 mol) in methylene chloride

(150 ml) is added to a glass reaction vessel equipped with a mechanical stirrer, thermometer and reflux condenser. 5-cyclobutyl-1,3,4-thiadiazol-2-yl-isocyanate dimer (0.1 mol) is then added under stirring

stirring at room temperature. After the addition is finished, the reaction mixture is heated at reflux for approx. 4 hours. The solvent and excess hydrazine are then evaporated from the reaction mixture so that the desired product 2-methyl-4-(5-cyclobutyl-1,3,4-thiadiazol-2-yl)semicarbazide is obtained.

c)

Preparation of 2-methyl-4-(5-cyclobutyl-1,3,4-thiadiazol-2-yl)-1,2,4-triazolidin-3-one

2-Methyl-4-(5-cyclobutyl-1,3,4-thiadiazol-2-yl)semicarbazide (0.1 mol) dissolved in methanol (100 ml) is added to a glass reaction vessel equipped with a mechanical stirrer and a thermometer.

Aqueous formaldehyde (0.2 mol, 37% concentration) is then added to the reaction vessel with stirring. Dilute aqueous potassium hydroxide is added to the reaction mixture to adjust the pH to between 7

and 8 and the stirring is continued for approx. 20 minutes, whereby a solid precipitate is formed. The precipitate is recovered by filtration, recrystallized and dried in vacuum so that the desired product 2-methyl-4-(5-cyclobutyl-1,3,4-thiadiazol-2-yl)-1,2,4-triazolidin-

3- on is achieved.

Example 17 a)

Preparation of 5-cyclohexyl-1,3,4-thiadiazol-2-yl isocyanate dimer

A saturated solution of phosgene in ethyl acetate (100 ml) is added to a glass reaction vessel equipped with a mechanical stirrer. A slurry of 5-cyclohexyl-2-amino-1,3,4-thiadiazole (50 grams)

in ethyl acetate (300 ml) is added to the reaction vessel and the resulting mixture is stirred for approx. 16 hours, whereby a precipitate is formed. The reaction mixture is then purified by blowing through nitrogen gas to remove unreacted phosgene. The purified mixture is then filtered to recover the precipitate. The precipitate is then recrystallized so that the desired product 5-cyclohexyl-1,3,4-thiadiazol-2-yl-i^ocyanate dimer is obtained.

b)

Preparation of 2-methyl-4-(5-cyclohexyl-1,3,4-thiadiazol-2-yl)-semicarbazide

A solution of methylhydrazine (0.3 mol) in methylene chloride.

(150 mL) is added to a glass reaction vessel equipped with a mechanical stirrer, a thermometer, and a reflux condenser • 5-cyclohexyl-1,3,4-thiadiazol-2-yl-isocyanate dimer (0.1 mol) is then added with stirring at room temperature. After the addition is finished, the reaction mixture is heated under reflux for approx. 4 hours. The solvent and excess hydrazine are then evaporated from the reaction mixture so that the desired product 2-methyl-4-(5-cyclohexyl-1,3,4-thiadiazol-2-yl)semicarbazide is obtained.

c)

Preparation of 2-methyl-4-(5-cyclohexyl-1,3,4-thiadiazol-2-yl)-1,2,4-triazolidin-3-one

2-Methyl-4-(5-cyclohexyl-1,3,4-thiadiazol-2-yl)semicarbazide (0.1 mol) dissolved in methanol (100 ml) is added to a glass reaction vessel equipped with a mechanical stirrer and a thermometer. Aqueous formaldehyde (0.2 mol, 37% concentration) is then added to the reaction vessel with stirring. Dilute aqueous potassium hydroxide is added to the reaction mixture to adjust the pH to between 7 and 8 and stirring is continued for approx. 20 minutes, whereby a solid precipitate is formed. The precipitate is recovered by filtration, recrystallized and dried in vacuum so that the desired product 2-methyl-4-(5-cyclohexyl-1,3,4-thiadiazol-2-yl)-1,2,4-triazolidin-3-one is achieved.

For practical use as herbicides, the compounds are mixed in

according to the invention usually in herbicidal preparations comprising an inert carrier and a quantity of the compounds which are toxic to weed plants. Such herbicidal preparations, which can also be called recipes, make it possible to use the active compound appropriately in a desired amount in places where weeds are found.

These preparations can be solid, such as e.g. dust, granules or wettable powders, or they can be liquids such as e.g. solutions, aerosols or emulsifiable concentrates.

Dust can, for example, be produced by grinding and mixing

the active compound with a solid, inert carrier such as e.g. talk,

clay, silica, pyrophyllite and the like. Granular preparations can be prepared by impregnating the compound,

usually dissolved in a suitable solvent, on and into granular carriers such as the attapulgites or vermiculites, usually in a particle size range. on from approx. 0.3 to 1.5 mm. Wettable powders, which can be dispersed in water or oil to any desired concentration of the active compound, can be prepared by mixing wetting agents into concentrated dusts.

preparations.

In some cases, the active compounds are sufficiently soluble in common organic solvents such as e.g. kerosene or xylene, so that they can be used directly as solutions in these solvents. Often solutions of herbicides can be dispersed under superatmospheric pressure as aerosols. However, preferred liquid herbicidal preparations are emulsifiable concentrates, which comprise an active compound according to the invention and which inertly carry a solvent and an emulsifier. Such emulsifiable concentrates can be diluted with water and/or oil to any desired concentration of active compound for application by spraying on the weed-infested sites. The most commonly used emulsifiers in these concentrates are non-ionic or mixtures of non-ionic and anionic surfactants. By using certain emulsifier systems, an inverted emulsion (water-in-oil) can be produced for direct application to weed-infested sites.

A typical herbicidal preparation according to the invention is illustrated by the following example, where the amounts are given as parts by weight.

Preparation of a dust.

The above-mentioned ingredients are mixed in a mechanical grinding-mixing machine and ground until a homogeneous, free-flowing dust with the desired particle size is obtained. This dust is suitable for direct application to weed-infested areas.

Compounds according to the invention can be applied as herbicides in any way that is recognized in the field. A method for combating weeds comprises bringing the locations of said weeds into contact with a herbicidal preparation comprising an inert carrier and, as an essential, active ingredient in an amount that is herbicidally toxic to said weeds, a compound according to the invention. The concentration of the new compounds according to the invention in the herbicidal preparations will vary greatly with the type of preparation and the purpose for which it is intended, but usually the herbicidal preparations contain from approx. 0.05 to approx. 95% by weight of the active compounds according to the invention. In a preferred embodiment of the invention, the herbicidal preparations comprise from approx. 5 to approx. 75% by weight of the active compound. The preparations may also contain such additional substances as other pesticides such as e.g. insecticides, nematocides, fungicides and the like, stabilizers, dispersants, deactivators, adhesives, fixing agents, fertilisers, activators, synergists and the like.

The compounds according to the invention are also usable when combined with other herbicides and/or leaf removers, drying agents, growth inhibitors and the like in herbicidal preparations described above. These other materials can include from approx. 5 to approx. 95% of the active ingredients in the herbicidal preparations. Use of combinations of these other herbicides and/or defoliants, desiccants etc. with the compounds according to the invention gives herbicidal preparations which are more effective for fighting weeds and often gives results which cannot be achieved with separate preparations of the individual herbicides. The other herbicides, defoliants, desiccants and plant growth inhibitors which can be used in conjunction with the compounds of the invention for controlling weeds may include: chlorophenoxy herbicides, which

e.g. 2,4-D, 2,4,5-T, MCPA, MCPB, 4(2,4-DB), 2,4-DEB, 4-CPB, 4-CPA, 4-CPP, 2,4,5 -TB, 2,4,5-TES, 3,4-DA, silvex and similar, carbamate herbicides such as IPC, CIPC, sweep, barban, BCPC, CEPC, CPPC and similar; thiocarbamate and dithiocarbamate herbicides such as CDEC, metham sodium, EPTC, diallate, PEBC, perbulate, vernolate and the like; substituted urea herbicides, such as norea, siduror, dichloral-urea, chloroxuron, cycluron, fenuron, monuron, monuron TCA, diuron, linuron, monolinuron, neburon, buturon, trimeturon and the like; symmetrical triazine herbicides such as simazine,

chlorazine, atraon, desmetryn, norazin, ipazine, prometryn, atazine, triethazine, simeton, prometon, propazine, ametryn and the like, chloracetamide herbicides such as 4-(chloroacetyl)morpholine, 1-(chloroacetyl)piperidine and the like; chlorinated aliphatic acid herbicides such as TCA, dalapone, 2,3-dichloropropionic acid, 2,2,3-TPA

and such; chlorinated benzoic acid and phenylacetic acid herbicides such as 2,3,6-TBA, 2,3,5,6-TBA, dicamba, tricamba, amoeba,

fenac, PBA, 2-methoxy-3,5-dichlorophenylacetic acid, 3-methoxy-2,6-dichlorophenylacetic acid, 2-methoxy-3,5,6-trichlorophenylacetic acid, 2,4-dichloro-3-nitrobenzoic acid and the like; and such compounds as aminotriazole, maleic hydrazide, phenylmercuric acetate, endothal, biuret, technical chlordane, dimethyl-2,3,5,6-tetrachloro-

terephthalate, diquat, erbon, DNC, DNBP, diclobenil, DPA, diphenamide, dipropalin, trifluralin, solan, dicryl, merphos, DMPA, DSMA, MSMA, potassium azide, acrolein, benefin, benzulide, AMS, bromacil, 2-(3,4 -dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione,

bromoxynil, cacodylic acid, CMA, CPMF, cypromide, DCB, DCPA, dichlone, diphenatrile, DMTT, DNAP, EBEP, EXD, HCA, ioxynil, IPX, isocyl, potassium cyanate, MAA, MAMA, MCPES, MCPP, MH, molinate, NPA, AND,

paraquat, PCP, picloram, DPA, PCA, pyrichlor, seson, terbacil,

terbutol, TCBA, brominil, CP-50144, H-176-1, H-732, M-2901,

planavin, sodium tetraborate, calcium cyanamide, DEF, ethyl xanthogen- . disulfide, sindone, sindone B, propanil and the like.

Such herbicides can also be used in the methods and preparations according to the invention in the form of their salts, esters,

amides and other derivatives, when these can be formed from the special parent compounds.

Weeds are unwanted plants that grow where they don't belong

desired, has no economic value and affects the growth of cultivated plants or ornamental plants or the health of livestock.

Many kinds of weeds are known and include annual plants such as e.g. perumelde, meldestick, foxtail, finger millet, field mustard,

common meadow grass, common ryegrass, gooseberry, water sedge, ragweed, purslane, hen's millet, "smartweed", knotweed,

hook seed, wild buckwheat, "kochia", snail shell, clint, ambrosia,

dyll, "coffeeweed", croton, "cuphea", creeping thread, earth smoke, field pig flower, doe, knavel, wart milk, common lindendel, "emex", jungle rice, tjønnaks, top goose flower, "carpetweed", wormwood,

ants, duckweed, "naiad", ryegrass, winter millet, prickly pear, common quack, "switchgrass", spring grass, "teaweed", wild turnips and tassel top,

biennial plants such as wild carrot, chamomile flower, wild barley,

cock's comb, goose flower, borre, king's wort, round-leaved cat's cheese, road thistle, dog's tongue, moth king's wort and violet budwort, or perennial plants such as e.g. white klinte, perennial ryegrass, quack,

"Johnson grass" (a species of sorghum), field thistle, sedge,

Bermuda grass, sorrel, curly sorrel, cypress grass, sedge, dandelion, bluebell, meadowsweet, Russian knotweed, "mesquite", cod's mouth, yarrow, asters, stone seed, horsetail, "ironweed", "sesbania", sivax, sedge, wintercress, sweet willow, storr, "milkweed" and skrinneblom.

Such weeds can be similarly classified as broad-leaved or grassy weeds. It is economically desirable to

control the growth of such weeds without harming useful plants or livestock.

The new compounds according to the invention are special

valuable for weed control because they are toxic to many species and groups of weeds, while being relatively non-toxic to many beneficial plants. The exact amount of compound required will depend on many factors, including the resistance of the particular weed species, weather, soil type, application

the way, which types of useful plants are found in the same area and the like. Thus, while the application of up to only approx. 11.1 or 22.3 grams of active compound per ar may be sufficient for effective control of light weed infestations that grow under unfavorable conditions, the application of 111 grams or more per ar be necessary for effective control of a heavy attack of hard-necked perennial weeds that grow under favorable conditions.

The herbicidal toxicity of the new compounds according to the invention can be illustrated using many of the established test techniques known in the field, such as e.g. pre- and post-germination tests.

The herbicidal activity of the compounds according to the invention was demonstrated by experiments carried out with pre-germination control of various weeds. In these experiments, different weed seeds were sown in small plastic greenhouse pots filled with dry soil. Twenty-four hours or less after sowing, the pots were watered

until the soil was wet and the test compounds in the form of aqueous emulsions of acetone solutions containing emulsifiers were showered in the indicated concentrations on the surface of the soil.

After the shower, the soil containers were placed in the greenhouse

and added extra heat if needed and watered daily or more often. The plants were kept under these conditions for from 15 to 21 days, when the condition of the plants and the degree of damage to the plants were judged on a scale from 0 to 10 as follows: 0 = no damage, 1.2 = slight damage, 3.4 = moderate damage , 5,6 = moderately severe injury, 7,8,9 = severe injury, 10 = death. The effectiveness of these compounds is shown by the following data:

The herbicidal activity of the compounds of the invention was also demonstrated in experiments conducted to determine post-emergence control of various weeds. In these experiments, the compounds to be tested were used in the form of aqueous emulsions that were showered in the specified dosages on weeds that had reached a certain size. After the shower, the plants were placed in the greenhouse and watered daily or more often. Water was not applied to the leaves of the treated plants. The severity of the damage was determined 10 to 15 days after the treatment and assessed according to the scale from 0 to 10 described above. The effectiveness of these compounds is shown by the following data:

Claims (1)

1,2,4-triazolidin-3-one derivatives with herbicidal action, characterized in that they have the formula: 1 2 where R is alkyl, and R is: where X is alkyl, alkoxy, alkylthio, halogen, haloalkyl or nitro and n is a number from 1 to 3, or R is: where R 3 is alkyl, trifluoromethyl, alkoxy, alkylthio, alkylsulfonyl, alkylsulfinyl or cycloalkyl with from 3 to 7 carbon atoms optionally substituted with 1 to 2 substituents selected from the group consisting of alkyl, alkoxy and halogen, all alkyl substituents or substituent parts having linear or branched carbon chains with 1 to 6 carbon atoms.