Field of the Invention
The present invention relates to a novel process for the preparation of Flazasulfuron of formula I or of salts thereof.
Background of the Invention Flazasulfuron is a representative of the sulfonylurea class of herbicides, chemically known as 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea, and is represented as:
The mode of action of Flazasulfuron is the inhibition of the enzyme acetolactase synthase (ALS), which results in the inhibition of amino acid synthesis, of cell division and ultimately of plant growth. Flazasulfuron can be used on both pre-emergent weeds and post-emergent weeds.
Processes for the preparation of Flazasulfuron have been already described in patents, e.g. in EP0184385, EP2450353 and EP2264023. These Processes involve the coupling of 3-(trifluoromethyl)-pyridine-2-sulfonamide and phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate to Flazasulfuron in presence of 1,8-diaza bicyclo[5.4.0]undec-7-ene, referred herein after as “DBU” and potassium carbonate base. Specially, in potassium carbonate reaction mixture is heterogeneous in nature, which does problem in reaction monitoring and reaction workup. Moreover, both the prior art bases are not recyclable, consequently, it produce more effluent, whereas base used in the present invention is completely recyclable, which is ultimately reduces the significant effluent generation.
These reported processes require high temperature and anhydrous condition. The present inventive process doesn’t require anhydrous environment and high temperature condition. The present process can be carried out in aquatic environment at room temperature, which were limiting factors in the prior art process.
These processes described in the prior art have shortcomings such as hazardous industrial waste disposal and low conversion rates. Hence there is still a demand for a simple and environmental friendly process that allows the preparation of Flazasulfuron or of salts thereof.
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Objective and Summary of the Invention:
It was therefore an objective to provide a simple, industrially feasible, safe and cost-effective process for the preparation of Flazasulfuron or of salts thereof.
Surprisingly, the present invention provides a solution to these objectives by offering a novel, high yielding and economically attractive process overcoming at least one of the shortcomings of the processes described in the prior art.
The objective was achieved according to the present invention by finding a process for preparing Flazasulfuron of formula I or of salts thereof,
by reacting a compound of formula II or of a salt thereof
with a compound of formula III or of a salt thereof
in the presence of a base and optionally in presence of a solvent, wherein base is selected from group comprising triethylamine, pyridine, potassium hydroxide, sodium hydroxide, and sodium carbonate; solvent is selected from group comprising is selected from group comprising acetonitrile, acetone, toluene, hexane, xylene, methylene dichloride, ethylene dichloride, chloroform, monochlorobenzene, orthodichlorobenzene, tetrahydrofuran, dimethyl sulfoxide, dimethylacetamide, 1,4-dioxane, diethyl ether, dimethylformamide, methylacetate, ethylacetate, methanol, ethanol, t-butanol and isopropyl alcohol.
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Detailed Description of the Invention
The present invention relates to a process for the preparation of Flazasulfuron of formula I or of salts thereof
which comprises reacting a compound of formula II or of a salt thereof
with a compound of formula III or of a salt thereof
in the presence of a base and optionally in presence of a solvent, wherein base is selected from group comprising triethylamine, pyridine, potassium hydroxide, sodium hydroxide, and sodium carbonate; solvent is selected from group comprising is selected from group comprising acetonitrile, acetone, toluene, hexane, xylene, methylene dichloride, ethylene dichloride, chloroform monochlorobenzene, orthodichlorobenzene, tetrahydrofuran, dimethyl sulfoxide, dimethylacetamide, , 1,4-dioxane, diethyl ether, dimethylformamide, methylacetate, ethylacetate, methanol, ethanol, t-butanol and isopropyl alcohol.
The reaction of compounds of formula II or salts thereof with compound of formula III or salts thereof may be carried out under reduced pressure, under atmospheric conditions or under higher then atmospheric pressure, for instance in an autoclave being operated under autogenous pressure or under application of external pressure, in all of these variations preferably in one inert solvent or in a mixture of more than one inert solvents, preferably under reflux conditions.
A specific embodiment of the present invention provides a novel process for preparing substituted heterocyclic compounds of formula I or of salts thereof, having a purity of more than 99 %, if measured by a HPLC method.
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The another embodiment of present invention discloses a process for the preparation of Flazasulfuron of formula I or of a salt thereof
by reacting a compound of formula II or of a salt thereof
with a compound of formula III or of a salt thereof
in presence of a triethylamine base and in presence of acetonitrile solvent.
According to the present invention, after completion of the reaction the isolation of the desired product is carried out by suitable conventional techniques known to a person being skilled in the art, such as separation/ solvent extraction/ triturating, acid-base wash, chromatography, filtration, sedimentation, centrifugation and/or washing.
The present invention is described in more details as illustrated in the following non-limiting examples. It should be understood that variation and modification of the inventive process are possible within the ambit of the invention broadly disclosed herein.
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Examples
Example 1: Preparation of 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea
A mixture of acetonitrile (40 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (8.5 g), triethyl amine (3 mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (11.2 g) was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid (Yield: 14.32 g, 93.6 %).
Example -1a
A mixture of acetonitrile (40 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (8.5 g), triethyl amine (3 mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (11.2 g) was kept at 10-15 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid (Yield: 14.40 g, 94 %).
Example -1b
A mixture of acetonitrile (40 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (8.5 g), triethyl amine (3 mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (11.2 g) was kept at 15-20 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -1c
A mixture of acetonitrile (40 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (8.5 g), triethyl amine (3 mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (11.2 g) was kept at 40-45 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed
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with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -1c
A mixture of acetonitrile (40 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (8.5 g), triethyl amine (3 mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (11.2 g) was kept at 0-5 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -1d
A mixture of acetonitrile (40 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (8.5 g), triethyl amine (3 mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (11.2 g) was kept at 5-10 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -1e
A mixture of acetonitrile (40 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (8.5 g), triethyl amine (3 mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (11.2 g) was kept at 30-35 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -1f
A mixture of acetonitrile (40 mL), (3-(trifluoromethyl)-pyridine-2-sulfonamide (8.5 g), triethyl amine (3 mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (11.2 g) was kept at 35-40 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -2
A mixture of acetonitrile (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), pyridine (0.41 mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed
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with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -3
A mixture of acetonitrile (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), sodium carbonate (0.44g), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g), was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -4
A mixture of acetonitrile (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), sodium bicarbonate (0.44g), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -5
A mixture of acetonitrile (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), dimethylformamide (0.38mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -6
A mixture of acetonitrile (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), caesium carbonate (1.7 g), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -7
A mixture of acetonitrile (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), 10% sodium hydroxide (2.09 mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
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Example -8
A mixture of acetonitrile (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), potassium hydroxide (0.29 g), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -9
A mixture of acetonitrile (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), 10% aq. potassium hydroxide (2.9 mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -10
A mixture of acetone (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), triethyl amine (3 mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -11
A mixture of toluene (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), triethyl amine (3 mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -12
A mixture of mono chloro benzene (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), triethyl amine (3 mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
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Example -13
A mixture of mix xylene (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), triethyl amine (3 mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -14
A mixture of methanol (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), triethyl amine (3 mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -15
A mixture of methylene dichloride (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), triethyl amine (3 mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -16
A mixture of ethylene dichloride (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), triethyl amine (3 mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -17
A mixture of tetrahydrofuran (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), triethyl amine (3 mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
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Example -18
A mixture of dimethyl sulfoxide (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), triethyl amine (3 mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -19
A mixture of dimethylacetamide (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), triethyl amine (3 mL) phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -20
A mixture of t-butanol (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), triethyl amine (3 mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -21
A mixture of 1,4-dioxane (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), triethyl amine (3 mL) phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. The reaction is monitored by HPLC analysis. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -22
A mixture of chloroform 4 mL, 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), triethyl amine (3 mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
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Example -23
A mixture of diethyl ether (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), triethyl amine (3 mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -24
A mixture of dimethylformamide (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), triethyl amine (3 mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. The reaction is monitored by HPLC analysis. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -25
A mixture of methylacetate (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), triethyl amine (3 mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -26
A mixture of ethylacetate (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), triethyl amine (3 mL), phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -27
A mixture of ethanol (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide) (0.85 g), triethyl amine (3 mL) phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
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Example -28 A mixture of isopropyl alcohol (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), triethyl amine (3 mL) phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -29
A mixture of hexane (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), triethyl amine (3 mL) phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.
Example -30
A mixture of orthodichlorobenzene (4 mL), 3-(trifluoromethyl)-pyridine-2-sulfonamide (0.85 g), triethyl amine (3 mL) phenyl (4,6-dimethoxypyrimidin-2-yl)-carbamate (1.12 g) was kept at 25-30 °C. After completion of the reaction, water was charged to the reaction mixture, and the pH was adjusted to a value between 3.5-4.0 by addition of hydrochloric acid. The slurry mass obtained was filtered, washed with water to obtain 1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(trifluoromethyl)pyridin-2-yl]sulfonylurea as a solid.

We Claim:
1. A process for the preparation of Flazasulfuron of formula I or of a salt thereof
by reacting a compound of formula II or of a salt thereof
with a compound of formula III or of a salt thereof
in presence of a base and optionally in presence of a solvent, wherein base is selected from group comprising triethylamine, pyridine, potassium hydroxide, sodium hydroxide, and sodium carbonate; solvent is selected from group comprising is selected from group comprising acetonitrile, acetone, toluene, hexane, xylene, methylene dichloride, ethylene dichloride, chloroform monochlorobenzene, orthodichlorobenzene, tetrahydrofuran, dimethyl sulfoxide, dimethylacetamide, 1,4-dioxane, diethyl ether, dimethylformamide, methyl acetate, ethyl acetate, methanol, ethanol, t-butanol and isopropyl alcohol.
2. A process according to claim 1, wherein the reaction of the compound of formula II with the compound of formula III is carried out in a temperature range between 60 °C and 180 °C.
3. A process according to claim 1, wherein the Flazasulfuron or of salts thereof, which is obtained has a purity of more than 99 %, when measured by HPLC method.
4. A process for the preparation of Flazasulfuron of formula I or of a salt thereof
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by reacting a compound of formula II or of a salt thereof
with a compound of formula III or of a salt thereof
in presence of a triethylamine base and acetonitrile solvent.