DESC:Form 2

The Patents Act, 1970
(39 of 1970)

COMPLETE SPECIFICATION
(Section 10; Rule 13)

“A process for preparation of Flubendiamide and its intermediates”

MEGHMANI ORGANICS LTD.
A Company Incorporated under the Indian Companies Act,
“Meghmani House”, B/H Safal Profitaire,
Corporate Road, Prahaladnagar,
Ahmedabad-380015,
Gujarat, India.

The following specification particularly describes the nature of the invention and the manner in which it is to be performed:
FIELD OF INVENTION:

The present invention generally relates to a process for preparation of Flubendiamide and its intermediates. In particular, it provides an oxidation process for preparation of N2-[1,1-dimethyl-2-(methylsulfonyl)ethyl]-3-iodo-N1-[2-methyl-4-[1,2, 2,2-tetrafluoro-1-(trifluo¬romethyl)ethyl]phenyl]-1,2-benzenedicarboxamide, also known as Flubendiamide and its intermediate Flubendiamide Sulfoxide.

BACKGROUND OF INVENTION:

Flubendiamide or Fipronil Bisamide; IUPAC name is as follows: the 1-N-[4-(1,1,1,2,3,3,3-heptafluoropropan-2-yl)-2-methylphenyl]-3-iodo-2-N-(2-methyl-1-methylsulfonylpropan-2-yl)benzene-1,2-dicarboxamide; Molecular formula: C23H22F7IN2O4S; Relatively Molecular mass: 682.39. Flubendiamide is the first example of benzene di-carboxamide or phthalic acid diamide insecticides, discovered by Nihon Nohyaku and developed jointly with Bayer Crop Science. It is a practical insecticide which activates ryanodine receptors. Conventionally, there are number of methods to synthesize Flubendiamide. One of which is, by oxidation of 3-iodo-N2-(2-methyl-1-(methylthio)propan-2-yl)-N1-(2-methyl-4-(perfluoropropan-2-yl) phenyl)phthalamide with various other oxidizing agents in suitable solvents. The other method is, by chemical synthesis,3- iodo phthalic anhydride. First, reacted with 2-methyl-1-(methylthio)-2-Propanamine, after indexing again with 2-Methyl-4-heptafluoro isopropyl aniline. But since indexing is needed, a large amount of trifluoroacetic anhydride and expensive oxidizing reagent like m-chloroperbenzoic acid (MCPBA) are required, which produces a large amount of strongly acid wastewaters, economic cost is higher and larger to environmental disruption.
Therefore, there is a need to provide a process for preparing Flubendiamide and its intermediates, which can be carried out at large commercial scale and provides reuse of the resin catalyst.
PRIOR ART AND ITS DISADVANTAGES:

One of the Chinese Patent Application CN101948413A provides a method for preparing Flubendiamide. The method comprises the following steps of: adding N2-[1,1-dimethyl-2-methylmercaptoacylethyl]-3-I-N1-[2-methyl-4-(1,2,2,2-tetrachloro-1-trifluoromethaneethyl)-1,2-phthalic diamide to a solvent; introducing air in the presence of nitric acid and manganese acetate which are used as catalysts to carry out an oxidizing reaction; and then collecting a target product from a reaction product. In the method, because the air is used for carrying out the oxidizing reaction, the cost is reduced, and the acid is reduced; the raw material conversion can reach higher than 99 percent; and the method has the advantages of reasonable process, simple and safe operation, low cost and convenience for industrial production.

Said invention provides the preparation method of Flubendiamide using solvent among DMF or the DMAC and catalyzer nitric acid and manganese acetate. The oxidizing reaction is carried out by bubbling air at 60-120°Cwhich is difficult to operate at large scale. Further, it is difficult to remove/ recover solvent (DMF or DMAC) from nitric acid solution and in order to get the pure material, additional purification in alcohol is required.
Another Chinese patent application CN109485588A relates to fipronil bisamide synthesis technical fields, the invention discloses a kind of synthetic methods of fipronil bisamide, comprising steps of a. amidation process: by the iodo- N- (1 of 3-, 1- dimethyl -2-methylmercaptoethyl) phthalamic acid and 2- methyl -4- hepta-fluoroiso-propyl aniline is under amidation catalyst effect, it is reacted in non-protonic solvent, obtains fipronil bisamide intermediate; b. sulfide oxidation reacts: by fipronil bisamide intermediate under the action of sulfide oxidation agent, reacting in non-protonic solvent, obtains fipronil bisamide. The present invention reduces single step reaction step compared with prior art, production time and energy consumption is greatly reduced, and cost is greatly saved instead of expensive trifluoroacetic anhydride with cheap thionyl chloride.
Said invention provides the synthesis of Flubendiamide by the oxidation of Flubendiamide-Sulfide with m-chloroperbenzoic acid (MCPBA) in presence of aprotic solvent, such as dichloromethane, acetonitrile Dimethylformamide, Toluene etc. It provides the use of oxidizing agent like m-chloroperoxybenzoic acid in different solvent and condition, which is relatively expensive and explosive in nature. Hence, it is difficult to carry out large-scale industrial production.
DISADVANTAGES OF THE PRIOR ARTS:

The prior art suffers from all or at least any of the following disadvantages:
• Most of the existing methods use expensive, toxic or rare oxidizing reagents which are difficult to prepare and thus cannot be used on commercial scale.
• Conventional prior arts provide a process which produces a large amount of strongly acid wastewaters and thus not environment-friendly.
• The existing prior art provides the use of oxidizing agent like m-chloroperoxybenzoic acid in different solvent and condition, which is relatively expensive and explosive in nature.
• Most of the prior art fail to provide a process for preparation of Flubendiamide and its intermediate which can be carried out at large commercial scale.
• Many of prior art processes fail to provide high product yield.
• Many of the prior art provide a process which requires an additional purification in order to get pure material.
OBJECTS OF THE INVENTION:
The main object of the present invention is to provide a process for preparation of Flubendiamide and its intermediates.
Another object of the present invention is to provide the process for preparation of Flubendiamide and its intermediates, which avoids the use of dangerous and expensive catalysts like m-CPBA (m-chloroperbenzoic acid).
Yet another object of the present invention is to provide the process for preparation of Flubendiamide and its intermediates, which also avoids the production of unwanted or harmful byproducts.
Another object of the present invention is to provide the process for preparation of Flubendiamide and its intermediates, which provides high product yield.
Yet another object of the present invention is to provide the process for preparation of Flubendiamide and its intermediates, which provides high purity.

Another object of the present invention is to provide the process for preparation of Flubendiamide and its intermediates, which involves effective degree of oxidation resulting with optimum purity at commercial scale.
Yet another object of the present invention is to provide the process for preparation of Flubendiamide and its intermediates, which is environment friendly and having convenient operational steps at commercial scale.
Another object of the present invention is to provide the process for preparation of Flubendiamide and its intermediates, which provides reuse of resin catalyst.
Yet another object of the present invention is to overcome the disadvantages and deficiencies of the prior art and to provide the process for preparation of Flubendiamide and its intermediates.
SUMMARY OF THE INVENTION:
In order to achieve the foregoing objects, the present invention provides a process for preparation of Flubendiamide and its intermediate Flubendiamide Sulfoxide by oxidation of Flubendiamide Sulfide, using a medium comprising an oxidizing agent, a solvent and a resin catalyst. Said process comprises steps of: 1. Adding the compound of Flubendiamide Sulfide in a solvent; 2. Adding a resin catalyst to said mixture; 3. Forming a reaction mass by adding an oxidizing agent to the mixture; 4. Stirring the reaction mass up to completion of reaction; 5. Quenching the excess oxidizing agent by adding sodium sulphite solution; 6.Adding mixture of solvent to dissolve excess residue; 7. Raising reaction temperature up to 60°C; 8. Recovering the resin catalyst by filtration followed by washing with the solvent and drying for reuse of the resin catalyst; 9. Obtaining Flubendiamide by solvent distillation and Flubendiamide Sulfoxide by solvent evaporation, stirring with water, filtration and drying. The process provides high product yield with high purity. Further, the process provides reuse of the resin catalyst and thus it can be carried out at large commercial scale.
DESCRIPTION OF THE INVENTION:
The present invention provides a process for preparing Flubendiamide and its intermediate Flubendiamide Sulfoxide by oxidation of Flubendiamide sulfide, using a medium comprising an oxidizing agent, a solvent and a resin catalyst.
Wherein, said process comprises steps of:

1. Adding the compound of Flubendiamide Sulfide in the solvent;
2. Adding the resin catalyst to said mixture;
3. Forming a reaction mass by adding an oxidizing agent to the mixture;
4. Stirring the reaction mass up to completion of reaction;
5. Quenching the excess oxidizing agent by adding quenching agent;
6. Adding mixture of solvent to dissolve excess residue;
7. Raising reaction temperature up to 60°C;
8. Recovering the resin catalyst by filtration followed by washing with the solvent and drying for reuse of the resin catalyst;
9. Obtaining Flubendiamide by solvent distillation and Flubendiamide Sulfoxide by solvent evaporation, stirring with water, filtration and drying.

Step 1: Adding the compound of Flubendiamide Sulfide in the solvent;
The first step is to add the compound of Flubendiamide Sulfide, (3-Iodo-N2-(2-methyl-1-(methylthio) propan-2-yl)-N1-(2-methyl-4-(perfluoro propan-2-yl) phenyl) Phthalamide) to the solvent. Wherein, said solvent is selected from the group comprising methanol, ethanol, propanol, acetonitrile, Isopropanol, Ethyl acetate or ethylene dichloride (EDC),toluene, methylene dichloride, ethylene dichloride, carbon tetrachloride, chloroform, o-dichlorobenzene, Chlorobenzene, bromobenzene, dibromomethane, dichloroethane, acetic acid, monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, dibromoacetic acid, tribromoacetic acid, trifluoroacetic acid, trifluoroacdtic anhydride or mixture(s). It is alcoholic, acetate or chlorinated methane, and the preferred solvent is methanol or Ethyl acetate or ethylene dichloride. The ratio of the solvent is from 1:1 w/w to 1:10 w/w.
Step 2: Adding the resin catalyst to said mixture;
The next step is to add the resin catalyst to the mixture prepared in step 1. Wherein, said resin catalyst is selected from the group comprising: DOWEX, INDION, AMBERLYST, DIAION, AMBERLITE and PUROLITE; It can include, but not limited to, INDION 140, INDION 130, INDION 190, INDION 770, DOWEX MONOSPHERE M-31, DOWEX M-31, DOWEX 88, DUOLITE C-26, AMBERLITE 15, AMBERLYST 15 DRY, AMBERLYST 15 WET, AMBERLYST 36 WET, DOWEX DR-2030, DOWEX 50WX2-100, DOWEX 50WX4-100, DOWEX 50WX8-100, DOWEX MARATHON C, AMBERLITE IRP 69. The most preferred resin catalyst is INDION. The ratio of the resin catalyst is from 1:5% w/w to 1:50% w/w and the particle size of the resin catalyst ranges from 0.2 to1.5 mm.
Step 3: Forming a reaction mass by adding the oxidizing agent to the mixture;
In order to form a reaction mass, add the oxidizing agent drop wise at 10-65°C to the mixture prepared in step 2. Wherein, said oxidizing agent is selected from a group consisting of hydrogen peroxide, tert-butyl hydrogen peroxide, benzoylperoxide and sodium peroxide. The most preferred oxidizing agent is hydrogen peroxide. The molar ratio of hydrogen peroxide is from 1:1 w/w to 1:4 w/w and having mass concentration of 10% to 50%.
Step 4: Stirring the reaction mass up to completion of reaction;
The next step is, stirring the reaction mass and monitoring the reaction upto the completion.
For Flubendiamide Sulfoxide, the reaction is carried out at 30°C for 3 hrs;
For Flubendiamide, the reaction is carried out at 30°C to 60°C for 3 to 12 hrs based on the reaction condition.

Step 5: Quenching the excess oxidizing agent by adding quenching reagent;
After completion of reaction, add quenching agent for quenching the excess oxidizing agent. Wherein, said quenching agent is selected from the group comprising: Sodium Sulphite Solution, Sodium Hydrogen Sulfite and other peroxide scavengers. The most preferred quenching agent is Sodium Sulphite Solution.
Step 6: Adding a mixture of solvent to dissolve excess residue;
For Flubendiamide, in order to dissolve excess residue, add water or solvent or both.

Step 7: Raising reaction temperature up to 60°C;
To dissolve the Flubendiamide and Flubendiamide Sulfoxide, raise the reaction temperature up to 60°C.

Step 8: Recovering the resin catalyst by filtration followed by washing with the solvent and drying for reuse of the resin catalyst;
The next step is to filter out the resin catalyst and wash with the solvent followed by drying for reuse of the resin catalyst in subsequent reactions.

Step 9: Obtaining Flubendiamide by solvent distillation and Flubendiamide Sulfoxide by solvent evaporation, stirring with water, filtration and drying.
In order to obtain Flubendiamide, separate an aqueous phase from an organic phase of filtrate mother liquor by solvent distillation;
In order to obtain Flubendiamide Sulfoxide, evaporate the solvent, followed by stirring of water with solid mass for 30 minutes, filtration and drying.

EXAMPLES:
A) For preparation of Flubendiamide Sulfoxide:
Example 1:
In a glass reactor,3-Iodo-N2-(2-methyl-1-(methylthio)propan-2-yl)-N1-(2-methyl-4-(perfluoro propan-2-yl) phenyl) Phthalamide (Compound of Flubendiamide sulfide) (5.0 g, 0.008 mole) and 20 g of methanol were charged. The mixture was stirred for 15 minutes. To this mass Indion-190, resin catalyst (0.5 g, 10% w/w) was added followed by slowly addition of 35% hydrogen peroxide (1.12 g, 0.011 mole, 1.5 mole equivalents) at 30 °C and the reaction was stirred 30 °C for 3.0 hrs. Then, saturated sodium sulphite solution was added drop-wise until the starch potassium iodide test paper did not change to blue. After stirring for 0.5 hours, the temperature was raised up to 60°Cto dissolve the product completely. The resin catalyst was filtered out and washed with Methanol (10 g) followed by drying for re-use of resin catalyst in subsequent reactions, the solvent was distilled off to get solid mass. Water (25 g) was added and mass was stirred for 30 minutes followed by filtration and drying to obtain Flubendiamide Sulfoxide (4.75 g.). The purity was 98.1% (HPLC).
Example 2:
In a glass reactor, 3-Iodo-N2-(2-methyl-1-(methylthio) propan-2-yl)-N1-(2-methyl-4-(perfluoro propan-2-yl) phenyl) Phthalamide (Compound of Flubendiamide sulfide) (5.0 g, 0.008 mole) and 20 g of 1,2-dichloroethane were charged. The mixture was stirred for 15 minutes. To this mass Indion-190, the resin catalyst (0.5 g, 10% w/w) was added followed by slowly addition of 35% hydrogen peroxide (1.12 g, 0.012 moles and 1.50 mole equivalents) at 30 °C and the reaction was stirred at 30 °C for 3.0 hrs. Then, saturated sodium sulphite solution was added drop-wise until the starch potassium iodide test paper did not change to blue. After stirring for 0.5 hours, the temperature was raised up to 60°C for dissolve the product completely. The resin was filtered out and washed with 1, 2-dichloroethane (10 g) followed by drying for re-use of resin catalyst in subsequent reactions, solvent was distilled to get solid mass. Water (25 g) was added and mass was stirred for 30 minutes followed by filtration and drying to obtain Flubendiamide Sulfoxide (4.80 g). The purity was 98.8% (HPLC).
B) For preparation of Flubendiamide:
Example 1:
In a glass reactor, 3-Iodo-N2-(2-methyl-1-(methylthio) propan-2-yl)-N1-(2-methyl-4-(perfluoro propan-2-yl) phenyl) Phthalamide (Compound of Flubendiamide sulfide) (5.0 g, 0.008 mole) and 30 g of Ethyl acetate were charged. The mixture was stirred for 15 minutes. To this mass Indion-190, the resin catalyst (0.5 g, 10% w/w) was added followed by slowly addition of 35% hydrogen peroxide (2.26 g, 0.023 mole, 3.0 mole equivalents) at 30 °C, and the reaction was carried out at 60 ° C for 9.0 hrs. Then, saturated sodium sulphite solution was added drop-wise until the starch potassium iodide test paper did not change to blue. After stirring for 0.5 hours, water (15 g) was added and the temperature was raised up to 60°C for dissolving the product completely. The resin catalyst was filtered out and washed with ethyl acetate (10 g) followed by drying for re-use of resin catalyst in subsequent reactions. Aqueous phase was separated from organic phase of filtrate mother liquor followed by solvent distillation to obtain Flubendiamide (5.2 g.) The purity was 98.5% (HPLC).
Example 2:
In a glass reactor, 3-Iodo-N2-(2-methyl-1-(methylthio) propan-2-yl)-N1-(2-methyl-4-(perfluoro propan-2-yl) phenyl) Phthalamide (Compound of Flubendiamide sulfide) (5.0 g, 0.008 mole) and 35g of 1, 2-Dichloroethane were charged. The mixture was stirred for 15 minutes. To this mass Indion-190, the resin catalyst (0.5 g, 10% w/w) was added followed by slowly addition of 35% hydrogen peroxide (2.26 g, 0.023 mole, 3.0 mole equivalents) at 30 °C, and the reaction was carried out at 60°C for 12.0 hrs. Then, saturated sodium sulphite solution was added drop-wise until the starch potassium iodide test paper did not change to blue. After stirring for 0.5 hours, water (15 g) was added and the temperature was raised up to 60°C for dissolving the product completely. The resin catalyst was filtered out and washed with 1,2-Dichloroethane(15 g) followed by drying for re-use of resin catalyst in subsequent reactions. Aqueous phase was separated from organic phase of filtrate mother liquor followed by solvent distillation from organic phase to obtain Flubendiamide (4.9 g). The purity was 97% (HPLC).
Example 3:
In a glass reactor,3-Iodo-N2-(2-methyl-1-(methylthio)propan-2-yl)-N1-(2-methyl-4-(perfluoro propan-2-yl)phenyl)Phthalamide (Compound of Flubendiamide sulfide) (5.0 g, 0.008 mole) and 37.5 g of Formic acid (85%) were charged. The mixture was stirred for 15 minutes. To this mass Indion-190, the resin catalyst (0.5 g, 10% w/w) was added followed by slowly addition of 35% hydrogen peroxide (2.26 g, 0.023 mole, 3.0 mole equivalents) at 30 °C and the reaction was stirred at 30°C for 3.0 hrs. Then, saturated sodium sulphite solution was added drop-wise until the starch potassium iodide test paper did not change to blue. After stirring for 0.5 hours, ethylene dichloride (15 g) was added and the temperature was raised up to 60°C for dissolving the product completely. The resin catalyst was filtered out and washed with ethylene dichloride (10 g) followed by drying for re-use of resin catalyst in subsequent reactions. Aqueous phase was separated from organic phase of filtrate mother liquor followed by solvent distillation from organic phase to obtain Flubendiamide (4.5 g.). The purity was 98.5% (HPLC).

Example 4:
In a glass reactor, 3-Iodo-N2-(2-methyl-1-(methylthio) propan-2-yl)-N1-(2-methyl-4-(perfluoro propan-2-yl) phenyl) Phthalamide (Compound of Flubendiamide sulfide) (5.0 g, 0.008 mole) and 27.5 g of Acetic acid were charged. The mixture was stirred for 15 minutes. To this mass Indion-190, the resin catalyst (0.5 g, 10% w/w) was added followed by the slowly addition of 35% hydrogen peroxide (2.26 g, 0.023 mole, 3.0 mole equivalents) at 30 °C, and the reaction was stirred at 30 °C for 6.0 hrs. Then, saturated sodium sulphite solution was added drop-wise until the starch potassium iodide test paper did not change to blue. After stirring for 0.5 hours, ethylene dichloride (30 g) and water (20 g) were added and the temperature was raised up to 60°C for dissolving the product completely. The resin was filtered out and washed with ethylene dichloride (30 g) followed by drying for re-use of resin catalyst in subsequent reactions. Aqueous phase was separated from organic phase of filtrate mother liquor followed by solvent distillation from organic phase to obtain Flubendiamide (4.5 g.). The purity was 98.7% (HPLC).
Example 5:
In a glass reactor, 3-Iodo-N2-(2-methyl-1-(methylthio) propan-2-yl)-N1-(2-methyl-4-(perfluoro propan-2-yl) phenyl) Phthalamide (Compound of Flubendiamide sulfide) (5.0 g, 0.008 mole) and 27.5 g of dichloroacetic acid were charged. After adding, the mixture was stirred for 15 minutes. To this mass Indion-190, the resin catalyst (0.5 g, 10% w/w) was added followed by slowly addition of 35% hydrogen peroxide (2.26 g, 0.023 mole, 3.0 mole equivalents) at 30 °C and the reaction was stirred at 30 °C for 5.0 hrs. Then, saturated sodium sulphite solution was added drop-wise until the starch potassium iodide test paper did not change to blue. After stirring for 0.5 hours, ethylene dichloride (30 g) and water (20 g) were added and the temperature was raised up to 60°C for dissolving the product completely. The resin was filtered out and washed with ethylene dichloride (30 g) followed by drying for re-use of resin catalyst in subsequent reactions. Aqueous phase was separated from organic phase of filtrate mother liquor followed by solvent distillation from organic phase to obtain Flubendiamide (4.2 g.). The purity was 98.1% (HPLC).
Example 6:
In a glass reactor,3-Iodo-N2-(2-methyl-1-(methylthio)propan-2-yl)-N1-(2-methyl-4-(perfluoro propan-2-yl)phenyl)Phthalamide (Compound of Flubendiamide sulfide) (5.0 g, 0.008 mole) and mixture of 18 g of Dichloro acetic acid and 9g of Trichloro acetic acid were charged. After adding, the mixture was stirred for 15 minutes. To this mass Indion-190, the resin catalyst (0.5 g, 10% w/w) was added followed by slowly addition of 35% hydrogen peroxide (2.26 g, 0.023 mole, 3.0 mole equivalents) at 30 °C, and the reaction was stirred at 30 °C for 6.0 hrs. Then, saturated sodium sulphite solution was added drop-wise until the starch potassium iodide test paper did not change to blue. After stirring for 0.5 hours, ethylene dichloride (30 g) and water (20 g) were added and the temperature was raised up to 60°C for dissolving the product completely. The resin catalyst was filtered out and washed with ethylene dichloride (30 g) followed by drying for re-use of resin catalyst in subsequent reactions. Aqueous phase was separated from organic phase of filtrate mother liquor followed by solvent distillation from organic phase to obtain Flubendiamide (4 g.). The purity was 98.1% (HPLC).
Example 7:
In a glass reactor, charged 3-Iodo-N2-(2-methyl-1-(methylthio) propan-2-yl)-N1-(2-methyl-4-(perfluoro propan-2-yl)phenyl)Phthalamide (Compound of Flubendiamide sulfide) (5.0 g, 0.008 mole) and 30 g of Ethyl acetate. The mixture was stirred for 15 minutes. To this mass recovered Indion-190, the resin catalyst (0.5 g) from example 1 was added followed by the slowly addition of 35% hydrogen peroxide (2.26 g, 0.023 mole, 3.0 mole equivalents) at 30 °C and the reaction was stirred at 60°C for 11 hrs. Then, saturated sodium sulphite solution was added drop-wise until the starch potassium iodide test paper did not change to blue. After stirring for 0.5 hours, water (15 g) was added and the temperature was raised up to 60°C for dissolving the product completely. The resin catalyst was filtered out and washed with ethyl acetate (10 g) followed by drying for re-use of resin catalyst in subsequent reactions. Aqueous phase was separated from organic phase followed of filtrate mother liquor by solvent distillation from organic phase to obtain Flubendiamide (5.1 g.). The purity was 98.4% (HPLC).

ADVANTAGES OF THE INVENTION:
The present invention provides many advantages over said prior arts:
• The present invention provides an oxidation process for preparation of Flubendiamide and its intermediates.
• The process avoids the production of unwanted or harmful byproducts through the built-up of eco-friendly green synthesis procedures.
• It involves effective degree of oxidation resulting with optimum purity at commercial scale.
• It is simple and cost-effective.
• It provides reuse of the resin catalyst.
• It provides high product yield with high purity. ,CLAIMS:WE CLAIM,

1. A process for preparation of Flubendiamide and its intermediate Flubendiamide Sulfoxide, wherein said process comprises steps of:
• Adding a compound of Flubendiamide Sulfide in a solvent and preparing its mixture;
• Adding a resin catalyst to said mixture;
• Forming a reaction mass by adding an oxidizing agent to mixture obtain in above step;
• Stirring the reaction mass up to completion of reaction;
• Quenching the excess oxidizing agent by adding quenching reagent;
• Adding mixture of solvent to dissolve excess residue;
• Raising reaction temperature up to 60°C;
• Recovering the resin catalyst by filtration followed by washing with the solvent and drying for reuse of the resin catalyst;
• Obtaining Flubendiamide by solvent distillation and Flubendiamide Sulfoxide by solvent evaporation, stirring with water, filtration and drying.

2. The process for preparation of Flubendiamide and its intermediate Flubendiamide Sulfoxide as claimed in claim 1, wherein said solvent is selected from the group comprising: methanol, ethanol, propanol, acetonitrile, Isopropanol, Ethyl acetate or ethylene dichloride (EDC),toluene, methylene dichloride, ethylene dichloride, carbon tetrachloride, chloroform, o-dichlorobenzene, Chlorobenzene, bromobenzene, dibromomethane, dichloroethane, acetic acid, monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, dibromoacetic acid, tribromoacetic acid, trifluoroacetic acid, trifluoroacdtic anhydride and mixtures.

3. The process for preparation of Flubendiamide and its intermediate Flubendiamide Sulfoxide as claimed in claim 1, wherein said resin catalyst is selected from the group comprising: DOWEX, INDION, AMBERLYST, DIAION, AMBERLITE and PUROLITE.

4. The process for preparation of Flubendiamide and its intermediate Flubendiamide Sulfoxide as claimed in claim 1 and 3, wherein the selected resin catalyst is INDION.

5. The process for preparation of Flubendiamide and its intermediate Flubendiamide Sulfoxide as claimed in claim 1, wherein said oxidizing agent is selected from a group comprising: hydrogen peroxide, tert-butyl hydrogen peroxide, benzoylperoxide and sodium peroxide.

6. The process for preparation of Flubendiamide and its intermediate Flubendiamide Sulfoxide as claimed in claim 1 and 5, wherein the selected oxidizing agent is hydrogen peroxide.

7. The process for preparation of Flubendiamide and its intermediate Flubendiamide Sulfoxide as claimed in claim 6, wherein the molar ratio of hydrogen peroxide is from 1:1 w/w to 1:4 w/w.

8. The process for preparation of Flubendiamide and its intermediate Flubendiamide Sulfoxide as claimed in claim 6, wherein the mass concentration of hydrogen peroxide is from 10 to 50 percent.

9. The process for preparation of Flubendiamide and its intermediate Flubendiamide Sulfoxide as claimed in claim 1 and 2, wherein the mass ratio of the solvent is from 1:1 w/w to 1:10 w/w.

10. The process for preparation of Flubendiamide and its intermediate Flubendiamide Sulfoxide as claimed in claim 1 and 3, wherein the particle size of the resin catalyst ranges from 0.2 to 1.5 mm.

11. The process for preparation of Flubendiamide and its intermediate Flubendiamide Sulfoxide as claimed in claim 10, wherein the mass ratio of the resin catalyst is from 1:5 percent to 1:50 percent.

12. The process for preparation of Flubendiamide and its intermediate Flubendiamide Sulfoxide as claimed in claim 1, wherein the % yield of the obtained product is 75 percent to 99 percent.

13. The process for preparation of Flubendiamide and its intermediate Flubendiamide Sulfoxide as claimed in claim 1 and 12, wherein purity of the product yield is 95 percent to 98 percent.

Dated this 27th day of July, 2021.

Gopi Trivedi (Ms.)
IN/PA 993
Authorized Agent of Applicant
To,
The Controller of Patents,
The Patent Office,
At Mumbai.