DESC:Field of the Invention:
The invention relates to the field of pesticide synthesis, particularly to a process of producing optically active agrochemicals, in particular to the Quizalofop-P-tefuryl, which is useful as herbicides.

Formula-1a
Background of the Invention:
Quizalofop-P-tefuryl is a selective, post-emergence herbicide used for the control of annual and perennial grasses in potato, sugar beet, sunflower, oilseed rape, peanut and other vegetable crops. Its mode of action involves the inhibition of acetyl CoA carboxylase activity. Earlier references disclose several methods to prepare this inventive compound. However, still there is a need for new methods that are less costly, more efficient and flexible, or more convenient to operate with minimum effluent generation. Thus, there is a need for a process of producing optically active propionate derivative which is simple in operation and by which the desired product with high optical purity may be obtained.
EP0410758A2 patent discloses the process of preparation of Quizalofop-P-tefuryl by reacting R-2-(4-hydroxyphenoxy) propionic acid tetrahydro furfuryl (terfuryl) ester with 2,6-dichloroquinoxaline in-presence of potassium carbonate in acetonitrile refluxed overnight followed by purification by silica gel column chromatography to produce Quizalofop-P-tefuryl. The said process has the following disadvantages, including yield of the reaction is very low, Requires longer reaction time and product was purifying in column chromatography. The column chromatography purifications process is a tedious procedure and results in the consumption expensive as higher quantities of solvent which increases the production cost. Considering all the above disadvantages, the above said process is not suitable for commercial scale production.
Further the prior art references disclose several methods to prepare this inventive compound, but in multiple steps that require either waste disposal and/or recycling which often results in elaborate or expensive apparatus and includes high energy expenditures. So, there is still a need for new methods that are less costly, efficient, and flexible, eco-friendly process which is more convenient to operate with minimum effluent generation. Thus, there is a need for a process like the present inventive process for producing the desired product, which is simple in operation, eco-friendly and cost-effective process for industrial production.
Objective of the Invention:
The main objective of the present invention is to provide a cost effective, least effluent generating and short synthesis of Quizalofop p-terfuryl ester starting from the commercially available raw materials.
Summary of the Invention
The first embodiment of the present invention provides a process for the preparation of Quizalofop p-terfuryl ester of formula-1a.
The second embodiment of the present invention provides a process for the preparation of DHPPA-terfuryl ester formula-3.
Detailed Description of the Invention
For the purpose of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiment illustrated in the figures and specific language will be used to describe them. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Such alterations and further modifications in the illustrated system, and such further applications of the principles of the disclosure as would normally occur to those skilled in the art are to be construed as being within the scope of the present disclosure.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this disclosure belongs. The system, methods, and examples provided herein are only illustrative and not intended to be limiting.
In the following specification and the claims, reference will be made to a number of terms, which shall be defined to have the following meanings. The singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise.
The term "solvent" used in the present invention refers to "non-polar solvents like “hydrocarbon solvents" selected from n-hexane, n-heptane, cyclohexane, petroleum ether, benzene, toluene, xylene or mixtures thereof; "ether solvents" selected from dimethyl ether, diisopropyl ether, diethyl ether, methyl tert-butyl ether, 1,2-dimethoxy ethane, tetrahydrofuran, 1,4-dioxane or mixtures thereof; "ester solvents" selected from methyl acetate, ethyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate or mixtures thereof; "polar-aprotic solvents selected from dimethylacetamide (DMAc), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP) or mixtures thereof; "chloro solvents" selected from dichloromethane, dichloroethane, chloroform, carbon tetrachloride or mixtures thereof; "ketone solvents" selected from acetone, methyl ethyl ketone, methyl isobutyl ketone and thereof; "nitrile solvents" selected from acetonitrile, propionitrile, isobutyronitrile or mixtures thereof; "alcoholic solvents" selected from methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol or mixtures thereof; "polar solvents" selected from water or mixtures thereof.
The term "acid" used in the present invention selected from but not limited to inorganic acids such as hydrochloric acid, hydrobromic acid, sulfuric acid, or phosphoric acid; and organic acids such as formic acid, acetic acid, propionic acid, methane sulfonic acid, para toluene sulfonic acid, ethane-1,2-disulfonic acid, camphor sulfonic acid, ethane sulfonic acid, naphthalene-2-sulfonic acid, benzene sulfonic acid, and thereof. The term “agrochemical acceptable salts” or “salts” described in hereinbefore are obtained by reacting compound with acid selected from the above description.
The term "base" used in the present invention selected from but not limited to inorganic bases selected from "alkali metal carbonates" such as sodium carbonate, potassium carbonate, lithium carbonate and the like; "alkali metal bicarbonates" such as sodium bicarbonate, potassium bicarbonate and the like; "alkali metal hydroxides" such as sodium hydroxide, potassium hydroxide, lithium hydroxide and the like; alkali metal hydrides such as sodium hydride, potassium hydride, lithium hydride and the like; alkali metal amides such as sodium amide, potassium amide, lithium amide and the like; and organic bases like dimethylamine, diethylamine, diisopropyl amine, diisopropylethylamine, diisobutylamine, trimethylamine, triethylamine, tertiary butyl amine, benzyl amine, pyridine, 4-dimethylaminopyridine (DMAP), N-methyl morpholine (NMM), 2,6-lutidine, lithium diisopropylamide; "alkali metal alkoxides" such as sodium methoxide, sodium ethoxide, potassium methoxide, potassium ethoxide, sodium tert.butoxide, potassium tert.butoxide, lithium tert.butoxide mixtures thereof.
The term "room temperature" as used in the present invention herein refers to the temperature in the range from about 25-35°C.
The chemical process describing the short synthesis of quizalofop-p-terfuryl ester at commercial scale in high yield and quality from the commercially available starting materials 2,6-dichloroquinoxaline and (R)-2-(4-hydroxyphenoxy) propanoic acid or DHPPA.

DHPPA is reacted with terfuryl alcohol to generate the corresponding terfuryl ester in toluene as solvent (to help remove the water formed during the reaction). DHPPA terfuryl ester is then treated with 2,6-DCQ in the presence of base like potassium carbonate to generate the quizalofop-p-terfuryl ester.
The first embodiment of the present invention provides a process for the preparation of Quizalofop p-terfuryl ester of formula-1a, comprising:
(a) reacting (R)-2-(4-hydroxyphenoxy) propanoic acid with terfuryl alcohol in presence of a catalyst in a solvent to provide DHPPA terfuryl ester of formula-3;

(b) reacting DHPPA terfuryl ester of formula-3 with 2,6-dichloroquinoxaline in presence of a base in a solvent to provide Quizalofop p-terfuryl ester of formula-1a

In the first aspect of first embodiment, catalyst used in step (a) selected from mineral acids but not limited to hydrochloric acid or sulfuric acid, preferably hydrochloric acid; solvent used in step (a) is selected from but not limited to hydrocarbon solvents selected from n-hexane, n-heptane, cyclohexane, petroleum ether, toluene, xylene or mixtures thereof, preferably toluene;

In the second aspect of first embodiment, base used in step (b) is selected from but not limited to inorganic bases such as metal carbonates or metal bicarbonates, preferably potassium carbonate; solvent used in step (b) is selected from but not limited to polar-aprotic solvents selected from dimethylacetamide (DMAc), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP) or mixtures thereof, preferably dimethylformamide;

The second embodiment of the present invention provides a process for the preparation of DHPPA terfuryl ester of formula-3, comprising: reacting (R)-2-(4-hydroxyphenoxy) propanoic acid with terfuryl alcohol in presence of a catalyst in a solvent to provide DHPPA terfuryl ester of formula-3;

In the first aspect of second the embodiment, catalyst selected from mineral acids but not limited to hydrochloric acid or sulfuric acid, preferably hydrochloric acid; solvent is selected from but not limited to hydrocarbon solvents selected from n-hexane, n-heptane, cyclohexane, petroleum ether, toluene, xylene or mixtures thereof, preferably toluene;
The novel features and advantages of this one-pot inventive process are as follows:
• The preparation of DHPPA-terfuryl ester may be achieved with quantitative yields and high purity of >99 %.
• The formation of Quizalofop p-terfuryl ester is achieved in a single stage through the reaction between 2,6-dichloroquinoxaline and DHPPA-terfuryl ester.
• Isolation of the product is best achieved through recrystallization from aqueous alcohol such as propanol.
Starting materials utilized in the present invention are commercially available in the market (or) they can be prepared according to any of the processes known in the prior art.
The present invention described in embodiments and examples are merely helping to understand the present invention. These examples are for illustrative purposes only and in no way limit the scope of the present invention.
Examples:
Example-1: Preparation of (R)-2-(4-hydroxyphenoxy) propanoic acid terfuryl ester or DHPPA terfuryl ester
Terfuryl alcohol (141 g, 2.51 mole equivalent) and hydrochloric acid (10 g, 0.5 mole equivalent) were added to the mixture of (R)-2-(4-hydroxyphenoxy) propanoic acid (100 g, 1 mole equivalent) and toluene (300 ml) at room temperature. Hearted the reaction mixture to 60-65? and stirred for one hour at same temperature. Azeotropically distilled out water formed in the reaction. Extracted the compound with ether and washed with sodium bicarbonate. Distilled off the solvent completely to get the titled compound.
Yield: 135.68 g (92.81%).
Example-2:
Potassium carbonate (52 g, 1 mole equivalent) and 2,6-dichloroquinoxaline (75 g, 1 mole equivalent) were added to the mixture of (R)-2-(4-hydroxyphenoxy) propanoic acid terfuryl ester (100 g, 1 mole equivalent) and dimethylformamide (500 ml) at room temperature. Heated the reaction mixture to 60-65? and stirred for 6 hours at same temperature. Cooled the mixture to room temperature and filtered the solids. Distilled off the solvent completely from the filtrate to get the titled compound.
Yield: 147.20 g (91.40%).
,CLAIMS:We Claim:
1. A process for the preparation of Quizalofop p-terfuryl ester of formula-1a, comprising:
(a) reacting (R)-2-(4-hydroxyphenoxy) propanoic acid with terfuryl alcohol in presence of a catalyst in a solvent to provide DHPPA terfuryl ester of formula-3;

(b) reacting DHPPA terfuryl ester of formula-3 with 2,6-dichloroquinoxaline in the presence of a base in a solvent to provide Quizalofop p-terfuryl ester of formula-1a.

2. The process as claimed in claim 1, the catalyst used in step (a) selected from mineral acids but not limited to hydrochloric acid or sulfuric acid.
3. The process as claimed in claim 1, the solvent used in step (a) is selected from hydrocarbon solvents but not limited to n-hexane, n-heptane, cyclohexane, petroleum ether, toluene, xylene or mixtures thereof.

4. The process as claimed in claim 1, the base used in step (b) is selected from inorganic bases but not limited to metal carbonates or metal bicarbonates.

5. The process as claimed in claim 1, the solvent used in step (b) is selected from polar-aprotic solvents but not limited to dimethylacetamide (DMAc), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP) or mixtures thereof.

6. A process for the preparation of DHPPA terfuryl ester of formula-3, comprising:
reacting (R)-2-(4-hydroxyphenoxy) propanoic acid of formula-2 with terfuryl alcohol in the presence of a catalyst in a solvent to provide DHPPA terfuryl ester of formula-3.

7. The process as claimed in claim 6, the catalyst used in step (a) selected from mineral acids but not limited to hydrochloric acid or sulfuric acid.
8. The process as claimed in claim 6, the solvent used in step (a) is selected from hydrocarbon solvents but not limited to n-hexane, n-heptane, cyclohexane, petroleum ether, toluene, xylene or mixtures thereof.