DESC:INTRODUCTION
The present invention relates to a process for the preparation of Lesinurad intermediate and their use in preparation of Lesinurad or its pharmaceutically acceptable salts thereof.

Lesinurad is a selective uric acid re-absorption inhibitor (SURI). Lesinurad or its salt is used for reducing serum uric acid level and for the treatment of gout and hyperurecemia. Lesinurad is chemically known as 2-(5-bromo-4-(4-cyclopropylnaphthalen-1-yl)-4H-1,2,4-triazol-3-ylthio)acetic acid and has following structural formula (I):

(I) (Ia)
The compound of formula (II) is a key intermediate useful in the preparation of Lesinurad (I).

Wherein R is R1 or OR1; R1 may be selected from hydrogen, C1-C10 alkyl.
Process for the preparation of Lesinurad (I) and its intermediates have been disclosed in US8084483B2 and US8173690B2, which is shown in scheme 1:
Scheme-1:

CN102040546A discloses the synthesis of isothiocyanate derivative as an intermediate in the preparation of lesinurad. The disclosed process starts from 4-cyclopropyl-1-naphthaldehyde and involves three steps, to get isothiocyanate derivative as an intermediate and thus avoiding the use of sulfur phosgene.

Keeping in view of the importance of lesinurad as a medicament, there remains a need to provide a novel process for the preparation of Lesinurad of formula (I), its related compounds and its intermediates that are simple, economical and commercially viable.
SUMMARY
In the first embodiment, the present application provides a process for the preparation of Lesinurad of formula (I) or its pharmaceutically acceptable salts, which comprises:
a) treating a compound of formula (III) with a compound of formula (IV) to form a compound of formula (II);

Wherein R is R1 or OR1; R1 may be selected from hydrogen, C1-C12 alkyl.
b) optionally, purifying the compound of formula (II);
c) brominating a compound of formula (II) with a brominating agent to form a compound of formula (V);

Wherein R is R1 or OR1; R1 may be selected from hydrogen, C1-C12 alkyl.
d) hydrolysis of compound of formula (V) in the presence of suitable base to provide Lesinurad of formula (I) or its pharmaceutically acceptable salts.
In the second embodiment, the present application provides a process for the preparation of Lesinurad of formula (I) or its pharmaceutically acceptable salts which comprises;
a) treating a compound of formula (VI) with 2-chloroacetyl chloride to form a compound of formula (IV);

Wherein R is R1 or OR1; R1 may be selected from hydrogen, C1-C12 alkyl.
b) optionally, purifying the compound of formula (IV);
c) converting a compound of formula (IV) to Lesinurad of formula (I) or its pharmaceutically acceptable salts.
In the third embodiment, the present application provides a process for the preparation of Lesinurad of formula (I) or its pharmaceutically acceptable salts which comprises;
a) converting a compound of formula (VII) to 4-cyclopropylnaphthalen-1-amine of formula (VIII);

Wherein X is chloro, bromo, iodo, triflate and tosylate;
b) optionally purifying a compound of formula (VIII);
c) converting a compound of formula (VIII) to Lesinurad of formula (I) or its pharmaceutically acceptable salts.
In the fourth embodiment of the present application provides a novel compound of formula (II).

Wherein R is R1 or OR1; R1 may be selected from hydrogen, C1-C12 alkyl.
In the fifth embodiment of the present application provides the use of compound of formula (II) in the preparation of Lesinurad of formula (I) or its pharmaceutically acceptable salts.
In the sixth embodiment of the present application provides pharmaceutical compositions comprising Lesinurad of formula (I) or its pharmaceutically acceptable salts thereof prepared according to processes of the present application together with one or more pharmaceutically acceptable excipient, carrier and diluents.
DETAILED DESCRIPTION
In the first embodiment, the present application provides a process for the preparation of Lesinurad of formula (I) or its pharmaceutically acceptable salts, which comprises:
a) treating a compound of formula (III) with a compound of formula (IV) to form a compound of formula (II);

Wherein R is R1 or OR1; R1 may be selected from hydrogen, C1-C12 alkyl.
b) optionally, purifying the compound of formula (II);
c) brominating a compound of formula (II) with a brominating agent to form a compound of formula (V);

Wherein R is R1 or OR1; R1 may be selected from hydrogen, C1-C12 alkyl.
d) hydrolysis of compound of formula (V) in the presence of suitable base to provide Lesinurad of formula (I) or its pharmaceutically acceptable salts.
The process for the preparation of starting material compound of formula (III) may be performed by any suitable process disclosed in the prior art references. Alternatively, the said starting material may be procured from commercial sources to perform the present invention.
Step (a) and step (d) may be carried out in the presence of one or more suitable bases. Suitable base that may be used in step (a) and/or step (d) include, but are not limited to organic bases like pyridine, piperidine, pyrimidine, triethylamine, tributylamine, N-methylmorpholine, N,N-diisopropylethylamine, diethylamine, 1,1,3,3-tetramethylguanidine, DBU, DABCO and the like; or inorganic bases like metal carbonates such as sodium carbonate, potassium carbonate; metal bicarbonates such as sodium bicarbonate, potassium bicarbonate; metal hydroxide like sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide and the like.
Step (b) which involves the isolation and purification of compound of formula (II) may be effected, if desired, by any suitable separation or purification procedure such as, for example, filtration, centrifugation, extraction, acid-base treatment, crystallization, conventional isolation and refining means such as concentration, concentration under reduced pressure, solvent-extraction, crystallization, phase-transfer chromatography, column chromatography, or by a combination of these procedures.
Suitable brominating agent that may be used in step (c) include, but are not limited to such as for example phosphorus tribromide, aluminum tribromide, N-bromosuccinimide (NBS) or liquid bromine and the like.
Step (a), step (c) and step (d) may be carried out in one or more suitable solvents. Suitable solvent that may be used in step (a) and/or step (c) and/or step (d) include, but are not limited to ketone solvents, such as, for example, acetone, ethyl methyl ketone, diethyl ketone, methyl isobutyl ketone, C3-C6 ketones and the like; aromatic hydrocarbon solvents, such as, for example, toluene, xylene, chlorobenzene, tetralin, and the like; halogenated hydrocarbons such as dichloromethane, chloroform and the like; alcoholic solvents like methanol, ethanol, isopropyl alcohol and the like; aliphatic hydrocarbon solvents, such as n-pentane, n-hexane, n-heptane and the like; ether solvents, such as, for example, diethyl ether, diisopropyl ether, tert-butyl methyl ether, dibutyl ether, tetrahydrofuran, 1,2-dimethoxyethane, 2-methoxyethanol, 2-ethoxyethanol, anisole, 1, 4-dioxane, and the like; nitrile solvent, such as, for example, acetonitrile, propionitrile, C2-C6 nitriles and the like; ester solvents, such as, for example, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propanoate, ethyl propanoate, methyl butanoate, ethyl butanoate, or the like; water or mixtures thereof.
The isolation and purification of Lesinurad (I) may be effected, if desired, by any suitable separation or purification procedure such as, for example, filtration, centrifugation, extraction, acid-base treatment, crystallization, conventional isolation and refining means such as concentration, concentration under reduced pressure, solvent-extraction, crystallization, phase-transfer chromatography, column chromatography, or by a combination of these procedures.
The temperature at which the above steps may be carried out in between about 0°C and about 200°C, preferably at about 0°C and about 150°C, most preferably at about 0°C and about 100°C, based on the solvent or mixture of solvent used in particular step.
The intermediates obtained in the present invention may be directly used for the next step with or without isolation or it may be further purified, if isolated, to improve the purity of the product.
In the second embodiment, the present application provides a process for the preparation of Lesinurad of formula (I) or its pharmaceutically acceptable salts which comprises;
a) treating a compound of formula (VI) with 2-chloroacetyl chloride to form a compound of formula (IV);

Wherein R is R1 or OR1; R1 may be selected from hydrogen, C1-C12 alkyl.
b) optionally, purifying the compound of formula (IV);
c) converting a compound of formula (IV) to Lesinurad of formula (I) or its pharmaceutically acceptable salts.
The process for the preparation of starting material compound of formula (VI) may be performed by any suitable process disclosed in the prior art references. Alternatively, the said starting material may be procured from commercial sources to perform the present invention.
Step (a) may be carried out in the presence of one or more suitable bases. Suitable base that may be used in step (a) include, but are not limited to organic bases like pyridine, piperidine, pyrimidine, triethylamine, tributylamine, N-methylmorpholine, N,N-diisopropylethylamine, diethylamine, 1,1,3,3-tetramethylguanidine, DBU, DABCO and the like; or inorganic bases like metal carbonates such as sodium carbonate, potassium carbonate; metal bicarbonates such as sodium bicarbonate, potassium bicarbonate; metal hydroxide like sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide and the like.
Step (a) may be carried out in one or more suitable solvents. Suitable solvent that may be used in step (a) but are not limited to ketone solvents, such as, for example, acetone, ethyl methyl ketone, diethyl ketone, methyl isobutyl ketone, C3-C6 ketones and the like; aromatic hydrocarbon solvents, such as, for example, toluene, xylene, chlorobenzene, tetralin, and the like; halogenated hydrocarbons such as dichloromethane, chloroform and the like; alcoholic solvents like methanol, ethanol, isopropyl alcohol and the like; aliphatic hydrocarbon solvents, such as n-pentane, n-hexane, n-heptane and the like; ether solvents, such as, for example, diethyl ether, diisopropyl ether, tert-butyl methyl ether, dibutyl ether, tetrahydrofuran, 1,2-dimethoxyethane, 2-methoxyethanol, 2-ethoxyethanol, anisole, 1, 4-dioxane, and the like; nitrile solvent, such as, for example, acetonitrile, propionitrile, C2-C6 nitriles and the like; ester solvents, such as, for example, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propanoate, ethyl propanoate, methyl butanoate, ethyl butanoate, or the like; water or mixtures thereof.
Step (b) which involves the isolation and purification of compound of formula (IV) may be effected, if desired, by any suitable separation or purification procedure such as, for example, filtration, centrifugation, extraction, acid-base treatment, crystallization, conventional isolation and refining means such as concentration, concentration under reduced pressure, solvent-extraction, crystallization, phase-transfer chromatography, column chromatography, or by a combination of these procedures.
The compound of formula (IV) may be converted to Lesinurad of formula (I) or its pharmaceutically acceptable salts by the methods known in the literature.
The intermediates obtained in the present invention may be directly used for the next step with or without isolation or it may be further purified, if isolated, to improve the purity of the product.
The temperature at which the above steps may be carried out in between about 0°C and about 200°C, preferably at about 0°C and about 150°C, most preferably at about 0°C and about 100°C, based on the solvent or mixture of solvent used in particular step.
In the third embodiment, the present application provides a process for the preparation of Lesinurad of formula (I) or its pharmaceutically acceptable salts which comprises;
a) converting a compound of formula (VII) to 4-cyclopropylnaphthalen-1-amine of formula (VIII);

Wherein X is chloro, bromo, iodo, triflate and tosylate;
b) optionally purifying a compound of formula (VIII);
c) converting a compound of formula (VIII) to Lesinurad of formula (I) or its pharmaceutically acceptable salts.
Conversion of a compound of formula (VII) may be carried out in the presence of a suitable reagent and a base to provide a compound of formula (VIII)
Suitable reagent that may be used in step a) include, but are not limited to copper iodide, copper bromide, copper oxide, copper cyanide, metallic copper, copper sulfate, copper acetate, copper stearate, copper triflate, copper Nitrate or any Cu(I) salts which can undergo oxidative coupling or can generate Cu(II) in situ under specific reaction conditions, ammonium acetate, ammonia, formamide, ammonium formate, ammonium chloride, ammonium hydroxide, ammonium carbonate or mixtures thereof.
Step a) may be carried out in the presence one or more suitable bases. Suitable base that may be used in step (a) include, but are not limited to sodium carbonate, potassium carbonate, lithium carbonate, cesium carbonate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, cesium hydroxide, sodium hydride, potassium hydride, sodium acetate, potassium acetate or mixtures thereof.
Suitable ligand that may be used in step a) include, but are not limited to trans-cyclohexane-1,2-diamine, trans-N1,N2-dimethylcyclohexane-1,2-diamine, N1,N1,N2,N2-tetramethylethane-1,2-diamine, N1,N2,-dimethylethane-1,2-diamine, proline, ascorbic acid, or any natural or unnatural amino acids, ethyl 2-oxocyclohexane-1-carboxylate, 2-aminopyrimidine-4,6-diol, N,N’-dimethyl glycine, N-methyl glycine, 4-hydroxyproline, 1,10-phenanthroline and its derivatives, quinolin-8-ol, quinolone-N-oxide, 8-aminoquinoline, diglyme, ethylene glycol, dimethoxyethane, diethoxyethane and its further alkyl derivatives.
Step (a) may be carried out in one or more suitable solvents. Suitable solvent that may be used in step (a) but are not limited to ketone solvents, such as, for example, acetone, ethyl methyl ketone, diethyl ketone, methyl isobutyl ketone, C3-C6 ketones and the like; aromatic hydrocarbon solvents, such as, for example, toluene, xylene, chlorobenzene, tetralin, and the like; halogenated hydrocarbons such as dichloromethane, chloroform and the like; alcoholic solvents like methanol, ethanol, isopropyl alcohol, 2-nitroethanol, 2-fluoroethanol, 2,2,2-trifluoroethanol, hexafluoroisopropyl alcohol, ethylene glycol, 1-propanol, 1-butanol, 2-butanol and the like; aliphatic hydrocarbon solvents, such as n-pentane, n-hexane, n-heptane and the like; ether solvents, such as, for example, diethyl ether, diisopropyl ether, tert-butyl methyl ether, dibutyl ether, tetrahydrofuran, 1,2-dimethoxyethane, 2-methoxyethanol, 2-ethoxyethanol, anisole, 1, 4-dioxane, and the like; nitrile solvent, such as, for example, acetonitrile, propionitrile, C2-C6 nitriles and the like; ester solvents, such as, for example, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propanoate, ethyl propanoate, methyl butanoate, ethyl butanoate, or the like; water or mixtures thereof.
Step (b) which involves the isolation and purification of compound of formula (VIII) may be effected, if desired, by any suitable separation or purification procedure such as, for example, filtration, centrifugation, extraction, acid-base treatment, crystallization, conventional isolation and refining means such as concentration, concentration under reduced pressure, solvent-extraction, crystallization, phase-transfer chromatography, column chromatography, or by a combination of these procedures.
The compound of formula (VIII) may be converted to Lesinurad of formula (I) or its pharmaceutically acceptable salts by the methods known in the literature.
The intermediates obtained in the present invention may be directly used for the next step with or without isolation or it may be further purified, if isolated, to improve the purity of the product.
The temperature at which the above steps may be carried out in between about 0°C and about 200°C, preferably at about 0°C and about 150°C, most preferably at about 0°C and about 100°C, based on the solvent or mixture of solvent used in particular step.
The compound of formula (VII) (wherein X is Br) may be prepared as per the processes disclosed in the literature. In one of the specific embodiment, the compound of formula (III) may be prepared by reacting 1-bromonaphthalene with cyclopropyl magnesium bromide in presence of (1,3-bis(diphenylphosphino propane)dichloronickel(II) under suitable conditions to produce 1-cyclopropylnaphthalene, followed by treating with N-bromosuccinimide under suitable conditions to produce a compound of formula (VII) (wherein X is Br). Alternatively, the said starting material may be procured from commercial sources to perform the present invention.
In the fourth embodiment of the present application provides a novel compound of formula (II).

Wherein R is R1 or OR1; R1 may be selected from hydrogen, C1-C12 alkyl.
In the fifth embodiment of the present application provides the use of compound of formula (II) in the preparation of Lesinurad of formula (I) or its pharmaceutically acceptable salts.
In the sixth embodiment of the present application provides pharmaceutical compositions comprising Lesinurad of formula (I) or its pharmaceutically acceptable salts thereof prepared according to processes of the present application together with one or more pharmaceutically acceptable excipient, carrier and diluents.
Lesinurad of formula (I) may be converted into its pharmaceutically acceptable salt comprising the reaction with suitable base. Suitable base include but are not limited to, metal hydroxide like sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide and the like. In a preferred embodiment, the pharmaceutically acceptable salt in the present invention is sodium salt of compound of formula (I).
In an embodiment, Lesinurad of formula (I) or its pharmaceutically acceptable salt obtained in the present invention may be further subjected to known purification techniques to get the required purity for qualifying ICH grade material.
The process of the present invention is easy to handle, environment friendly, provides better yield and purity; and it may also be practiced on industrial scale.
DEFINITIONS
The following definitions are used in connection with the present
application unless the context indicates otherwise.
The terms "about," "general, ‘generally," and the like are to be construed as modifying a term or value such that it is not an absolute. Such terms will be defined by the circumstances and the terms that they modify as those terms are understood by those of skill in the art. This includes, at very least, the degree of expected experimental error, technique error and instrument error for a given technique used to measure a value.
The term “optional” or “optionally” is taken to mean that the event or circumstance described in the specification may or may not occur, and that the description includes instances where the event occurs and instances where it does not.
The term “alkyl” as used in the present application refers to an hydrocarbon monoradical having from one to about ten carbon atoms, more preferably one to six carbon atoms. Examples include, but are not limited to methyl, ethyl, n-propyl, isopropyl, 2-methyl-1-propyl, 2-methyl-2-propyl, 2-methyl-1-butyl, 3-methyl-1-butyl, 2-methyl-3-butyl, 2,2-dimethyl-1-propyl, 2-methyl-1-pentyl, 3-methyl-1-pentyl, 4-methyl-1-pentyl, 2-methyl-2-pentyl, 3-methyl-2-pentyl, 4-methyl-2-pentyl, 2,2-dimethyl-1-butyl, 3,3-dimethyl-1-butyl, 2-ethyl-1-butyl, n-butyl, isobutyl, sec-butyl, t-butyl, n-pentyl, isopentyl, neopentyl, tert-amyl and hexyl, and longer alkyl groups, such as heptyl, octyl and the like.

EXAMPLES
Example 1: Preparation of 4-methoxybenzyl 2-chloroacetate (IV) (wherein R is OMe).
(4-Methoxyphenyl)methanol (VI) (wherein R is OMe; 5.0 g, 36.2 moles) and dichloromethane (25 mL) were charged at room temperature under nitrogen atmosphere and was cooled to -5°C to 0°C. Triethylamine (7.32 g, 72.4 moles) was slowly added to the reaction mixture at 0°C over a period of 10 minutes. 2-Chloroacetyl chloride (4.09 g, 36.2 moles) was also slowly added to the reaction mixture at 0°C over a period of 45 minutes. The temperature of the reaction was raised to 15-20°C and maintained for 30-60 minutes. HCl (0.1N, 10 mL) was added to the reaction mixture at 25°C and stirred for 5- 10 minutes. The layers were separated and the organic layer was washed with brine solution (10 mL). The solvent from the organic layer was concentrated at 40-45°C under vacuum and the obtained crude compound was purified by column chromatography to give the title compound.
Yield: 3.2 g

Example 2: Preparation of 4-methoxybenzyl 2-((4-(4-cyclopropyl naphthalen -1-yl)-4H-1,2,4-triazol-3-yl)thio)acetate (II) (wherein R is OMe).
4-(4-cyclopropylnaphthalen-1-yl)-4H-1,2,4-triazole-3-thiol (III; 2.076 g; 7.76 moles), Triethylamine (0.856g; 8.46 moles) and acetone were charged at room temperature under nitrogen atmosphere and was cooled to -5°C to 0°C. 4-Methoxybenzyl 2-chloroacetate (IV) (wherein R is OMe; 2.0g; 9.32 moles) in acetone (10 mL) was added to the reaction mixture at 0°C and maintained for 4-5 hours. The solvent from the reaction mass was concentrated completely under vacuum at 40°C. HCl (0.1N, 10 mL) and ethyl acetate (15 mL) were added to the reaction mixture at 25°C and stirred for 5- 10 minutes. The layers were separated and the organic layer was washed with brine solution (10 mL). The solvent from the organic layer was concentrated at 50-55°C under vacuum and the obtained crude compound was purified by column chromatography to give the title compound.
Yield: 2.8 g

Example 3: Preparation of 3-bromo-4-methoxybenzyl 2-((5-bromo-4-(4-cyclopropylnaphthalen-1-yl)-4H-1,2,4-triazol-3-yl)thio)acetate (V) (Wherein R is OMe).
4-Methoxybenzyl 2-((4-(4-cyclopropylnaphthalen-1-yl)-4H-1,2,4-triazol-3-yl)thio)acetate (II) (wherein R is OMe; 5.0g; 1.122 moles) and acetonitrile (5 mL) were charged at room temperature under nitrogen atmosphere and stirred for 5-10 minutes. N-Bromosuccinimide (0.22 g; 1.234 moles) was slowly added to the reaction mixture at 25°C and maintained for 24-26 hours. Water (10 mL) and ethyl acetate (10 mL) were charged into the reaction mass and stirred for 10-15 minutes. The layers were separated and the organic layer was concentrated at 55-60°C under vacuum. The obtained crude compound was purified by column chromatography to give the title compound.
Yield: 0.4 g

Example-4: Preparation of Lesinurad (I).
3-Bromo-4-methoxybenzyl-2-((5-bromo-4-(4-cyclopropylnaphthalen-1-yl)-4H-1,2,4-triazol-3-yl)thio)acetate (V) (wherein R is OMe; 0.25 g; 0.477 moles), THF (2 mL), water (2mL) and LiOH.H2O (0.040 g; 0.953 moles) were charged at room temperature under nitrogen atmosphere and maintained for 2-3 hours. Water (2 mL) and ethyl acetate (5 mL) were added to the reaction mixture at 25°C and stirred for 10 minutes. The reaction mass was cooled to 0°C and adjusted the reaction mass pH by using 1N HCl solution (1 M L). The layers were separated and the organic layer was washed with brine solution (0.25 mL). The solvent from the organic layer was concentrated completely at 50-55°C under vacuum to give the title compound.
Yield: 0.1 g.

Example-5: Preparation of 4-cyclopropylnaphthalen-1-amine (VIII).
1-Bromo-4-cyclopropylnaphthalene (VII) (wherein X is Br; 3.0 g, 0.012 moles), ethylene glycol (20 mL) were charged at room temperature under nitrogen atmosphere. Potassium carbonate (0.11 g; 0.8 moles), copper(I) iodide (0.076 g; 0.4 moles) were charged at room temperature and stirred for 5-10 minutes. N,N-dimethylethane-1,2-diamine (0.071g; 0.8 moles) and 25% aqueous ammonia solution (5 mL) were also added to the reaction mixture. The above obtained solution was transferred to autoclave at room temperature. The temperature of the autoclave was raised to 80°C-85°C and maintained for 7-8 hours. Ethyl acetate (50 mL) and water (2X500 mL) were added to the reaction mass at room temperature. The layers were separated and the organic layer was washed with brine water (200 mL). The solvent from the organic layer was concentrated at 50-55°C under vacuum to give the title compound. The product was then purified by column chromatography.
Yield: 1.45 gm
,CLAIMS:1) A process for the preparation of Lesinurad of formula (I) or its pharmaceutically acceptable salts, which comprises:
a) treating a compound of formula (III) with a compound of formula (IV) to form a compound of formula (II);

wherein R is R1 or OR1; R1 may be selected from hydrogen, C1-C12 alkyl.
b) optionally, purifying the compound of formula (II);
c) brominating a compound of formula (II) with a brominating agent to form a compound of formula (V);

wherein R is R1 or OR1; R1 may be selected from hydrogen, C1-C12 alkyl.
d) hydrolysis of compound of formula (V) in the presence of suitable base to provide Lesinurad of formula (I) or its pharmaceutically acceptable salts.

2) The process as claimed in claim 1, wherein base used in step a) and step d) is selected from pyridine, piperidine, pyrimidine, triethylamine, tributylamine, N-methylmorpholine, N,N-diisopropyl ethylamine, diethylamine, 1,1,3,3-tetramethylguanidine, DBU, DABCO, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide or mixtures thereof.

3) The process as claimed in claim 1, brominating agent used in step c) is selected from phosphorus tribromide, aluminum tribromide, N-bromosuccinimide (NBS), liquid bromine or mixtures thereof.

4) A process for the preparation of Lesinurad of formula (I) or its pharmaceutically acceptable salts which comprises;
a) treating a compound of formula (VI) with 2-chloroacetyl chloride to form a compound of formula (IV);

wherein R is R1 or OR1; R1 may be selected from hydrogen, C1-C12 alkyl.
b) optionally, purifying the compound of formula (IV);
c) converting a compound of formula (IV) to Lesinurad of formula (I) or its pharmaceutically acceptable salts.
5) The process as claimed in claim 4, wherein base used in step a) is selected from pyridine, piperidine, pyrimidine, triethylamine, tributylamine, N-methylmorpholine, N,N-diisopropyl ethylamine, diethylamine, 1,1,3,3-tetramethylguanidine, DBU, DABCO, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide or mixtures thereof.

6) A process for the preparation of Lesinurad of formula (I) or its pharmaceutically acceptable salts which comprises;
a) converting a compound of formula (VII) to 4-cyclopropylnaphthalen-1-amine of formula (VIII);

wherein X is chloro, bromo, iodo, triflate and tosylate;
b) optionally purifying a compound of formula (VIII);
c) converting a compound of formula (VIII) to Lesinurad of formula (I) or its pharmaceutically acceptable salts.
7) The process as claimed in claim 6, wherein base used in step a) is selected from sodium carbonate, potassium carbonate, lithium carbonate, cesium carbonate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, cesium hydroxide, sodium hydride, potassium hydride, sodium acetate, potassium acetate or mixtures thereof.

8) The process as claimed in claim 6, wherein ligand used in step a) is selected from trans-cyclohexane-1,2-diamine, trans-N1,N2-dimethylcyclohexane-1,2-diamine, N1,N1,N2,N2-tetramethylethane-1,2-diamine, N1,N2,-dimethylethane-1,2-diamine, proline, ascorbic acid, ethyl 2-oxocyclohexane-1-carboxylate, 2-aminopyrimidine-4,6-diol, N,N’-dimethyl glycine, N-methyl glycine, 4-hydroxyproline, 1,10-phenanthroline, quinolin-8-ol, quinolone-N-oxide, 8-aminoquinoline, diglyme, ethylene glycol, dimethoxyethane, diethoxyethane or mixtures thereof.

9) A compound of formula (II).

wherein R is R1 or OR1; R1 may be selected from hydrogen, C1-C12 alkyl.
10) The use of a compound of formula (II) in the preparation of Lesinurad of formula (I) or its pharmaceutically acceptable salts.