WO2010064109A2

WO2010064109A2 - An improved process for the preparation of montelukast sodium and its intermediates

Info

Publication number: WO2010064109A2
Application number: PCT/IB2009/007594
Authority: WO
Inventors: Chandra Sekhar Nakka Krishnamurthy; Tapan Kashyap; Jagat Singh
Original assignee: Mayuka Labs Private Limited
Priority date: 2008-12-02
Filing date: 2009-12-01
Publication date: 2010-06-10
Also published as: WO2010064109A3

Abstract

The present invention relates to a process for the preparation of montelukast sodium (formula 1) and formula 4. The invention concerns the coupling of thiol derivative, Methyl 1 - (mercaptomethyl)cyclopropane acetate with mesylate of formula 4 compound using alkyl substituted ammonium hydroxide base, alkali amides and purification of Montelukast acid by crystallization in suitable organic solvents. The invention further concerns to provide an improved process of montelukast intermediates having good yield and quality

Description

"AN IMPROVED PROCESS FOR THE PREPARATION OF MONTELUKAST SODIUM AND ITS INTERMEDIATES"

FIELD OF THE INVENTION: The present invention provides an improved process for the preparation of montelukast sodium compound l [[[(R)-l-[3-[(lE)-2-(7-chloro-2-quinolinyl) ethenyl] phenyl] 3-[2-( I - hydroxy-1-methylethyl) phenyl-propyl] thio] methyl] cyclopropane acetic acid sodium salt of formula 1. The present invention also provides an improved process for the preparation of [(S)-(E)]-2-[3-[3-[2-(7-chloro-2-quinolinyl)-ethenyl]-phenyl]-3-hydroxy propyl]-phenyl]-2- Propanol of formula 4, useful as an intermediate in the process.

BACKGROUND OF THE INVENTION:

Leukotrienes constitute a group of locally acting hormones, which are produced in living systems from arachidonic acid. The biosynthesis of Leukotrienes is based on enzymatic transformation; beginning with the 5-lipoxygenase on arachidonic acid. 5-lipoxygenase on arachidonic acid converted to an epoxide known as A₄ Leukotrienes (abbreviated as LTA₄₎, which is further transformated into other Leukotrienes like LTB₄, LTC₄, LTD₄ and LTE₄. Biosynthesis, metabolism and action of Leukotrienes in living systems and contribution in several diseases are discussed in the book Leukotrienes and Lipoxygenases, ed. J. Rokach, Elsevier and Amsterdam (1989).

A Montelukast sodium, the Leukotrienes antagonist chemically known as 1 -[[[(R)- 1 -[3-[( I E)- 2-(7-chloro-2-quinolinyl)ethenyl]phenyl]-3-[2-(l -hydroxy- 1-methy lethyl)pheny I]- propyl]thio]methyl]cyclopropane acetic acid sodium salt and represented by the following formula (1):

EP 480,717 A l, discloses the process of manufacturing Montelukast sodium via, montelukast methyl ester preparation. Methyl ester was prepared from the nucleophilic substitution of chiral mesylate (4) with methyl l-(mercaptomethyl) cyclopropyl acetate with simultaneous inversion of configuration. The methyl ester is hydrolyzed and converted into its sodium salt, resulting in sodium salt of montelukast. This is characterized by chemical analysis and mass spectrometry. Scheme-1: Depicts a schematic diagram for the preparation of montelukast sodium according to the EP 480, 717Al.

Scheme-1 This process of montelukast sodium is not suitable for the industrial production because it demands chromatographic purification of montelukast sodium and its advance intermediates. And more importantly, the overall yield of montelukast is very low.

In US 5,614,632, a method for the preparation of montelukast is disclosed, wherein montelukast is obtained by the nucleophilic substitution of a chiral mesylate (S-isomer) with dilithium dianion of 1 -(mercaptomethyl) cyclopropane acetic acid with the configuration inversion (S-isomer to R-isomer) of secondary alcohol (of diol intermediate). It is very important to preserve the chirality of the product to avoid the racemization. Further, said process involves use of n-butyl lithium for the preparation of dilithium dianoin of 1 - (mercaptomethylcyclopropane acetic acid and dicyclohexylamine for the purification of montelukast sodium. The n-butyl lithium is highly moisture sensitive and expensive reagent and dicyclohexylamine is highly toxic substance.

Scheme-2: depicts a schematic diagram for the preparation of montelukast sodium according to US 5, 614, 632.

In nutshell, the above prior art process for the preparation of compound of formula (I) has the following disadvantages, which are: 1) Low yield of montelukast 2) Need to purify the final product through chromatographic techniques, which is not industrially feasible and which also decreases the yield.

3) Use of toxic dicyclohexylamine

4) Use of expensive and highly moisture sensitive n-butyl lithium reagent

Thus, there is a need for a process for manufacturing montelukast compounds and their salts which apart from being cost effective and eco-friendly; avoid chromatographic purification, improves the yield and quality of Montelukast compounds and further can be compatible with the economics of manufacturing/ commercialization.

OBJECT OF THE INVENTION

The primary objective of the invention is to provide simple and cost effective process for the preparation of Montelukast sodium of formula (1) and formula (4). Another object of the invention is to provide a process for the preparation of Montelukast sodium wherein the process excludes the use of n-butyl lithium reagent, Dicyclohexyl amine and use of class 3 solvents in place of class 2 solvents.

Yet another objective of the invention is to reduce the steps of the reaction by eliminating the conversion of Montelukast amine to Montelukast acid and thereby reducing the overall period for completion of the batch, making the process more suitable for commercial applications.

SUMMARY OF THE INVENTION

The prime aspect is to develop an improved process for the preparation of montelukast sodium of formula 1 by developing a process to obtain highly pure advanced diol compound of formula 4 and eliminating the conversion of montelukast amine salt to montelukast acid. Thus method embodied in this invention increases the yields, reduces the use of toxic and sensitive reagents and reduces the time cycle for each batch run, reduces cost, efforts and thereby makes the process highly economical and eco-friendly.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides an improved method for the preparation of pharmaceutically acceptable salt of montelukast from a compound of formula (4).The conversion of the compound (4) into montelukast of formula (1). The process comprising the following steps that are explained in scheme 3:

Scheme-3

Scheme-3: depicts a schematic diagram for the preparation of montelukast sodium according to the present invention. i) Condensation of 7-chloroquinaldine with isophthaldehyde in acetic acid or in a suitable solvent in the presence of acetic acid. Reaction mass was filtered to remove salt/dimmer and crude benzaldehyde derivative was purified by slurry wash with ester solvents like ethyl acetate, isopropyl acetate or protic solvent like methanol, ethanol, IPA or t-butanol etc or mixture thereof. Most preferred solvent is ethyl acetate.

Suitable solvents may be ethereal solvents like THF, IPE, MTBE and dioxane etc., hydrocarbon solvents like benzene, toluene or xylene etc. halogenated hydrocarbon solvents like chloroform, methylene chloride and ethylene chloride etc. ketonic solvents like MIBK, acetone, ethyl methyl ketone etc. Ester solvents like ethyl acetate, isopropyl acetate etc. aminde solvents like DMF, sulfoxide solvents like DMSO and protic solvents like methanol, ethanol, IPA or t-butanol etc. or mixture thereof. Most preferred solvent is toluene.

Acetic acid

ii) Benzaldehyde derivative reacts with vinyl magnesium bromide in a suitable solvent at - 15 to -5O⁰C and isolate the product after quenching the reaction mass in ammonium acetate or ammonium chloride. Suitable solvents may be ethereal solvents like THF, IPE, MTBE and dioxane etc., hydrocarbon solvents like benzene, toluene or xylene etc. halogenated hydrocarbon solvents like chloroform, methylene chloride and ethylene chloride etc. or mixture thereof. Most preferred solvent is a mixture of toluene and tetrahydrofuran and temperature is -35 to -30 ⁰C. Proceed the product for next step without isolation after workup and partial recovery to get moisture content within the limit.

VMgBr

iii) Heck reaction performed by using isolated or insitu propenol derivative with methyl 2- iodo benzoate in presence of a suitable catalyst (Palladium acetate/ Palladium halide or palladium complexes like Palladium triphenyl phosphene halide) and triethyl amine in a suitable solvent. Crude keto ester is purified in toluene, xylene, acetonitrile, methanol or mixture thereof and preferred solvent is methanol or a mixture of toluene and methanol. Suitable catalyst is Palladium acetate, Palladium halide or palladium complexes like Palladium triphenyl phosphene halide and preferable catalyst is Palladium acetate. Suitable solvents are toluene, xylene, tetrahyhdrofuran or acetonitrile and preferred solvent is toluene.

iv) Chiral/ asymmetric reduction of keto ester by using (-)Diisopinocampheylchloroborane in THF/MDC in presence of base(like diisopropyl ethyl amine, triethyl amine or ammonia). Crude hydroxyl ester is purified in ethyl acetate, methanol, water or mixture thereof with or without base.

(-) DIPCI

v) Double Grignard reaction performed using methyl magnesium chloride in a suitable solvent at -10 to -15 ⁰C and isolate the product after quenching the reaction mass in ammonium acetate or ammonium chloride. Suitable solvents may be ethereal solvents like THF, IPE, MTBE and dioxane etc., hydrocarbon solvents like benzene, toluene or xylene etc. halogenated hydrocarbon solvents like chloroform, methylene chloride and ethylene chloride etc. or mixture thereof. Preferred solvents are Toluene, tetrahydrofuran, methylene dichloride or mixture thereof. Most preferred solvent is methylene chloride. Crude diol is purified in toluene, xylene, ethyl acetate, diisopropyl ether, petroleum ether, hexanes, heptane or mixture thereof.

vi) Reacting a chiral mesylate, [(S)-(E)]-2-[3-[3-[2-(7-chloro-2-quinolinyl)-ethenyl]-phenyl]- 3-methanesulfonyloxypropyl]-phenyl]-2-Propanol with methyl l -(mercaptomethyl)cyclo- propane acetate in a suitable solvent in the presence of suitable substituted ammonium bases or suitable alkali metal amides etc. like Lithium amide sodium amide, potassium amide and mixture there of suitable solvents may be ethereal solvents like THF, IPE, MTBE and dioxane etc., hydrocarbon solvents like benzene, toluene or xylene etc. halogenated hydrocarbon solvents like chloroform, methylene chloride and ethylene chloride etc. ketonic solvents like MIBK, acetone, ethyl methyl ketone etc. Ester solvents like ethyl acetate, isopropyl acetate etc. amide solvents like DMF, sulfoxide solvents like DMSO and protic solvents like methanol, ethanol, IPA or t-butanol etc. or mixture thereof.

Suitable bases may be substituted quaternary ammonium bases like tetra methyl ammonium hydroxide and its solution, tetra n-butyl ammonium hydroxide and its solution, alkali metal amides like Lithium amide, sodium amide, potassium amide and preferably tetra methyl ammonium hydroxide and its solution.

vii) Purification of montelukast acid obtained from step (i) by crystallization in suitable organic solvents Suitable solvents may be ethereal solvents like THF, IPE, MTBE and dioxane etc., hydrocarbon solvents like benzene, toluene or xylene etc. halogenated hydrocarbon solvents like chloroform, methylene chloride and ethylene chloride etc. ketonic solvents like MIBK, acetone, ethyl methyl ketone etc. Ester solvents like ethyl acetate, isopropyl acetate etc. and protic solvents like methanol, ethanol, IPA or t-butanol etc. or mixture thereof. Preferable solvents are methanol, ethanol, isopropanol, t-butanol, diisopropyl ether, t-butyl methyl ether, toluene or xylene and most preferable methanol/diisopropyl ether or mixture thereof. viii) converting pure Montelukast acid obtained from step (vii) to Montelukast sodium amoφhous dissolving the first in a mixture of ketonic solvent like methyl isobutyl ketone, ethyl methyl ketone etc. and methanolic sodium hydroxide, decolorization of the solution, recovery of solvent and precipitation/ titration adding n-heptane or n-hexane or mixture thereof for complete precipitation of montelukast sodium of formula 1 in amorphous form.

ADVANTAGES OF INVENTION: i) Chromatographic purification of Montelukast acid or its sodium salt is not required, ii) Avoid use of expensive and hazardous reagents like n-Butyl lithium and dicyclohexyl amine. iii) Highly economically and eco-friendly process. iv) ICH class 3 (least toxic) ketonic solvent like methyl isobutyl ketone (MIBK), ethyl methyl ketone or mixture thereof are used instead of more toxic class 2 solvent, methanol. Also, limits of class 2 solvents are less then class 3 solvents in drugs. The following examples further describe and demonstrate embodiments within the scope of the present invention. The examples are given solely for the purpose of illustration and not to be construed as limitations of the present invention, as many variations are possible without departing from the spirit and scope of the invention. Example 1

Preparation of [E]-3-[2-(7- chloro-2-quinolinyI) ethenylj-Benzaldehyde Method A

In a 1 ltr 4-necked flask equipped with a thermometer and mechanical stirrer, acetic acid (25 g, 0.4163 moles) was added in a mixture of 7-chloroquinaldine (100 g. 0.5630 moles), isophthalaldehyde (90 g, 0.6710 moles) in toluene (400 ml) at room temperature. Reflux the reaction mass azeotropically for 20 to 30 hrs at 1 10 ⁰C (±5 ⁰C). Cool the reaction mass to 95 ⁰C (±5 ⁰C) and filter through leaf filter. Recover the solvent under vacuum and charge ethyl acetate (300 ml). Reflux the suspension for 1-2 hrs and cool to room temperature. Filter the product and wash with ethyl acetate (50 ml). Dry the material 40- 50 ⁰C for 4 - 6 hrs to obtain pure [E]-3-[2-(7- chloro-2-quinolinyl) ethenylj-Benzaldehyde ( 1 10 g, HPLC purity 99%). Method B

In a 1 ltr 4-necked flask equipped with a thermometer and mechanical stirrer, a solution of 7-chloroquinaldine (100 g, 0.5630 moles) in toluene (300 ml) was added in a mixture of acetic acid (25 g, 0.4163 moles) and isophthalaldehyde (90 g, 0.6710 moles) in toluene (200 ml) at refluxing temperature. Reflux the reaction mass azeotropically for 20 to 30 hrs at 1 10 ⁰C (±5 ⁰C). Cool the reaction mass to 95 ⁰C (±5 ⁰C) and filter through leaf filter. Recover the solvent under vacuum and charge ethyl acetate (300 ml). Reflux the suspension for 1-2 hrs and cool to room temperature. Filter the product and wash with ethyl acetate (50 ml). Dry the material 40- 50 ⁰C for 4 - 6 hrs to obtain pure [E]-3-[2-(7- chloro-2-quinolinyl) ethenyl]-Benzaldehyde (100 g, HPLC purity 99%). Method C

In a 1 ltr 4-necked flask equipped with a thermometer and mechanical stirrer, 7- chloroquinaldine (100 g, 0.5630 moles) and isophthalaldehyde (90 g, 0.6710 moles) was added in acetic acid (200 ml) at room temperature. Reflux the reaction mass for 20 to 30 hrs at 1 15 ⁰C (±5 ⁰C). Cool the reaction mass to room temperature, add water (1 ltr) and filter the product. Charge the crude product and ethyl acetate (300 ml) in RBF. Reflux the suspension for 1-2 hrs and cool to room temperature. Filter the product and wash with ethyl acetate (50 ml). Dry the material 40- 50 ⁰C for 4 - 6 hrs to obtain pure [E]-3-[2-(7- chloro-2-quinolinyl) ethenyl]-Benzaldehyde (1 15 g, HPLC purity 99%). Method D

In a 1 ltr 4-necked flask equipped with a thermometer and mechanical stirrer, acetic acid (25 g, 0.4163 moles) was added in a mixture of 7-chloroquinaldine (100 g, 0.5630 moles), isophthalaldehyde (90 g, 0.6710 moles) in ethyl acetate (700 ml) at room temperature. Reflux the reaction mass for 20 to 30 hrs at 75 ⁰C (±5 ⁰C). Filter the dimmer through leaf filter and recover the solvent under vacuum (50%). Cool the suspension to room temperature and stir for 2-4 hrs. Filter the product and wash with ethyl acetate (50 ml). Dry the material 40- 50 ⁰C for 4 - 6 hrs to obtain pure [E]-3-[2-(7- chloro-2-quinolinyl) ethenyl]- Benzaldehyde (100 g, HPLC purity 99%). Example 2

Preparation of [E]-l-[3-[2-(7- chloro-2-quinolinyl)-ethenyl]-phenyl]-2-propen-l-ol

In a 2 ltr 4-necked flask equipped with a thermometer and mechanical stirrer, (400 g, 0.40 moles) vinyl magnesium bromide (I M solution in THF) was added in a solution of [E]-3-[2- (7- chloro-2-quinolinyl) ethenyl]-Benzaldehyde (100 g, 0.34 moles) in toluene (700 ml) and tetrahydrofuran (200 ml) at -40 ⁰C (±5 ⁰C). Stir the reaction mass for 2-4 hrs at -40 ⁰C (±5 ⁰C) and quench the reaction mass in 10% ammonium chloride solution ( 1 ltr). Organic layer washed with water then with 10%sodium chloride solution. Recover the solvent under vacuum to get moisture content NMT 0.05% and proceed to next stage immediately.

Example 3

Preparation of Methyl-[E]-2-[3-[3-[2-(7- chloro-2-quinolinyl)-ethenyl]-phenyl| -3-oxo- propylj-benzoate

In a 2 ltr 4-necked flask equipped with a thermometer and mechanical stirrer, methyl 2- iodobenzoate( 105.6 g, 0.40 moles), triethyl amine (78 g, 0.77 moles) and palladium acetate

(0.48 g, 0.007 moles) was added in a solution of [E]-l-[3-[2-(7- chloro-2-quinolinyl)- ethenyl]-phenyl]-2-propen-l-ol in toluene (obtained from example 2). Reflux the reaction mass for 24 to 30 hrs at 100 ⁰C (±5 ⁰C). Filter the salt/catalyst and filtrate washed with water and 10%sodium chloride solution. Recover the solvent under vacuum and product was crystallized in methanol, toluene, acetonitrile or mixture thereof. Filter the product and wash with methanol, toluene, acetonitrile or mixture thereof. Dry the material 40- 45 ⁰C for 4 - 6 hrs to obtain pure Methyl-[E]-2-[3-[3-[2-(7- chloro-2-quinolinyl)-ethenyl]-phenyl] -3-oxo- propyl]-benzoate ( 1 10 g, HPLC purity 99%).

Example 4 Preparation of Methyl-[E]-2-[3(S)-[3-[2-(7-chloro-2-quinolinyl)-ethenyl]-phenyll-3- hydroxypropyl]benzoate

Method A

In a 2 ltr 4-necked flask equipped with a thermometer and mechanical stirrer, a solution of

Methyl-[E]-2-[3-[3-[2-(7- chloro-2-quinolinyl)-ethenyl]-phenyl]-3-oxo-propyl]-benzoate (100 g, 0.22 moles) and diisopropyl ethyl amine ( 18 g, 0.14 moles) in tetrahydrofuran (450 ml) was added in a solution of (-) Diisopinocampheyl chloroborane (126 g, 0.39 moles) in tetrahydrofuran (250 ml) at 0 ⁰C (±5 ⁰C). Stir the reaction mass for 2 to 4 hrs at 25 ⁰C (±5 ⁰C) and quench the reaction mass in sodium bicarbonate (55 g, 0.66 moles) solution (3.5 ltr). Crystallized the product by adding petroleum ether (500 ml) and filter the crude product. Crude product was purified after dissolution in triethyl amine (30 g, 0.30 moles) and methanol, filtration, cooling to get slurry, addition of water, filtration of product and washing with methanol, water or mixture thereof. Dry the material 30- 35 ⁰C for 10 - 1 5 hrs to obtain pure Methyl-[E]-2-[3(S)-[3-[2-(7-chloro-2-quinolinyl)-ethenyl]-phenyl] -3-hydroxy propyljbenzoate (90 g, HPLC purity 99%).

Method B

Methyl-[E]-2-[3-[3-[2-(7- chloro-2-quinolinyl)-ethenyl]-phenyl] -3-oxo-propyl]-benzoate (100 g, 0.22 moles) in methylene dichloride (800 ml) was added in a solution of (-) Diisopinocampheyl chloroborane (126 g, 0.39 moles) in methylene dichloride (750 ml) at 0 ⁰C (±5 ⁰C). Stir the reaction mass for 2 to 4 hrs at 20 ⁰C (±5 ⁰C), cool to 0-5 ⁰C and add 20% ammonia solution (100 ml). Reaction mass wash with 20% sodium chloride solution (3 x 300 ml) and aqueous layer extract with methylene dichloride (2 x 200 ml). Recover the solvent under vacuum completely and product crystallized in ethyl acetate. Crude product was purified in triethyl amine (30 g, 0.30 moles) and methanol, water or mixture thereof. Filter the product and wash with methanol, water or mixture thereof. Dry the material 30- 35 ⁰C for 10 - 15 hrs to obtain pure Methyl-[E]-2-[3(S)-[3-[2-(7-chloro-2-quinolinyl)-ethenyl]-phenyl | -3-hydroxy propyl] benzoate (90 g, HPLC purity 99%). Optional purification:

In a 1 ltr 4-necked flask equipped with a thermometer and mechanical stirrer, Methyl-[E]-2- [3(S)-[3-[2-(7-chloro-2-quinolinyl)-ethenyl]-phenyl]-3-hydroxypropyl]benzoate ( 10Og) was added in methanol (600 ml), water (30 ml) and carbon (2 g) was added at 62 ⁰C (±2 ⁰C) and stir for 30 minute at 62 ⁰C (±2 ⁰C). Filter through hyflo and wash with methanol (50 ml). Crystallized the product by adding water (40 ml) at 20 - 25 ⁰C. Filter the product and wash with petroleum ether (50 ml). Dry the material 30- 40 ⁰C for 16-20 hrs to obtain pure Methyl- [E]-2-[3(S)-[3-[2-(7-chloro-2-quinolinyl)-ethenyl]phenyl]-3-hydroxypropyl]benzoate (80 g,

HPLC purity 99%).

Example S

Preparation of [(S)-(E)]-2-[3-[3-[2-(7-chloro-2-quinolinyl)-ethenyl]-phenyl]-3-hydroxy propyl]-phenyl]-2-Propanol

Method A In a 2 ltr 4-necked flask equipped with a thermometer and mechanical stirrer, Methyl-[E]-2-

[3(S)-[3-[2-(7-chloro-2-quinolinyl)-ethenyl]-phenyl]-3-hydroxypropy l]-benzoate( 100 g, 0.22 moles) was added in toluene (500 ml) and reflux azeotropically to get moisture content NMT 0.1%. Recover the solvent under vacuum and add dichlomethane (500 ml). Methyl magnesium chloride (400 g, 1.2 moles, 3M solution in THF) was added in a solution of Methyl-[E]-2-[3(S)-[3-[2-(7-chloro-2-quinolinyl)-ethenyl]-phenyl]-3-hydroxypropyl]- benzoate in dichloromethane (500 ml) at -5 ⁰C (±5 ⁰C). Stir the reaction mass for 2-4 hrs at -5 ⁰C (±5 ⁰C) and quench the reaction mass in 10% acetic acid aqueous solution ( 1 .2 ltr). Organic layer washed with 10% sodium bicarbonate solution (700 ml), water (500 ml) then with 10%sodium chloride solution (500 ml). Recover the solvent azeotropically to get moisture content NMT 0.1%. Cool the reaction mass and add dichloromethane. Methyl magnesium chloride (200 g, 0.6 moles, 3M solution in THF) was added in a solution of 1 ^st reaction product in dichloromethane (500 ml) at -5 ⁰C (±5 ⁰C). Stir the reaction mass for 2-4 hrs at -5 ⁰C (±5 ⁰C) and quench the reaction mass in 10% acetic acid aqueous solution (0.6 ltr). Organic layer washed with 10% sodium bicarbonate solution (700 ml), water (500 ml) then with 10%sodium chloride solution (500 ml). Recover the solvent under vacuum and product was crystallized in mixture of toluene (50 ml) and diisopropyl ether (300 ml). Filter the product and wash with diisopropyl ether (50 ml). Dry the material 40- 50 ⁰C for 8-10 hrs to obtain pure [(S)-(E)]-2-[3-[3-[2-(7-chloro-2-quinolinyl)-ethenyl]-phenyl]-3-hydroxy propyl]-phenyl]-2-Propanol (75 g, HPLC purity 98%). Method B

In a 2 ltr 4-necked flask equipped with a thermometer and mechanical stirrer, Methyl-[E]-2-

[3(S)-[3-[2-(7-chloro-2-quinolinyl)-ethenyl]-phenyl]-3-hydroxypropyl]-benzoate ( 100 g, 0.22 moles) was added in toluene (1 ltr) and reflux azeotropically to get moisture content NMT 0.1%. Recover the solvent under vacuum (50%) and add tetrahydrofuran (200 ml). Methyl magnesium chloride (300 g, 0.9 moles, 3M solution in THF) was added at -15 ⁰C (±2 ⁰C). Stir the reaction mass for 2-4 hrs at -15 ⁰C (±2 ⁰C) and quench the reaction mass in 10% ammonium chloride solution (1.6 ltr). Organic layer washed with water (500 ml) then with 10% sodium chloride solution (500 ml). Recover the solvent azeotropically to get moisture content NMT 0.1%. Cool the reaction mass, add toluene (500 ml) and tetrahydrofuran (200 ml). Methyl magnesium chloride (200 g, 0.6 moles, 3M solution in THF) was added at -15 ⁰C (±2 ⁰C) and quench the reaction mass in 10% ammonium chloride solution (800 ml). Organic layer washed with water (500 ml) then with 10% sodium chloride solution (500 ml). Recover the solvent under vacuum and product was crystallized in mixture of toluene (50 ml) and diisopropyl ether (300 ml). Filter the product and wash with diisopropyl ether (50 ml). Dry the material 40- 50 ⁰C for 8-10 hrs to obtain pure [(S)-(E)]-2-[3-[3-[2-(7-chloro-2- quinolinyl)-ethenyl]-phenyl]-3-hydroxy propyl]-phenyl]-2-Propanol (70 g, HPLC purity 98%). Optional purification: Method A

In a 2 ltr 4-necked flask equipped with a thermometer and mechanical stirrer, [(S)- (E)]-2-[3-[3-[2-(7-chloro-2-quinolinyl)ethenyl]phenyl]-3-hydroxypropyl]-phenyl]-2-Propanol (10Og) was added in ethyl acetate (400 ml). n-Heptane (1.2 ltr) was added at 78 ⁰C (±2 ⁰C) and stir for 8-10 hrs at 20- 25 ⁰C. Filter the product and wash with n-heptane (50 ml). Dry the material 40- 50 ⁰C for 8-10 hrs to obtain pure [(S)-(E)]-2-[3-[3-[2-(7-chloro-2-quinolinyl)- ethenyl]-phenyl]-3-hydroxy propyl]-phenyl]-2-Propanol (80 g, HPLC purity 99%). Method B In a 2 ltr 4-necked flask equipped with a thermometer and mechanical stirrer, [(S)-(E)]-2-[3- [3-[2-(7-chloro-2-quinolinyl)ethenyl]phenyl]-3-hydroxypropyl]-phenyl]-2-Propanol ( 10Og) was added in toluene (100 ml). Diisopropyl ether (300 ml) was added at 40 ⁰C (±2 ⁰C) and stir for 4-6 hrs at 20- 25 ⁰C. Filter the product and wash with Diisopropyl ether (50 ml). Dry the material 40- 50 ⁰C for 8-10 hrs to obtain pure [(S)-(E)]-2-[3-[3-[2-(7-chloro-2- quinolinyl)-ethenyl]-phenyl]-3-hydroxypropyl]-phenyl]-2-Propanol (80 g, HPLC purity

30/

Method C

In a 2 ltr 4-necked flask equipped with a thermometer and mechanical stirrer, [(S)-(E)]-2-[3- [3-[2-(7-chloro-2-quinolinyl)ethenyl]phenyl]-3-hydroxypropyl]-phenyl]-2-Propanol ( 10Og) was added in Diisopropyl ether (400 ml). Reflux the suspension for 1 -2 hrs and stir for 2-4 hrs at 20- 25 ⁰C. Filter the product and wash with Diisopropyl ether (50 ml). Dry the material 40- 50 ⁰C for 8-10 hrs to obtain pure [(S)-(E)]-2-[3-[3-[2-(7-chloro-2-quinolinyl)-ethenyl]- phenyl]-3-hydroxy propyl]-phenyl]-2-Propanol (80 g, HPLC purity 98%). Method D

In a 2 ltr 4-necked flask equipped with a thermometer and mechanical stirrer, [(S)-(E)]-2-[3- [3-[2-(7-chloro-2-quinolinyl)ethenyl]phenyl]-3-hydroxypropyl]-phenyl]-2-Propanol ( 10Og) was added in toluene (400 ml). Petroleum ether (1 ltr) was added at 40 ⁰C (±2 ⁰C) and stir for 4-6 hrs at 20- 25 ⁰C. Filter the product and wash with Diisopropyl ether (50 ml). Dry the material 40- 50 ⁰C for 8-10 hrs to obtain pure [(S)-(E)]-2-[3-[3-[2-(7-chloro-2-quinolinyl)- ethenyl]-phenyl]-3-hydroxy propyl]-phenyl]-2-Propanol (80 g, HPLC purity 98%).

Example 6

Preparation of [(S)-(E)]-2-[3-[3-[2-(7-chloro-2-quinolinyI)-ethenyl|-phenyl]-3- methanesulfonyloxy propyl]-phenyl]-2-Propanol

In a 2 ltr 4-necked flask equipped with a thermometer and mechanical stirrer, [(S)-(E)]-2-[3- [3-[2-(7-chloro-2-quinolinyl)ethenyl]phenyl]-3-hydroxypropyl]-phenyl]-2-Propanol ( 100g, 0.22 moles), (formula 4) and N,N-diisopropylethyl amine (42.0 g, 0.33 moles) was charged in a mixture of toluene (300 ml) and acetonitrile (800 ml) under nitrogen atmosphere at room temperature and cooled to -35 ⁰C. A solution of methanesulfonyl chloride (30.0 g, 0.26 moles) in acetonitrile (100 ml) was added slowly at about -35 ⁰C. Stirring was maintained for 2 hrs and check HPLC to ensure that NMT 5 % of the starting material was present in the reaction mixture. Stirring continued for 4-5 hrs to crystallize the product (if required add 0.5 g seeds/starting material). Filter the product and wash with chilled acetonitrile (100 ml) then chilled petroleum ether (200 ml). Chiral mesylate product was used in the next step immediately or store at -10 ⁰C. Optional purification:

In a 2 ltr 4-necked flask equipped with a thermometer and mechanical stirrer, [(S)-(E)]-2-[3- [3-[2-(7-chloro-2-quinolinyl)ethenyl]phenyl]3-methanesulfonyloxypropyl]-phenyl]-2- Propanol (prepared in example 6) was charged in hexanes (1 ltr) at -15 ±5 ⁰C and stir for 30 min. Filter the product and wash with chilled hexane (400 ml). Product was slurry wash with chilled acetonitrile (200 ml) then chilled diisopropyl ether (200 ml) at - 15 ±5 ⁰C. Purified chiral mesylate was used in the next step immediately or store at -10 ⁰C.

Example 7 Preparation of Methyl l-[[[(R)-l-[3-[(lE)-2-(7-chloro-2-quinolinyl)ethenyl]-phenyl]-3- ^-(l-hydroxy-l-methylethyljphenyllpropyllthiolmethyljcyclopropane acetate

In a 1 ltr 4-necked flask equipped with a thermometer and mechanical stirrer, methyl 1 - (mercaptomethyl)cyclopropane acetate (70 g, 0.44 moles) and tetra methyl ammonium hydroxide (80 g, 0.22 moles, 25% solution in MeOH) was charged in THF (200 ml) under nitrogen atmosphere at 0-5 ⁰C. Stir the reaction mass for 30 min. and add chiral mesylate, [(S)-(E)]-2-[3-[3-[2-(7-chloro-2-quinolinyl)ethenyl]-phenyl]-3-methanesulfonyloxy propyl]- phenyl]-2-Propanol (200 g, prepared in example 1) solution in THF (300 ml) at 0 ±2 ⁰C. Stirring was maintained for 10-12 hrs at 25- 30 ⁰C and check HPLC to ensure that starting material was present NMT 0.5 % in the reaction mixture. Reaction was quenched by adding water (500 ml), layer was separated and aqueous layer was extracted with ethyl acetate. Combined organic layer washes with water, dried over sodium sulphate and solvent was recovered under vacuum to obtain Methyl l-[[[(R)-l-[3-[( l E)-2-(7-chloro-2-quinolinyl) ethenyl]-phenyl]-3-[2-(l -hydroxy- l-methylethyl)phenyl]propyl]-thio]methyl]-cyclopropane acetate as a viscous oil (120 g, HPLC purity 79.3%).

Example 8

Preparation of l-[[[(R)-l-[3-[(lE)-2-(7-chloro-2-quinolinyl) ethenyl]-phenyl]-3-[2-(l- hydroxy-1-methylethyl) phenyl]propyl]thio]methyl]cyclopropane acetic acid (Montelukast acid) Method A

In a 2 ltr 4-necked flask equipped with a thermometer and mechanical stirrer, Methyl 1 -

[[[(R)- 1 -[3-[( 1 E)-2-(7-chloro-2-quinolinyl)-etheny l]-pheny l]-3-[2-( 1 -hydroxy- 1 -methy I- ethyl)-phenyl]propyl]thio]methyl]cyclopropane acetate (120 g) was added in a mixture of methanol (960 ml) and THF (240 ml) under nitrogen atmosphere and cool to 0-5 ⁰C. Add 50% aqueous NaOH solution (80 ml) slowly keeping temperature 0- 10 ⁰C. Stirring was maintained for 10-12 hrs at 25- 30 ⁰C and check HPLC to ensure that NMT 0.5 % of the starting material was present in the reaction mixture. Solvent was recovered under vacuum and add 10% NaCl solution (400 ml). Product was extracted with THF then ethyl acetate and adjust pH 4.0 to 4.5 with 10% tartaric acid solution. Organic layer washed with water to get pH 6.5 to 7.0 and organic layer dried over sodium sulphate. Solvent was recovered under vacuum to get oily crude montelukast acid (100 g). Cool the oily residue at room temperature and add methanol (250 ml). Stir the reaction mixture for complete crystallization for 20-30 hrs. Filter the product and slurry wash with methanol. Product was dried under vacuum to get montelukast acid (60 g, HPLC purity 99.4%).

Method B

[[[(R)- 1 -[3-[( 1 E)-2-(7-chloro-2-quinolinyl)etheny l]-phenyl]-3-[2-( 1 -hydroxy- 1 -methy I- ethyl)phenyl]propyl]thio]methyl]cyclopropane acetate (120 g) was added in a mixture of methanol (960 ml) and THF (240 ml) under nitrogen atmosphere and cool to 0-5 ⁰C. Add 50% aqueous NaOH solution (80 ml) slowly keeping temperature 0-10 ⁰C. Stirring was maintained for 10-12 hrs at 25-30 ⁰C and check HPLC to ensure that NMT 0.5 % of the starting material was present in the reaction mixture. Solvent was recovered under. vacuum and add 10% NaCl solution (400 ml). Product was extracted with THF then ethyl acetate and adjust pH 4.0 to 4.5 with 10% tartaric acid solution. Organic layer washed with water to get pH 6.5 to 7.0 and organic layer dried over sodium sulphate. Solvent was recovered under vacuum to get oily crude montelukast acid (100 g). Cool the oily residue at room temperature and add diisopropyl ether (400 ml). Stir the reaction mixture for complete crystallization for 20-30 hrs. Filter the product and slurry wash with methanol ( 100 ml). Product was dried under vacuum to get montelukast acid (80 g, HPLC purity 97.8%).

Example 9

Preparation of l-[[[(R)-l-[3-[(lE)-2-(7-chloro-2-quinolinyl)ethenyl]-phenyl]-3-[2-(l- hydroxy-l-methylethyl)phenyl]propyl]thio]methyl]cyclopropane acetic acid, sodium salt (Montelukast sodium)

Method A

In a 5 ltr 4-necked flask equipped with a thermometer and mechanical stirrer, 100 g (0.1706 moles) montelukast acid was suspended in methyl isobutyl ketone (800 ml) under nitrogen atmosphere at room temperature, stir for 30 min and cool to 0-10 ⁰C. Add 0.5 M NaOH solution in methanol (360 ml) at 0-10 ⁰C and stir for 30 min. Charcoalise the product for 1 5 min. and filter through hyflo. Solvent was recovered under vacuum at 40-45 ⁰C. Add methyl isobutyl ketone (100 ml) and recovery continued under vacuum. Remove traces of methyl isobutyl ketone under vacuum at 40-45 ⁰C. Add n-Heptane ( 1 ltr.) to the product and stir for 4-6 hrs. Filter the product under nitrogen atmosphere and dry the material at 45-50 ⁰C to get montelukast sodium (95 g, HPLC purity 99.4%).

Method B

In a 5 ltr 4-necked flask equipped with a thermometer and mechanical stirrer, 100 g (0.1706 moles) montelukast acid was suspended in ethyl methyl ketone (800 ml) under nitrogen atmosphere at room temperature, stir for 30 min and cool to 0-10 ⁰C. Add 0.5 M NaOH solution in methanol (360 ml) at 0-10 ⁰C and stir for 30 min. charcoalise the product for 15 min. and filter through hyflo. Solvent was recovered under vacuum at 40-45 ⁰C. Add ethyl methyl ketone (100 ml) and recovery continued under vacuum. Remove trace of ethyl methyl ketone under vacuum at 40-45 ⁰C. Add n-Heptane (1 ltr.) to the product and stir for 4-6 hrs. Filter the product under nitrogen atmosphere and dry the material at 45-50 ⁰C to get montelukast sodium (95 g, HPLC purity 99.4%).

Claims

We claim

1. A process for producing montelukast sodium of formula (1), comprising the steps of; (i) reacting a chiral mesylate, [(S)-(E)]-2-[3-[3-[2-(7-chloro-2-quinolinyl)-ethenyl]- phenyl]-3-methanesulfonyloxypropyl]-phenyl]-2-Propanol of [(S)-(E)]-2-[3-[3-[2- (7-chloro-2-quinolinyl)-ethenyl]-phenyl]-3-hydroxy propyl]-phenyl]-2-Propanol

(formula 5) with methyl l-(mercaptomethyl)cyclopropane acetate in a suitable solvent in the presence of a suitable base

(ii) purification of montelukast acid obtained from step (i) by crystallization from organic solvent (iii)Converting pure Montelukast acid obtained from step (ii) to Montelukast sodium amorphous by dissolving in a ketonic solvent and precipitating by a water immiscible solvent.

2. A process as claimed in claim 1, step (i) wherein the solvent is selected from Tetrahydrofuran (THF), Dimethylformamide (DMF), Methyl tert-Butyl ether (MTBE), toluene, Dioxane, chloroform, methylene chloride and ethylene chloride, ketonic solvents like Methyl Isobutyl Ketone (MIBK), acetone, ethyl methyl ketone, ethyl acetate, isopropyl acetate, DMSO, methanol, ethanol, IPA or t-butanol or mixtures thereof.

3. A process as claimed in claim 1 , step (i), wherein the base is selected from substituted quaternary ammonium bases such as tetra methyl ammonium hydroxide, tetra n-butyl ammonium hydroxide, alkali metal amides such as Lithium amide, sodium amide, potassium amide or their solutions

4. A process as claimed in claim 1, step (i), wherein the base is tetra methyl ammonium hydroxide and its solution.

5. A process as claimed in claim 1, step (ii) wherein the solvent is selected from Tetrahydrofuran (THF), Dimethylformamide (DMF), Methyl tert-Butyl ether (MTBE), toluene, Dioxane, chloroform, methylene chloride and ethylene chloride, ketonic solvents like Methyl Isobutyl Ketone (MIBK), acetone, ethyl methyl ketone, ethyl acetate, isopropyl acetate DMSO methanol, ethanol, IPA or t-butanol or mixtures thereof.

6. A process as claimed in claim 1, step (iii) wherein the ketonic solvent is selected from methyl isobutyl ketone, ethyl methyl ketone and methanolic sodium hydroxide

7. A process as claimed in claim 1 , step (iii) wherein the ketonic solvent is methyl isobutyl ketone

8. A process as claimed in claim 1 , step (iii), wherein the water immiscible solvent is selected from hexane, n-heptane or mixtures thereof.

9. A process for producing [(S)-(E)]-2-[3-[3-[2-(7-chloro-2-quinolinyl)-ethenyl]- phenyl]-3-hydroxy propyl]-phenyl]-2-Propanol of formula (4), comprising the steps of:

I. Condensing 7-chloroquinaldine with isophthalaldehyde in the presence of acetic acid optionally with organic solvents at a given temperature in the range of 105- 1 15°C and obtaining benzaldehyde compound,

II. reacting benzaldehyde compound of step (i) with vinyl magnesium bromide in the presence of a solvent at -50 to -15°C to obtain propenol compound of formula (7),

III. reacting isolated or insitu propenol compound of step (ii) with methyl 2-iodo benzoate in presence of palladium catalyst and organic amines in the presence of solvent to obtain keto ester of formula (6), IV. reducing asymmetrically or chirally keto ester of step (iii) with (-)

Diisopinocampheylchloroborane in tetrahyhdrofuran/methylene dichloridc in presence of base to obtain hydroxyl ester of formula (5),

V. converting hydroxyl ketoester obtained in step (iv) to diol compound of formula (4) by using methyl magnesium chloride in the presence of a solvent at 5 to -20 0C.

10. The process as claimed in claim 9, wherein solvent is selected from a group comprising of benzene, toluene or xylene, halogenated hydrocarbon solvents selected from chloroform, methylene chloride and ethylene chloride, ketonic solvents selected from methyl isobutyl ketone, acetone, ethyl methyl ketone, ester solvents selected from ethyl acetate, isopropyl acetate, amide solvents selected from DMF, sulfoxide solvents and protic solvents selected from DMSO and methanol, ethanol, IPA or t- butanol respectively or mixture thereof.

1 1. The process as claimed in claim 10, wherein solvent is toluene (9 step i), mixture of toluene and tetrahyhdrofuran (9 step ii), methanol or a mixture of toluene and methanol (9 step iii).

12. The process as claimed in claim 9 step iv, wherein base is selected from diisopropyl ethyl amine, triethyl amine or ammonia.

13. The process as claimed in claim 9, wherein catalyst is selected from palladium acetate, palladium halide or palladium complexes selected from palladium triphenyl phosphene halide.

14. The process as claimed in claim 13, wherein catalyst is palladium acetate.