FIELD OF THE INVENTION:

The present invention primarily discloses novel processes for the preparation and purification of Rivaroxaban. Also disclosed herein are the processes for the preparation and purification of its various intermediates such as 2-[(2R)-2-Hydroxy-3-{[4-(3-oxo morpholin-4-yl)phenyl]amino}propyl]-2,3-dihydro-1H-isoindole-1,3-dione(Formula I), 2-[[5S)-2-Oxo-3-[4-(3-Oxomorpholin-4-yl)phenyl]-1,3-oxazolidin-5-yl]methyl]-1H-iso indole-1,3(2H)-dione (Formula II), 4-{4-[(5S)-5-(Amino methyl)-2-oxo-1,3-oxazoli din-3-yl]phenyl}morpholin-3-one Hydrochloride (Formula III) and 5-Chloro-N-{[(5S)-2-oxo-3-[4-(3-oxomorpholin-4-yl)phenyl]-1,3-oxazolidin-5-yl]methyl}thiophene-2-car boxamide (Formula IV or Rivaroxaban).

2-[(2R)-2-Hydroxy-3-{[4-(3-oxomorpholin-4-yl)phenyl]amino} propyl]-2,3-dihydro -1H- isoindole-1, 3-dione (Formula I)

Mol. Formula: C21H21N3O5
Mol. Weight : 395.40

2-[[5S)-2-Oxo-3-[4-(3-Oxomorpholin-4-yl)phenyl]-1,3-oxazolidin-5-yl]methyl]-1H-isoindole-1,3(2H)-dione (Formula II)

Mol. Formula: C22H19N3O6
Mol. Weight : 421.40

4-{4-[(5S)-5-(Aminomethyl)-2-oxo-1,3-oxazolidin-3-yl] phenyl}morpholin-3-one Hydrochloride (Formula III)

Mol. Formula: C22H25N3O7
Mol. Weight : 443.45

5-Chloro-N-{[(5S)-2-oxo-3-[4-(3-oxo morpholin-4-yl) phenyl]-1,3-oxazolidin-5-yl]methyl} thiophene-2-carboxamide
(Formula IV) or Rivaroxaban

Mol. Formula: C19H18ClN3O5S
Mol. Weight : 435.88

BACKGROUND OF THE INVENTION:
Rivaroxaban, sold under the brand name Xarelto, among others, is an oral anticoagulant medication (blood thinner). It is commonly used to prevent blood clots. It was initially developed by Bayer. In the United States, it is marketed by Janssen Pharmaceutica (a part of Johnson and Johnson). It is the first available active direct factor Xa inhibitor which is taken by mouth. The maximum inhibition of factor Xa occurs four hours after a dose. The effects last approximately 8–12 hours, but factor Xa activity does not return to normal within 24 hours, so once-daily dosing is possible.
Rivaroxaban was patented in the United States in 2007 having priority date of 1999 and approved for medical use in 2011.
In those with non-valvular atrial fibrillation, it appears to be as effective as Warfarin in preventing non-hemorrhagic strokes and embolic events. Rivaroxaban is associated with lower rates of serious and fatal bleeding events than Warfarin though Rivaroxaban is associated with higher rates of bleeding in the gastrointestinal tract.
In July 2012, the UK´s National Institute for Health and Clinical Excellence recommended Rivaroxaban to prevent and treat venous thromboembolism.
Rivaroxaban inhibits both free Factor Xa and Factor Xa bound in the prothrombinase complex. It is a highly selective direct Factor Xa inhibitor with oral bioavailability and rapid onset of action. Inhibition of Factor Xa interrupts the intrinsic and extrinsic pathway of the blood coagulation cascade, inhibiting both thrombin formation and development of thrombi. Rivaroxaban does not inhibit thrombin (activated Factor II), and no effects on platelets have been demonstrated. It allows predictable anticoagulation and dose adjustments and routine coagulation monitoring as well as dietary restrictions are not needed.
Unfractionated heparin (UFH), low molecular weight heparin (LMWH), and fondaparinux also inhibit the activity of factor Xa but indirectly by binding to circulating antithrombin (AT III) and must be injected. Whereas, the orally active Warfarin, phenprocoumon, and acenocoumarol are vitamin K antagonists (VKA) decrease a number of coagulation factors, including Factor X.
Rivaroxaban has predictable pharmacokinetics across a wide spectrum of patients (age, gender, weight, race) and has a flat dose response across an eightfold dose range (5–40 mg).
Rivaroxaban bears a striking structural similarity to the antibacterial Linezolid: both drugs share the same oxazolidinone-derived core structure. Accordingly, Rivaroxaban was studied for any possible antimicrobial effects and for the possibility of mitochondrial toxicity, which is a known complication of long-term Linezolid use. Studies found that neither Rivaroxaban nor its metabolites have any antibacterial/ antibiotic effect against Gram-positive bacteria. As for mitochondrial toxicity, in vitro studies published before 2008 found the risk to be low.
In September 2008, Health Canada granted marketing authorization for Rivaroxaban to prevent venous thromboembolism (VTE) in people who have undergone elective total hip replacement or total knee replacement surgery.
In the same month, the European Commission also granted marketing authorization of Rivaroxaban to prevent venous thromboembolism in adults undergoing elective hip and knee replacement.
On July 1, 2011, the U.S. Food and Drug Administration (FDA) approved Rivaroxaban for prophylaxis of deep vein thrombosis (DVT), which may lead to pulmonary embolism (PE), in adults undergoing hip and knee replacement surgery.
On November 4, 2011, the U.S. FDA approved Rivaroxaban for stroke prevention in people with non-valvular atrial fibrillation.
Rivaroxaban, chemically (S)-5-chloro-N-({2-oxo-3-[4-(3-oxomorpholin-4-yl)phenyl]-l,3- oxazolidin-5-yl}methyl)thiophene-2-carboxamide, described by formula (1), was developed by the company Bayer Healthcare (WO 01/47919, 2001). Rivaroxaban is applied in the clinical practice as the active ingredient of an orally available anticoagulant that is commercially marketed as Xarelto and is used in the prevention and treatment of arterial or venous thromboembolic disorders. In its effect, Rivaroxaban is characterized by direct selective inhibition of the FXa coagulation enzyme (Drugs of the Future 2006, 31(6): 484-493).
The family of compounds of which Rivaroxaban is a part was described for the first time in patent WO 01/47919 A1, which also reports possible synthesis pathways. Other patent documents, such as for example WO 201 1 /012321 A1, describe the preparation and isolation of polymorphs of the compound.
A similar process is described also in Journal of Medicinal chemistry, 2005, 48, 5900-5908 and DE 10129725. WO 2004/060887 discloses a method for producing Rivaroxaban from 5-Chlorothiophene-2-carbonyl chloride, (25)-3-Amino-propane-1,-diol and 4- (4-Aminophenyl)-3-morpholinone .
For the preparation of Rivaroxaban several key structures, referred to as building blocks, can be used as advanced intermediates. Virtually all the so far described syntheses are using two such building blocks. The first one are derivatives of 4-(4-Aminophenyl)morpholin-3-one, where it may be the case of an unsubstituted amine, or a derivative alkylated on nitrogen, or a carbamate derived from this compound. The other general and commonly used building block for the Rivaroxaban molecule are derivatives of 5-chlorothiophene-2-carboxylic acid, or its functional derivatives such as the chloride and amide.
U.S. Patent No. 8,106,192 provides a process for the preparation of N-((S)-3-Bromo-2-hydroxypropyl)-5-chlorothiophene-2-carboxamide, wherein (2S)-3-aminopropane-l,2-diol hydrochloride is reacted with 5-Chlorothiophene-2-carbonyl chloride to provide N-((S)-2,3-Dihydroxypropyl)-5-chlorothiophene-2-carboxamide. The resulting compound is treated with hydrobromic acid in acetic acid at 21-26°C. Acetic anhydride is added and the mixture is stirred at 60-65°C for 3 hours. Then Methanol is added at 20-26°C and the reaction is stirred under reflux for 2 to 2.5 hours, then overnight at 20-26°C to yield N-((S)-3-bromo-2-hydroxypropyl)-5-chlorothiophene-2-carboxamide, which is then converted into Rivaroxaban.
U.S. Publication No. 2010/0273789 provides a process for the preparation of 5- chloro-N-[(2S)-oxiran-2-ylmethyl]thiophene-2-carboxamide, wherein ((S)-3-bromo-2-hydroxypropyl)-5-chlorothiophene-2-carboxamide is stirred with potassium carbonate in the presence of anhydrous tetrahydrofuran for three days at room temperature to give 5-chloro-N-[(2S)-oxiran-2- ylmethyl]thiophene-2-carboxamide.
U.S. Publication No. 2007/0066615 provides a process for the preparation of 5- chloro-N-((2R)-2-hydroxy-3-{[4-(3-oxo-4-morpholinyl)-phenyl]amino}propyl)-2-thiophenecarboxamide, wherein a solution of 4-(4-aminophenyl)morpholin-3-one and 5-chloro-N-[(2S)-oxiranylmethyl]-2-thiophenecarboxamide in tetrahydrofuran is stirred overnight at 60°C in the presence of ytterbium(III) trifluoromethanesulfonate to give a precipitate, which is filtered off to provide the product in 54% yield. The remaining filtrate is concentrated and the residue obtained is purified by preparative HPLC to provide a further 38% of the product.
The third synthetic process was mainly used for preparation of deuterated analogs of Rivaroxaban (WO 2009/023233 Al, Concert Pharm.). It also represents the first synthetic process in which (R)-epichlorohydrin was used as the chiral building block. The other key starting material for the third process was 4-(4- aminophenyl) morpholin-3-one.
The fourth synthetic process, which proceeds according to WO 2010/124835, (Apotex), again uses (R)-Epichlorohydrin as the chiral building block, which reacts with the alkyl carbamate derived from 4-(4- aminophenyl) morpholin-3-one in the key stage.
The fifth synthetic process, which proceeds according to US 20110034465, also uses (R)-Epichlorohydrin as the chiral building block, which directly reacts with 4-(4-aminophenyl)morpholin-3-one in the key stage, which is the same reaction as in the third process. The differences between the third and fifth processes is in the preparation of the 2-oxo-l,3-oxazolidine cycle and in the carbonylation agent used. While the third process uses carbonyldiimidazol (CDI) as the carbonylation agent, the fifth process uses more available and cheaper alkyl chloroformates.
The sixths synthetic process, which proceeds according to WO 2011/080341, uses (7R)-Glycidyl butyrate (7) as the chiral building block, which in the key stage reacts with the alkyl carbamate derived from 4-(4-Aminophenyl)morpholin-3-one.
The last, seventh synthetic process leading to Rivaroxaban proceeds according to WO2011/098501 Al, uses (S)-3-aminopropane-l,2-diol as the chiral building block. The differences between the other and seventh process consist in the preparation process of the 2-oxo-l,3-oxazolidine cycle and the carbonylation agent used. While the second process uses Carbonyldiimidazol (CDI) as the carbonylation agent, the fifth process uses the cheaper, but very toxic phosgene.
U.S. Patent No, 7, 157,456 (hereinafter referred to as the '456 patent) discloses process for the preparation of Rivaroxaban which comprises of reducing 4-(4-morpholin-3- onyl)nitrobenzene by hydrogenation to 4-(4-aminophenyl)-3-morpholinone using 5% Pd/ C in tetrahydrofuran at 70°C for 8 hours. Then 2-[(2S)-2-oxiranylmethyl]-lH-isoindole-l,3(2H)-dione is reacted with 4-(4-aminophenyl)-3- morpholinone in ethanol/water to give 2-((2R)-2-Hydroxy-3-{[4-(3-oxo-4- morpholinyl) phenyl] amino}propyl)-lH-isoindole-l,3(2H)-dione. Subsequently 2-((2R)-2- Hydroxy-3-{[4-(3-oxo-4-morpholinyl)phenyl]amino}propyl)-lH-isoindole-l,3(2H)-dione is cyclized with ?,?'-carbonyldiimidazole in tetrahydrofuran to give 2-({(5S)-2-Oxo-3-[4-(3- oxo -4 -morpholinyl) phenyl] - 1 , 3 -oxazolidin- 5-yl}methyl) - 1 H-isoindole - 1 , 3 (2 H) –dione. The Phthalimide group is deprotected using methylamine (40% strength in water) in ethanol, which is reacted with 5-chlorothiophene-2-carbonyl chloride in pyridine. The process for the preparation of Rivaroxaban disclosed in '456 patent makes the use of ethers tetrahydrofuran, diethyl ether and Pyridine as a solvent in large volume and hence may not be safe and economical. Reduction is also carried out in autoclave by hydrogenation at high temperature, elevated pressure and the reaction time is also prolonged. Pd/' C is an expensive reagent and hence would add to the cost. Purity of intermediates and final product is not disclosed in this patent.
U.S. Pat. No. 7,598,378 provides a process for preparing 4-(4-aminophenyl)-3-morpholinone by reacting 4-(4-nitrophenyl)-3-morpholinone with hydrogen in the presence of a hydrogenation catalyst at 80°C for one hour in an aliphatic alcohol.
SUMMARY OF THE INVENTION:
The present invention primarily cites novel preparation and purification method of Rivaroxaban (Formula IV). Also disclosed is the preparation and purification method of its various intermediates such as 2-[(2R)-2-Hydroxy-3-{[4-(3-oxo morpholin-4-yl)phenyl] amino}propyl]-2,3-dihydro-1H-isoindole-1,3-dione (Formula I), 2-[[5S)-2-Oxo-3-[4-(3-Oxo morpholin-4-yl)phenyl]-1,3-oxazolidin-5-yl]methyl]-1H-iso indole-1,3(2H)-dione (Formula II), 4-{4-[(5S)-5-(Amino methyl)-2-oxo-1,3-oxazoli din-3-yl]phenyl}morpholin-3-one Hydrochloride (Formula III). The purified intermediates prepared using the invention disclosed herein is/are used to prepare highly pure 5-Chloro-N-{[(5S)-2-oxo-3-[4-(3-oxomorpholin-4-yl)phenyl]-1,3-oxazolidin-5-yl]methyl}thiophene-2-carboxamide (Formula IV or Rivaroxaban).
DETAILED DESCRIPTION OF THE INVENTION:
According to the first embodiment of the present invention, a novel process for the preparation and purification of 2-[(2R)-2-Hydroxy-3-{[4-(3-oxomorpholin-4-yl)phenyl]amino}propyl]-2,3-dihydro-1H- isoindole-1,3-dione is disclosed which comprises (Example 1):
i. refluxing 4-(4-Aminophenyl) morpholin-3-one and (S)-(+)-Glycidyl Phthalimide under stirring in C1-C4 aliphatic alcohol such as methanol, ethanol, 1-propanol, 2-propanol, butanol, monoethylene glycol, diethylene glycol or mixture thereof in presence of water for 20-24 hours;
ii. allowing the reaction mass to cool to room temperature;
iii. stirring for 2-3 hours to ensure complete crystallization;
iv. isolating the crude product by filtration and drying of the wet cake at 60-70°C for 8-12 hours;
v. heating the material of step (iv) in solvent as used in step (i) above to 60-70°C under stirring for 1-2 hours;
vi. cooling the resulting mass to 20-30°C; and
vii. isolating the pure product by filtration and drying the wet cake at 60-70°C for 8-12 hours to get pure 2-[(2R)-2-Hydroxy-3-{[4-(3-oxomorpholin-4-yl)phenyl]amino}propyl]-2,3-dihydro-1H- isoindole-1,3-dione.
According to the second embodiment of the present invention, a novel process for purification of 2-[[5S)-2-Oxo-3-[4-(3-Oxomorpholin-4-yl)phenyl]-1,3-oxazolidin-5-yl]methyl]-1H-isoindole-1,3(2H)-dione is disclosed which comprises (Example 2):
i. heating 2-[[5S)-2-Oxo-3-[4-(3-Oxomorpholin-4-yl)phenyl]-1,3-oxazolidin-5-yl]methyl]-1H-isoindole-1,3(2H)-dione with stirring for 1-2 hours in cyclic or acyclic ethers such as 2-Methyl Tetrahydrofuran, cyclopentyl methyl ether, tetrahydrofuran, dioxane, diisopropyl ether, tert-butyl methyl ether or a mixture thereof;
ii. cooling the resulting mass to room temperature and then further cooling to -5 to 5°C for complete crystallization; and
iii. isolating pure 2-[[5S)-2-Oxo-3-[4-(3-Oxomorpholin-4-yl)phenyl]-1,3-oxazolidin-5-yl]methyl]-1H-isoindole-1,3(2H)-dione by filtration and drying the wet cake at 60-70°C for 8-12 hours.
According to the third embodiment of the present invention, a novel process for the purification of 4-{4-[(5S)-5-(Aminomethyl)-2-oxo-1,3-oxazolidin-3-yl]phenyl}morpholin-3-one Hydrochloride is disclosed which comprises (Example 3):
i. heating the 4-{4-[(5S)-5-(Aminomethyl)-2-oxo-1,3-oxazolidin-3-yl]phenyl}morpholin-3-one Hydrochloride with stirring at reflux in a C1-C4 aliphatic alcohol such as methanol, ethanol, 1-propanol, 2-propanol, butanol, monoethylene glycol, diethylene glycol or a mixture thereof for 2-4 hours;
ii. cooling the reaction mass to 0-10°C with stirring for 2-3 hours; and
iii. isolating the pure product 4-{4-[(5S)-5-(Aminomethyl)-2-oxo-1,3-oxazolidin-3-yl] phenyl} morpholin-3-one Hydrochloride by filtration and drying the wet cake at 45-55°C for 6-8 hours.
According to the fourth embodiment of the present invention, a novel process for the preparation and purification of Rivaroxaban is disclosed which comprises (Example 4):
i. reacting 5-Chlorothiophene-2-carboxylic acid with thionyl chloride in a halogenated hydrocarbon such as methylene dichloride, chloroform, carbon tetrachloride or mixture thereof in presence of N,N-dimethylformamide at 40-50°C to get 5-Chlorothiophene-2-carbonyl chloride.
ii. reacting 5-Chlorothiophene-2-carbonyl chloride with 4-{4-[(5S)-5-(Aminomethyl)-2-oxo-1,3-oxazolidin-3-yl] phenyl}morpholin-3-one Hydrochloride in solvent as used in step (i) in presence of triethylamine or N, N-diisopropylethylamine at 10-20°C;
iii. quenching the reaction mass by adding water to it;
iv. isolating crude Rivaroxaban by filtration and drying the wet cake at 50-60°C;
v. redissolving the crude Rivaroxaban in aliphatic amide such as N,N-dimethylformamide, N,N-dimethylacetamide or a mixture thereof by heating at 40-50°C under stirring;
vi. charcolizing of reaction mass followed by filtration through hyflow-bed;
vii. recrystallizing the material by adding water at 40-50°C;
viii. isolating pure Rivaroxaban by filtration and drying the wet cake at 45-55°C for 4-8 hours;
ix. optionally purifying the Rivaroxaban of step (viii) by heating in a C1-C4 aliphatic alcohol such as Methanol, Ethanol, Propanol or a mixture thereof at reflux for 1-2 hours;
x. cooling the mass to 10-20°C with stirring for 2-4 hours; and
xi. isolating pure Rivaroxaban by filtration and drying the wet cake at 45-55°C for 4-8 hours.
According to the fifth embodiment of the present invention, a novel process for the preparation/purification of Rivaroxaban is disclosed which comprises (Example 5):
i. reacting 4-{4-[(5S)-5-(Aminomethyl)-2-oxo-1,3-oxazolidin-3-yl] phenyl}morpholin-3-one Hydrochloride and 5-Chlorothiophene-2-carboxylic acid in a halogenated hydrocarbon such as methylene dichloride, chloroform, carbon tetrachloride or mixture thereof in presence of N-(3-Dimethylaminopropyl)-N-ethylcarbodiimide and 1-Hydroxybenzotriazole under stirring at 20-30 °C for 20-24 hours;
ii. quenching of reaction by adding water to it;
iii. isolating crude Rivaroxaban by filtration and drying the wet cake at 50-60°C;
iv. redissolving the crude Rivaroxaban in aliphatic amide such as N,N-dimethylformamide, N,N-dimethylacetamide or a mixture thereof by heating at 40-50°C under stirring;
v. charcolizing of reaction mass followed by filtration through hyflow-bed;
vi. recrystallizing the material by adding water at 40-50°C;
vii. isolating pure Rivaroxaban by filtration and drying the wet cake at 45-55°C for 4-8 hours;
viii. optionally purifying the Rivaroxaban of step (viii) by heating in a C1-C4 aliphatic alcohol such as Methanol, Ethanol, Propanol or a mixture thereof at reflux for 1-2 hours;
ix. cooling the mass to 10-20°C with stirring for 2-4 hours; and
x. isolating pure Rivaroxaban by filtration and drying the wet cake at 45-55°C for 4-8 hours.
According to sixth embodiment of the present invention, a novel HPLC method of the accurate estimation of Rivaroxaban and its related substances is disclosed which is given as follows:
Related Substances by HPLC (for ICH grade Rivaroxaban):
Reagents
n-Pentane sulphonic acid sodium salt (AR Grade)
Trifluroaceticacid
Acetonitrile (HPLC Grade)
Orthophosphoric acid (HPLC Grade)
Milli Q water
Buffer Preparation-A: 0.96 g n-Pentane sulphonic acid sodium salt in 1000 ml water and adjust the pH 3.0 with dilute Orthophosphoric acid.
Buffer Preparation-B: 3 ml Trifluroaceticacid in 100 ml water
Mobile Phase Composition
Mobile phase A : Buffer-A: Acetonitrile (800:200)
Mobile phase B : Buffer-B: Water: Acetonitrile (1:200:800)
Preparation of Diluent: Acetonitrile: Water (50:50)
Chromatographic Parameters
Use a suitable High Performance Liquid Chromatography (HPLC) with following parameters.
Column : Unisol C18, 250*4.6mm,3 micron OR Equivelent
Flow : 0.6 ml
Detector : UV at ?=250 nm
Injection volume : 10 µL
Run time : 50 minutes
Column Temp : 35°C
Delay time : 10 minutes
Gradient Program : Time MP A MP B Curve (minutes) (%) (%)
00 60 40 ------
15 60 40 6
35 30 70 6
50 30 70 6
51 60 40 1
Preparation of System Suitability Solution
Accurately weigh and transfer about 3.0 mg each APMO(RV01), HOPODID(RV02), OOPOMID(RV03), AOOPMA(RV05) and CTCA(RVS02) to be analyzed in a 100 ml of volumetric flask. Dissolve in 10.0 ml diluent by sonication if necessary and dilute to volume with diluent. Then accurately dilute 1 ml of this solution+ 20.0 mg RV06 to 100 ml with diluent.
Preparation of Diluted Standard Solution
Accurately weigh and transfer about 75.0 mg Rivaroxaban Standard in to a 50.0 ml of volumetric flask. Dissolve in 10.0 ml diluent by sonication if necessary and dilute to volume with diluent solution (A). Then accurately dilute 1 ml of solution (A) in to 100 ml with diluent solution (B). Then accurately dilute 2.0 ml of solution (B) in to 100 ml with diluent.
Preparation of Sample Solution
Accurately weigh and transfer about 50.0 mg sample in to a 50.0 ml of volumetric flask. Dissolve in 10.0 ml diluent by sonication if necessary and dilute to volume with diluent. Then accurately dilute 2.0 ml of solution in to 10.0 ml with diluent.
Examine the blank run chromatogram for any extraneous peaks and disregard peaks due to blank and area below 0.05 observed in the chromatogram of the sample solution.
Injection Sequence as below

Sr.No Sample ID No. of Injections
1.0 Blank 01
2.0 SST 01
3.0 Diluted standard Solution 02
4.0 Sample Solution 01

RT of Rivaroxaban as below
Sr.No: Name Approximate Retention Time
(Minute) RRT w.r.t
Rivaroxaban Response Factor
1 AOOPMA (RV05) 3.5 0.33 1.21
2 APMO (RV01) 4.3 0.39 1.78
3 HOPODID (RV02) 7.5 0.69 1.45
4 OOPOMID( RV03) 10.0 0.91 1.35
5 RV06 (API) 11.0 1.00 -------
6 CTCA (RVS02) 13.1 1.19 1.07

The chemical name of impurities as listed above is given below:
S.No Name/Code Chemical Name
1. APMO (RV01) 4-(4-Aminophenyl) morpholin-3-one
2. HOPODID (RV02) 2-[(2R)-2-Hydroxy-3-{[4-(3-oxomorpholin-4-yl)phenyl]amino} propyl]-2,3-dihydro -1H- isoindole-1, 3-dione
3. OOPOMID( RV03) 2-[[5S)-2-Oxo-3-[4-(3-Oxomorpholin-4-yl)phenyl]-1,3-oxazolidin-5-yl]methyl]-1H-isoindole-1,3(2H)-dione
4. CTCA (RVS02) 5-Chlorothiophene-2-carboxyllic acid
5. AOOPMA (RV05) 4-{4-[(5S)-5-(Aminomethyl)-2-oxo-1,3-oxazolidin-3-yl] phenyl}morpholin-3-one Hydrochloride
6. RV06 (API) 5-Chloro-N-{[(5S)-2-oxo-3-[4-(3-oxo morpholin-4-yl) phenyl]-1,3-oxazolidin-5-yl]methyl}thiophene-2-carboxamide

Evaluation of System Suitability
The chromatographic system is suitable for analysis if and only if Resolution NLT 2.0 between Rivaroxaban and OOPOMID(RV03) impurity in SST solution
The % RSD for two replicate injections of diluted standard is NMT 10.0
If the system suitability passes, inject sample solution and record the chromatograms
Calculation
AT AT
% Known Impurity = ------ X 0.15 X RF, % Unknown Impurity = ------ X 0.15
AS AS
where,
AT = Area of individual impurity in test.
AS = Average area of Rivaroxaban in diluted standard
Assay by HPLC:
n-Pentane sulphonic acid sodium salt (AR Grade)
Trifluroaceticacid
Acetonitrile (HPLC Grade)
Orthophosphoric acid (HPLC Grade)
Milli Q water
Buffer Preparation-A: 0.96 g n-Pentane sulphonic acid sodium salt in 1000 ml water and adjust the pH 3.0 with dilute Orthophosphoric acid.

Buffer Preparation-B: 3 ml Trifluroaceticacid in 100 ml water
Mobile Phase Composition
Mobile phase A : Buffer-A: Acetonitrile (800:200)
Mobile phase B : Buffer-B: Water: Acetonitrile (1:200:800)
Preparation of Diluent: Acetonitrile: Water (50:50)
Chromatographic Parameters
Use a suitable High Performance Liquid Chromatography (HPLC) with following parameters.
Column : Unisol C18, 250*4.6mm,3 micron OR Equivalent
Flow : 0.6 ml
Detector : UV at ?=250 nm
Injection volume : 10 µL
Run time : 25 minutes
Column Temp : 35°C
Delay time : 10 minutes
Gradient Program : Time MP A MP B Curve (min.) (%) (%)
00 60 40 ------
15 60 40 6
25 30 70 6
26 60 40 1

Preparation of Standard Solution-A
Accurately weigh and transfer about 50 mg Standard to be analyzed in a 50 ml of volumetric flask. Dissolve in 10 ml Acetonitrile by sonication if necessary and dilute to volume with diluent. And further 5 ml this solution in 50 ml volumetric flask and dilute to volume with diluent.
Preparation of Standard Solution-B
Accurately weigh and transfer about 50.0 mg Standard to be analyzed in a 50.0 ml of volumetric flask. Dissolve in 10.0 ml Acetonitrile by sonication if necessary and dilute to volume with diluent. And further 5 ml this solution in 50.0 ml volumetric flask and dilute to volume with diluent.
Preparation of Sample Solution-A
Accurately weigh and transfer about 50.0 mg sample to be analyzed in a 50.0 ml of volumetric flask. Dissolve in 10.0 ml Acetonitrile by sonication if necessary and dilute to volume with diluent. And further 5.0 ml this solution in 50.0 ml volumetric flask and dilute to volume with diluent.

Preparation of Sample Solution-B
Accurately weigh and transfer about 50.0 mg sample to be analyzed in a 50.0 ml of volumetric flask. Dissolve in 10.0 ml Acetonitrile by sonication if necessary and dilute to volume with diluent. And further 5.0 ml this solution in 50.0 ml volumetric flask and dilute to volume with diluent.
Injection Sequence as below
Sr.No Sample ID No. of Injections
1.0 Blank 01
2.0 Standard Preparation-A 01
3.0 Standard Preparation-B 05
4.0 Sample Preparation-A 01
5.0 Sample Preparation-B 01

Procedure
Equilibrate the column and instrument until base line stabilizes, then Inject one injection of blank, one injection of standard preparation –A and standard preparation –B.
The retention time of Rivaroxaban peak is about 11 minutes approximately.
Calculate the similarity factor as follows
Area of standard preparation –A Wt. of standard preparation –B
-------------------------------------------- x --------------------------------------------
Area of standard preparation –B Wt. of standard preparation –A
The similarity factor should be 0.98 to 1.02
Evaluation of System Suitability
The chromatographic system is suitable for analysis if and only if
The % RSD for five replicate injections of standard preparation –B is NMT 2.0%
Tailing for the Rivaroxaban peak should be NMT 2.0%
If the system suitability passes inject sample preparation as per sequence.
Calculate the assay of both sample preparations individual as follows and take the average of the both value.
AT x WS x P x 100
Assay (OAB) = ----------------------------------------------
AS x WT x (100-MC of TEST)
Where,
AT= Average area of test peak of Rivaroxaban
AS= Average area of standard peak of Rivaroxaban
WS= Weight of standard (mg)
WT= Weight of test (mg)
P= Potency of Standard
MC= Moisture Content
The above mentioned invention is supported by the following non limiting examples.
EXAMPLES:
Preparation and purification of 2-[(2R)-2-Hydroxy-3-{[4-(3-oxomorpholin -4-yl)phenyl] amino} propyl]-2,3-dihydro -1H- isoindole-1, 3-dione
Example 1: 4-(4-Aminophenyl) morpholin-3-one (100g) and S)-(+)-Glycidyl Phthalimide (158g) are refluxed in Methanol (1350 ml) and water (150 ml) mixture for 20-24 hours for completion of reaction. The reaction mass is cooled to 20-30° C and stirred for 2-3 hours. The resulting solid is filtered and given running washed with Methanol (25 ml) and water mixture (10ml) followed by drying of wet cake at 45-55°C to get 195g of the product which is purified by heating in Methanol (1000ml) at 60-70°C followed by cooling to 20-30°C, filtration and drying of wet cake at 60-70°C for 8-12 hours to get pure product 2-[(2R)-2-Hydroxy-3-{[4-(3-oxomorpholin-4-yl)phenyl]amino} propyl]-2,3-dihydro -1H- isoindole-1, 3-dione (HPLC purity= 99.01%).

Preparation and purification of 2-[[5S)-2-Oxo-3-[4-(3-Oxomorpholin-4-yl)phenyl]-1,3-oxazolidin-5-yl]methyl]-1H-isoindole-1,3(2H)-dione
Example 2: 2-[(2R)-2-Hydroxy-3-{[4-(3-oxomorpholin-4-yl)phenyl]amino} propyl]-2,3-dihydro -1H- isoindole-1, 3-dione (100g) and Carbonyldiimidazole (150g) are refluxed in THF (1500 ml) in presence of 5g of 4-Dimethylaminopyridine (DMAP) for 20-24 hours till completion of reaction. The reaction mass is cooled to room temperature and then further cooling to -5 to 5°C 20-30°C and stirred for 2-3 hours. The resulting solid is filtered and given running washing with THF (25 ml) followed by drying of wet cake at 45-55°C to get 95g of the product which is purified by heating in THF (500ml) at reflux for 2-4 hours followed by cooling to room temperature and then further cooling to -5 to 5°C with stirring for 1-2 hours. The resulting solid is filtered and dried at 60-70°C for 8-12 hours to get pure product 2-[[5S)-2-Oxo-3-[4-(3-Oxomorpholin-4-yl)phenyl]-1,3-oxazolidin-5-yl]methyl]-1H-isoindole-1,3(2H)-dione (HPLC purity= 99.89%).
Preparation and purification of 4-{4-[(5S)-5-(Aminomethyl)-2-oxo-1,3-oxazolidin-3-yl] phenyl}morpholin-3-one Hydrochloride
Example 3: 2-[[5S)-2-Oxo-3-[4-(3-Oxomorpholin-4-yl)phenyl]-1,3-oxazolidin-5-yl]methyl]-1H-isoindole-1,3(2H)-dione (100g) and aqueous 38-43% Methylamine (100ml) are refluxed in Methanol (250 ml) for 2-4 hours for completion of reaction. Then complete recovery of Methanol is done under vacuum to get solid residue which is dissolved in Methanol (500ml) at 30-40°C followed by addition of water (200ml) and Hydrochloric acid (40ml) and stirred for 2-4 hours. The resulting solid is cooled to 0-10°C followed by stirring for 2-3 hours. The product is filtered and given running washed with Methanol (10 ml) followed by drying of wet cake at 45-55°C to get 60g of the product which is purified by heating in Methanol (500ml) at 60-70°C for 2-4 hours followed by cooling to 0-10°C and stirring for 1-2 hours. The product is filtered, running washed with Methanol (25 ml) and dried at 45-55°C for 4-8 hours to get pure product 4-{4-[(5S)-5-(Aminomethyl)-2-oxo-1,3-oxazolidin-3-yl] phenyl}morpholin-3-one Hydrochloride (HPLC purity= 99.85%).
Preparation and purification of 5-Chloro-N-{[(5S)-2-oxo-3-[4-(3-oxomorpholin-4-yl) phenyl]-1,3-oxazolidin-5-yl]methyl} thiophene-2-carboxamide (Rivaroxaban)
Example 4: 5-Chlorothiophene-20carboxylic acid (65g) is reacted with Thionyl chloride (65g) in Methylene chloride (650 ml) in presence of DMF at 40-50°C. After completion of reaction, complete recovery of Methylene chloride is done under vacuum. Then fresh MDC (150ml) is added to it. Then it is added to a solution of 4-{4-[(5S)-5-(Aminomethyl)-2-oxo-1,3-oxa zolidin-3-yl] phenyl}morpholin-3-one Hydrochloride (100g) in Methylene chloride (800ml) and TEA (100g) at 10-20°C and stirred for 1-3 hours for completion of reaction. Then water (500ml) followed by drying of wet cake at 50-60°C and resulting solid is recrystallized by dissolving in DMF (700ml) followed by charcoalization and filtering off carbon. The product is crystallized by adding water (700ml) at 40-50°C. The product is isolated by filtration and wet cake is refluxed in Methanol (500ml) for 1-2 hours followed by filtration of product at 0-5°C and drying at 45-55°C for 10-15 hours to get 115 g of the pure Rivaroxaban i.e. 5-Chloro-N-{[(5S)-2-oxo-3-[4-(3-oxomorpholin-4-yl) phenyl]-1,3-oxazolidin-5-yl]methyl} thiophene-2-carboxamide (HPLC purity= 99.95%).
Example 5: 4-{4-[(5S)-5-(Aminomethyl)-2-oxo-1,3-oxazolidin-3-yl] phenyl}morpholin-3-one Hydrochloride (100g) is reacted with 5-Chlorothiophene-20carboxylic acid (50g) in Methylene chloride (500 ml) in presence of EDAC (75g) and HOBT (50g) at 20-30°C for 20-24 hrs. After completion of reaction, water (500ml) is added to it and organic layer is separated. Complete recovery of Methylene chloride is done under vacuum. The resulting solid residue is recrystallized by dissolving in DMF (700ml) followed by charcoalization and filtering off carbon. The product is crystallized by adding water (700ml) at 40-50°C. The product is isolated by filtration and wet cake is refluxed in Methanol (500ml) for 1-2 hours followed by filtration of product at 0-5°C and drying at 45-55°C for 10-15 hours to get 115g of the pure Rivaroxaban i.e. 5-Chloro-N-{[(5S)-2-oxo-3-[4-(3-oxomorpholin-4-yl)phenyl]-1,3-oxazolidin-5-yl]methyl}thio phene-2-carboxamide (HPLC purity= ~99%).

WE CLAIM:

An improved process for preparation and purification of 2-[(2R)-2-Hydroxy-3-{[4-(3-oxomorpholin-4-yl)phenyl]amino}propyl]-2,3-dihydro-1H-isoindole-1,3-dione which comprises:
stirring 4-(4-Aminophenyl) morpholin-3-one and (S)-(+)-Glycidyl Phthalimide in C1-C4 aliphatic alcohol such as methanol, ethanol, 1-propanol, 2-propanol, butanol, monoethylene glycol, diethylene glycol or mixture and water;
dissolving by heating to reflux and stirring for 20-24 hours;
allowing the reaction mass to attain ambient temperature;
further stirring of reaction mass to ensure proper crystallization;
isolating crude product as wet cake by filtration and semi drying the material at 60-70°C for 8-12 hours;
re-dissolving the material in solvent of Step I and stirring the reaction mass under reflux for 1-2 hours;
cooling the reaction mass to 20-30°C;
isolating the pure product as wet cake by filtration; and
drying of the wet cake at 60-70°C for 8-12 hours to get pure 2-[(2R)-2-Hydroxy-3-{[4-(3-oxomorpholin-4-yl)phenyl]amino}propyl]-2,3-dihydro-1H-isoindole-1,3-dione.
An improved process for the purification of 2-[[5S)-2-Oxo-3-[4-(3-Oxomorpholin-4-yl)phenyl]-1,3-oxazolidin-5-yl]methyl]-1H-isoindole-1,3(2H)-dione which comprises:
stirring 2-[[5S)-2-Oxo-3-[4-(3-Oxomorpholin-4-yl)phenyl]-1,3-oxazolidin-5-yl]methyl]-1H-isoindole-1,3(2H)-dione in cyclic or acyclic ethers such as 2-Methyl Tetrahydrofuran, cyclopentyl methyl ether, tetrahydrofuran, dioxane, diisopropyl ether, tert-butyl methyl ether or a mixture thereof at room temperature;
heating and stirring to dissolve and stirring further for 1-2 hours;
cooling the reaction mass to -5 to +5 °C;
isolating the product as wet cake by filtration; and
drying of the wet cake at 50-60°C for 10-20 hours to get the desired pure 2-[[5S)-2-Oxo-3-[4-(3-Oxomorpholin-4-yl)phenyl]-1,3-oxazolidin-5-yl]methyl]-1H-isoindole-1,3(2H)-dione.
An improved process for the purification of 4-{4-[(5S)-5-(Aminomethyl)-2-oxo-1,3-oxazolidin-3-yl]phenyl}morpholin-3-one Hydrochloride which comprises:
stirring 4-{4-[(5S)-5-(Aminomethyl)-2-oxo-1,3-oxazolidin-3-yl]phenyl}morpholin-3-one Hydrochloride in a C1-C4 aliphatic alcohol such as methanol, ethanol, 1-propanol, 2-propanol, butanol, monoethylene glycol, diethylene glycol or a mixture thereof;
heating and stirring to dissolve and reflux for 2-4 hours;
cooling the reaction mass to 0 to +10 °C;
further stirring for 2-3 hours to ensure proper crystallization;
isolating the product as wet cake by filtration; and
drying of the wet cake at 50-60°C for 10-20 hours to get desired pure 4-{4-[(5S)-5-(Aminomethyl)-2-oxo-1,3-oxazolidin-3-yl]phenyl}morpholin-3-one Hydrochloride.
An improved process for the preparation and purification of Rivaroxaban which comprises:
dissolving 5-Chlorothiophene-2-carboxylic acid in a halogenated hydrocarbon such as methylene dichloride, chloroform, carbon tetrachloride or mixture thereof and adding thionyl chloride in presence of N,N-dimethylformamide at 40-50°C to get 5-Chlorothioph ene-2-carbonyl chloride;
dissolving 4-{4-[(5S)-5-(Aminomethyl)-2-oxo-1,3-oxazolidin-3-yl]phenyl}morpholin-3-one Hydrochloride with stirring in a C1-C4 aliphatic alcohol such as methanol, ethanol, 1-propanol, 2-propanol, butanol, monoethylene glycol, diethylene glycol or a mixture thereof and adding 5-Chlorothiophene-2-carbonyl chloride, Triethylamine at 10-20°C;
stirring for 2-3 hours till reaction completion;
adding water and stirring till complete crystallization;
isolating crude Rivaroxaban by filtration and drying the wet cake at 50-60°C;
re-dissolving the crude Rivaroxaban in aliphatic amide such as N,N-dimethylformamide, N,N-dimethylacetamide or a mixture thereof by heating at 40-50°C under stirring;
charcoaling of reaction mass followed by filtration through hyflow-bed at 40-50°C;
adding water to the filtrate of step vii) at 40-50°C;
isolating pure Rivaroxaban as wet cake by filtration and drying at 45-55°C for 4-8 hours; and
optionally purifying the Rivaroxaban of step (ix) by heating in a C1-C4 aliphatic alcohol such as Methanol, Ethanol, Propanol or a mixture thereof at reflux for 1-2 hours by repeating step nos. vi) to ix).
An improved process for the preparation and purification of Rivaroxaban which comprises:
dissolving 4-{4-[(5S)-5-(Aminomethyl)-2-oxo-1,3-oxazolidin-3-yl]phenyl}morpholin-3-one Hydrochloride and adding 5-Chlorothiophene-2-carboxylic acid to it in a halogenated hydrocarbon such as methylene dichloride, chloroform, carbon tetrachloride or mixture thereof in presence N-(3-Dimethylaminopropyl)-N-ethylcarbodiimide and 1-Hydroxybenzotriazole under stirring at 20-30 °C for 20-24 hours;
stirring for 2-3 hours till reaction completion;
adding of water and stirring till complete crystallization;
isolating crude Rivaroxaban by filtration and drying the wet cake at 50-60°C;
re-dissolving the crude Rivaroxaban in aliphatic amide such as N,N-dimethylformamide, N,N-dimethylacetamide or a mixture thereof by heating at 40-50°C under stirring;
charcoaling of reaction mass followed by filtration through hyflow-bed at 40-50°C;
adding water to filtrate of step vi) at 40-50°C;
isolating pure Rivaroxaban as wet cake by filtration and drying at 45-55°C for 4-8 hours; and
optionally purifying the Rivaroxaban of step (viii) by heating in a C1-C4 aliphatic alcohol such as Methanol, Ethanol, Propanol or a mixture thereof at reflux for 1-2 hours by repeating step nos. v) to viii).
A novel HPLC method for the accurate estimation of all the related products is also disclosed which is capable of separating all the impurities with good resolution, LOD and LOQ.