DESC:FIELD OF THE INVENTION
The present application relates to an improved process for preparation of Ruxolitinib, its pharmaceutically acceptable salts, its intermediate compounds and pharmaceutical compositions thereof.

BACKGROUND OF THE INVENTION
The drug compound having the adopted name Ruxolitinib, has a chemical name (R)-3-cyclo-pentyl-3-(4-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)-1H-pyrazol-1-yl)propanenitrile, and is represented by the structure of formula I.

Ruxolitinib is a selective JAK1/JAK2 tyrosine kinase inhibitor and is available for the treatment of myelofibrosis related indications.
Ruxolitinib, its synthetic process and its pharmaceutical compositions are described in US patent No. 7,598,257 (US ‘257). US patent No. 8,722,693 discloses the phosphate salt of Ruxolitinib.
The process described in US ‘257 involves separation of isomeric intermediate compounds as well final Ruxolitinib base using preparative HPLC method, and the intermediate compounds and the Ruxolitinib base of Formula I were purified by column chromatography.
US patent No. 8,410,265 (US ‘265) describes a process for preparation of Ruxolitinib base by resolution of the compound of Formula IIa with (+)-2,3-dibenzoyl-D-tartaric acid to obtain (2S,3S)-2,3-bis(benzoyloxy) succinic acid-(3R)-3-cyclopentyl-3-[4-(7-{[2-trimethylsilyl)ethoxy]methyl}-7H-pyrrolo[2,3-d]-pyrimidin-4-yl)-1H-pyrazol-1-yl]propanenitrile (1:1) and its subsequent treatment with a base.
Drugs of the Future (2010), 35(6), 457-465 provides a review of the Ruxolitinib synthetic processes described in the art. In the route disclosed in the review, the chiral resolution is set to close to the step of forming final Ruxolitinib base, and the atomic utilization rate is relatively low. The structure of the chiral catalyst is relatively complex and the amount of the catalyst used therein is relatively high.
US patent No. 10,562,904 (US ‘904) describes a process for preparation of Ruxolitinib. This process to convert compound of formula VI to compound of formula V requires the use of methyl magnesium bromide in diethyl ether (a challenging solvent to handle on large scale due to its’ low boiling point and volatility) as well as a palladium catalyst. Palladium is a relatively expensive precious metal, and in this case an expensive phosphine ligand (dppf) is also required. These two factors meant that this would be a difficult and expensive reaction to operate on larger scale.
The ee value of the Ruxolitinib obtained by the prior art processes is not high and the chiral purity is low, and the final product still needs purification by multi-step refining process.
In order to overcome the shortcomings of the synthetic processes described in the prior art, the present application aims to provide an improved method for preparing Ruxolitinib with high chiral purity and which is suitable for industrial production.

SUMMARY OF THE INVENTION

In one aspect, the present application provides a process for purification of Ruxolitinib, comprising the following steps:
(i) treating crude Ruxolitinib base with active carbon,
(ii) treating the crude Ruxolitinib base of step (i) with dibenzoyl-D-tartaric acid to form dibenzoyl-D-tartrate salt,
(iii) isolating pure Ruxolitinib base from the dibenzoyl-D-tartrate salt.
In another aspect, the present application provides a process for preparation of Ruxolitinib having less than about 0.5% of methyl ester of compound of Formula-III, comprising the following steps:
(i) treating crude Ruxolitinib base with active carbon,
(ii) treating the crude Ruxolitinib base of step (i) with dibenzoyl-D-tartaric acid to form dibenzoyl-D-tartrate salt,
(iii) isolating pure Ruxolitinib base having less than about 0.5% of methyl ester of compound of Formula-III from the dibenzoyl-D-tartrate salt.
In another aspect, the present application provides a process for preparation of Ruxolitinib having less than about 0.2% of methyl ester of compound of Formula-III, comprising the following steps:
(iv) treating crude Ruxolitinib base with active carbon,
(v) treating the crude Ruxolitinib base of step (i) with dibenzoyl-D-tartaric acid to form dibenzoyl-D-tartrate salt,
(vi) isolating pure Ruxolitinib base having less than about 0.2% of methyl ester of compound of Formula-III from the dibenzoyl-D-tartrate salt.
In another aspect, the present application provides a pharmaceutical composition comprising Ruxolitinib or a pharmaceutically acceptable salt thereof having less than about 0.5% of methyl ester of compound of Formula-III

BRIEF DESCRIPTION OF DRAWINGS
Figure-1 is powder X-ray diffraction (PXRD) pattern of D-tartaric acid salt of acetone adduct of compound of Formula VII prepared according to example 2.
Figure-2 is powder X-ray diffraction (PXRD) pattern of Sodium salt of compound of Formula III prepared according to example 4.
Figure-3 is powder X-ray diffraction (PXRD) pattern of DBTA salt of Ruxolitinib prepared according to example 9.

DETAILED DESCRITPION OF THE INVENTION
In one aspect, the present application provides a process for preparation of compound of Formula III as shown in below synthetic scheme.

The present inventors have also found that the sodium salt of the compound of formula III can be isolated as a solid by treating crude compound of formula III with sodium methoxide in methanol, followed by addition of MTBE. The PXRD pattern of the sodium salt of the compound of formula III is shown in Figure 3.
In another aspect, the present application provides a process for preparing Ruxolitinib, comprising the following steps:
(i) reacting the compound of formula III with CDI, or a salt thereof with CDI and, optionally, imidazole hydrochloride to obtain an intermediate imidazolide, and then reacting the intermediate compound with aqueous ammonia to form the compound of Formula II.
R is H or Na,
(ii) converting the compound of formula II to Ruxolitinib base, and
(iii) optionally, converting Ruxolitinib base to pharmaceutically acceptable salts thereof.
The step 1 process involves reaction of compound of formula III or its sodium salt with CDI to form the intermediate imidazolide and further reaction of the intermediate imidazolide with aqueous ammonia to form the compound of formula II. If the sodium salt of the compound of formula III is used, imidazole hydrochloride can be added to enhance the rate of reaction.
The compound of formula III, or its sodium salt and, optionally, imidazole hydrochloride, are suspended in a suitable solvent such as THF. CDI is then added in portions until the reaction to the intermediate imidazolide is completed. Aqueous ammonia is then added and the mixture stirred until reaction is completed. The product is isolated by extraction into a suitable solvent such as ethyl acetate or 2-MeTHF, and concentration. The product can also be precipitated from ethyl acetate and heptane mixtures.
Direct use of sodium salt of compound of formula III, optionally adding imidazole hydrochloride, is beneficial as it removes the need to first convert the salt to the corresponding acid. Compared to the prior art, avoiding the use of NMP as a co-solvent for the reaction simplifies the work-up, the product is obtained with much reduced solvent content, and can be isolated as a solid. Using CDI instead of oxalyl chloride, as in the prior art, affords a much lighter colored product, reducing the purification burden on the downstream stages.
In step 2, the compound of formula II and POCl3 are reacted in a suitable solvent such as dichloromethane. After the reaction is completed, water is added to the mixture and the pH may be adjusted to 7 using a suitable base. The product is extracted into a suitable solvent such as ethyl acetate or 2-MeTHF. The organic layer was separated and concentrated to get Ruxolitinib base.
The Ruxolitinib base may be converted to pharmaceutically acceptable salts, such as the phosphate salt.
In another aspect, the present application provides a process for purification of Ruxolitinib base, comprising the following steps:
(i) treating the crude Ruxolitinib base with activated carbon,
(ii) treating the Ruxolitinib base of step (i) with dibenzoyl-D-tartaric acid to form dibenzoyl-D-tartrate salt,
(iii) isolating pure Ruxolitinib base from the dibenzoyl-D-tartrate salt.
The crude Ruxolitinib base is treated with activated carbon, particularly Norit grade carbon. Ruxolitinib base is dissolved in ethyl acetate and Norit grade carbon is added and the slurry is stirred for about 5 minutes to about 45 hours. The mixture was filtered and the ethyl acetate layer was concentrated to get pure Ruxolitinib base.
The above purified Ruxolitinib base may be further treated with (+)-2,3-dibenzoyl-D-tartaric acid to give the dibenzoyl-D-tartrate salt and is carried out in a suitable solvent such as acetonitrile, ethyl acetate, isopropanol or THF at about 20 °C to about 70 °C.
The dibenzoyl-D-tartrate salt is isolated and dried. The PXRD pattern of the dibenzoyl-D-tartrate salt Ruxolitinib is shown in Figure 4. The dibenzoyl-D-tartrate salt is treated with a suitable base to isolate pure Ruxolitinib base.
The pure Ruxolitinib base is converted into pharmaceutically acceptable salt of Ruxolitinib, preferably phosphate by treating the Ruxolitinib base with phosphoric acid in a suitable solvent like isopropanol. The Ruxolitinib phosphate prepared by the process of the present invention contains less than about 0.5% of methyl ester of
compound of Formula-III

In another aspect, the present application provides Ruxolitinib or its pharmaceutically acceptable salt, preferably Ruxolitinib phosphate prepared by the process of the present invention having purity of about 99.5% and contains less than about 0.5% of methyl ester of compound of Formula-III.
In another aspect, the present application provides Ruxolitinib or its pharmaceutically acceptable salt, preferably Ruxolitinib phosphate prepared by the process of the present invention having purity of about 99.8% and contains less than about 0.2% of methyl ester of compound of Formula-III.
The compounds at various stages of the process may be recovered using conventional techniques known in the art. For example, useful techniques include, but are not limited to, decantation, centrifugation, gravity filtration, suction filtration, evaporation, flash evaporation, simple evaporation, rotational drying, spray drying, thin-film drying, freeze-drying, and the like. The isolation may be optionally carried out at atmospheric pressure or under a reduced pressure. The solid that is obtained may carry a small proportion of occluded mother liquor containing a higher than desired percentage of impurities and, if desired, the solid may be washed with a solvent to wash out the mother liquor. Evaporation as used herein refers to distilling a solvent completely, or almost completely, at atmospheric pressure or under a reduced pressure. Flash evaporation as used herein refers to distilling of solvent using techniques including, but not limited to, tray drying, spray drying, fluidized bed drying, or thin-film drying, under atmospheric or a reduced pressure.
A recovered solid may optionally be dried. Drying may be suitably carried out using equipment such as a tray dryer, vacuum oven, air oven, fluidized bed dryer, spin flash dryer, flash dryer, and the like, at atmospheric pressure or under reduced pressure. Drying may be carried out at temperatures less than about 150°C, less than about 100°C, less than about 60°C, or any other suitable temperatures, in the presence or absence of an inert atmosphere such as nitrogen, argon, neon, or helium. The drying may be carried out for any desired time periods to achieve a desired purity of the product, such as, for example, from about 1 hour to about 15 hours, or longer.

DEFINITIONS
The following definitions are used in connection with the present application unless the context indicates otherwise.
The following definitions are used in connection with the present application, unless the context indicates otherwise.
Polymorphs are different solids sharing the same molecular formula, yet having distinct physical properties when compared to other polymorphs of the same formula.
As used herein, "comprising" means the elements recited, or their equivalents in structure or function, plus any other element or elements which are not recited. The terms "having" and "including" are also to be construed as open ended unless the context suggests otherwise. Terms such as "about," "generally," "substantially," 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, or instrument error for a given technique used to measure a value.
In addition, where a reference is made to a figure, it is permissible to, and this document includes and contemplates, the selection of any number of data points illustrated in the figure which uniquely define that crystalline form, salt and/or optical isomer, within any associated and recited margin of error, for purposes of identification.
As used herein, the term "overnight" refers to a time interval from about 14 hours to about 24 hours, or about 14 hours to about 20 hours, for example, about 16 hours.
Any organic solvents may be used alone, or any two or more may be used in combination, or one or more may be used in combination with water in desired ratios.
An “alcohol” is an organic compound containing a carbon bound to a hydroxyl group. “C1-C6 alcohols” include, but are not limited to, methanol, ethanol, 2-nitroethanol, 2-fluoroethanol, 2,2,2-trifluoroethanol, hexafluoroisopropyl alcohol, ethylene glycol, 1-propanol, 2-propanol (isopropyl alcohol), 2-methoxyethanol, 1-butanol, 2-butanol, i-butyl alcohol, t-butyl alcohol, 2-ethoxyethanol, diethylene glycol, 1-, 2-, or 3-pentanol, neo-pentyl alcohol, t-pentyl alcohol, isoamyl alcohol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, cyclohexanol, phenol, glycerol, or the like.
A “hydrocarbon” is a liquid hydrocarbon compound, which may be linear, branched, or cyclic and may be saturated or have as many as two double bonds. A liquid hydrocarbon compound that contains a six-carbon group having three double bonds in a ring is called “aromatic.” Examples of “C5-C8 aliphatic or aromatic hydrocarbons” include, but are not limited to, isopentane, neopentane, isohexane, 3-methylpentane, 2,3-dimethylbutane, neohexane, isoheptane, 3-methylhexane, neoheptane, 2,3-dimethylpentane, 2,4-dimethylpentane, 3,3-dimethylpentane, 3-ethylpentane, 2,2,3-trimethylbutane, n-octane, isooctane, 3-methylheptane, neooctane, cyclohexane, methylcyclohexane, cycloheptane, petroleum ethers, benzene toluene, ethylbenzene, m-xylene, o-xylene, p-xylene, trimethylbenzene, chlorobenzene, fluorobenzene, trifluorotoluene, anisole, or any mixtures thereof.
A “halogenated hydrocarbon” is an organic compound containing a carbon bound to a halogen. Halogenated hydrocarbons include, but are not limited to, dichloromethane, 1,2-dichloroethane, trichloroethylene, perchloroethylene, 1,1,1-trichloroethane, 1,1,2-trichloroethane, chloroform, carbon tetrachloride, or the like.
An “ester” is an organic compound containing a carboxyl group -(C=O)-O- bonded to two other carbon atoms. “C3-C6 esters” include, but are not limited to, ethyl acetate, n-propyl acetate, n-butyl acetate, isobutyl acetate, t-butyl acetate, ethyl formate, methyl acetate, methyl propanoate, ethyl propanoate, methyl butanoate, ethyl butanoate, or the like.
An “ether” is an organic compound containing an oxygen atom –O- bonded to two other carbon atoms. “C2-C6 ethers” include, but are not limited to, diethyl ether, diisopropyl ether, dimethoxy ethane, methyl t-butyl ether, glyme, diglyme, tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, dibutyl ether, dimethylfuran, 2-methoxyethanol, 2-ethoxyethanol, anisole, or the like.
A “ketone” is an organic compound containing a carbonyl group -(C=O)- bonded to two other carbon atoms. “C3-C6 ketones” include, but are not limited to, acetone, ethyl methyl ketone, diethyl ketone, methyl isobutyl ketone, ketones, or the like.
A “nitrile” is an organic compound containing a cyano -(C=N) bonded to another carbon atom. “C2-C6 Nitriles” include, but are not limited to, acetonitrile, propionitrile, butanenitrile, or the like.
Any organic solvents may be used alone, or any two or more may be used in combination, or one or more may be used in combination with water in desired ratios.
Acid addition salts are typically pharmaceutically acceptable, non-toxic addition salts with “suitable acids,” including, but not limited to: inorganic acids such as hydrohalic acids (for example, hydrofluoric, hydrochloric, hydrobromic, and hydroiodic acids) or other inorganic acids (for example, nitric, perchloric, sulfuric, and phosphoric acids); organic acids, such as organic carboxylic acids (for example, xinafoic, oxalic, propionic, butyric, glycolic, lactic, mandelic, citric, acetic, benzoic, 2- or 4-methoxybenzoic, 2- or 4-hydroxybenzoic, 2- or 4-chlorobenzoic, salicylic, succinic, malic, hydroxysuccinic, tartaric, fumaric, maleic, hydroxymaleic, oleic, and glutaric acids), organic sulfonic acids (for example, methanesulfonic, trifluoromethanesulfonic, ethanesulfonic, 2-hydroxyethanesulphonic, benzenesulfonic, toluene-p-sulfonic, naphthalene-2-sulphonic, and camphorsulfonic acids), and amino acids (for example, ornithinic, glutamic, and aspartic acids).
All percentages and ratios used herein are by weight of the total composition and all measurements made are at about 25°C and about atmospheric pressure, unless otherwise designated. All temperatures are in degrees Celsius unless specified otherwise. As used herein, “comprising” means the elements recited, or their equivalents in structure or function, plus any other element or elements which are not recited. The terms “having” and “including” are also to be construed as open ended. All ranges recited herein include the endpoints, including those that recite a range “between” two values. Whether so indicated or not, all values recited herein are approximate as defined by the circumstances, including the degree of expected experimental error, technique error, and instrument error for a given technique used to measure a value.
Terms such as "about," "generally," "substantially," 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 the very least, the degree of expected experimental error, technique error and instrument error for a given technique used to measure a value.
When a molecule or other material is identified herein as "pure", it generally means, unless specified otherwise, that the material has 99% purity or higher, as determined using methods conventional in the art such as high performance liquid chromatography (HPLC), gas chromatography (GC), or spectroscopic methods. In general, this refers to purity with regard to unwanted residual solvents, reaction by-products, impurities, and unreacted starting materials. In the case of stereoisomers, "pure" also means 99% of one enantiomer or diastereomer, as appropriate. "Substantially pure” refers to the same as "pure,” except that the lower limit is about 98% purity or higher and, likewise, "essentially pure” means the same as "pure" except that the lower limit is about 97% purity.
The compounds of this application are best characterized by the X-ray powder diffraction pattern determined in accordance with procedures that are known in the art. PXRD data reported herein was obtained using CuK? radiation, having the wavelength 1.5406 Å and were obtained using a PANalytical X’Pert PRO instruments. For a discussion of these techniques see J. Haleblain, J. Pharm. Sci. 1975 64:1269-1288, and J. Haleblain and W. McCrone, J. Pharm. Sci. 1969 58:911-929.
Generally, a diffraction angle (2?) in powder X-ray diffractometry may have an error in the range of ± 0.2o. Therefore, the aforementioned diffraction angle values should be understood as including values in the range of about ± 0.2o. Accordingly, the present application includes not only crystals whose peak diffraction angles in powder X-ray diffractometry completely coincide with each other, but also crystals whose peak diffraction angles coincide with each other with an error of about ± 0.2o. Therefore, in the present specification, the phrase "having a diffraction peak at a diffraction angle (2? ± 0.2o) of 7.9o " means "having a diffraction peak at a diffraction angle (2?) of 7.7 o?to 8.1 o”. Although the intensities of peaks in the x-ray powder diffraction patterns of different batches of a compound may vary slightly, the peaks and the peak locations are characteristic for a specific polymorphic form. Alternatively, the term "about" means within an acceptable standard error of the mean, when considered by one of ordinary skill in the art. The relative intensities of the PXRD peaks can vary depending on the sample preparation technique, crystal size distribution, various filters used, the sample mounting procedure, and the particular instrument employed. Moreover, instrument variation and other factors can affect the 2-theta values. Therefore, the term "substantially" in the context of PXRD is meant to encompass that peak assignments can vary by plus or minus about 0.2 degree. Moreover, new peaks may be observed or existing peaks may disappear, depending on the type of the machine or the settings (for example, whether a Ni filter is used or not).
Certain specific aspects and embodiments of the present application will be explained in greater detail with reference to the following examples, which are provided only for purposes of illustration and should not be construed as limiting the scope of the application in any manner. Reasonable variations of the described procedures are intended to be within the scope of the present invention. While particular aspects of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.

EXAMPLES
Example-1: Resolution of 5-Cyclopentylpyrazolidin-3-one using D-tartaric acid

5-Cyclopentylpyrazolidin-3-one (25 g) and Acetone (250 mL) were charged into a 500 mL round bottom flask and stirred for 15 minutes. A yellow colored clear solution was observed. D-tartaric acid (12.2 g) was dissolved in water (12 mL) and added to the acetone solution. A white solid precipitated rapidly from the solution and the slurry was stirred for 10 minutes. The precipitated solid was filtered and washed with 10 mL of acetone. The solid was dried under suction for 10 minutes and then dried at 40 °C under vacuum. Wt.: 25.56 g. The salt was charged into 500 mL round bottom flask and 250 mL of acetone was added. The mixture was stirred for about 10 minutes and filtered. The solid was dried under suction for 10 minutes and then dried at 40 °C under vacuum. Wt.: 21.37 g. Chiral analysis: >99.5% ee.
The above solid was charged into a 500 mL Buchi flask and water (210 mL) added. The solid was dissolved in water. Placed the Buchi flask on rotary evaporator and distilled about 130 mL of water at 45 °C under vacuum leaving a pale yellow clear solution. The mixture was then adjusted to pH 7.5 using 4M aqueous NaOH, thick precipitate was formed. The mixture was then extracted with dichloromethane (2 x 50 mL). The DCM layer was filtered through MgSO4 and concentrated to dryness on rotary evaporator to give white solid (9.07 g). Chiral analysis: 99.9% ee.
Example-2: Resolution of 5-Cyclopentylpyrazolidin-3-one using D-tartaric acid

5-Cyclopentylpyrazolidin-3-one (238 g) and Acetone (2.5 L) were charged into 5 L round bottom flask and stirred for 15 minutes at 20 °C. Yellow colored clear solution observed. D-tartaric acid (232 g) is dissolved into water (100 mL) and added to the acetone solution. A white solid precipitated rapidly from the solution and the slurry was stirred for 10 minutes. The mixture was filtered and the solid was washed with 10 mL of acetone. The solid was dried under suction for 10 minutes and then dried at 40 °C under vacuum. The solid was charged into 5 L round bottom flask and 3.5 L of acetone was added. The mixture was stirred for about 30 minutes and filtered. The solid was dried under suction for 10 minutes and then dried at 40 °C under vacuum. Wt.: 203.5 g. PXRD of the D-tartaric acid salt of the acetonide adduct is shown in Figure 1.
The above solid was charged into a 5 L Buchi flask and water (1.4 L) added. The solid was dissolved in water. Placed the Buchi flask on rotary evaporator and distilled about 400 mL of water at 40 °C under vacuum leaving a pale yellow clear solution. The mixture was then adjusted to pH 7.5 using 4M aqueous NaOH (290 mL), a thick precipitate was formed. The mixture was then cooled to 8 °C and filtered. The cake was washed with MTBE (200 mL) and dried under suction to give off-white solid (85.4 g). The solid was dried under vacuum at 35 °C to give the product as a white solid (79.8 g). Purity (UPLC) 95.9%, Chiral analysis: 99.9% ee.
Example-3: Preparation of 4-methyl-7H-pyrrolo[2,3-d]pyrimidine (Compound of formula V)

A 5L reaction flask equipped with an overhead stirrer and a 500 mL addition funnel was charged with 4-chloro-7H-pyrrolo[2,3-d]pyrimidine (100.2 g) and Fe(acac)3 (11.52 g). The flask was purged with nitrogen. Anhydrous THF (1.5 L) and anhydrous NMP (150 mL) were added to the solids, stirring was started and the solids dissolve to give a red solution. The solution was cooled to ca 4.5°C.
MeMgCl solution (3 M in THF, 330 mL) was transferred to the addition funnel and was then added slowly to the substrate, keeping T < 10 °C, the addition took about 90 min.
MeMgCl solution (3 M in THF, 330 mL) was transferred to the addition funnel and was then added slowly to the substrate, keeping T < 10 °C, the addition took about 30 min.
MeMgCl solution (3 M in THF, 100 mL) was transferred to the addition funnel and was then added slowly to the substrate, keeping T < 10 °C, the addition took about 5 min.
The reaction mixture warmed to 21°C under nitrogen and stirred for 1h. The mixture was then cooled to 5°C and a mixture of saturated aqueous ammonium chloride (1.3 L) and water (500 mL) was added in portions, keeping the internal temperature < 10 °C. Once the addition was complete the mixture was warmed to 21°C. EtOAc (500 mL) was added, the mixture was stirred for 30 min and then left to settle.
The mixture was transferred to a separating funnel, washing across with 150 mL EtOAc. After 30 min, the phases were separated. The aqueous phase was extracted with EtOAc (3 x 1.5 L, 1 x 1.0L). The combined organic extracts were dried over Na2SO4, filtered and then the solution was charged to a 10L reactor. Hydrogen chloride in dioxane (4M, 180 mL) was added over 30 min to give a slurry which was aged at 21°C for 1h. The solid was isolated by filtration, washing with EtOAc to give 4-methyl-7H-pyrrolo[2,3-d]pyrimidine hydrochloride (124.9 g) as an orange solid.
This salt was charged to a 500 mL flask, 500 mL water was added and the mixture stirred to give a foamy brown solution. The solution was transferred to a 3L RBF, a calibrated pH probe was inserted into the solution. Aqueous NaOH solution (4M) was added slowly until the pH was between 7.5-8.5. EtOAc (500 mL) was added, making two clear phases, followed by NaCl (210 g). The mixture was stirred until the solids had dissolved, then the solution was transferred to a 3 L separating funnel, washing across with EtOAc (500 mL). The phases were separated; the aqueous phase was extracted with EtOAc (1000 mL). The organic extracts were combined, dried over Na2SO4, filtered and concentrated to give the product, 4-methyl-7H-pyrrolo[2,3-d]pyrimidine, as an orange-brown solid (70.3 g). Purity (UPLC), 96.45%. 1H-NMR (DMSO-d6): d (ppm) 12.01 (s, 1H), 8.60 (s, 1H), 7.48 (dd, J = 3.4, 2.4 Hz, 1H), 6.63 (dd, J = 3.4, 1.7 Hz, 1H), 2.64 (s, 3H). MS (ES): [M+H]+ 134.0.
Example-4: Preparation of Sodium (R)-3-(4-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)-(1H-pyrazol-1-yl)-3-cyclopentylpropanoate (Compound of formula III)

The compound of Formula-V (2.10 g) was dissolved in DMF (21 ml) in a dry 100 ml 3-necked flask under nitrogen. The stirred solution was cooled in an ice bath to 2°C and oxalyl chloride (3.0 mL) was added drop-wise keeping temperature below 10°C. Once the addition was completed, the flask was placed in a heating block and heated to 80-85°C for 2h to give a solution containing intermediate imine dihydrochloride in DMF.
In a separate 250 ml 3-necked flask, the R-isomer of the compound of Formula-VII (2.92 g) was dissolved in a mixture of sodium hydroxide (50% aqueous solution, 6.3 g) and water (70 ml). The solution was placed under a nitrogen atmosphere and was heated to 95°C (heating block 115°C) for 2h.
After 2h, the DMF solution containing the intermediate imine was transferred to the aqueous solution of the compound of Formula-VII, washing in with water (10 ml), and the resulting mixture was heated at 85-95°C for 4h. The reaction was then cooled to 21°C and extracted with ethyl acetate (30 mL). The ethyl acetate extract was discarded to waste, the aqueous was retained.
The retained aqueous phase was diluted with ethyl acetate (30 mL), then 4M aqueous hydrochloric acid was added until pH 4.0-4.5 was reached (9 mL added). The phases were separated and the aqueous was extracted with ethyl acetate (30 mL). The combined organic phases were filtered through celite to remove fine solids and evaporated to give a deep red oil, 6.78 g. This was dissolved in methanol (15 ml) and stirred at 21°C while a solution of sodium methoxide in methanol (5.4M; 3.5 ml) was added. MTBE (80 ml) was then added to precipitate a solid, this slurry was aged for 1h, then the solid was isolated by filtration, washing with MTBE (15 mL). The solid was then dried under vacuum to give the compound of formula-III-Na as a yellow solid (4.69 g). Purity (UPLC) 99.6%. PXRD pattern is shown in Figure 2.
Example-5: Preparation of (R)-3-(4-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)- 1H-pyrazol-1-yl)-3-cyclopentylpropanamide (Compound of formula II)

Sodium (R)-3-(4-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)-(1H-pyrazol-1-yl)-3-cyclopentylpropanoate (Compound of formula III, 68.8 g), Imidazole HCl (22.6 g) and THF (500 mL) were charged into a 2 L round bottom flask. 1,1-Carbonyldiimidazole (CDI, 47.6 g) was added portion-wise over a period of 5 minutes. The mixture was stirred for 2 hours. Ammonium hydroxide (26.7 g) was added slowly and the mixture was stirred for 30 minutes. The reaction mixture was concentrated under high vacuum. Acetonitrile (500 mL) added to the residue and stirred for 10 minutes. The mixture was concentrated under high vacuum. Acetonitrile (500 mL) added to the residue, heated to 55° C and stirred for 30 minutes. The mixture was cooled to 15° C and stirred for 4 hours. The precipitation was filtered, cake washed through with Acetonitrile (50 ml). The solid dried under vacuum. (46.5 g). Purity (UPLC) 92.25%. 1H NMR (400 MHz, DMSO-d6): d 12.06 (br. s, 1H), 8.64 (s, 1H), 8.57 (s, 1H), 8.26 (s, 1H), 7.56 (dd, 1H, J = 3.6, 2.6 Hz), 7.35 (s, 1H), 6.97 (dd, 1H, J = 3.5, 1.7 Hz), 6.78 (s, 1H), 4.57 (dt, 1H, J = 9.6, 3.8 Hz), 2.89 (dd, 1H, J = 15.3, 9.9 Hz), 2.64 (dd, 1H, J = 15.3, 3.9 Hz), 2.34 (sextet, 1H, J = 8.6 Hz), 1.82-1.76 (m, 1H), 1.61-1.47 (m, 3H), 1.46-1.38 (m, 1H), 1.31-1.17 (m, 3H). MS (ES): [M+H]+ 325.4, [M-H]- 323.5
Example-6: Preparation of Ruxolitinib base (Compound of formula I)

The compound of Formula-II (45.3 g) was charged to a suitable reactor and placed under nitrogen. NMP (70 mL) was added and the mixture was stirred until the solids had dissolved. Dichloromethane (500 mL) was added to give a red/brown solution. POCl3 (15.5 ml) was added dropwise from a syringe over 30 min. After 2.5h, further POCl3 (1.0 ml) was added dropwise. After a further 75 min, water (100 mL) was added, the mixture was cooled to ~15°C and the pH was adjusted to 7 by addition of saturated aqueous sodium hydrogen carbonate (580 mL). The mixture was transferred to a separating funnel and extracted with ethyl acetate (2 x 500 mL). The combined ethyl acetate extracts were washed with water (500 mL, 2 x 250 mL) and brine (250 mL), then dried over sodium sulfate, filtered and concentrated to give crude compound of formula-I as an orange-brown glassy solid mass (37.3 g). UPLC analysis shows 91.6% purity (0.41% Methyl ester of compound of Formula-III), chiral analysis indicates 99.97% ee.
Example-7: Purification of Ruxolitinib base using activated carbon

Crude Ruxolitinib (11 g) was dissolved in ethyl acetate (150 mL) and the solution was charged into a 250 mL round bottom flask. Activated carbon (Norit CGP Super, 9.9 g) was added and stirred for 45 hours. The mixture was filtered and the carbon was washed with 50 mL of ethyl acetate. The filtrate was concentrated under vacuum to get an orange colored oil (6.8 g). UPLC Purity 95.0%, chiral purity: 98.5% ee.
Example-8: Preparation of Ruxolitinib base (Compound of formula I)

DCM (700 mL), DMF (8.67 g) and the compound of Formula-II (35 g) was charged to a suitable reactor and placed under nitrogen. The mixture was cooled to -10° C. Oxalyl chloride (68.5 g) was added dropwise over 30 min. The reaction mass was heated to 80° C and stirred for 3 hours. After a further 75 min, water (100 mL) was added, the mixture was cooled to ~15°C and the pH was adjusted to 7.5 by addition of saturated aqueous sodium hydrogen carbonate (350 mL). The mixture was transferred to a separating funnel and extracted with DCM (2 x 300 mL). The combined DCM extracts were washed with water (300 mL, 2 x 150 mL) and brine (150 mL), then dried over sodium sulfate, filtered and concentrated. Methanol (100 mL) added to the residue and heated to 60° C and stirred for 10 hours. Ethyl acetate (200 mL) was added and distilled off under vacuum. The crude is purified over silica gel chromatography to yield 26 g of compound of formula-I. Purity: 99.3% (0.11% Methyl ester of compound of Formula-III), chiral analysis indicates 99.97% ee.
Example-9: Purification of Ruxolitinib base using Dibenzoyl-D-tartaric acid

Dibenzoyl-D-tartaric acid (3.98 g) and acetonitrile (36 mL) were charged into 250 mL round bottom flask. Crude Ruxolitinib base (6.8 g) dissolved in 50 mL of acetonitrile and added to DBTA solution. 50 mL of acetonitrile added and the mixture was heated to 70 °C and stirred for 30 minutes. The mixture was cooled to 25 °C and the precipitation was filtered and the wet solid was washed with 20 mL of acetonitrile. The solid was dried under vacuum overnight at 40 °C to yield 6.49 g of the DBTA salt. UPLC analysis indicates 99.8% purity. Chiral analysis shows 99.7% ee. PXRD pattern is shown in Figure 3.
Example-10: Preparation of Ruxolitinib phosphate
Ruxolitinib base (2.77 g) and isopropyl alcohol (27 mL) were charged into a 100 mL round bottom flask and heated to 50 °C and stirred for 10 minutes. A solution of phosphoric acid (1.062 g of phosphoric acid dissolved in 8.1 mL of isopropyl alcohol) was added dropwise to the Ruxolitinib base solution. The mixture was heated to 80 °C and stirred for 30 minutes. The mixture was cooled to 20 °C and stirred for 12 hours. The solid was filtered and washed with 5 mL of isopropyl alcohol and dried under vacuum to obtain 3.47 g of Ruxolitinib phosphate. UPLC Purity 99.86%, chiral purity 99.8% ee.
Example-11: Preparation of Ruxolitinib phosphate
Ruxolitinib base (48.35 g, purified as described above, containing 0.18% of the Methyl ester of compound of Formula-III) and isopropyl alcohol (480 mL) were charged into a suitable reaction vessel and heated to 60 °C and stirred for 10 minutes. A solution of phosphoric acid (18.6 g) in 145 mL of isopropyl alcohol was added dropwise to the Ruxolitinib base solution. The mixture was heated to 80-85 °C and stirred for 2 hours. The mixture was cooled to 20 °C and stirred for 16 hours. The solid was filtered and washed with 100 mL of isopropyl alcohol followed by 200 mL of n-heptane. The solid was then dried at 40°C in a vacuum oven to obtain 63.2 g of Ruxolitinib phosphate. UPLC Purity 99.85% (0.13% of the Methyl ester of compound of Formula-III), chiral purity 99.99% ee.
Example-12: Preparation of Ruxolitinib hemifumarate
Ruxolitinib base (125 g, purified as described above, containing 0.18% of the Methyl ester of compound of Formula-III) and ethanol (1100 mL) and fumaric acid (47 g) were charged into a 5 L reaction vessel and heated to 70 °C and stirred for 30 minutes. The reaction mass was filtered through a 0.2-micron cartridge filter. The mixture was cooled to 25 °C and stirred for 5 hours. The solid was filtered and washed with 125 mL of ethanol. The solid was then dried at 60°C in a vacuum oven to obtain 120 g of Ruxolitinib hemifumarate. UPLC Purity 99.85% (0.12% of the Methyl ester of compound of Formula-III), chiral purity 99.9% ee. ,CLAIMS:We claim
1. A process for preparation of Ruxolitinib having less than about 0.5% of methyl ester of compound of Formula-III, comprising the following steps:
(vii) treating crude Ruxolitinib base with active carbon,
(viii) treating the crude Ruxolitinib base of step (i) with dibenzoyl-D-tartaric acid to form dibenzoyl-D-tartrate salt,
(ix) isolating pure Ruxolitinib base having less than about 0.5% of methyl ester of compound of Formula-III from the dibenzoyl-D-tartrate salt.
2. A process for preparation of Ruxolitinib having less than about 0.2% of methyl ester of compound of Formula-III, comprising the following steps:
(i) treating crude Ruxolitinib base with active carbon,
(ii) treating the crude Ruxolitinib base of step (i) with dibenzoyl-D-tartaric acid to form dibenzoyl-D-tartrate salt,
(iii) isolating pure Ruxolitinib base having less than about 0.2% of methyl ester of compound of Formula-III from the dibenzoyl-D-tartrate salt.
3. A process for preparation of Ruxolitinib phosphate having less than about 0.5% of methyl ester of compound of Formula-III, comprising the following steps:
(i) treating crude Ruxolitinib base with active carbon,
(ii) treating the crude Ruxolitinib base of step (i) with dibenzoyl-D-tartaric acid to form dibenzoyl-D-tartrate salt,
(iii) isolating pure Ruxolitinib base having less than about 0.5% of methyl ester of compound of Formula-III from the dibenzoyl-D-tartrate salt, and
(iv) converting Ruxolitinib base having less than about 0.5% of methyl ester of compound of Formula-III of step (iii) into Ruxolitinib phosphate.
4. A process for preparation of Ruxolitinib phosphate having less than about 0.2% of methyl ester of compound of Formula-III, comprising the following steps:
(i) treating crude Ruxolitinib base with active carbon,
(ii) treating the crude Ruxolitinib base of step (i) with dibenzoyl-D-tartaric acid to form dibenzoyl-D-tartrate salt,
(iii) isolating pure Ruxolitinib base having less than about 0.2% of methyl ester of compound of Formula-III from the dibenzoyl-D-tartrate salt, and
(iv) converting Ruxolitinib base having less than about 0.2% of methyl ester of compound of Formula-III of step (iii) into Ruxolitinib phosphate.
5. A process for preparation of Ruxolitinib hemifumarate having less than about 0.2% of methyl ester of compound of Formula-III, comprising the following steps:
(i) treating crude Ruxolitinib base with active carbon,
(ii) treating the crude Ruxolitinib base of step (i) with dibenzoyl-D-tartaric acid to form dibenzoyl-D-tartrate salt,
(iii) isolating pure Ruxolitinib base having less than about 0.2% of methyl ester of compound of Formula-III from the dibenzoyl-D-tartrate salt, and
(iv) converting Ruxolitinib base having less than about 0.2% of methyl ester of compound of Formula-III of step (iii) into Ruxolitinib hemifumarate.
6. A pharmaceutical composition comprising Ruxolitinib or a pharmaceutically acceptable salt thereof having less than about 0.5% of methyl ester of compound of Formula-III.
7. A pharmaceutical composition comprising Ruxolitinib or a pharmaceutically acceptable salt thereof having less than about 0.2% of methyl ester of compound of Formula-III.