FIELD OF THE INVENTION

The present invention relates to an improved process for the preparation of Modafinil and its enantiomer of Formula I.

BACKGROUND OF THE INVENTION

Modafinil is chemically known as 2-[(diphenylmethyl)sulfinyl]acetamide or 2-[(benzhydryl)sulfinyl]-acetamide. Modafinil is currently marketed by Cephalon, under the brand name Provigil® as a racemic mixture. Provigil® is indicated for the treatment of excessive sleepiness associated with narcolepsy shift work sleep disorder (SWSD) and obstructive sleep apnea/hypopnea syndrome (OSA/HS).

Armodafinil is chemically known as 2-[(R)-(diphenylmethyl)sulfinyl]acetamide or 2-[(R)-(benzhydryl)sulfinyl]-acetamide. Armodafinil is currently marketed by Cephalon, under the brand name Nuvigil®.

Modafinil was first disclosed in US 4,177,290. This patent discloses different methods to prepare modafinil. The processes are as shown below:

Process I:

By following the above methods the over oxidation product viz sulfone of Formula X is obtained, which is an impurity. This impurity cannot be easily removed from the pure modafinil product and obtaining the lesser purity of the final product.


Armodafinil is first disclosed in US 4,927,855. This patent discloses a process for the preparation of Armodafinil, which is as shown below.

In the above process the esterification step was carried out in water, which makes the reaction incomplete and therefore the final product yields and purity are less.

WO 2007/103221 A2 discloses a process for the preparation of Armodafinil, which comprises combining armodafinic acid with at least one acidic reagent and a solvent selected from the group consisting of methanol/C7_9 aromatic hydrocarbon, methanol/acetate ester, methanol and ethanol to obtain alkyl ester of armodafinic acid followed by the reaction with ammonia or ammonium hydroxide to obtain armodafinil, which further treated with alumina to reduce the amounts of modafinic acid in armodafinil product.

The disadvantage of the above process, is the formation of bis(diphenylmethyl)disulphide of Formula XIII at a level of-2.5% in Armodafinil crude product, which needs additional purification. Also, use and removal of basic alumina is an additional operation, which consumes lot of time in commercial scale.

Based on the aforementioned drawbacks, the prior art processes may be unsuitable for preparation of Modafinil and its enantiomer in commercial scale operations. A need remains for an improved and commercially viable process for preparing a pure compound Modafinil and its enantiomer of Formula I, substantially free of sulfone and other impurities.

We have now found an improved process for preparing Modafinil and its enantiomer, substantially free of sulfone and other impurities, which is useful for commercial scale preparation.

OBJECTIVE OF THE INVENTION

The main objective of the present invention is to provide a simple and cost effective process for the preparation of Modafinil and its enantiomer with high purity and good yield on commercial scale.'

In yet another objective of the present invention is to provide a process for the preparation of Modafinil and its enantiomer, which is simple, industrially applicable and economically viable.

In yet another objective of the present invention is to provide an improved process for the preparation of methyl-2-[(diphenyl)sulfinyl]acetate and its enantiomer with high yield and high purity.

SUMMARY OF THE INVENTION

The present invention relates to an improved process for the preparation of Modafinil and its enantiomer of Formula I,

which comprises:

a) reacting 2-[(diphenylmethyl)sulfinyl)] acetic acid (Modafinic acid) of
Formula V,

with chlorinating agent in the presence of methanol and a water immiscible solvent to give methyl-2-[(diphenylmethyl)sulfinyl)]acetate of
Formula VI;

b) extracting the reaction mass containing methyl-2-[(diphenylmethyl)sulfinyl)]acetate of Formula VI with water, base and solvent;

c) crystallizing methyl-2-[(diphenylmethyl)sulfinyl)]acetate of Formula VI;

d) amidating methyl-2-[(diphenylmethyl)sulfinyl)]acetate of Formula VI with methanolic ammonia in the presence of a solvent;

e) adding water and solvent to the reaction mass; and

f) isolating the title compound.

In another embodiment, the present invention also relates to a process for the preparation of pure Modafinil and its enantiomer of Formula I,

which comprises:

i) dissolving Modafinil in a solvent in presence of aqueous ammonia or
gaseous ammonia; and
ii) isolating the title compound.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to an improved process for preparing Modafinil and its enantiomer, which comprises, reacting 2-[(diphenylmethyl)sulfinyl]acetic acid of Formula V with chlorinating agent selected from phosphorous oxychloride in the presence of methanol and a water immiscible solvent selected from methylene chloride, ethylene chloride, chloroform, diisopropyl ether, diethylether, tert-butylmethyl ether and methyl isobutyl ketone at a temperature 0-10°C.

After the completion of reaction, the reaction mass containing methyl-2-[(diphenylmethyl)sulfinyl]acetate of Formula VI is diluted with water. The organic layer is washed with a base, selected from sodium hydroxide, potassium hydroxide, lithium hydroxide, barium hydroxide, alkali carbonate and bicarbonates such as sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, triethylamine, diisopropylethylamine, pyridine, dimethylamine to remove the unreacted acid. The organic layer is partially concentrated at ambient pressure and the concentrated mass is dissolved in a solvent selected from heptane, cyclohexane, toluene, xylenes, diisopropylether, diethylether or tert-butylmethyl ester to precipitate the compound methyl-2-[(diphenylmethyl)sulfinyl)]acetate of Formula VI.

Methyl-2-[(diphenylmethyl)sulfinyl)]acetate of Formula VI is treated with methanolic ammonia in the presence of a solvent selected from methanol^ ethanol, toluene, xylenes, ethyl acetate, methyl acetate, t-butyl acetate, diisopropyl ether, diethyl ether, t-butylmethyl ether, tetrahydrofuran, hexanes, cyclohexane, methylene chloride, ethylene chloride, chloroform or mixtures thereof at 15-30°C, preferably at 20-30°C to give Modafinil.

The reaction mass containing Modafinil is diluted with water and water immiscible solvent selected from ethyl acetate, butyl acetate, dichloromethane, dichloroethane, heptane, diisopropyl ether, diethyl ether, toluene, xylenes, cyclohexane, tert-butylmethyl ether or mixtures thereof and agitating the reaction mixture till complete crystallization of Modafinil at a temperature 15-30°C, preferably at 20-30°C.

Methyl-2-[(diphenylmethyl)sulfinyl)]acetate of Formula VI obtained by the process described herein, has a chromatographic purity (Measure by HPLC) greater than 99% and the sulfone impurity less than 0.05%.

In another aspect of the present invention, the enantiomer of Modafinil herein described is Armodafinil of Formula II.

The present invention also relates to an improved process for preparing Armodafinil, which comprises reacting 2-[(R)-(diphenylmethyl)sulfinyl]acetic acid of Formula XI with chlorinating agent, selected from phosphorous oxychloride in the presence of methanol and a water immiscible solvent selected from methylene chloride, ethylene chloride, chloroform, diisopropyl ether, diethylether, tert-butylmethylether, methyl isobutyl ketone at a temperature of 0-10°C.

After completion of the reaction, the reaction mass containing methyl-2-[(R)-(diphenylmethyl)sulfinyl]acetate of Formula XII is diluted with water. The organic layer is washed with a base, selected from sodium hydroxide, potassium hydroxide, lithium hydroxide, barium hydroxide, alkali carbonate or bicarbonates such as sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, triethylamine, diisopropylethylarnine, pyridine, dimethylamine to remove the unreacted acid. The organic layer is partially concentrated at ambient pressure and the concentrated mass is dissolved in a solvent selected from heptane, cyclohexane, toluene, xylenes, diisopropylether, diethylether or tert-butylmethyl ester to precipitate Methyl-2-[(R)-(diphenylmethyl)sulfinyl)] acetate of Formula XII.

Methyl-2-[(R)-(diphenylmethyl)sulfinyl]acetate of Formula XII is reacted with methanolic ammonia in the presence of a solvent selected from methanol, ethanol, toluene, xylenes, ethyl acetate, methyl acetate, t-butyl acetate, diisopropyl ether, diethyl ether, t-butylmethyl ether, tetrahydrofuran, hexanes, cyclohexane, methylene chloride, ethylene chloride, chloroform or mixtures thereof at 15-30°C, preferably at 20-3 0°C to give Armodafinil.

The reaction mass containing Armodafinil is diluted with water and water immiscible solvent selected from ethyl acetate, butyl acetate, dichloromethane, dichloroethane, heptane, diisopropyl ether, diehthyl ether, toluene, xylenes, cyclohexane, tert-butylmethyl ether or a mixture of two or more thereof and agitating the reaction mixture till complete crystallization of Armodafinil at a temperature 15-30°C, preferably at 20-30°C.

Methyl-2-[(R)-(diphenylmethyl)sulfmyl)]acetate of Formula XII obtained by the process described herein, has a chromatographic purity (Measure by HPLC) greater than 99% and the sulfone impurity less than 0.05%.

The process to prepare modafinic acid of Formula V,

which comprises, reacting 2-[(diphenyl)thio]acetic acid of Formula VII with a suitable oxidizing agent, selected from 50% hydrogen peroxide in acetic acid in presence of a solvent, selected from water, methanol, butanol, ethanol, acetone, isopropyl alcohol, acetonitrile, methylisobutyl ketone, cyclohexane, toluene, xylenes, heptane, diisopropylether, diethylether, tert-butylmethylether, ethyl acetate, methyl acetate, butyl acetate or mixtures thereof, at 30-60°C, preferably 40-50°C.

The process to prepare armodafinic acid of Formula XI,

which comprises,

i) reacting 2-[(diphenyl)thio]acetic acid of Formula VII with a suitable oxidizing agent, selected from 50% hydrogen peroxide in acetic acid in presence of a solvent, selected from water, methanol, butanol, ethanol, acetone, isopropyl alcohol, acetonitrile, methylisobutyl ketone, cyclohexane, toluene, xylenes, heptane, diisopropylether, diethylether, tert-butylmethylether, ethyl acetate, methyl acetate, butyl acetate or mixtures thereof, at 30-60°C, preferably at 40-50°C to give modafinic acid of Formula V;

ii) reacting modafinic acid of Formula V with (S)-benzylmethylamine in water to give (S)-benzylmethylammonium (R)-2-[(diphenylmethyl) sulfinyl]acetate; and

iii) acidifying (S)-benzylmethylammonium (R)-2-[(diphenylmethyl)sulfinyl] acetate with acid to give armodafinic acid of Formula XI.

In another aspect, the present invention also relates to a process for the preparation of pure Modafinil and its enantiomer, which comprises, dissolving Modafinil in a solvent selected from ethanol, methanol, isopropyl alcohol, butanol, isobutanol, ethylene glycol, acetonitrile, acetone, methyl ethyl ketone, polar aprotic solvents selected from dimethylformamide, dimethylacetate, dimethylsulfoxide or mixtures thereof in the presence of aqueous ammonia or gaseous ammonia to give pure Modafinil and its enantiomer has a chromatographic purity (Measure by HPLC) greater than 99.8% and the sulfone impurity less than 0.05%.

The following examples illustrate the nature of the invention and are provided for illustrative purposes only and should not be construed to limit the scope of the invention.

EXAMPLE 1

PROCESS TO PREPARE 2-[(DIPHENYLMETHYL)SULFINYL]ACETIC ACID

2-[(Diphenylmethyl)thio]acetic acid (lOOg) was dissolved in acetic acid (250 ml) at 25-30°C and water (50 ml) was added. Diluted the 50% Hydrogen peroxide (30.3 lg) in water (100 ml) and this mixture was added to the reaction mixture over a period of about lh. Thereafter, the temperature of the reaction mass was raised to 40-45 °C and continued stirring at this temperature to complete the conversion of sulfide into corresponding sulfoxide. Thereafter, the reaction mixture was quenched with aqueous solution of sodium metabisulfite. Cyclohexane (300 ml) was added to the resulting slurry and the suspension was stirred for about 30 min. The solid was filtered, washed with water and dried to yield the title compound as white crystalline powder.

Yield: 94%

Chromatographic Purity (by HPLC): 99.58%

EXAMPLE 2

PROCESS TO PREPARE METHYL 2-[(DIPHENYLMETHYL) SULFINYL]
ACETATE

2-[(Diphenylmethyl)sulfinyl]acetic acid (lOOg) was dissolved in a mixture of methanol (500 ml) and methylene chloride (300 ml) and cooled the solution to 0-5°C. Thereafter, POCl3 (16.80 g) was added at 0-5°C and stirred at room temperature till completion of the reaction. Water was added to the reaction mixture and the layers were separated. The aqueous layer was extracted with methylene chloride (200 ml) and the combined organic layer was washed with sodium bicarbonate solution followed by water. Thereafter, methylene chloride was removed partially and cyclohexane was added to the concentrated mass and continued distillation till the reaction mass temperature reaches 67-71°C. The concentrated mass was cooled to 25-30°C. The precipitate product was filtered, washed with cyclohexane and dried to afford methyl 2-[(diphenylmethyl)sulfmyl]acetate as white crystalline material.

Yield: 85%

Chromatographic Purity (by HPLC): 99.48%

EXAMPLE 3

PROCESS TO PREPARE 2-[(DIPHENYLMETHYL)SULFINYL] ACETAMIDE

(MODAFINIL)

Methyl 2-[(diphenylmethyl)sulfmyl]acetate (100 g) was suspended in a cooled mixture of methanol (200 ml) and methanolic ammonia (335 ml, 18-20%w/w) at 0-5°C. Thereafter, the temperature was raised to 20-25°C and continued stirring at this temperature till completion of the reaction. Thereafter, water (1000 ml) was added followed by cyclohexane (300 ml) and the suspension was stirred for 30 min at 20-25°C. The product was filtered, washed with water and dried to afford Modafinil.

Yield: 88%

Chromatographic Purity (by HPLC): 99.79%

EXAMPLE 4

PROCESS TO PREPARE PURE 2-[(DIPHENYLMETHYL) SULFINYLJACETAMIDE (MODAFINIL)

Modafinil crude (70g) was suspended in a mixture of methanol (840 ml) at 20-25°C and carbon (lg) was added and heated the suspension to reflux for 30 min and filtered the carbon, washed the residue with hot methanol (140 ml). The filtrate was concentrated to a volume of about 500 ml and cooled to 45-45°C and stirred at this temperature for lh. Thereafter, the precipitate was cooled to 0-5 °C and continued stirring at this temperature for 30 min. Filtered the precipitated product and washed with pre-cooled methanol to afford modafinil. Yield: 90% Chromatographic Purity (by HPLC): 99.92%

EXAMPLE 5

PROCESS TO PREPARE 2-[(R)-(DIPHENYLMETHYL)SULFINYL] ACETIC ACID

2-[(Diphenylmethyl)sulfinyl]acetic acid (lOOg) was suspended in water (1200 ml) and (S)-benzylmethylamine (48.58g) was added at 25-30°C. The reaction mixture was heated to 80-85°C and continued stirring for 30 min. Thereafter, the temperature was brought to 55-60°C and stirred at this temperature for 30 min. The resulting precipitate was cooled to 35-40°C and stirred for lh. The precipitated (S)-benzylmethylammohium (R)-2-[(diphenylmethyl)sulfinyl]acetate was filtered and washed with water. Thereafter, the wet (S)-benzylmethylammonium (R)-2-[(diphenylmethyl)sulfinyl]-acetate was suspended in water (1000 ml) and heated to dissolve at 80-85°C. The resulting solution was cooled to 55-60°C and stirred at this temperature for 30 min. Further, the resulting precipitate was cooled to 35-40°C and stirred for lh. The precipitated (S)- benzylmethylammonium (R)-2-[(diphenylmethyl)sulfinyl]acetate was filtered and washed with water. This wet material was suspended in water and pH was adjusted to 1.5-2.0 with hydrochloric acid to precipitate 2-[(R)-

(Diphenylmethyl)sulfinyl]aceticacid.

Yield: 35%

Chromatographic Purity (by HPLC): 99.47%

Chiral purity: 99.98; s-isomer: 0.02%

EXAMPLE 6

PROCESS TO PREPARE METHYL 2-[(R)-(DIPHENYLMETHYL)

SULFINYLJACETATE

2-[(R)-(Diphenylmethyl)sulfinyl]acetic acid (40 g) was dissolved in a mixture of methanol (200 ml) and methylene chloride (120 ml) and the solution was cooled to 0-5°C. Thereafter, a solution of 6.72g of POCI3 in 20 ml of methylene chloride was added at 0-5 °C and stirred at room temperature till completion of the reaction. Water was added to the reaction mixture and the layers were separated. The aqueous layer was extracted with methylene chloride (80 ml) and the combined organic layer was washed with sodium bicarbonate solution followed by water. Thereafter, methylene chloride layer was concentrated till the reaction mass temperature reaches 44-45°C. Thereafter, cyclohexane (400 ml) was added to the concentrated mass and distillation was continued till the reaction mass temperature reaches 67-71°C. The concentrated mass was cooled to 25-30°C and stirred at this temperature for lh. Thereafter, cooled the slurry to 10°C and stirred for lh at his temperature. The obtained product was filtered, washed with cyclohexane and dried to afford methyl 2-[(R)-(diphenylmethyl)sulfinyl]acetate as white crystalline powder
Yield: 85%
Chromatographic Purity (by HPLC): 99.53%

EXAMPLE 7

PROCESS TO PREPARE 2-[(R)-(DIPHENYLMETHYL)SULFINYL]
ACETAMIDE [ARMODAFINIL]

Methyl 2-[(R)-(diphenylmethyl)sulfinyl]acetate (25 g) was suspended in a cooled mixture of methanol (50 ml) and methanolic ammonia (84 ml, 18-20%w/w) at 0-5°C. Thereafter, the temperature was raised to 20-25°C and continued stirring at this temperature till completion of the reaction. Thereafter, water (250 ml) was added followed by cyclohexane (75 ml) and stirred the suspension for 30 min at 20-25°C. The product was filtered, washed with water and dried to afford armodafinil.

Yield: 86%

Chromatographic Purity (by HPLC): 99.50%

EXAMPLE 8

PROCESS TO PREPARE 2-[(R)-(DIPHENYLMETHYL)SULFINYL]
ACETAMIDE [ARMODAFINIL]

Methyl 2-[(R)-(diphenylmethyl)sulfinyl]acetate (25 g) was suspended in a cooled mixture of methanol (50 ml) and methanolic ammonia (84 ml, 18-20%w/w) at 0-5°C. Thereafter, the temperature was raised to 20-25°C and continued stirring at this temperature till completion of the reaction. Thereafter, water (250 ml) was added and stirred the suspension for 30 min at 20-25 °C. The product was filtered, washed with water and dried to afford armodafinil.
Yield: 70%
Chromatographic Purity (by HPLC): 99.10%

EXAMPLE 9

PROCESS TO PREPARE PURE 2-[(R)-(DIPHENYLMETHYL)
SULFINYLJACETAMIDE (ARMODAFINIL)

Armodafinil crude (15g) was suspended in a mixture of ethanol (105 ml) and methanolic ammonia (7.5 ml, 18-20% w/w) at 20-25°C and carbon (lg) was added and heated the suspension to reflux for 30 min and filtered the carbon, washed the residue with hot ethanol (15 ml). The filtrate was cooled to 25-30°C and continued stirring at this temperature for lh. Thereafter, the precipitate was cooled to 0-5°C and continued stirring at this temperature for 30 min. The precipitated product was filtered and washed with water followed by pre-cooled ethanol to afford armodafinil.

Yield: 80%

Chromatographic Purity (by HPLC): 99.98%

Chiral purity: 99.92; s-isomer: 0.08%

EXAMPLE 10

PURIFICATION OF ARMODAFINIL

Armodafinil (lOg) was suspended in a mixture of ethanol (50 ml) and methanolic ammonia (1ml, 18-20w/w) at 20-25°C and heated to reflux for 15 min. Add carbon (lg) and stirred for lh at reflux temperature. Carbon was filtered through hyflo and washed the residue with hot ethanol (10 ml). Cooled the filtrate to 25-30°C and stirred at this temperature for lh. Thereafter, cooled the slurry to0-5°C and stirred for lh. Filtered the solid, washed with pre-cooled ethanol (10 ml, 0-5°C) and dried to obtain Armodafinil as white crystalline powder.
Yield: 75%
Chromatographic Purity (by HPLC): 99.98%

EXAMPLE 11

PURIFICATION OF ARMODAFINIL

Armodafinil (lOg) was suspended in a mixture of ethanol (60 ml) and methanolic ammonia (0.5 ml, 18-20%w/w) at 20-25°C and heated to reflux for 15 min. Carbon (lg) was added and stirred for lh at reflux temperature. Carbon was filtered through hyflo and washed the residue with hot ethanol (10 ml). Cooled the filtrate to 25-30°C and stirred at this temperature for lh. Thereafter, cooled the slurry to0-5°C and stirred for lh. Filtered the solid, washed with pre-cooled ethanol (10 ml, 0-5°C) and dried to obtain Armodafinil as white crystalline powder.
Yield: 76%
Chromatographic Purity (by HPLC): 99.89%

EXAMPLE 12

PURIFICATION OF ARMODAFINIL

Armodafinil (lOg) was suspended in a mixture of ethanol (50 ml) and aqueous ammonia (0.5 ml, ~20%w/w) at 20-25°C and heated to reflux for 15 min. Carbon (lg) was added and stirred for lh at reflux temperature. Carbon was filtered through hyflo and washed the residue with hot ethanol (10 ml). Cooled the filtrate to 25-30°C and stirred at this temperature for lh. Thereafter, cooled the slurry to 0-5°C and stirred for lh. Filtered the solid, washed with pre-cooled ethanol (10 ml, 0-5°C) and dried to obtain Armodafinil as white crystalline powder.
Yield: 79%
Chromatographic Purity (by HPLC): 99.51%

EXAMPLE 13

PURIFICATION OF ARMODAFINIL

Armodafinil (lOg) was suspended in ethanol (80 ml) at 20-25°C and carbon (lg) was added and heated to reflux for 30 min. Carbon was removed through hyflo and washed the residue with hot ethanol (10 ml). Cooled the filtrate to 25-30°C and stirred at this temperature for lh. Thereafter, cool the resulting slurry to 0-5°C and stirred for lh. Filtered the solid, washed with pre-cooled ethanol (10 ml, 0- 5°C) and dried to obtain Armodafinil as white crystalline powder.

Yield: 81%

Chromatographic Purity (by HPLC): 99.90%

WE CLAIM

1) An improved process for the preparation of Modafinil and its enantiomer of Formula I,

which comprises:

a) reacting 2-[(diphenylmethyl)sulfinyl)]acetic acid of Formula V,

with chlorinating agent in the presence of methanol and a water immiscible solvent to give methyl-2-[(diphenylmethyl)sulfinyl)]acetate of Formula VI;

b) extracting the reaction mass containing methyl-2-[(diphenylmethyl)sulfinyl)]acetate of Formula VI with water, base and solvent;

c) crystallizing methyl-2-[(diphenylmethyl)sulfinyl)] acetate of Formula VI;

d) amidating methyl-2-[(diphenylmethyl)sulfinyl)]acetate of Formula VI with methanolic ammonia in the presence of a solvent;

e) adding water and solvent to the reaction mass; and

f) isolating the title compound.

2) The process according to claim 1, wherein the water immiscible solvent used in step (a) is selected from methylene chloride, ethylene chloride, chloroform, diisopropyl ether, diethyl ether, tert-butylmethyl ether, methylisobutyl ketone or mixtures thereof.

3) The process according to claim 1, wherein the base used in step (b) is an inorganic or organic base, which is selected from sodium hydroxide, potassium hydroxide, lithium hydroxide, barium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, triethylamine, diisopropylethylamine, pyridine, dimethylamine.

4) The process according to claim 1, wherein the solvent used in step (d) is selected from methanol, ethanol, toluene, xylenes, ethyl acetate, methyl acetate, t-butyl acetate, diisopropyl ether, diethyl ether, t-butylmethyl ether, tetrahydrofuran, hexanes, cyclohexane, methylene chloride, ethylene chloride, chloroform or mixtures thereof.

5) The process according to claim 1, wherein the solvent used in step (e) is an water immiscible solvent, which is selected from ethyl acetate, butyl acetate, dichloromethane, dichloroethane, heptane, diisopropyl ether, diethyl ether, toluene, xylenes, cyclohexane, tert-butylmethyl ether or mixtures thereof.

6) A process for the preparation of pure Modafinil and its enantiomer of Formula
I,

which comprises,

i) dissolving Modafinil in a solvent in presence of aqueous ammonia or gaseous ammonia; and

ii) isolating the pure title compound.

7) The process according to claim 6, wherein the solvent is selected from ethanol, methanol, isopropyl alcohol, butanol, isobutanol, ethylene glycol, acetonitrile, acetone, methyl ethyl ketone, dimethylformamide, dimethylacetate, dimethylsulfoxide or mixtures thereof.

8) The process according to claims 1 and 6, wherein the enantiomer is
Armodafinil of Formula II.

9) An improved process for the preparation of Modafinil of Formula I and its enantiomer, as described in claims 1 and 6, substantially as herein described with reference to the examples.