Title of Invention

INDUSTRIAL PREPARATION OF 11-[4-{2-(2- HYDROXYETHOXY) ETHYL} -1- PIPERZINYL] DIBENZO [B,F ] - [1,4 ] THIAZEPINE

Abstract

Disclosed herein is an industrial process for preparation of Quetiapine by the reaction of ll-piperazinyldibenzo[b,f][l,4]-thiazepine or its salt with 2-(2-chloroethoxy)ethanol in presence of an inorganic base in aqueous condition to form ll-[4-{2-(2-hydroxyethoxy) ethyl}-1-piperazinyl] dibenzo [b,f]-[l, 4]thiazepine. The quetiapine free base obtained is further converted to its hemi-fumarate salt.

Full Text

FORM 2 THE PATENT ACT 1970 (39 of 1970) & The Patents Rules, 2003 COMPLETE SPECIFICATION (See section 10 and rule 13) 2. TITLE OF THE INVENTION: "Industrial preparation of ll-[4-{2-(2-Hydroxyethoxy) ethyl}-l-Piperzinyl] Dibenzo[b,f]-[l,4] Thiazepine" 2. APPLICANT (S): (a) NAME: IPCA LABORATORIES LIMITED (b) NATIONALITY: Indian Company incorporated under the Indian Companies ACT, 1956 (c) ADDRESS: 48 Kandivli Industrial Estate, Mumbai - 400 067, Maharashtra, India 3. PREAMBLE TO THE DESCRIPTION: The following specification particularly describes the invention and the manner in which it is to be performed. WO 2006/077602 PCT/IN2005/000028 Industrial preparation of ll-[4-{2-(2-hydroxyethoxy) ethyl}-l-piperazinyl] dibenzo [b,f]-[l> 4] thiazepine Field of invention The present invention relates to an industrial process for the preparation of 1l-[4-{2-(2-hydroxy- ethoxy) ethyl} -1-piperazinyl] dibenzo [b,f]-[l, 4]thiazepine of Formula I, a known pharmaceutical agent for curing schizophrenia. Background of the invention ll-[4-{2-(2-hydroxyethoxy) ethyl}-1-piperazinyl] dibenzo [b,f]-[l, 4]thiazepine of the Formula I known under the international non-proprietary name quetiapine has anti-dopaminergic and/or serotonin receptor antagonist activity, and is used in the clinical practice as an anti-psychotic or neuroleptic agent especially in the treatment of Schizophrenia. Quetiapine and its process for preparation is first disclosed in the patent specification EP0240228 and various other processes for the preparation are disclosed in EP0282236, WO0155125, WO9906381, WO 2004076431. In the '228 patent, quetiapine was prepared by condensing a compound of Formula II (ll-piperazinyldibenzo[b,f][l,4]-thiazepine) with 2-(2-chloroethoxy)ethanol of Formula III in polar organic solvents or aprotic organic solvents, e.g., N.N-dimethylformamide, WO 2006/077602 PCT/IN2005/000028 2 N-methylpyrrolidone. Polar solvents exemplified were methanol, ethanol, isopropanol or hexanol or their isomers. Compound of Formula II may be employed in the reaction as its free base or its acid addition salt. An inorganic base like sodium carbonate or potassium carbonate was used in the reaction. The reaction was optionally carried out in the presence of promoter/catalyst such as sodium iodide also. The reaction times were reported to be 24 hours or more, but in practice even after 35 hours about 7 to 8 % of starting ll-piperazinyldibenzo[b,f][l,4]-thiazepine has been found to be remained unreacted in the reaction. The reaction does not go up to completion, even if excess 2-(2-chloroethoxy)ethanol is used. This incomplete reaction necessitates further purification, incurring heavy losses of product and the purification is difficult due to similar properties of product and starting material 1 l-piperazinyldibenzo[b,f][l,4]-thiazepine. A modification of '228 patent was reported in WO2004076431 which deals with an attempt to reduce the reaction time and in this improved process the 11-piperazinyldibenzo[b,f][l,4]-thiazepine dihydrochloride was reacted with 2-(2-chloroethoxy)ethanol in presence of a base and a phase transfer catalyst in order to complete reaction in a lesser time. According to '431 patent process, after 4 hours of reaction unreacted ll-piperazinyldibenzo[b,f][l,4]-thiazepine was found to be about 9.7% (see example JO). As per the details, the reaction completes only in 17 hours and the product in the reaction mass is only 95.5% and unreacted starting material was 1.1% to 0.26%. '431 patent also teaches the use of optional alkali metal halide as a promoter. '431 patent highlights the use of phase transfer catalyst (improved subject matter) for the completion of reaction and the yields reported are still on a lower side ranging from about 60 to 73% (see examples) This indicates that there is a need for improvement in the process of making Quetiapine wherein the complete reaction is achieved in much shorter time in high yield and purity. Objective of the present invention It is an objective of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art or to provide a useful alternative. WO 2006/077602 3 PCT/IN2005/000028 It is an objective of the present invention, in its preferred form, to provide an industrial process for preparation of ll-[4-{2-(2-hydroxyethoxy)'ethyl}-l-piperazinyl] dibenzo [b,f]-[l, 4]thiazepine and its pharmaceutically acceptable salts wherein the complete reaction of ll-piperazinyldibenzo[b,f][l,4]-thiazepme and 2-(2-chloroethoxy)ethanol is achieved in much shorter time leading to a product of higher quality in higher yield. Summary of the invention Accordingly, in the present invention, the compound of Formula II is reacted with 2-(2-chloroethoxy) ethanol in presence of an inorganic base in aqueous condition to form 11-[4-{2-(2-hydroxyethoxy) ethyl}-1-piperazinyl] dibenzo [b,f)-[l, 4]thiazepine. In a preferred embodiment of the present invention, the compound of Formula II and 2-(2-chloroethoxy)ethanol is treated in presence of a base in water as solvent at a temperature of about 100 to 105°C for a period of about 4 to 9 hours during which the reaction is complete to the extent of 99.9% or more. In yet another embodiment of the present invention the reaction is performed in water medium in presence of an alkali metal iodide such as sodium iodide or potassium iodide in catalytic amounts. In another aspect the present invention relates to quetiapine hemi-fumarate (hereinafter also referred as quetiapine fumarate) made by the process of the present invention. Detailed description of the invention This invention provides an improved industrial process for preparation of Quetiapine and its hemi-fumarate salt by the reaction of an intermediate compound of Formula II with 2-(2-chloroethoxy)ethanol in shorter duration of time with minimal impurity generation and almost complete transformation of compound of ll-piperazinyldibenzo[b,f][l,4]-thiazepine. The quetiapine free base obtained by the process of the present invention is further converted to its hemi-fumarate salt. WO 2006/077602 PCT/IN2005/000028 4 It is now surprisingly found that the above reaction when carried out in a water medium -a green solvent- as against the prior teachings of organic solvents, both protic and aprotic, the reaction leads to completion with only traces of starting material (less than 0.1%). Another important feature of the present invention is the stability of both the reactants and product, the ll-[4-{2-(2-hydroxyethoxy) ethyl}-1-piperazinyl] dibenzo [b,f]-[l,4]thiazepine, in aqueous condition and the much faster rate of reaction which allows high conversion in shorter duration. The reaction is found to be reproducible in large scale. In the process of the present invention, a mixture of compound of Formula II, 2-(2-chloroethoxy) ethanol and an inorganic base is heated in a medium of water at reflux temperature for a period of 4 to 8 hours. The ideal temperature of reaction is in the range of 100 to 105 °C. The compound of Formula II (ll-piperazinyldibenzo[b,f][l,4]-thiazepine) can be used either as free base or its hydrochloride salt in the reaction. When an acid salt of compound of Formula II like hydrochloride salt is used in the reaction, an excess amount of inorganic base is used which is required to neutralize the hydrochloride salt to liberate free base in the reaction. The inorganic base used in the present invention is known in literature such as sodium carbonate or bicarbonate or potassium carbonate. The selection of base is not critical for the success of the reaction. The inorganic base is preferably used in molar amounts of about 1 to 6 moles relative to the compound of Formula II. The 2-(2-chloroethoxy)ethanol is preferably used in a molar amount ranging from about 1 to 1.5 molar equivalents relative to compound of Formula II. The volume of solvent used is preferably in the range of 2 to 4 volume with respect to the starting compound of Formula II. Higher volumes of water can also be used but concentrated reaction medium is preferred on operating in large scale. WO 2006/077602 PCT/IN2005/000028 5 In a preferred embodiment of the reaction, an alkali metal iodide such as sodium iodide or potassium iodide is used as a promoting agent along with mixture of compound of Formula II, 2-(2-chloroethoxy)ethanol & inorganic base in an aqueous medium In an optional feature of the invention, a phase transfer catalyst may be used along with the reactants of Formula II and Formula III, base and sodium iodide in aqueous medium. When a phase transfer catalyst (PTC) is used in present process, the reaction time is further reduced to about 3 to 6 hours in place of 4 to 9 hours without PTC. It is, however, ( observed that other than reduction of reaction time by 1 to 2 hours no other significant advantages are observed relates to the purity or yield of product, i.e., the ll-[4-{2-(2-hydroxyethoxy) ethyl}-1-piperazinyl] dibenzo [b,f]-[l, 4]thiazepine, when a phase transfer catalyst is used. The phase transfer catalyst of choice is tertrabutyl ammonium halide and specifically tertrabutyl ammonium bromide. The quetiapine free base formed in the reaction is isolated as an oily mass by the steps of extracting the product using an organic solvent selected from hydrocarbon solvents like toluene, xylene, heptane or chlorinated hydrocarbon solvent such as methylene chloride, and removing the organic solvent by distillation, preferably under reduced pressure. The isolated crude quetiapine free base is further converted directly to the hemi-fumarate salt without subjecting to additional purification by suspending the oily mass in ethanol and combining it with fumaric acid in 0.55 to 1.0 molar equivalents relative to free base. The ethanol solution is cooled to precipitate the quetiapine hemi-fumarate in an yield of about 75 to 80%. The purity of quetiapine hemifumarate so obtained is at least 99.5%. Apart from greening of the process the drastic yield and purity improvement caused by the above described variation can lead to an efficient and commercially acceptable synthetic process for the preparation of quetiapine hemi-fumarate. The starting material ll-piperazinyldibenzo[b,f][l,4]-thiazepine was prepared according to the process disclosed in US3539573. WO 2006/077602 6 PCT/IN2005/000028 It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative examples and that the present invention may be embodied in other specific forms without departing from the essential attributes thereof, and it is therefore desired that the present embodiments and examples be considered in all respects as illustrative and not restrictive, reference being made to the appended claims, rather than to the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Examples Example 1 In a reaction vessel, a mixture of 1 l-piperazinyldibenzo[b,f][l,4]-thiazepine (10 Kg), 2-(2-chIoroethoxy)ethanol (6.33 kg), sodium carbonate (21.55 kg) and 0.2 kg sodium iodide was heated in 30 liters of water to about 100 °C. The reaction mixture was maintained at about 100 to 105 °C for about 7 hours. The starting 11-piperazinyldibenzo[b,f][l,4]-thiazepine was about 0.26% by HPLC. Maintained for another 2 hours till the 1 l-piperazinyldibenzo[b:f][l,4]-thiazepine was about less than 0.1 % by HPLC analysis. The reaction mass was cooled to about 30 °C and aqueous layer extracted with methylenedichloride (100 liters). The organic layer was washed with water and concentrated under reduced pressure. The oily residue was so obtained was suspended in 100 liters of ethanol (commercial) and 4.1 kg fumaric acid was added. The mixture was stirred for about 6 hours and cooled to about 10 °C. The precipitated quetiapine hemi-fumarate salt was filtered and dried to give 12 Kg ( yield 80 %, purity 99.6% by HPLC analysis). Example 2 In a reaction vessel, a mixture of 1 l-piperazinyldibenzo[b,f][l,4]-thiazepine (10 Kg), 2-(2-chloroethoxy)ethanol (6.33 kg), sodium carbonate (21.55 kg), 1 kg tetrabutyl ammonium bromide and 0.2 kg sodium iodide was heated in 30 liters of water to about 100 °C. The reaction mixture was maintained at about 100° to 105°C for about 5 hours. WO 2006/077602 PCT/IN2005/000028 7 Starting ll-piperazinyldibenzo[b,f][l,4]-thiazepine was about 0.3 % by HPLC. Maintained for another 2 hours till the H-piperazinyldibenzo[b,f][l,4]-thiazepine was about less than 0.08 % by HPLC analysis. The reaction mass was cooled to about 30 °C and aqueous layer extracted with methylenedichloride(100 liters). The organic layer was washed with water and concentrated under reduced pressure. The oily residue was so obtained was suspended in 100 litres of ethanol ( commercial) and 4.1 kg fumaric acid was added. The mixture was stirred for about 4 hours and cooled to about 10°C. The precipitated quetiapine hemi-fumarate salt was filtered and dried to give 12Kg ( yield 80 % & purity 99.8% by HPLC analysis) Example 3 In a reaction vessel, a mixture of ll.-piperazinyldibenzo[b,f][l,4]-thiazepine dihydrochloride (10 Kg), 2-(2-chloroethoxy)ethanol (5.1 kg), sodium carbonate (17.3 kg), and 0.16 kg sodium iodide was heated in 30 liters of water to about 100°C. The reaction mixture was maintained at about 100° to 105 °C for about 7 hours. Starting 11-piperazinyldibenzo[b,f][l,4]-thiazepine was about 0.25% by HPLC. Maintained for another 2 hours till ll-piperazinyldibenzo[b,f][l,4]-thiazepine was about less than 0.1 % by HPLC analysis. The reaction mass was cooled to about 30 °C and aqueous layer extracted with methylenedichloride. The organic layer was washed with water and concentrated under reduced pressure. The oily residue was so obtained was suspended in 100 litres of ethanol (commercial) and 3.3 kg fumaric acid was added. The mixture was stirred for about 6 hours and cooled to about 15 °C. The precipitated quetiapine hemi-fumarate salt was filtered and dried to give 9.6 Kg (yield 80 % & purity 99.5% by HPLC analysis) WO 2006/077602 PCT/IN2005/000028 8 We claim, 1. An industrial process for preparation of quetiapine of Formula I comprising the step of heating a mixture of 1 l-piperazinyldibenzo[b,f][l,4]-thiazepine (Formula II) or its salt, 2-(2-chloroethoxy)ethanol ( Formula III), an inorganic base in aqueous medium under refluxing temperature, and isolating said quetiapine from said medium. 2. The process as claimed in claim 1, wherein the inorganic base is selected from the group of sodium carbonate, sodium bicarbonate, and potassium carbonate. 3. The process as claimed in claim 1 or 2, wherein the reaction is performed in the presence of an alkali metal iodide. 4. The process as claimed in claim 3, wherein the alkali metal iodide is sodium iodide or potassium iodide. 5. The process as claimed in any one of the preceding claim, wherein the reaction is performed in the presence of a phase transfer catalyst. 6. The process as claimed in claim 5, wherein the phase transfer catalyst is tetrabutylammonium bromide. 7. The process as claimed in any one of the preceding claim, wherein the reflux temperature is in the range of 100 to 105°C. 8. The process as claimed in any one of the preceding claim wherein the aqueous medium is water. WO 2006/077602 PCT/IN2005/000028 9 9. The process as claimed in any one of the preceding claim, wherein the volume of water used is in the range of 2 to 4 volume/weight relative to 11-piperazinyldibenzo[b,f][l,4]-thiazepine of Formula II. 10. The process as claimed in any one of the preceding claim wherein the quetiapine is isolated from aqueous medium by extraction using an organic solvent. 11. The process as claimed in claim 10, wherein the organic solvent is selected from hydrocarbon solvents or chlorinated hydrocarbon solvents. 12. The process as claimed in claim 11, wherein the organic solvent is toluene or methylenedichloride. 13. The process as claimed in any one of the preceding claims, wherein the quetiapine is further converted to quetiapine hemi-fumarate. 14. Quetiapine or quetiapine hemi-fumarate prepared substantially according to any one of the preceding claims. 15. An industrial process for preparation of quetiapine or quetiapine hemi-fumarate as substantially described herein with reference to the foregoing examples 1 to 3. Dated this 3rd day of May 2007 GNA 205 WO 10 ABSTRACT Disclosed herein is an industrial process for preparation of Quetiapine by the reaction of ll-piperazinyldibenzo[b,f][l,4]-thiazepine or its salt with 2-(2-chloroethoxy)ethanol in presence of an inorganic base in aqueous condition to form ll-[4-{2-(2-hydroxyethoxy) ethyl}-1-piperazinyl] dibenzo [b,f]-[l, 4]thiazepine. The quetiapine free base obtained is further converted to its hemi-fumarate salt.

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