Process for the preparation of paroxetine substantially free of alkoxy impurities
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a technology of paroxetine and impurities, which is applied in the direction of biocide, heterocyclic compound active ingredients, drug compositions, etc., can solve the problems of defluorination of intermediates, particularly problematic defluorination, and inability to effectively separate alkoxy impurities from paroxetine or its intermediates
Inactive Publication Date: 2005-09-15
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One problem with the synthesis of paroxetine is the defluorination of the intermediates.
Defluorination is particularly problematic when the condensation of the cinnamate and the alkyl amidomalonate occurs in the presence of a metal alkoxide as disclosed in the '517 and '801 patents.
The alkoxy impurities can not be effectively separated from paroxetine or its intermediates by traditional techniques such as recrystallization.
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Purification of 1-methyl-3-hydroxymethyl-4-(4′-fluorophenyl)piperidine (PMA)
[0059] PMA (30 grams—containing approximately 2.6% by HPLC area percentage of the corresponding alkoxy impurity) was added to a solution of HBr (180 ml, 48%). The reaction mixture was then heated to strong reflux for about 1.50 hours until completion of the reaction. The reaction was followed by HPLC until the area percentage of the peak representing the alkoxy impurity is less than 0.5%. The reaction mixture was then allowed to cool to OEC, and was then basified to pH=11.5 with a solution 40% NaOH to increase the solubility of the corresponding phenol in the aqueous phase. Methylene chloride (150 ml) was then added, and the aqueous phase was extracted 3 times with methylene chloride (3×150 ml). The organic phase was then dried on sodium sulfate, filtrated and evaporated under reduced pressure, leaving about 15 g of methylene chloride. The oily mixture was then seeded with PMA crystal and after 1 hour the e...
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Abstract
The present invention is directed to methods for preparing intermediates useful in the synthesis of paroxetine wherein the intermediates are substantially free of alkoxy impurities as well as to methods for preparing paroxetine and pharmaceutically acceptable salts thereof substantially free of alkoxy impurities. The alkoxy impurity is reacted with an ether cleaving agent to generate the corresponding phenol, which is separated, yielding the desired product substantially free of alkoxy impurities. Paroxetine intermediates such as PMA, paroxetine, and pharmaceutically acceptable salts thereof substantially free of alkoxy impurities also form part of the present invention.
Description
CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims the benefit of provisional application Ser. No. 60 / 297,881, filed Jun. 13, 2001, which is incorporated herein by reference.BACKGROUND OF THE INVENTION [0002] Paroxetine, trans (−)-3-[(1,3-benzodioxol-5-yloxy)methyl]-4-(4-fluorophenyl) piperidine, is a serotonin (5-hydroxy-tryptamine; 5-HT) re-uptake inhibitor, having the formula (I): [0003] Paroxetine is orally administered, inter alia, for the treatment of depression, social anxiety disorders, obsessive compulsive disorder, panic disorder, generalized anxiety disorder and posttraumatic stress disorder. [0004] U.S. Pat. Nos. 4,902,801 and 5,258,517, and EP 223,334 A1, each of which is incorporated herein in its entirety, disclose preparation of paroxetine by condensation of cinnamate of formula 1 with alkyl amidomalonate of formula 2 to produce imide of formula 3, followed by subsequent transformations, as shown in Scheme 1 below: The '801 and the '517 patents ...
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