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Details for Patent: 4,743,693

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Details for Patent: 4,743,693

Title: Process for the preparation of a stable modification of torasemide
Abstract:The present invention provides a process for the preparation of crystalline torasemide in the pure modification I (monoclinic, space group P2.sub.1 /c, melting point 162.degree. C.) from torasemide of modification II (monoclinic, space group P2/n, melting point 169.degree. C.), wherein a suspension of torasemide of modification II is stirred in water with the addition of a catalytic amount of modification I until the rearrangement is complete. The present invention also provides a pharmaceutical compositions containing torasemide of modification I.
Inventor(s): Topfmeier; Fritz (Heidelberg, DE), Lettenbauer; Gustav (Lampertheim, DE)
Assignee: Boehringer Mannheim GmbH (Mannheim, DE)
Filing Date:Aug 11, 1986
Application Number:06/895,355
Claims:1. A process for the preparation of torasemide in the pure modification I (monoclinic, space group P2.sub.1 /c, metling point 162.degree. C.) from torasemide of modification II (monoclinic, space group P2/n, melting point 169.degree. C.), comprising stirring a suspension of torasemide of modification II in water with at least a catalytic amount of modification I, to rearrange the torasemide in modification II into torasemide of modification I.

2. The process of claim 1, wherein the rearrangement is carried out at a temperature of from ambient temperature to 90.degree. C. and the rearrangement is carried out for a time of from 3 hours to 14 days.

3. The process of claim 2, wherein the torasemide of modification II is used in the form of a salt-containing, approximately neutral solution, obtained by the precipitation of torasemide from alkaline solution.

4. The process of claim 2, wherein crystalline torasemide of modification I is recovered from the rearrangement reaction mixture.

5. The process of claim 1, wherein crystalline torasemide of modification I is recovered from the rearrangement reaction mixture.

6. The process of claim 1, wherein the torasemide of modification II is used in the form of a salt-containing, approximately neutral solution, obtained by the precipitation of torasemide from alkaline solution.
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