Process for the preparation of pyridine-2, 3-dicarboxylic acid esters and novel 2-amino-3 halomaleic acid esters
CA 2004012 A1 · Owner: Krageloh, Konrad · Inventors: Meier, Josef; Krageloh, Konrad; Deinhammer, Wolfgang
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
The invention relates to a process for the preparation of pyridine-2,3dicarboxylic acid esters using novel maleic acid esters as starting materials. In the process, in a first process step, 2,3-dihalomaleic acid esters are reacted with ammonia, or ammonium salts, with the exclusion of water at a temperature of at least 50°C to form novel 2-amino-3-halomaleic acid esters and these are, subsequently reacted further in a second process step with .alpha..beta.-unsaturated aldehydes, or ketones, in the presence of an acidic catalyst and acid-binding agents at a temperature of at least 50°C with heat being supplied until the pyridine-2,3-dicarboxylic acid esters have been formed. …
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Listed from its CIPO record in Patent Yard's archive of Canadian patents past their term. Its claims, description and drawings are in the CIPO record and on Google Patents, and the Claude kit works from them.
Why it's free to use
- Filed November 28, 1989. No grant is recorded for it in Canada; had it been granted, its 20-year term would have ended November 28, 2009.
- A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by November 28, 2011.
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Everything on this page comes from the CIPO record linked above. Contains information licensed under the Open Government Licence – Canada.