Substituted pent-2-enyl derivatives of malonic acid; a method for their preparation, and their use in the synthesis of a precursor of chrysanthemic acid

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Listed from its EPO record in Patent Yard's archive of European patents past their term. Its claims, description and drawings are in the EPO PDF and on Google Patents, and the Claude kit works from them.

Why it's free to use

• Filed November 23, 1979 and granted November 4, 1981. A European patent lasts at most 20 years from filing, so its term ended November 23, 1999.
• A supplementary protection certificate, which can extend a medicine or crop-protection patent, adds at most five and a half years, so even that would have ended by May 23, 2005.
• We check European rights only. A US or other national patent in its family could still be in force: check its family on Espacenet or Google Patents.