| 摘要 |
A novel process for the epimerization of alkyl trans chrysanthemates comprising reacting at a low temperature in an anhydrous organic solvent an alkyl trans chrysanthemate of the formula <IMAGE> II of the 1S, trans or 1R, trans configuration wherein R is alkyl of 1 to 6 carbon atoms with a strong alkali metal base to obtain a compound of the formula <IMAGE> III wherein R has the above definition and M is an alkali metal, reacting the latter compound with a reactant of the formula Y-A wherein A is selected from the group consisting of chlorine, bromine, iodine and anion derived from a hydrogen acid and Y is an organic radical capable of forming a ketal of a ketene to obtain a compound of the formula <IMAGE> IV reacting the latter at a low temperature in an anhydrous organic solvent with a proton donor to obtain a mixture of the corresponding alkyl cis chrysanthemate and alkyl trans chrysanthemate and recovering the cis chrysanthemic acid of the formula <IMAGE> I with the 1R, cis or 1S, cis configuration.
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