| 摘要 |
A process for preparing racemic alkyl-5-halopent-4-enecarboxylic acids and esters thereof of the formula (I), in which R is a C1-C6-alkyl radical, R1 is H or C1-4-alkyl and X is chlorine, bromine or iodine, which comprises a) reacting a dialkyl alkylmalonate of the formula (II),in which R is as defined above and R2 is a C1-C4-alkyl radical, in the presence of a metal alkoxide of the formula MOR3, in which M may be Na, K or Li, and R3 is a C1-C4-alkyl radical, and in an organic solvent, with 1,3-dihalopropene to give the corresponding allylated malonate, then b) after full conversion, adding an inorganic salt and a C1-C6 alcohol to the reaction mixture, heating the reaction mixture to reflux temperature, then c) isolating the desired racemic ester of the formula (I) from the reaction mixture by extraction or direct distillation and d) if the racemic acid is the desired end product, hydrolyzing the ester function.
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