| 摘要 |
PROBLEM TO BE SOLVED: To advance a stereoisomerization reaction and to convert a stereoisomer of a halofluorocyclopropanecarboxylic acid derivative regarded unnecessary into a necessary stereoisomer by treating the unnecessary stereoisomer with a base. SOLUTION: A 2-halo-2-fluorocyclopropanecarboxylic acid derivative of the formula (X is Cl, Br or I; R is a 1-10C alkoxy, an aryloxy, an aralkyloxy, a 1-10C alkylthio, an arylthio or the like; * is an asymmetric carbon atom) is treated with a base (preferably an alkyl metal alkoxide) to subject the 2- halo-2-fluorocyclopropanecarboxylic acid derivative to stereoisomerization. The reaction is preferably carried out by the treatment with the base in the presence of a Lewis acid (preferably a titanium tetraalkoxide). The (1S, 2R) derivative is isomerized into a (1R, 2R)derivative and the (1R, 2R)derivative is to the (1S, 2R)derivative, respectively to give an equilibrium mixture.
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