| 摘要 |
Described is a method of preparing essentially pure .alpha.-bis-oxime isomers of the formula (Ia): R1O-N=CR2-CR3=N-OR4, in which the groups R1O- and R2 are in the cis configuration with respect to the N=C bond, from a mixture of the cis and trans isomers (Ia and Ib), the various groups being defined as follows: R1, R4 are hydrogen, or an organic carbon group; R2 is hydrogen, cyano, nitro, hydroxy, amino, halogen or an organic group which may be bound directly or via an oxygen, sulphur or nitrogen atom to the main chain; R3 is hydrogen, cyano, nitro, hydroxy, amino, halogen, alkyl, haloalkyl, alkoxy, haloa lkoxy, alkylthio, alkylamino, dialkylamino or cycloalkyl, Said method is characterized in that the mixture is treated in an organic solven t with a Lewis acid.
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