The Beckmann Rearrangement of Aliphatic Ketone Oximes -The Influences of Steric Factor and Migratory Aptitudes-

Abstract

The Beckmann rearrangement of the aliphatic ketone oximes, R(CH₃)C=NOH (R=Et [1]; n-Pr [2]; iso-Pr [3], iso-Bu [4]; t-Bu [5]), with various kinds of the catalysts was tried and the influence of steric bulkiness of alkyl group and the effect of catalysts were investigated. These data are shown in Table 2.
From these results, it was found that the migratory aptitudes of alkyl group in this reaction depend on the steric effect of alkyl group and the catalyst. In the cases of thionyl chloride and formic acid as the catalyst, only N-alkyl acetamides were yielded. On the other hand, when borontrifluoride-acetic acid complex was used, the migratory aptitudes were considerably deviated from the ratios of anti-alkyl form/syn-alkyl form of aliphatic ketone oximes in benzene (A1) or DMSO (A2) (see Table 1). In other cases, they nearly approach to Al or A2. This demonstrates that these catalysts are inactive for isomerization of the oximes during the reaction.