Mechanistic Insight into Self-Propagation of Organo-Mediated Beckmann Rearrangement: A Combined Experimental and Computational Study

Organo-mediated Beckmann rearrangement
in the liquid phase, which
has the advantage of high efficiency and straightforward experimental
procedures, plays an important role in the synthesis of amides from
oximes. However, the catalytic mechanisms of these organic-based promoters
are still not well understood. In this work, we report a combined
experimental and computational study on the mechanism of Beckmann
rearrangement mediated by organic-based promoters, using TsCl as an
example. A novel self-propagating cycle is proposed, and key intermediates
of this self-propagating cycle are confirmed by both experiments and
DFT calculations. In addition, the reason why cyclohexanone oxime
is not a good substrate of the organo-mediated Beckmann rearrangement
is discussed, and a strategy for improving the yield is proposed.