Beckmann rearrangements cations formed

Oximes derived from p-silyl and P-stannyl ketones undergo unusual Beckmann rearrangement, giving rise to nitriles as predominant products. For example, Beckmann rearrangement of 3-trimethylsilylcyclohexanone oxime 88 (Scheme 15) proceeds to the formation of the acyclic alkenyl nitrile 89 as the major product.90 The nitrile is believed to be formed by fragmentation of the protonated oxime, giving the P-silyl—stabilized cation 90, followed by desilylation. Our... 

A few caprolactam containing PILs were successfully used as solvents and catalysts for the Beckmann rearrangement of cyclohexanone to produce caprolactam. Unusually, the caprolactam product is the same as the neutral form of the cation in the PIL, shown in Scheme 15. The caprolactam BF4 PIL under optimized conditions led to yields of 93% with 89% selectivity. In comparison, under the same conditions, [HMIm]BF4 only had yields of 44% with 33% selectivity, showing the particular suitability of the caprolactam containing PILs for this reaction. Other anions were trialed with the caprolactam cation with good performance, though the BF4 anion gave the best results. ... 

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