We investigated the reaction of ketoximes with hypervalent iodine reagents. A combination of PhI(OAc)2 and BF3·Et2O promoted the Beckmann rearrangement of ketoximes, thus yielding the corresponding amides. From the detailed investigation of the reaction, we determined that the Beckmann rearrangement is preceded by acetylation of the hydroxy group of the ketoxime in situ, accelerating the Beckmann rearrangement. We confirmed that the acetylated ketoxime undergoes the Beckmann rearrangement with BF3·Et2O. The reaction of ketoximes with Koser’s reagent (PhI(OH)OTs) in the presence of tetrahydrofuran results in the hydrolysis, affording the corresponding ketones at high yields at room temperature.

We developed a Beckmann rearrangement employing hypervalent iodine reagent under mild conditions. The reaction of ketoxime with hypervalent iodine afforded the corresponding ketone, but premixing of hypervalent iodine and a Lewis acid was effective for promoting Beckmann rearrangement. Aromatic and aliphatic ketoximes were converted into their corresponding amides in good to high yields.