Beckmann rearrangement of ketoximes on solid metaboric acid: a simple and effective procedure

When ketoximes admixed with solid metaboric acid (formed from boric acid at 100°C/0.1 Torr) are heated (∼140°C/7–42 h), the corresponding amides or lactams are produced in excellent yields (62–92%) via the Beckmann reaction. Aromatic aldoximes undergo both dehydration to the nitrile as well as (non-stereospecific) rearrangement under the above conditions. The absence of solvent, and the mildness and low toxicity of boric acid, characterise the present procedure.