Beckmann Rearrangement

Named after the German chemist Ernst Otto Beckmann, the Beckmann rearrangement involves the conversion of aldoximes and ketoximes to their corresponding amides under acidic conditions. The reaction is usually carried out under under termperatures greater than 130°C, and in the presence of a large excess of strong Brønsted acids such as sulfuric acid or acetic acid. These conditions suggest that sensitive substrates are not suitable for this process.

To date, the Beckmann rearrangement is important in industry as a key step in the manufacture of caprolactam, a precursor to the synthesis of filaments and fibers such as nylon. The synthesis involves converting cyclohexanone to its oxime, and subsequently treating this with acid to generate caprolactam via a Beckmann rearrangement.

The total synthesis of the non-natural (+)-codeine utilized the Beckmann rearrangement to install a six-membered piperidine ring in the molecule.