Beckmann Rearrangement

An acid-induced rearrangement of oximes to give amides.

This reaction is related to the Hofmann and Schmidt Reactions and the Curtius Rearrangement, in that an electropositive nitrogen is formed that initiates an alkyl migration.

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Mechanism

Oximes generally have a high barrier to inversion, and accordingly this reaction is envisioned to proceed by protonation of the oxime hydroxyl, followed by migration of the alkyl substituent "trans" to nitrogen. The N-O bond is simultaneously cleaved with the expulsion of water, so that formation of a free nitrene is avoided.

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Recent Literature

Beckmann Rearrangement of Oximes under Very Mild Conditions
L. De Luca, G. Giacomelli, A. Porcheddu, J. Org. Chem., 2002, 67, 6272-6274.

Beckmann reaction of oximes catalysed by chloral: mild and neutral procedures
S. Chandrasekhar, K. Gopalaiah, Tetrahedron Lett., 2003, 44, 755-756.

Mercury-Catalyzed Rearrangement of Ketoximes into Amides and Lactams in Acetonitrile
C. Ramalingan, Y.-T. Park, J. Org. Chem., 2007, 72, 4536-4538.

Solvent-Free and One-Step Beckmann Rearrangement of Ketones and Aldehydes by Zinc Oxide
H. Sharghi, M. Hosseini, Synthesis, 2002, 1057-1059.