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.
Mechanism of the Beckmann Rearrangement
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.
An efficient Beckmann rearrangement at room temperature involves an eosin Y
catalyzed, visible-light-mediated in situ formation of the Vilsmeier-Haack
reagent from CBr4 and a catalytic amount of DMF. This operationally
simple method for the activation of ketoximes avoids the need for any corrosive,
water-sensitive reagents and elevated temperatures.
V. P. Srivastava, A. K. Yadav, L. D. S. Yadav, Synlett, 2014, 25,
Beckmann Rearrangement of Ketoximes to Lactams by Triphosphazene Catalyst
M. Hashimoto, Y. Obora, S. Sakaguchi, Y. Ishii, J. Org. Chem., 2008,
Efficient Iodine-Mediated Beckmann Rearrangement of Ketoximes to Amides
under Mild Neutral Conditions
N. C. Ganguly, P. Mondal, Synthesis, 2010, 3705-3709.
Beckmann Rearrangement of Oximes under Very Mild Conditions
L. De Luca, G. Giacomelli, A.
Porcheddu, J. Org. Chem., 2002, 67, 6272-6274.
Bromodimethylsulfonium Bromide-ZnCl2: A Mild and Efficient Catalytic System
for Beckmann Rearrangement
L. D. S. Yadav, R. Patel, V. P. Srivastava, Synthesis, 2010,
Au/Ag-Cocatalyzed Aldoximes to Amides Rearrangement under Solvent- and
R. S. Ramón, J. Bosson, S. Díez-González, N. Marion, S. P. Nolan, J. Org. Chem., 2010,
Beckmann reaction of oximes catalysed by chloral: mild and neutral
S. Chandrasekhar, K. Gopalaiah,
Tetrahedron Lett., 2003, 44, 755-756.
Mercury-Catalyzed Rearrangement of Ketoximes into Amides and Lactams in
C. Ramalingan, Y.-T. Park, J. Org. Chem., 2007,
Solvent-Free and One-Step Beckmann Rearrangement of Ketones and Aldehydes by
H. Sharghi, M. Hosseini, Synthesis,