Beckmann, E. Isonitroso compounds. Ber. Dtsch. Chem. Ges. 1886, 19, 988-993.
Donaruma, L. G., Heldt, W. Z. The Beckmann rearrangement. Org. React. 1960, 11, 1-156.
Use conversion of oximes to the corresponding amide under acidic conditions, these reactions are especially important as the cyclic oximes yield lactams. For example cyclohexanoxime synthesized from cyclohexanone may be converted via the Beckmann rearrangement to the cyclic caprolactam which is an important feed stock for the preparation of Nylon 6. The most common Beckmann solution is made up from hydrochloric acid acetic acid and acetic anhydride
Unless the oxime isomerizes under the reaction conditions, in which case a mixture of the two amides will be obtained the stereo outcome of the Beckmann rearrangement is very predictable. The R group anti to X will always migrate.
1. Addition of an electrophile to X results in the formation of the leaving group
2. The expulsion of the leaving group and subsequent [1,2]shift results in migration of the R-group anti to X.
3. Reaction of the resulting carbocation with a nucleophile (either water or the leaving group) followed by tautomerization results in the formation of the amide