Migration to electron-deficient

Another important reaction involving migration to electron-deficient nitrogen is the Beckmann rearrangement, in which oximes are converted to amides.282... 

Another important reaction involving migration to electron-deficient nitrogen is the... 

The etcroospocific character of this reaction was indicated by the nature of produets secured from cw- and (rana-stilbeue oxides. Whereas the former afforded only deeoxybenzoin, (he latter yielded diphenyl-acetaldehyde exclusively (Eq. 492). T njike acid-catalyzed migrations to electron-deficient centers, therefore, the base-catalyzed epoxide jiuimerizations under scrutiny appear to involve cis-migratioa and fronts attack upon an anionic center. 39... 

Our consideration of rearrangements to electron-deficient heteroatoms must be brief. In discussing migrations to electron-deficient nitrogen, we first discuss three rearrangements that occur in carbonyl derivatives, the Beckmann, Hofmann, and Schmidt rearrangements, and then consider rearrangements of nitrenium ions. 

Similar migrations to electron-deficient oxygen also occur. In the Baeyer-Villiger rearrangement a ketone is reacted with a peracid. The product is an ester in which one of the alkyl groups of the ketone has migrated to oxygen ... 

Rearrangement of NJV-dilmloanunesf N,N-Dichloro-tri-n-butylcarbinamine (2), prepared by treatment of tri-n-butylcarbinamine (I) with calcium hypochlorite, when treated with aluminum chloride in methylene chloride at - 30°, followed by acid hydrolysis, gives di-n-butyl ketone (3) and n-butylaminc (4) in high yield. The reaction is considered to involve alkyl migration to electron-deficient nitrogen. 

Hofmann rearrangement. Migration to electron-deficient nitrogen... 

We have depicted the pinacol rearrangement as a two-step process with an actual carbonium ion as intermediate. There is good evidence that this is so, at least when a tertiary or benzylic cation can be formed. Evidently the stability of the incipient cation in the transition state permits (SNl-lihe) loss of water without anchimeric assistance from the migrating group. This is, we note, in contrast to what happens in migration to electron-deficient nitrogen or oxygen. 

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