Rearrangement to Electron-Deficient Nitrogen and Oxygen

The acid-catalyzed conversion of ketoximes and aldoximes to amides or amines (the amide is often hydrolyzed to the corresponding amine under the reaction conditions) is known as the Beckmann rearrangement after its discoverer.147 The reaction and its widely accepted mechanism are shown in Equation 6.54. 

The observation that picryl ethers of oximes (106) rearrange without a catalyst established that the role of the catalyst was to convert the hydroxyl 

When the catalyst is a Bronsted acid, migration is not stereospecific. Under these conditions, syn and anti forms are readily interconverted, presumably via the pathway shown in Equation 6.55. 

That intermediate 105 in Equation 6.54 is formed in the Beckmann rearrangement has been amply demonstrated both by diverting it to other products155 and by direct observation by nmr.156 

If the mechanism in Equation 6.54 is correct, then oxygen transfer should be an intermolecular process. And in fact, when unlabeled acetophenone 

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Rearrangements to Electron-Deficient Nitrogen and Oxygen Centers Migration of an alkyl group was discussed in Section 6.2.1.2. The well-known... 

In this chapter we shall discuss intramolecular rearrangements to electron-deficient carbon, nitrogen, and oxygen. 

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