8.5 Rearrangement to Electron-Rich Carbon
This group of reaction has been less explored , and is less of synthetic importance compared to the rearrangements to electron deficient carbons. The rearrangements to electron deficient hetero atom may be generally explained as :
8.5.1 Stevens Rearrangement
Quaternary ammonium salt which has β -hydrogen proceeds E2 (Hofmann) elimination with base.
In case of quaternary ammonium salts containing β -ketone or ester or aryl group, an a -hydrogen is removed by base to give an ylide and then the rearrangement occurs.
Mechanism
Examples:
