Fritsch–Buttenberg–Wiechell rearrangement
The Fritsch–Buttenberg–Wiechell rearrangement, named for Paul Ernst Moritz Fritsch, Wilhelm Paul Buttenberg, and Heinrich G. Wiechell, is a chemical reaction whereby a 1,1-diaryl-2-bromo-alkene rearranges to a 1,2-diaryl-alkyne by reaction with a strong base such as an alkoxide.
This rearrangement is also possible with alkyl substituents.The strong base deprotonates the vinylic hydrogen, which after alpha-elimination forms a vinyl carbene. A 1,2-aryl migration forms the 1,2-diaryl-alkyne product. The mechanism of the FBW rearrangement was a subject of on-surface studies where the vinyl radical was visualised with sub-atomic resolution.
Scope
One study explored this reaction for the synthesis of novel polyynes:
