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Rearrangement of β-halo ketones and cyclobutanones From Wikipedia, the free encyclopedia
The homo Favorskii rearrangement is the rearrangement of β-halo ketones and cyclobutanones, which in ring systems may yield ring contraction.[1] This rearrangement takes place in the presence of a base, yielding a carboxylic acid derivative corresponding to the nucleophile (most often the base itself). E1cb will occur if α-carbon adjacent to the halogen atom has hydrogens on it.
Favorskii rearrangement | |
---|---|
Named after | Alexei Yevgrafovich Favorskii |
Reaction type | Rearrangement reaction |
Identifiers | |
Organic Chemistry Portal | homo-favorsky-reaction |
The reaction proceeds in an analogous manner to that of the Favorskii rearrangement. The major difference is that the cyclopropanone intermediate is replaced by a cyclobutanone intermediate, and therefore the intermediate's formation cannot be viewed as a 2-electron electrocyclization reaction.[1]
The selectivity is similar to the Favorskii rearrangement in that the most stable carbanion is formed.
The homo-Favorskii rearrangement is a key step in the synthesis of Kelsoene, constructing its four-membered ring. In this particular example, the nucleophile is absent and the base, t-BuOK, is very bulky. Therefore, the cyclobutanone intermediate can be isolated and is further reacted to yield the product.[2][3]
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