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 |
Reaction mechanism
editThe 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]
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The selectivity is similar to the Favorskii rearrangement in that the most stable carbanion is formed.
Examples
editThe 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]
See also
editReferences
edit- ^ a b Kurti 1 Czako 2, Laszlo 1 Barbara 2 (15 September 2005). Strategic Applications of Named Reactions in Organic Synthesis. Elsevier. pp. 164–165. ISBN 0-12-429785-4.
{{cite book}}: CS1 maint: numeric names: authors list (link) - ^ Zhang, Liming; Koreeda, Masato (1 October 2002). "Stereocontrolled Synthesis of Kelsoene by the Homo-Favorskii Rearrangement". Organic Letters. 4 (21): 3755–3758. doi:10.1021/ol026739q. ISSN 1523-7060. PMID 12375936.
- ^ "Homo-Favorskii rearrangement - Big Chemical Encyclopedia". chempedia.info. Retrieved 2 June 2024.