| Favorskii rearrangement | |
|---|---|
| Named after | Alexei Yevgrafovich Favorskii |
| Reaction type | Rearrangement reaction |
| Identifiers | |
| Organic Chemistry Portal | homo-favorsky-reaction |
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). It must be noted that E1cb will occur if α-carbon adjacent to the halogen atom has hydrogens on it.
Reaction mechanism edit
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]
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The selectivity is similar to the Favorskii rearrangement in that the most stable carbanion is formed.
Examples edit
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]
See also edit
References 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.
- ^ "Homo-Favorskii rearrangement - Big Chemical Encyclopedia". chempedia.info. Retrieved 2 June 2024.