Favorskii rearrangement of some Î±-bromo-ketones
Nicholas J. Turro; Robert B. Gagosian; Christoffer Rappe; Leif Knutsson
- Favorskii rearrangement of some Î±-bromo-ketones
Turro, Nicholas J.
Gagosian, Robert B.
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- Journal of the Chemical Society D: Chemical Communications
- The base-induced rearrangement of a-halogenoketones to give carboxylic acid derivatives (Favorskii rearrangements1) occurs by at least two mechanisms. The stereochemi~try29~ and structure* of many Favorskii products can be explained in terms of a cyclopropanone intermediate. However, a â€œbenzylic-likeâ€ rearrangement appears to operate when the substrate ketone bears no aâ€™-hydrogen,5 when the =â€™-hydrogen is relatively non-acidic,6 or when steric or strain factors inhibit cyclopropanone formation.â€™ In addition, the formation of a dipolar intermediate which may precede (or follow) cyclopropanone formation is supported by theoretical considerations,s loss of stereospecificity upon rearrangement in polar solvents,B the formation of a-substitution products* as a side reaction, and the trapping of a possible Favorskii intermediate â€œdehydrohalogenateâ€ to form a common intermediate leading to the same product.
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