TheFavorskiĭ Rearrangement of Haloketones

Abstract

The Favorskii rearrangement is the skeletal rearrangement of a alpha‐halogenated ketones in the presence of certain nucleophilic bases, such as hydroxides, alkoxides, or amines to give carboxylic acid salts, esters or amides, respectively. Monohaloketones undergo the reaction to yield derivatives of saturated acids having the same number of carbon atoms. In a similar manner, suitable dihaloketiones produce unsaturated carboxylic acids. Analogous rearrangements of trihaloketones can give rise to unsaturated halo acids. The Favorskii reaction has found application for the preparation of highly branched acyclic carboxylic acids. It is a preferred route to various 1‐cycloalkanecarboxylic acids and provides a direct method for ring contraction in simple alicyclic systems and in steroids.

A Photo-Favorskii Ring Contraction Reaction: The Effect of Ring Size

“…23 Unlike its namesake, the classic ground-state Favorskii rearrangement that has received extensive investigation, 24–30 the range of possibilities and the theoretical treatments of the photo-Favorskii rearrangement 14 have not been adequately addressed. The current understanding of the photo-Favorskii mechanism also continues to be the subject of considerable debate.…”

Halocycloalkenones as Diels–Alder Dienophiles. Applications to Generating Useful Structural Patterns

“…For example, when treated with sodium hydroxide, compounds 6 , 5d , and 5e easily undergo a quasi-Favorskii ring contraction to provide the corresponding cyclopropane acids 21a – 21c (Table 3, entries 1–3). 12 Amazingly, this process occurs with a reaction time of just five minutes, likely proceeding through a semi-benzilic mechanism. Interestingly, compound 5f proceeded to give the α-hydroxy ketone 21d with net replacement of the bromide with hydroxide (entry 4).…”

Synthesis of ent-[3]-Ladderanol: Development and Application of Intramolecular Chirality Transfer [2+2] Cycloadditions of Allenic Ketones and Alkenes

“…26 This strategy would require a ring contraction, which we reasoned could be accomplished by application of the Favorskii 27 or Wolff rearrangements. 5b,28 In the event, stereoselective cycloaddition of cyclobutene 28 with cyclopentenone led to formation of 30 as a mixture of regioisomers (only one shown as it is inconsequential to the synthesis) (Scheme 4).…”