Ketones acyl migrations

Crossover experiments have been used to establish that the novel N to C acyl migration reaction of acyclic imides (69), to give o -amino ketones (70), proceeds by intramolecular reaction of the base-generated carbanion. ... 

Hara, O. Ito, M. Hamada, Y. Novel N-C acyl migration reaction of acyclic imides a facile method for a-amino ketones and / -amino alcohols. Tetrahedron Lett. 1998, 39, 5537—... 

The Oxa Di-n-methane Reaction and Related Processes - A detailed examination of the triplet and singlet state reactions of a series of P,y-unsaturated enones has been reported. Many examples are cited and are typified by the conversion of the enone (140) into (141) on sensitized irradiation. This reaction is a typical example of the well known oxa-di-n-methane process, which fundamentally involves a 1,2-migration of the acyl group. Direct irradiation populates the singlet state of the enone (140) and this yields (142) by a 1,3-acyl migration. The oxa-di-n-methane reaction of chiral bicyclo[2.2.2]oct-5-en-2-one systems has been used as a path to tricyclic ketones. 

This conclusion is in general agreement with experimental studies that indicate that several excited states can lead to oxadi-ir-methane rearrangement and the related reactions.For example, l,2-dimethylcylopent-2-enyl methyl ketone reacts by all three pathways. In the gas phase about 25% of the 1,3-acyl migration occurs by a dissociation mechanism, as indicated by the ability of NO and O2 to divert a part but not all of the intermediate. 

Acetone sensitization of the enone (130) yields the isomer (131) as a result of a 1,2-acyl migration.78 This reaction is to be contrasted with the direct irradiation of the ketone (130) which yielded the cage compound (132) by 1,3-acyl shift and [2 + 2] addition.80... 

The photochemical 1,3-acyl migration which converts certain jSy-unsaturated ketones into isomeric enones has been investigated for a series of compounds, including cholest-4-en-7-one (651) and its 6,6-dimethyl derivative (652). Photoequilibration affords the isomers (653), considered to arise via n — tt triplet states. The reactions are influenced by conformational and conjugative features which effect the stability of an intermediate radical pair of the type (654). Other workers have studied the phosphorescence spectra and lifetimes of triplet excited states of a number of j y-unsaturated ketones, including some... 

Wl. Sawaki, Y., and Y. Ogata Acyl Migration in the Acid-catalyzed Decomposition of a-Hydroperoxy Ketones. J. Amer. Chem. Soc. 100, 856 (1978). 

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