Cleavage of Cyclopropyl Ketones

Although not formally a type I cleavage process, j3-cleavage of cyclopropyl ketones to form propenyl ketones and/or epimerized cyclopropyl groups bears such a close similarity to a-cleavage that it should be discussed in combination with the latter. The first report of a reaction thought to occur by j3-cleavage was made by Pitts in 1954 for the formation of methyl propenyl ketone from methyl cydopropyl ketone,  

When ketones bearing substituted cyclopropyl groups are photolyzed, products having different stereochemistry result, indicating that the initial j8-cleavage is reversible. 

The mode of bond cleavage is extremely sensitive to alkyl substitution, -  

Irradiation of the following ketone in acetic acid-d4 failed to produce product containing deuterium. Thus an enol intermediate cannot be involved in the ring opening  

The photochemical interconversion of cis- and /runs S,6-diphenyl-bicyclo[3.1.0]hexanones has been extensively studied by Zimmerman, Hancock, and Licke. Using isotope dilution analysis, these workers obtained very accurate quantum yields for the various photochemical processes involved in this reaction  

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See also in sourсe #XX -- [ , , , , , ]

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