Reductive cleavage of arylcyclopropyl ketones

Abstract

Arylcyclopropyl aryl ketones undergo clean but slow reductive cleavage to 4-arylbutyrophenones when heated with zinc in ethanol. Replacement of one of the aryl groups by an alkyl group strongly inhibits reaction. This effect is in part overcome by the use of a higher boiling alcohol. When substituted at the cyclopropyl methylene position by an ethoxycarbonyl group these cyclopropyl ketones also undergo cleavage but with the unexpected formation of the ethyl 3,5-diaryl-5-oxopentanoates (22). In general, the results are consistent with the formation of an anion-radical intermediate.