Among the substrates we tested (1, 6, 9, 19, and 22), bicyclo [4.1. 0] heptan-2-one (6) and 1- acetylbicyclo [4.1. 0]-heptane (19) gave a selective ring fission reaction, while other substrates (1 and 9) gave products coming from the two possible modes of cyclopropyl ring fission (Table I). Clearly this point is a limiting factor for the synthetic scope of this reaction, although, in most cases, a satisfactory chromatographic separation of the two chloro ...