Rhodium-catalyzed [(3+2)+1] carbocyclizations of alkynylidenecyclopropanes with carbon monoxide: construction of polysubstituted bicyclohexa-2,5-dienones.

A rhodium-catalyzed carbocyclization reaction of alkynylidenecyclopropanes with carbon monoxide to prepare bicyclohexa-2,5-dienones is described. This protocol offers convenient access to doubly conjugated cyclic enones and is tolerant of functionalized alkynes and cyclopropanes. Furthermore, a photochemical rearrangement of a bicyclohexa-2,5-dienone facilitates the construction of a highly functionalized bicyclopentenone containing two contiguous stereogenic centres, which represents a versatile intermediate for target directed synthesis.