Rhodium(I)-Catalyzed Regioselective Ring- Expanding Rearrangement of Allenylcyclopropanes into Methylenecyclopentenes

A highly regioselective C–C bond cleavage of the cyclopropane rings occurs in substituted allenylcyclopropanes in the presence of cationic rhodium(I ) complexes. Thus, ring expansion of readily accessible allenylcyclopropanes can be achieved to give 3-methylenecyclopentenes, which could have applications as multifunctional synthetic building blocks.