Rhodium(I)-catalyzed [3+2+2]-cyclization of alkenyl Fischer carbene complexes with methyl buta-2,3-dienoate

A variety of alkenyl chromium Fischer carbene complexes react with methyl buta-2,3-dienoate in the presence of a rhodium catalyst to afford substituted cycloheptene derivatives 7, along with minor amounts of cyclopentene derivatives 6. Through this [3+2+2]-cyclization two allene units and one alkenyl carbene ligand are assembled in a selective manner.