Depending on the thermolytic conditions, dicobalthexacarbonyl-complexed enynes underwent cyclizations to provide different carbocyclic frameworks. Bicyclopentanones were formed from enyne-Co2 (CO) 6 complexes, or from enynes that were treated with Co2 (CO) 8, or more effectively, with Co4 (CO) 12 in an alcoholic solvent under a H2 or N2 atmosphere. This transformation proceeded via a sequential cyclocarbonylation and 1, 4- ...