Promoters for the (alkyne)hexacarbonyldicobalt-based cyclopentenone synthesis

Dimethyl sulfoxide and a variety of other highly polar solvents are shown to promote both inter- and intramolecular cyclopentenone formation from alkenes and (alkyne)hexacarbonyldicobalt complexes. Their use leads to significant changes in both regio- and stereoselectivity when compared to other reaction conditions. 12 refs., 5 tabs.