Iodine-mediated synthesis of benzo[ a ]fluorenones from yne-enones.

The chalcones derived from o -alkynylacetophenones and aromatic aldehydes (yne-enones) when heated under reflux with iodine in acetic acid gave a range of benzo[ a ]fluorenone derivatives in moderate to good yields. The transformation involves the formation of a vinyl indenone intermediate through regioselective alkyne hydration and intramolecular aldol condensation followed by electrocyclic ring closure and aromatization.