Cyclization of 5-alkynones with chromium alkylidene equivalents generated in situ from gem-dichromiomethanes

A rare example of cyclization with alkynylketones, which possess non-polar alkynyl and less electrophilic polar keto carbonyl groups, was demonstrated. The key to promoting carbene/alkyne metathesis followed by alkylidenation with pendant C=O double bonds was the Schrock-type nucleophilic reactivity of the generated chromium carbene equivalents from readily available diiodomethanes and CrCl2 by simple heating.