Metal-Free, Base-Promoted, Tandem Pericyclic Reaction: A One-Pot Approach for Cycloheptane-Annelated Chromones from gamma-Alkynyl-1,3-Diketones

A microwave-assisted, base-promoted, tandem cyclization reaction strategy has been developed for the synthesis of cyclohepta[b]chromones and spiro cyclohepta[b]chromones. Readily accessible gamma-alkynyl-1,3-diketones undergo intramolecular cyclization and 7-endo-trig carbocyclization to afford various cycloheptane-annelated chromones in one-pot reactions. This metal-free protocol also led to the generation of polycyclic ring with a new C-C bond and a new C-O bond.