Generation and reaction of heteroaromatic zirconocene: synthetic application to polycyclic heterocycles

Heteroaromatic zirconocene intermediates were generated by the reaction of ‘Cp2Zr’ with alkoxymethyl-(TMS-ethynyl)-indole, -benzofuran or -benzothiophene derivatives under mild conditions in moderate to good yields. Copper-catalyzed C–C bond formation of the zirconocene intermediate with allylic halides gave allylation products, which were transformed into heterocyclic dienes through enyne metathesis. Preliminary Diels–Alder reaction of the dienes with DMAD showed notable site selectivity.