Double cyclization via intramolecular coupling between cyclohexadiene-Fe(CO)3 complexes and pendant conjugated dienes.

Intramolecular double cyclization between a cyclohexadiene-Fe(CO)3 complex and a pendant diene yielded a tricyclic molecule containing a spirocenter, with defined relative stereochemistry of four contiguous carbon centers. The nature of the substituent on the pendant diene moiety has a significant effect on the yield: an ester group leads to lower yield. The product has a conjugated cyclohexadiene or methoxycyclohexadiene system; the latter was converted to an enone.