Consecutive enolate addition/cyclization of Fischer enynyl carbene complexes: facile access to cyclopentenoids

Functionalized cyclopentenoids were synthesized from Fischer enynyl carbene complexes by a sequence that involves regioselective nucleophilic 1,4-addition of enolates and anionic electrocyclization of the resulting intermediate. Moreover, the method is effective for the C2–C3 annulation of heterocyclic rings like benzofuran and indole. The methoxycyclopentadiene thus obtained can be hydrolyzed to substituted cyclopentenones, which are not straightforwardly accessible by other methods.