Troponeiron tricarbonyl, 2-methyltroponeiron tricarbonyl, and 4-methyltroponeiron tricarbonyl are converted to fluxional tropyliumiron tricarbonyl salts by treatment with either trimethylsilyl or di-n-butylboron triflate. These pentadienyliron cations react with (η 1 -allyl)-, (η 1 -propargyl)-, and (η 1 -allenyl)Fp complexes [Fp=C 5 H 5 Fe(CO) 2 ] to give ketohydroazulene cycloadducts derived, in each reaction, from a single tautomeric tropyllium cation. The further reaction of two such cycloadducts with lithium dimethyl cuprate gave tricyclic ketones, through a sequence depicted as involving initial formation of an anionic acyliron complex, followed by migratory insertion and an intramolecular aldol condensation