Rare Earth Solid Superacid Catalyzed Friedel–Crafts Acylation of Ferrocene

Electrophilic Carboxamidation of Ferrocenes with Isocyanates

Ferrocenes undergo one-step carboxamidation by reaction with isocyanates in CF₃SO₃H solution. The chemistry is most efficient in excess superacid, and it has been accomplished with aryl and aliphatic isocyanates. In conversions with ferrocene carboxylic acids, isocyanates provide imides in good yields. A mechanism for this conversion is suggested involving carbamic acid anhydride formation and subsequent intramolecular reaction at the substituted cyclopentadienyl ring.