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.