Electrophilic Carboxamidation of Ferrocenes with Isocyanates

Abstract

Ferrocenes undergo one-step carboxamidation by reaction with isocyanates in CFSOH 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.

Superelectrophiles in Synthesis: Preparation of Aromatic Imides

“…The metalated ortho -position may then be reacted with an electrophilic or nucleophilic reagent, depending on the nature of the coordinating metal. Recently, we reported the superacid-promoted reactions of ferrocenes with isocyanates . When ferrocene carboxylic acids are used, the corresponding ferrocenyl imides are formed in good yields (eq ).…”

“…Recently, we reported the superacid-promoted reactions of ferrocenes with isocyanates. 4 When ferrocene carboxylic acids are used, the corresponding ferrocenyl imides are formed in good yields (eq 2). This result suggested to us a potentially new method for directing incoming electrophilic groups to the ortho-position of an aromatic carboxylic acid, resulting in the temporary covalent attachment of an electrophile.…”