Neat Formic Acid: An Excellent N-Formylating Agent for Carbazoles, 3-Alkylindoles, Diphenylamine and Moderately Weak Nucleophilic Anilines.

Abstract Neat formic acid alone efficiently N-formylates carbazoles, 3-alkylindoles, diphenylamine and even moderately weak nucleophilic anilines to furnish the corresponding N-formyl derivatives in 72--87% yields.