Vicarious Nucleophilic Substitution of hydrogen (VNS) offers a great potential for nucleophilic substitution of aromatic hydrogen with carbon, oxygen and nitrogen groups. Typical VNS consists of a reaction of nitroarenes with nucleophiles bearing a good leaving group at the nucleophilic center to furnish the corresponding
ortho-or
para-substituted nitroarenes. In this reaction, the leaving group connected with the nucleophile is eliminated from σ
H-adduct instead of unstable hydride anion. Thus, the leaving group acts as a
vicarious leaving group; hence, this reaction is called “
vicarious nucleophilic substitution of hydrogen” (VNS). Among the VNS reactions, VNS amination is of great importance as a direct introduction of an amino group (NH
2) into an aromatic ring to give aminonitroarenes. Sulfenamides, 4-amino-1, 2, 4-triazole, 1, 1, 1-trimethylhydrazinium iodide, hydroxylamine and
O-alkylhydroxylamine have been reported as VNS aminating agents so far. This review summarizes the VNS aminations by classifying into each aminating agents.
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