The origins of the dichotomy of amine effects in aromatic nucleophilic substitution reactions

Abstract

The reactions of 2-trifluoromethyl- and 2-cyano-4-nitrofluoro-benzenes with piperidine, n-butylamine and benzylamine in acetonitrile are not base catalysed, but the reactions with morpholine are catalysed. In benzene, the reactions of the 2-cyano-substrate with all four nucleophiles are catalysed. In acetonitrile, the reaction of 2-cyano-4-nitrophenyl phenyl ether with piperidine is base catalysed, whereas that of n-butylamine is not. In benzene, the reactions of this substrate with both nucleophiles are catalysed. The reasons why the reactions of secondary amines in aromatic nucleophilic substitution reactions are more prone to base catalysis than the corresponding reactions with primary amines of the same basicity are discussed.