Catalysis by amine salts of some aromatic nucleophilic substitution reactions

Abstract

The reaction of 1-chloro-2,4-dinitrobenzene with aniline in acetonitrile is catalysed by R₄NY where Y is Cl, Br, I, or toluene-p-sulphonate, but not by 1,4-diazabicyclo [2.2.2.] octane (DABCO). When the nucleophile is changed to n-butylamine or morpholine, addition of tetraethylammonium chloride has only a small effect; the reactions of all three nucleophiles are not catalysed by tetraethylammonium perchlorate. The reaction of 1-fluoro-2,4-dinitrobenzene with aniline is strongly catalysed by tetraethylammonium chloride, to a lesser extent by the bromide and toluene-p-sulphonate and also by trimethylamine hydrochloride, but not by tetraethylammonium perchlorate. The reactions of morpholine with 1-fluoro-2,4-dinitrobenzene and piperidine with 2,4-dinitrophenyl phenyl ether are not catalysed by amine salts. The results are consistent with the formation and stabilisation of the intermediate formed in aromatic nucleophilic substitution reactions by the anions of the salts, when the nucleophile is aniline.