Nucleophilic aromatic substitution reactions promoted by aryl and heteroaryl amine nitranions

The nucleophilic substitution reaction of chlorine in 4-chloronitrobenzene by N-anions from aryl and heteroarylamines 1-4, to give the corresponding diarylamines, has been studied in solvents of different polarity (toluene and DMSO). The reactivity of these nitranions is found to be two orders of magnitude higher in DMSO. Such a difference is attributed to the different reacting species lion pairs and free ions in toluene and DMSO, respectively). The beta(Nu) values obtained (0.31 and 0.26), very similar and relatively low, suggest a moderate extent of charge transfer from nucleophile to substrate in the transition state of both systems.