On the reaction between 3-bromo-2-nitrobenzo[b]thiophene and some amines: a novel aromatic nucleophilic substitution with rearrangement

3-Bromo-2-nitrobenzo[b]thiophene reacted with some amines in N,N-dimethylformamide giving, together with the expected N-substituted 3-amino-2-nitrobenzo[b]thiophenes 3 deriving from aromatic nucleophilic substitution, their isomers 4, whose unexpected structure of N-substituted 2-amino-3-nitrobenzo[b]thiophenes has been determined by means of spectroscopic techniques. As 2-bromo-3-nitrobenzo[b]thiophene gave tars with nucleophiles, the observed reaction could be of use for the synthesis of 4. Some hypotheses on the mechanism of formation of 3 and 4 are suggested.