Copper-catalysed nucleophilic substitution of the type NHAr₂+ Ar′Br → NAr₂Ar′ occurred in dimethylacetamide between diphenylamine and o-bromonitrobenzene, giving NN-diphenyl-o-nitroaniline (ca. 50%), accompanied by nitrobenzene (up to 50%), a compound of probable structure o-NO₂·C₆H₄·NPh·C₆H₄·NPh₂(up to 3%), and only traces of 2,2′-dinitrobiphenyl. Methyl o-bromobenzoate was less reactive, and m- and p-bromonitrobenzene were unreactive. Heterogeneous copper catalysts (preferable Cu₂O) were much superior to homogeneous catalysts (CuHal) for this particular nucleophilic substitution.