Nucleophilic aromatic substitutions on 4,5-dicyanopyridazine. Pyrrole and indole systems as carbon nucleophiles

4,5-Dicyanopyridazine was found to react with pyrrole and indole counterparts not only as heterocyclic azadiene in inverse electron-demand Hetero Diels–Alder reactions, as previously evidenced, but even as a very reactive heterocyclic electrophile at C-4 carbon, in formal S_NAr2 processes where a CN group acts as leaving group. In particular, operating in acetic acid as solvent, nucleophilic addition–elimination sequences allowed a facile access to pyrrolyl- and indolylpyridazines, through the corresponding 1,4-dihydropyridazine adducts.