['O=[N+]([O-])c1ccccc1', 'c1ccc(-c2nc[nH]n2)cc1', 'c1ccccc1', 'O=[N+]([O-])c1ccccc1-c1ncn[nH]1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccc(-c2n[nH]c(-c3ccccc3)n2)cc1.