['O=[N+]([O-])c1ccccc1', 'Cc1ccc(-c2cnn[nH]2)cc1', 'Cc1ccccc1', 'O=[N+]([O-])c1ccc(-n2ccnn2)cc1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccc(-c2cnnn2-c2ccccc2)cc1.