['Clc1cccc(Cl)c1Cl', 'Cc1nc(/C=C/C=O)c2ccccn12', 'Cc1nc(C)n2ccccc12', 'CC(=O)c1ccc(Cl)c(Cl)c1Cl']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C(/C=C/c1ncn2ccccc12)c1ccccc1.