['CCC', 'N#CCNCn1ncc2ccccc2c1=O', 'CC#N', 'CCCNCn1ncc2ccccc2c1=O', 'CCCN(C)CC#N', 'O=c1[nH]ncc2ccccc12']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=c1[nH]ncc2ccccc12.