['C#CCN', 'Cc1nc2ccc(Cl)cc2cc1C=O', 'C#CC', 'Cc1nc2ccc(Cl)cc2cc1C(N)=O', 'C#CCNC=O', 'Cc1ccc2cc(Cl)ccc2n1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccc2ncccc2c1.