['C#CCN', 'O=CCCn1cnc2ccc(Br)cc2c1=O', 'C#CC', 'NC(=O)CCn1cnc2ccc(Br)cc2c1=O', 'C#CCNC(=O)CC', 'O=c1[nH]cnc2ccc(Br)cc12']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=c1[nH]cnc2ccccc12.