Using O=C(O)Cc1cccc2c(=O)cc(C3=CCCCC3)oc12, CO to produce COC(=O)Cc1cccc2c(=O)cc(C3=CCCCC3)oc12, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.