Using CCOC(=O)c1oc2c(Cl)cc(Cl)c(O)c2c1C, O=C([O-])[O-] to produce CCOC(=O)c1oc2c(Cl)cc(Cl)c(OC)c2c1C, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.