Using COC(=O)c1snc(-c2ccc(Cl)c(Cl)c2)c1C(=O)OC to produce O=C(O)c1snc(-c2ccc(Cl)c(Cl)c2)c1C(=O)O, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.