Using COCCBr, O=C(O)c1cc(CO)nn1Cc1cc(-c2ccc(Cl)s2)on1 to produce COCCOCc1cc(C(=O)O)n(Cc2cc(-c3ccc(Cl)s3)on2)n1, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.