Using COC(=O)C(O)Cn1c2ccc(Br)cc2c2cc(Br)ccc21 to produce O=C(O)C(O)Cn1c2ccc(Br)cc2c2cc(Br)ccc21, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.