Using COC=CC12CCC(c3ccc(Cl)cc3)(OC1)C(Br)C2, O=[Cr](=O)([O-])Cl to produce COC(=O)CC12CCC(c3ccc(Cl)cc3)(OC1)C(Br)C2, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.