Using BrCCCBr, CCCc1c(O)ccc2c1OC(C)(C(=O)OC)CC2 to produce CCCc1c(OCCCBr)ccc2c1OC(C)(C(=O)OC)CC2, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.