Using O=C1C=C(O)C(=O)c2ccccc21, CC(C)(C)OC(=O)CBr to produce CC(C)(C)OC(=O)COC1=CC(=O)c2ccccc2C1=O, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.