Using COCCBr, Cc1nc(NC(=O)C2C(C)(C)C2(C)C)sc1Cl to produce COCCn1c(C)c(Cl)sc1=NC(=O)C1C(C)(C)C1(C)C, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.