Using C[Mg+], COC(=O)c1nc2c(s1)C(=O)COc1ccc(Br)cc1-2 to produce COC(=O)c1nc2c(s1)C(C)(O)COc1ccc(Br)cc1-2, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.