Using COc1cc(CC2C(=O)C=CCC2(C)C)c(C(C)(C)C)c(O[SiH](C)C)c1Br, C[Mg]Br to produce COc1cc(C[C@@H]2C(=O)C[C@H](C)CC2(C)C)c(C(C)(C)C)c(O[SiH](C)C)c1Br, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.