Using COc1cc(Br)c2c(c1)C(C)(C)CCC2=O, C=C[Sn](CCCC)(CCCC)CCCC to produce C=Cc1cc(OC)cc2c1C(=O)CCC2(C)C, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.