Using Brc1ccncc1, CSc1nccc(-n2cnc3cc([Sn](C)(C)C)ccc32)n1 to produce CSc1nccc(-n2cnc3cc(-c4ccncc4)ccc32)n1, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.