Using CSc1nc2c(Br)cccc2c(=O)n1C, C=C(OCC)[Sn](CCCC)(CCCC)CCCC to produce CSc1nc2c(C(C)=O)cccc2c(=O)n1C, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.