Using CC=Cc1ccc(-c2ccc(-c3ccc(OCCC)c(F)c3F)cc2)[se]1 to produce CCCOc1ccc(-c2ccc(-c3ccc(CCC)[se]3)cc2)c(F)c1F, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.