Using O=C(O)C1(C(=O)O)CC=C(c2c(-c3ccccc3)[nH]c3ccccc23)CC1 to produce O=C(O)C1(C(=O)O)CCC(c2c(-c3ccccc3)[nH]c3ccccc23)CC1, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.