Using O=P(Cl)(Cl)Cl, CCOC(=O)C1C(=O)CC(=O)CC1c1ccc(C)cc1 to produce CCOC(=O)C1C(=O)C=C(Cl)CC1c1ccc(C)cc1, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.