Using CCOC(=O)C(C1CCc2cc(Br)ccc21)P(=O)(OCC)OCC, O=C([O-])[O-] to produce C=C(C(=O)OCC)C1CCc2cc(Br)ccc21, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.