You are a chemist. Now you are given a product molecule. Please predict the the reactant molecules of the reaction.
The reaction equation has the following format:
```
reactant1.reactant2. ... .reactantN>>product
```
Your task is to predict the structure representation of the reactant molecule. We provide the SMILES of the reactants.
system
Could you tell which reactants might have been used to generate the following product? <molecule_2d>
user
BrBr.O=C(O)c1ccc(Cl)cc1O
assistant