[{"from": "human", "value": "Given this chemical reaction, what are some reagents that could have been used? [Br][Br].[C][C][O][C][=Branch1][C][=O][C][C][Branch1][C][C][=O]>>[C][C][O][C][=Branch1][C][=O][C][C][=Branch1][C][=O][C][Br]"}, {"from": "gpt", "value": "[C][C][=Branch1][C][=O][O]"}]