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The low yield of the Ullmann reaction is not usually caused by a single factor, but rather is the result of the combined effects of several aspects such as substrate activity, catalytic system, reaction conditions, and product purification. Systematic troubleshooting and optimization can be carried out from these aspects to precisely control parameters such as temperature, base, and solvent, which can inhibit side reactions and increase the yield. It is recommended that you start by changing the catalytic system (adding appropriate ligands) and strictly removing water and oxygen. These two steps usually bring the most significant improvement.
