Chemoselective borylation of bromoiodoarene in continuous flow: synthesis of bromoarylboronic acids

The chemoselective borylation of bromoiodoarenes under continuous flow conditions is described. Bromoarylboronic acids were synthesized in high yields using iPrMgCl•LiCl as the halogen-metal exchange reagent, with 5.7–86 s residence time at room temperature. The process is compatible with a variety of functional groups, including carbanion-reactive moieties, enabling post-product functionalization. A gram-scale reaction, including a continuous-flow work-up, afforded the desired product in a highly efficient manner. Successful telescoping with a Suzuki coupling has also been performed, converting 1-bromo-3-iodobenzene to 3-bromo-1,1′-biphenyl on a gram-scale in a good yield.