Pd-Catalyzed Borylation\nin Water and Its Application\nto the Synthesis of Active Pharmaceutical Ingredient (API) Intermediates

An efficient catalytic borylation\nreaction of aryl bromides in\nwater based on Pd catalysis under micellar conditions is presented.\nThe peculiar combination of the proper Pd precursor with a Sphos ligand\nand a hindered lipophilic base ensures good yields in the synthesis\nof a wide range of boronic esters, even for heteroaryl derivatives\nwith a good purity profile. The method is specifically developed for\nthe <i>in situ</i> preparation of boronic esters that are\ndirectly converted into examples of relevant active pharmaceutical\ningredient intermediates through cross-coupling reactions or via oxidation\nto phenols.