One-pot ipso-hydroxylation and ortho-/para-halogenation of (hetero)arylboronic acids under tungsten catalysis

A concise preparation of halophenols directly from (hetero)aryl boronic acids/esters via tungstate-catalyzed one-pot ipso-hydroxylation bromination and iodination has been developed in the current work. A broad substrate scope, good functional group tolerance and formal synthesis of several bioactive molecules have been achieved. Utilizing environmentally and costlyfriendly reagents (NaBr, NaI, H2O2, weak organic acids) and green solvents (EtOH/H2O), this reaction can work at room temperature in the open air. It was also found to be dependent on pH, and to work smoothly with weak/moderate-strength organic acids without a tungsten catalyst. Compared to strategies developed in previous research with the same starting materials, this one-pot strategy was more step-economically friendly. Notably, the (hetero)aryl boronic acid played an interesting “one stone, two birds” role: as a starting material and promoter of the reaction by releasing B(OH)3 as a co-catalyst. B(OH)3 has normally been treated as waste in ipso-hydroxylation, but we expect the “turn waste into wealth (catalyst)” approach of the current work to inspire related research.