Directing group controlled regioselective C–H borylation of 2-arylphenolic compounds at room temperature†

Regioselective borylation of (hetero)arenes under mild conditions is an appealing strategy for constructing boron-containing compounds, particularly considering their broad applications in organic synthesis, medicinal chemistry and material science. In this manuscript, we developed a Fe(OTf)₃-promoted, DG (directing group)-controlled, regioselective electrophilic C–H borylation of 2-arylphenolic compounds with BBr₃ at room temperature. C2′-borylation was dramatically accelerated by an LA-catalyst, affording DAOB (diaryloxaborin) with a broad substrate scope in moderate-to-excellent yields. The selective ortho-borylation was successfully achieved by introducing phenolic carbamate as a directing group to overcome the competing Fries rearrangement, giving desired 2-HAB ((2-hydroxyaryl)boronic acid) in good yields for most substrates.