Pd-Catalyzed Hydroboration of Vinylarenes with B 2 pin 2 .

A palladium(II)-catalyzed Markovnikov hydroboration of aryl alkenes with readily available bis(pinacolato)diboron (B 2 pin 2 ) is reported. The reaction proceeded with low catalyst loading (0.5 mol %) in the absence of N - or P -containing ligands, affording the products in up to 90% yield. Trifluoracetic acid serves as the hydrogen source, enabling the synthesis of benzylic boronic esters under mild ambient conditions.