Synthesis and Stabilities of 3-Borylated Indoles

We report herein that 3-pinacol boronic esters undergo facile protodeborylation in the presence of palladium catalysts and base, and this contributes significantly to the generation of nonborylated indole byproducts in the B2Pin2-mediated palladium-catalysed borylative cyclization of 2-alkynylanilides. Suginome’s reagent provides an alternative method to access 3-borylated indoles as these compounds are less susceptible to protodeborylation.