Hydroboration of arynes with N-heterocyclic carbene boranes

Arynes were generated in situ from ortho-silyl aryl triflates and fluoride ions in the presence of stable N-heterocyclic carbene boranes (NHC-BH3). Spontaneous hydroboration ensued to provide stable B-aryl-substituted NHC-boranes (NHC-BH2Ar). The reaction shows good scope in terms of both the NHC-borane and aryne components and provides direct access to mono-and disubstituted NHC-boranes. The formation of unusual ortho regioisomers in the hydroboration of arynes with an electron-withdrawing group supports a hydroboration process with hydride-transfer character