Iridium-catalyzed hydroboration of alkenes with pinacolborane

Hydroboration of terminal and internal alkenes with pinacolborane (1.2 equiv) was carried out at room temperature in the presence of an iridium(I) catalyst (3 mol%). Addition of dppm (2 equiv) to [Ir(cod)Cl]₂ gave the best catalyst for hydroboration of aliphatic terminal and internal alkenes at room temperature, resulting in addition of the boron atom to the terminal carbon of 1-alkenes with more than 99% selectivities. On the other hand, a complex prepared from dppe (2 equiv) and [Ir(cod)Cl]₂ resulted in the best yields for vinylarenes such as styrene. These complexes exhibited higher levels of catalyst activity and selectivity than those of corresponding rhodium complexes.