Selective Borylation of [4]Helicene

The Ir-catalyzed borylation of [4] helicene under different reaction conditions was studied for the first time. The results indicate that monoborylation proceeds to give a mixture of 2- and 3-borylated products in good yields (up to 74 % isolated yield). It was possible to shift the selectivity in favor of the 3-borylated product by using sterically demanding ligands. The monoborylated [4] helicenes were further arylated by using a Suzuki-Miyaura cross-coupling or oxidized to the corresponding phenols in very good yields.