Pushing the Ir-Catalyzed C-H Polyborylation of Aromatic Compounds to Maximum Capacity by Exploiting Reversibility

Small amounts of base (e.g.,.10% potassium t-butoxide or sodium methoxide) have been found to promote equilibration of the kinetically favored products from Ir-catalyzed C-H polyborylations of aromatic compounds. In the presence of excess borylating agent, bis(pinacolato)diborane (B(2)pin(2)), repetitive deborylation/reborylations reposition the Bpin substituents until a pattern that accommodates the maximum number of Bpin substituents is achieved. A high-yield, one-step synthesis of 1,3,5,7,9-pentakis(Bpin)corannulene is reported that illustrates this useful extension of the Ir-catalyzed borylation reaction.