Triarylboranes Bearing (ortho-Carboran-1-yl)aryl Groups for Catalytic Hydrogenation with Pure or Crude H2

Structural diversification of triarylboranes with unexplored substituents can expand their applications in organic synthesis. We synthesized triarylboranes that bear 2,6-F2-4-(o-carboran-1-yl)phenyl (Ar) groups and evaluated their Lewis acidity and catalytic activity. B(2,6-Cl2C6H3)Ar2 exhibited high activity in the hydrogenation of N-heteroaromatics using pure (TON = up to 3960) and crude H2 (TON = up to 2400). This borane also catalyzes the dehydrogenation of tetrahydroquinoline and the reductive alkylation of aliphatic amino-acid esters with H2, demonstrating the first catalytic applications of carboranyl-substituted triarylboranes in diverse molecular transformations.