Ir-catalyzed cascade dehydrogenative CH/BH and BH/OH cross-coupling of carboranyl carboxylic acid with readily available benzoic acid has been achieved,leading to the facile synthesis of previously unavailable carborano-coumarin in a simple one-pot process.Two cage B-H,one aryl C-H and one O-H bonds are activated to construct efficiently new B-C and B-O bonds.The cascade cyclization can stop at the first B-H/C-H cross-coupling step by tuning the reaction conditions,resulting in a series of α-carboranyl benzoic acid and aryl carborane derivatives.Control experiments indicate that B-H/C-H dehydrocoupling proceeds preferentially over B-H/O-H dehydrocoupling,and both directing groups and oxidants are crucial for this reaction.An iridium(V) intermediate is proposed to be involved in the catalytic cycle.