Iridium‐Catalyzed Regioselective B(3)‐Alkenylation/B(3,6)‐Dialkenylation of o‐Carboranes by Direct B−H Activation

Abstract

Iridium‐catalyzed formal alkyne hydroboration with cage B−H of o‐carborane has been achieved, leading to the controlled synthesis of a series of 3,6‐[trans‐(AlkCH=CH)]2‐o‐carboranes (Alk=alkyl), 3‐cis‐(ArCH=CH)‐o‐carboranes (Ar=aryl), and 3‐cis‐(ArCH=CH)‐6‐trans‐(AlkCH=CH)‐o‐carboranes in high yields with excellent regio‐ and very good cis–trans selectivity. The most electron‐deficient B(3,6)−H vertices favor oxidative addition on electron‐rich metal centers, which is responsible for the regioselectivity. On the other hand, the configuration of the resultant olefinic units is dominated by alkyne substituents. Alkyl groups lead to a trans‐configuration whereas bulky aryl substitutions result in cis‐configuration.

A Strategy for Selective Catalytic B–H Functionalization of o-Carboranes

“…In addition to the aforementioned examples, catalytic B­(3,6)-oxygenation, -arylation, and -alkenylation have also been reported.…”

Iridium Catalyzed Selective Arylation of B(3)‐H Bond of o‐Carborane via B−H/C−H Activation

“…Based on the experimental results and documented iridium catalyzed B(3)‐H activation, [7a,b,d,11] a plausible mechanism was proposed in Scheme 3. Firstly, the Cp*IrX 2 should be formed via ligand exchange.…”

Predicting Dinitrogen Activation by Carborane-Based Frustrated Lewis Pairs

“…Specifically, the chemistry of o -carboranes has been extensively expanded to diverse areas, including organometallic chemistry, − materials science, , energy storage, optoelectronics, , medicine, and so forth. Therefore, the B–H and C–H functionalization of o -carboranes has attracted enormous interest, ,− such as borylation, − alkylation, , alkenylation, , alkynylation, arylation, , halogenation, , and so on. Consequently, a large number of carborane derivatives have been synthesized and successfully utilized in small-molecule activation, such as NH 3 , CO, H 2 O, H 2 , CO 2 , and so on.…”