Recent Advance in Transition Metal‐Catalyzed Carboxylic Acid Guided B−H Functionalization of Carboranes
Qian Wang, Bifu Liu, Kejun Feng, A. Stephen K. Hashmi
Abstract
Abstract Carboranes, a three‐dimensional class of carbon‐boron molecular clusters with remarkable electronic, physical, chemical characteristics, have proved as useful building blocks in boron neutron capture therapy agents, supramolecular design, optoelectronics, nanomaterials and organometallic/coordination chemistry. Thus, various organic modifications of the B−H and C−H functionalities in carboranes have been developed. These methods with great success utilize directing groups, such as carboxylic acids, to achieve a selective B−H functionalization of carboranes. The carboxyl group can be easily introduced to carboranes and then be removed after reactions. On the other hand, assisted by the carboxyl group a highly regioselective electrophilic attack at the electron‐rich positions B(4) and B(5) of the cage generates five‐membered metallacyclic intermediates, which then undergo further transformation. In this review, we show that transition metal‐catalyzed decarboxylation cross coupling reactions offer an opportunity for the selective and direct B−H activation of carboranes. magnified image