B–H Functionalization of o-Carborane
Carboranes, which are recognized as a type of three-dimensional kindred of benzene, have found a number of applications in boron neutron capture therapy (BNCT) as medication, in organometallic and coordination chemistry as novel ligands, and in supramolecular design and materials as building blocks. However, the distinctive structures of carboranes make their derivatization laborious, which results in a restricted application range. Therefore, it is highly required to develop new synthetic methods for the functionalization of carboranes. In general, cage boron functionalization is much more challenging than cage carbon functionalization because of not only its site-selectivity among ten cage B−H bonds over only three reactive sites in arene C−H activation but also its much lower reactivity of cage B−H over cage C−H bond. Herein, we present transition metal-catalyzed cyclative indenylation, dienylation, allenylation, amidation, acyloxyation, diacetoxylation, acylmethylation, pyrazolization, and triarylation of o-carboran
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