Regioselective Nucleophilic Alkylation/Arylation of B–H Bonds in o‑Carboranes: An Alternative Method for Selective Cage Boron Functionalization

A new protocol for regioselective nucleophilic cage B–H substitution in o-carboranes has been proposed that is complementary to the strategies of transition metal catalysis and electrophilic substitution. Magnesium-mediated site-selective nucleophilic cage B­(3,6)–H and B(9)–H substitution reactions of o-carboranes give a series of B­(3,6)-dialkylated and B(9)-alkylated/arylated o-carboranes in high yields. Both steric and electronic factors of cage C substituents play crucial roles in controlling the site selectivity.