Sterically directed functionalization of aromatic C-H bonds: selective borylation ortho to cyano groups in arenes and heterocycles.

摘要: Ir-catalyzed borylations of 4-substituted benzonitriles are described. In contrast to electrophilic aromatic substitutions and directed ortho metalations, C-H activation/borylation enables functionalization at the 2-position, adjacent cyano group, when 4-subsitutent is larger than cyano. When an excess borane reagent used, diborylation can be achieved with a single regioisomer being formed in certain cases. Extension sterically borylation cyano-substituted, five- six-membered ring heterocycles also reported.