Boryl-Directed, Ir-Catalyzed C(sp)-H Borylation of Alkylboronic Acids Leading to Site-Selective Synthesis of Polyborylalkanes.

Pyrazolylaniline serves as a temporary directing group attached to the boron atom of alkylboronic acids in Ir-catalyzed C(sp)-H borylation. The reaction takes place at α-, β-, and γ-C-H bonds, giving polyborylated products including di-, tri-, tetra-, and even pentaborylalkanes. α-C-H borylation was generally found to be the preferred reaction of primary alkylboronic acid derivatives, whereas β- or γ-borylation also occurred if β- or γ-C-H bonds were located on the methyl group.