Boryl-Directed, Ir-Catalyzed C(sp3)-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(sp3)-H borylation. The reaction takes place at α-, ß-, 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 ß- or γ-borylation also occurred if ß- or γ-C-H bonds were located on the methyl group.

Regioselective Synthesis of o-Benzenediboronic Acids via Ir-Catalyzed o-C-H Borylation Directed by a Pyrazolylaniline-Modified Boronyl Group.

Ir-catalyzed ortho-directed C-H borylation of pyrazolylaniline (PZA)-modified arylboronic acids with bis(pinacolate)diboron afforded o-benzenediboronic acids in which two boronyl groups are differentially modified by pinacol (PIN) and PZA. By using this borylation after nondirected Ir-catalyzed C-H borylation, o-benzenediboronic acids are conveniently synthesized from unfunctionalized arenes. The differentially modified o-benzenediboronic acids undergo selective oxidation and Suzuki-Miyaura cross-coupling at the PZA-modified boronyl groups, affording o-functionalized arylboronic acids selectively.