Iridium-Catalyzed C-H Borylation of CF₃-Substituted Pyridines

Iridium-catalyzed C-H borylation of CF₃-substituted pyridines is described in this paper. The boronic ester group can be installed on the α, β, or γ position of pyridine by an appropriate substitution pattern. Sterically governed regioselectivity provides convenient access to a variety of CF₃-substituted pyridylboronic esters. These catalytic C-H borylation reactions were carried out neatly without the use of any solvent. Several functional groups, such as halo, ester, alkoxy, amino, etc., are compatible with this methodology. These pyridylboronic esters are amenable to column chromatography and the products were isolated in good to excellent yields. α-Borylated pyridines, although isolated in good yields, do not have a long shelf life. The boronic ester derivatives of these CF₃-substituted pyridines can serve as useful precursors in the synthesis regime.