Cobalt-catalyzed, directed arylation of C-H bonds in N-aryl pyrazoles.

We report a method for directed ortho-arylation of N-aryl pyrazoles with arylboronic acids. Reactions proceeded in the presence of a Co(hfacac)2 catalyst, CeSO4 oxidant, and HFIP solvent. Functionalities such as nitro, ester, bromo, and ketone groups were compatible with the reaction conditions. Using heterocycles including thiophene and carbazole was also feasible.