Regiodivergent Arylation of Pyridines via Zincke Intermediates

An arylation protocol for pyridines is described, via the ring‐opened Zincke intermediate. Treatment of pyridines with triflic anhydride and a secondary amine produces an azahexatriene species, which undergoes regioselective Pd‐catalyzed arylation at the putative C4 position. Recyclization then provides the pyridine products. Alternatively, metal‐free arylation with a diaryliodonium salt is selective for the pyridine meta‐position, affording a regiodivergent approach to pyridine biaryls from a common intermediate. Arylation of pyridines is possible through ring‐opened Zincke imines. A Pd‐catalyzed Heck‐type process is selective for the C4 position, while a metal‐free arylation using an iodonium salt addresses the C5‐position. Sequential triflation, arylation, and pyridine recyclization enables the process to be conducted in one pot, representing a new approach to valuable biaryl structures.