A selective catalytic meta sulfonation of 2-phenylpyridines was found to occur in the presence of (arene)ruthenium(II) complexes upon reaction with sulfonyl chlorides. The 2-pyridyl group facilitates the formation of a stable Ru-C(aryl) sigma bond that induces a strong para-directing effect. Electrophilic aromatic substitution proceeds with the sulfonyl chloride to furnish a sulfone at the position meta to the chelating group. This new catalytic process offers access to atypical regioselectivity for reactions involving chelation-assisted cyclometalation.
Saidi, O., Marafie, J., Ledger, A. E. W., Liu, P. M., Mahon, M. F., Kociok-Kohn, G., ... Frost, C. G. (2011). Ruthenium-catalyzed meta sulfonation of 2-phenylpyridines. Journal of the American Chemical Society, 133(48), 19298-19301. https://doi.org/10.1021/ja208286b