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Palladium-Catalyzed Directed Halogenation of Bipyridine N‑Oxides
journal contribution
posted on 2017-05-24, 00:29 authored by Sina P. Zucker, Friedrich Wossidlo, Manuela Weber, Dieter Lentz, C. Christoph TzschuckeThe
palladium-catalyzed directed C–H halogenation of bipyridine N-oxides was investigated. Using NCS or NBS (N-chloro- or N-bromosuccinimide) and 5 mol % Pd(OAc)2 in chlorobenzene (0.10 molar) at 110 °C, pyridine-directed
functionalization took place and 3-chloro- or 3-bromobipyridine N-oxides were obtained in high yields. The reaction is sensitive
to steric hindrance by 4- and 6′-substituents. Only in the
latter case, where coordination of palladium by the pyridine is hindered,
3′-halogenation directed by the N-oxide function
was observed. The halogenated products were deoxygenated by PCl3 or PBr3.