Schlosser, ManfredBobbio, CarlaRausis, Thierry2006-03-032006-03-032006-03-03200510.1021/jo047962zhttps://infoscience.epfl.ch/handle/20.500.14299/227045WOS:00022792820000965842,4-Difluoropyridine, 2,4-dichloropyridine, 2,4,6-trifluoropyridine, 2,4,6-trichloropyridine and 2,3,4,6-tetrafluoropyridine react with std. nucleophiles exclusively at the 4-position under halogen displacement. However, the regioselectivity can be completely reversed if a trialkylsilyl group is introduced in the 5-position of the 2,4-dihalopyridines or in the 3-position of the 2,4,6-trihalopyridines or 2,3,4,6-tetrahalopyridine. Then only the halogen most remote from the bulky silyl unit (at the 2-position in the case of the 2,4-halopyridines, at the 6-position with the other substrates) gets involved in the exchange process. After removal of the silyl protective group the nucleophile is invariably found to occupy the nitrogen-neighboring position. [on SciFinder (R)]Substitution reaction (regioselectivearom.; regiochem. flexible substitutions of di-tri-and tetrahalopyridines)substitution regioselective polyhalopyridinetext::journal::journal article::research article