American Chemical Society
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Rerouting Nucleophilic Substitution from the 4-Position to the 2- or 6-Position of 2,4-Dihalopyridines and 2,4,6-Trihalopyridines: The Solution to a Long-Standing Problem

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journal contribution
posted on 2005-01-06, 00:00 authored by Manfred Schlosser, Thierry Rausis, Carla Bobbio
2,4-Difluoro-, 2,4,6-trifluoro-, and 2,3,4,6-tetrafluoropyridine undergo nucleophilic substitution preferentially if not exclusively at the 4-position. However, after the introduction of a trialkylsilyl group at C-3 or C-5, the halogen at the 6-(2-)position is displaced selectively. This synthetically valuable regiocontrol can also be realized with other halopyridines such as 2,4-dichloro- and 2,4,6-trichloropyridine.