Removal of Fluorine from and Introduction of Fluorine into Polyhalopyridines: An Exercise in Nucleophilic Hetarenic Substitution

✍ Scribed by Carla Bobbio; Thierry Rausis; Manfred Schlosser

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 152 KB
• Volume: 11
• Category: Article
• ISSN: 0947-6539
• DOI: 10.1002/chem.200400837

✦ Synopsis

Abstract

Starting from six industrially available fluorinated pyridines, an expedient access to all three tetrafluoropyridines (2–4), all six trifluoropyridines (5–10), and the five non‐commercial difluoropyridines (11–14 and 16) was developed. The methods employed for the selective removal of fluorine from polyfluoropyridines were the reduction by metals or complex hydrides and the site‐selective replacement by hydrazine followed by dehydrogenation–dediazotation or dehydrochlorination–dediazotation. To introduce an extra fluorine atom, a suitable precursor was metalated and chlorinated before being subjected to a chlorine/fluorine displacement process.