514798-04-0Relevant articles and documents
Creating structural manifolds from a common precursor: Basicity gradient-driven isomerization of halopyridines
Schlosser, Manfred,Bobbio, Carla
, p. 4174 - 4180 (2007/10/03)
5-Chloro-2,3-difluoropyridine, an intermediate in the manufacturing process of an industrial pesticide, can be hydrolyzed to 5-chloro-3-fluoro-2H-pyridinone and the latter converted into 2,5-dichloro-3-fluoropyridine (1a), 2-bromo-5-chloro-3-fluoropyridine (1b), 5-chloro-3-fluoro-2-iodopyridine (1c) and 3-chloro-5-fluoropyridine (1d). Consecutive treatment of these four substrates with lithium diisopropylamide and carbon dioxide or lithium diisopropylamide and iodine affords the corresponding 4-pyridinecarboxylic acids 2 and 4-iodopyridines 3, respectively. Amide-promoted deprotonation of such 4-iodopyridines 3 triggers an isomerization in which lithium and iodine change places. The resulting species can be trapped with carbon dioxide to give the acids 5a-c or neutralized to give the halopyridines 4a-c. The iodopyridines 4a and 4b can be converted into the acids 6a and 6b, the latter product leading also to the congeners 6c and 6d. The diiodopyridine 4c provides an entry to the halopyridine 4d, which at the same time may act as the precursor to the acid 5d, the acid 7 or the bisacid 8. Finally, the acid 9 is accessible from either one of the 5-chloro-3-fluoro-2-halopyridines 1b and 1c. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2002).
