The preparation of 27 isomers of chiral hexahalogeno-4,4'-bipyridines by means of two complementary methods is described. The first one is convergent and based on the LDA-induced 4,4'-dimerization of trihalopyridines, whereas the second method is divergent and achieved through regioselective halogenation reactions of 4,4'-bipyridine-2,2'-diones. Iodine in 2,2' -positions of the 4,4'bipyridines was introduced by a copper -catalyzed Finkelstein reaction (Buchwald procedure) performed on 2,2'-dibromo derivatives. Selected compounds of this new family of atropisomeric 4,4'-bipyridines were enantioseparated by high performance liquid chromatography on chiral stationary phases, and the absolute configurations of the separated enantiomers were assigned by using X-ray diffraction analysis. The latter revealed that various halogen bond types are responsible for crystal cohesion.
|Titolo:||Chiral Hexahalogenated 4,4 '-Bipyridines|
|Data di pubblicazione:||2016|
|Appare nelle tipologie:||2.1 Articolo su rivista |
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|2016 JOC.pdf||Chiral Hexahalogenated 4,4′-Bipyridines||Documento in Post-print||Accesso chiuso-personale||Riservato|