A chiral polyhalogenated 4,4′-bipyridine derivative is described allowing an easy access to a new family of chiral 4,4′-bipyridines by site-selective cross-coupling reactions. The absoluteconfigurations of all the HPLC separated enantiomers were determined by X-ray diffraction and electronic circular dichroism coupled with time-dependent density functional theory calculations.
Coordinationpolymers (CP) assembled from 3,3′,5,5′-tetrasubstituted 4,4′-bipyridines and silver salts have been prepared and characterized by X-ray diffraction. Silver-CPs based on infinite Ag–bipyridine chains were obtained where one or two halogen atoms strongly interacted with Ag. A homochiral MOF was also prepared using the enantiopure 3,3′-dibromo-5,5′-bis(4-methoxyphenyl)-4,4′-bipyridine as
Synthesis of Polyhalogenated 4,4′-Bipyridines via a Simple Dimerization Procedure
作者:Mohamed Abboud、Victor Mamane、Emmanuel Aubert、Claude Lecomte、Yves Fort
DOI:10.1021/jo100152e
日期:2010.5.21
Polyhalogenated 4,4'-bipyridines were conveniently synthesized in a single step starting from dihalo-pyridines. A mechanism was proposed on the basis of experiments performed with 2-chloro-5-bromopyridine I a. 2-Chloro-4-lithio-5-bromopyridine A1 was produced via ortholithiation of la by using either LDA or t-BuLi bases. When LDA was used, chiller 3a containing two chlorines and two bromine atoms was formed predominantly accompanied by several byproducts whose structure and mechanism of formation are discussed. In the case of t-BuLi, although the major product was 2-chloropyridine 7, a new pyridone product 8 was formed that is probably the result of the dihydropyridine intermediate hydrolysis. The dimerization procedure involving LDA was employed to prepare a large number of halogenated 4,4'-bipyridines in moderate to good yields. In some specific cases, halogenated 3,4' and 2,4'-bipyridines were obtained in lower yields and their structures were unambiguously assigned by X-ray diffraction analysis.