Synthesis of polyhalogenated 4,4'-bipyridines via a simple dimerization procedure.
Polyhalogenated 4,4'-bipyridines were conveniently synthesized in a single step starting from dihalopyridines. A mechanism was proposed on the basis of experiments performed with 2-chloro-5-bromopyridine 1a. 2-Chloro-4-lithio-5-bromopyridine A1 was produced via ortholithiation of 1a by using either LDA or t-BuLi bases. When LDA was used, dimer 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.
Abboud
Mohamed
M
Equipe Synthèse Organométallique et Réactivité (SOR), Laboratoire SRSMC, UMR CNRS-UHP 7565 Institut Jean Barriol, Nancy Université, BP 70239, Bd des Aiguillettes, 54506 Vandoeuvre-les-Nancy, France.
Mamane
Victor
V
Aubert
Emmanuel
E
Lecomte
Claude
C
Fort
Yves
Y
D019281:Dimerization; D015394:Molecular Structure; D011108:Polymers / Q000138:chemical synthesis* / Q000737:chemistry; D011725:Pyridines / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
D011108:Polymers; D011725:Pyridines; C034306:4,4'-bipyridyl