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Lithiation of Prochiral 2,2 `-Dichloro-5,5 `-dibromo-4,4 `-bipyridine as a Tool for the Synthesis of Chiral Polyhalogenated 4,4 `-Bipyridines

Abstract : Lithiation of the achiral tetrahalogenated 4,4'-bipyridine 1 with alkyllithiums was investigated. n-BuLi was found to induce either the chlorine-directed deprotolithiation reaction alone or with a concomitant halogen-lithium exchange furnishing after iodine trapping chiral 4,4'-bipyridines 2 and 6, respectively. The role of n-BuLi in the deprotolithiation process of 1 was elucidated on the basis of isolated secondary derivatives. After deprotolithiation, the lithiated species could be trapped by different electrophiles such as MeI, TMSCl, MeSSMe, R3SnCl (R = Me or n-Bu), and PPh2Cl. Moreover, 4,4'-bipyridine 2 was submitted to cross-coupling reactions (Suzuki and Sonogashira) which occurred selectively at the carbon-iodine bond. All compounds of this new family of atropisomeric 4,4'-bipyridines were separated by chiral HPLC (high-performance liquid chromatography), and the absolute configurations of obtained enantiomers were mainly assigned by XRD (X-ray diffraction) using anomalous dispersion.
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https://hal.univ-lorraine.fr/hal-01494097
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Submitted on : Wednesday, March 22, 2017 - 4:40:45 PM
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Victor Mamane, Emmanuel Aubert, Paola Peluso, Sergio Cossu. Lithiation of Prochiral 2,2 `-Dichloro-5,5 `-dibromo-4,4 `-bipyridine as a Tool for the Synthesis of Chiral Polyhalogenated 4,4 `-Bipyridines. Journal of Organic Chemistry, American Chemical Society, 2013, 78 (15), pp.7683-7689. ⟨10.1021/jo401255q⟩. ⟨hal-01494097⟩

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