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Mechanism of lithium diisopropylamide-mediated substitution of 2,6-difluoropyridine.

Journal of the American Chemical Society (2010-04-20)
Mihai S Viciu, Lekha Gupta, David B Collum
ZUSAMMENFASSUNG

Treatment of 2,6-difluoropyridine with lithium diisopropylamide in THF solution at -78 degrees C effects ortholithiation quantitatively. Warming the solution to 0 degrees C converts the aryllithium to 2-fluoro-6-(diisopropylamino)pyridine. Rate studies reveal evidence of a reversal of the ortholithiation and a subsequent 1,2-addition via two monomer-based pathways of stoichiometries [ArH*i-Pr(2)NLi(THF)](double dagger) and [ArH*i-Pr(2)NLi(THF)(3)](double dagger). Computational studies fill in the structural details and provide evidence of a direct substitution without the intermediacy of a Meisenheimer complex.

MATERIALIEN
Produktnummer
Marke
Produktbeschreibung

Sigma-Aldrich
Lithiumdiisopropylamid -Lösung, 2.0 M in THF/heptane/ethylbenzene
Sigma-Aldrich
Lithiumdiisopropylamid, 97%
Sigma-Aldrich
Diisopropylamin, ≥99.5%
Sigma-Aldrich
Diisopropylamin, purified by redistillation, 99.95%
Sigma-Aldrich
Diisopropylamin, puriss. p.a., ≥99.0% (GC)
Supelco
Diisopropylamin, analytical standard