Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA.
J Am Chem Soc. 2010 May 12;132(18):6361-5. doi: 10.1021/ja910834b.
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.
用二异丙基胺锂在四氢呋喃溶液中处理 2,6-二氟吡啶，在-78°C 下定量进行邻位锂化。将溶液加热至 0°C，将芳基锂转化为 2-氟-6-(二异丙基氨基)吡啶。速率研究表明，存在邻位锂化的反转和随后通过两种基于单体的途径进行 1,2-加成的证据，其化学计量比为ArH*i-Pr(2)NLi(THF)和ArH*i-Pr(2)NLi(THF)(3)。计算研究填补了结构细节，并提供了直接取代而没有 Meisenheimer 络合物中间体的证据。
