SOR, SRSMC, Nancy Université, CNRS, Boulevard des Aiguillettes, 54506 Vandoeuvre-Lès-Nancy, France.
Chemistry. 2010 Nov 2;16(41):12425-33. doi: 10.1002/chem.201001664.
Homoleptic lithium tri- and tetraalkyl zincates were reacted with a set of bromopyridines. Efficient and chemoselective bromine-metal exchanges were realized at room temperature with a substoichiometric amount of nBu(4)ZnLi(2)·TMEDA reagent (1/3 equiv; TMEDA=N,N,N',N'-tetramethylethylenediamine). This reactivity contrasted with that of tBu(4)ZnLi(2)·TMEDA, which was inefficient below one equivalent. DFT calculations allowed us to rationalize the formation of N···Li stabilized polypyridyl zincates in the reaction. The one-pot difunctionalization of dibromopyridines was also realized using the reagent stoichiometrically. The direct creation of C-Zn bonds in bromopyridines enabled us to perform efficient Negishi-type cross-couplings.
具有强配位能力的锂三烷基和四烷基锌试剂与一系列溴代吡啶反应。在室温下，使用亚化学计量的 nBu(4)ZnLi(2)·TMEDA（1/3 当量；TMEDA=N,N,N',N'-四甲基乙二胺）试剂，可以实现高效和选择性的溴-金属交换。这种反应性与 tBu(4)ZnLi(2)·TMEDA 形成鲜明对比，后者在低于一个当量时效率较低。DFT 计算允许我们对反应中形成的 N···Li 稳定的多吡啶基锌盐进行合理的解释。该试剂的化学计量还可用于一锅法实现二溴代吡啶的双官能化。在溴代吡啶中直接形成 C-Zn 键，使我们能够进行高效的 Negishi 型交叉偶联。
