Homoleptic Zincate‐Promoted Room‐Temperature Halogen–Metal Exchange of Bromopyridines
作者:Nguyet Trang Thanh Chau、Maxime Meyer、Shinsuke Komagawa、Floris Chevallier、Yves Fort、Masanobu Uchiyama、Florence Mongin、Philippe C. Gros
DOI:10.1002/chem.201001664
日期:2010.11.2
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 nBu4ZnLi2⋅TMEDA reagent (1/3 equiv; TMEDA=N,N,N′,N′‐tetramethylethylenediamine). This reactivity contrasted with that of tBu4ZnLi2⋅TMEDA, which was inefficient below one equivalent. DFT calculations
均三酸锌和四烷基锌酸锂与一组溴吡啶反应。高效和化学选择性溴-金属交换是在室温下以低于化学计算量实现Ñ卜4 ZnLi 2 ⋅TMEDA试剂(1/3当量; TMEDA = Ñ,Ñ,N' ,N'四甲基乙二胺)。该反应性与t Bu 4 ZnLi 2的反应性相反⋅TMEDA,在一个当量以下效率低下。DFT计算使我们能够合理化反应中N⋅⋅⋅Li稳定的聚吡啶基锌盐的形成。使用化学计量的试剂也可以实现二溴吡啶的一锅双功能化。在溴吡啶中直接形成CZn键使我们能够进行有效的Negishi型交叉偶联。