Lou Hanyun, Blum Suzanne A
Department of Chemistry, University of California, Irvine; Irvine, CA, 92697, USA.
Organometallics. 2025 Sep 3. doi: 10.1021/acs.organomet.5c00238.
-Tetramethylethylenediamine (TMEDA) is known to increase yields in Negishi-type cross-coupling reactions in aqueous-surfactant mixtures, presumably by increasing the persistence of the organozinc intermediates toward protodemetalation. The degree to which such stabilization enhances the key surface intermediates, however, is unknown. Here, the persistence of surface organozinc reaction intermediates was examined by fluorescence lifetime imaging microscopy (FLIM). TMEDA did not increase the persistence of these oxidative addition intermediates toward protodemetalation by water in THF or DMF, indicating that its stabilizing effect may be limited to the solution phase. TMEDA, however, enhanced the persistence of these oxidative addition intermediates toward trimethylsilyl chloride (TMSCl) and 1,2-dibromoethane, reagents commonly used in preparative organozinc reagent syntheses that presumably act through zinc surface etching. The data suggest that TMEDA hinders this surface etching. The results pinpoint the elementary steps that result in enhanced water stability of organometallics, for use in developing aqueous-organic reaction systems.
已知四甲基乙二胺（TMEDA）可提高水 - 表面活性剂混合物中Negishi型交叉偶联反应的产率，推测这是通过增加有机锌中间体对质子脱金属作用的持久性来实现的。然而，这种稳定作用增强关键表面中间体的程度尚不清楚。在此，通过荧光寿命成像显微镜（FLIM）研究了表面有机锌反应中间体的持久性。TMEDA并未增加这些氧化加成中间体在四氢呋喃（THF）或二甲基甲酰胺（DMF）中对水的质子脱金属作用的持久性，这表明其稳定作用可能仅限于溶液相。然而，TMEDA增强了这些氧化加成中间体对三甲基氯硅烷（TMSCl）和1,2 - 二溴乙烷的持久性，这两种试剂常用于制备有机锌试剂合成中，推测它们是通过锌表面蚀刻起作用的。数据表明TMEDA阻碍了这种表面蚀刻。这些结果确定了导致有机金属化合物水稳定性增强的基本步骤，可用于开发水 - 有机反应体系。
