Electron transfer in reactions of ketones with organolithium reagents. A carbon-14 kinetic isotope effect probe
作者:Hiroshi Yamataka、Naoya Fujimura、Yukie Kawafuji、Terukiyo Hanafusa
DOI:10.1021/ja00248a027
日期:1987.7
of ketones and reagents. The reaction of benzophenone with MeLi proceeds via rate-determining electron transfer; the change in nucleophile from MeLi to Me/sub 2/CuLi shifts the rate-determining step from electron transfer to recombination; the change in ketone from benzophenone to 2,4,6-trimethylbenzophenone also shifts the rate-determining step from electron transfer to recombination because the latter
对于在羰基碳上用碳 14 标记的酮与 MeLi 和 Me/sub 2/CuLi 在二乙醚中在 0/sup 0/C 下的反应,已经确定了动力学同位素效应。观察到的同位素效应如下:(C/sub 6/H/sub 5/)/sub 2/C 双键 O + MeLi,/sup 12/k//sup 14/k = 1.000 +/- 0.002;(C/sub 6/H/sub 5/)/sub 2/C 双键 O + Me/sub 2/CuLi,1.029 +/- 0.005;2,4,6-Me/sub 3/C/sub 6/H/sub 2/COC/sub 6/H/sub 5/ + MeLi,1.023 +/- 0.004。邻位、间位和对位取代的二苯甲酮与这些试剂的相对反应性也由竞争实验确定。这些结果与电子转移步骤一致,随后是碳-碳键形成步骤,该步骤取决于酮和试剂的结构决定或不决定速率。二苯甲酮与MeLi的反应通过限速电子转移进行;亲核试剂从