Nine 1,3-dichlorobenzene congeners were selected as model compds. to assess the relative rates of proton abstraction from 4- and 5-positions ("ortho" vs. "meta" metalation). Using lithium 2,2,6,6-tetramethylpiperidide as the basic reagent, the chlorine-adjacent 4-position underwent metalation exclusively. In contrast, attack at the chlorine-remote 5-position became significant even in the case of moderately
选择九个
1,3-二氯苯同系物作为模型化合物。评估从 4 位和 5 位(“邻位”与“元”
金属化)提取质子的相对速率。使用
2,2,6,6-四甲基哌啶锂作为碱性试剂,4 位
氯附近专门进行
金属化。相比之下,当使用
仲丁基锂时,即使在中等大小的 2-取代基(如
二甲氨基或乙基)的情况下,对
氯远程 5-位的攻击也变得显着。“邻位/对位”(4-/5-) 比率范围为 80:20 至 65:35。与碳取代基相反,
硅更显着的“元取向”效应可归因于芳族的 pi 极化的不同。戒指。[在 SciFinder (R) 上]