Variation of the ease of α-sulfonyl carbanion formation with the orientation of different β-substituents: Experimental evidence for the generality of negative hyperconjugation as an important substituent effect
作者:James F King、Manqing Li、Allan Zijun Cheng、Vinod Dave、Nicholas C Payne
DOI:10.1139/v03-015
日期:2003.6.1
Following up on our previous observation that the rate of formation of a β-alkoxy-substituted α-sulfonyl carbanion depends on the stereochemistry of the alkoxy group, we have found similar behaviour when the β-substituent is R2N, RS, or R3N+. With each substituent, the variation of kN (defined by kN = (kexch)X /(kexch)model) is consistent with an equation of the form log kN = a + b cos2θ, where θ is
继我们之前观察到的 β-烷氧基取代的 α-磺酰基碳负离子的形成速率取决于烷氧基的立体化学之后,我们发现当 β-取代基为 R2N、RS 或 R3N+ 时也有类似的行为。对于每个取代基,kN 的变化(由 kN = (kexch)X /(kexch) 模型定义)与 log kN = a + b cos2θ 形式的方程一致,其中 θ 是 HCCX 扭转角。我们建议 a 项描述极性(场加感应)效应,b 项描述取代基的负超共轭效应;我们展示了如何在这个框架内轻松适应 a 和 b 的变化。根据我们的结果讨论了先前在文献中假设的三烷基氨基的一些特征。 关键词:负超共轭,取代基效应,