Di- and Triarylmethylium Ions as Probes for the Ambident Reactivities of Carbanions Derived from 5-Benzylated Meldrum’s Acid
作者:Xi Chen、Yue Tan、Guillaume Berionni、Armin R. Ofial、Herbert Mayr
DOI:10.1002/chem.201403161
日期:2014.8.25
The kinetics of the reactions of carbocations with carbanions 1 derived from 5‐benzyl‐substituted Meldrum’s acids 1‐H (Meldrum’s acid=2,2‐dimethyl‐1,3‐dioxane‐4,6‐dione) were investigated by UV/Vis spectroscopic methods. Benzhydryl cations Ar2CH+ added exclusively to C‐5 of the Meldrum’s acid moiety. As the second‐order rate constants (kC) of these reactions in DMSO followed the linear free‐energy
通过UV / Vis研究了由5-苄基取代的麦德鲁姆酸1-H(Meldrum的酸= 2,2-二甲基-1,3-二恶烷-4,6-二酮)衍生的碳正离子与碳负离子1的反应动力学。光谱方法。苯甲基阳离子Ar 2 CH +仅添加到Meldrum酸部分的C-5中。由于这些反应在DMSO中的二阶速率常数(k C)遵循线性自由能关系lg k = s N(N + E),因此碳负离子的亲核试剂特异性反应性参数N和s N为1可以确定。相反,三苯甲基阳离子Ar 3 C +反应不同。虽然低亲电性(E <−2)的三苯乙稀离子通过速率确定β-氢化物抽象而与1反应,但更多的路易斯酸性三苯乙稀离子最初在1的羰基氧上反应形成三苯甲基烯醇盐,随后再离子化并最终生成三芳基甲烷和通过氢化物转移生成5-亚苄基Meldrum酸。