作者:Herbert Mayr、Claudia Fichtner、Armin R. Ofial
DOI:10.1039/b203554e
日期:——
The 1,1,3-triphenylallyl cation and its p-methoxy and p-dimethylamino substituted derivatives have been generated in dichloromethane solution or as stable salts. Allylsilanes, allylstannanes, silylated enol ethers and ketene acetals, as well as enamines attack the sterically less hindered 3-position of the allyl cation as derived from the structures of the reaction products. Kinetic investigations of these reactions revealed that they follow the equation log k(20 °C) =
s(N
+
E), which allows one to derive the electrophilicity parameters E of Ph2CCH–CH+Ph (E
=
+0.98 ± 0.20), (p-MeOC6H4)2CCH–CH+Ph (E
=
−2.67 ± 0.30), (p-Me2NC6H4)2CCH–CH+Ph (E
=
−8.97 ±
0.32) and (p-Me2NC6H4)2CCH–CH+(p-Me2NC6H4) (E
=
−9.84 ± 0.21).
生成了1,1,3-三苯基烯丙基阳离子及其对甲氧基和对二甲基氨基取代的衍生物,这些阳离子在二氯甲烷溶液中或作为稳定盐生成。烯丙基硅烷、烯丙基锡烷、硅化的烯醇醚和酮乙缩醛,以及烯胺进攻了来自反应产物结构推导出的烯丙基阳离子的立体位阻较小的3位。对这些反应的动力学研究表明,它们遵循方程式log k(20 °C) = s(N + E),这使得我们能够推导出Ph2CCH–CH+Ph的电亲和性参数E(E = +0.98 ± 0.20),(p-MeOC6H4)2CCH–CH+Ph(E = −2.67 ± 0.30),(p-Me2NC6H4)2CCH–CH+Ph(E = −8.97 ± 0.32)和(p-Me2NC6H4)2CCH–CH+(p-Me2NC6H4)(E = −9.84 ± 0.21)。