Vinyl Carbocations: Solution Studies of Alkenyl(aryl)iodonium Triflate Fragmentations
作者:Anne J. McNeil、Robert J. Hinkle、E. Ashley Rouse、Quinn A. Thomas、David B. Thomas
DOI:10.1021/jo015746+
日期:2001.8.1
reaction with rearranged secondary cations derived from those salts. G2 calculations of the theoretical isodesmic hydride-transfer reaction between secondary vinyl cation 7 and primary vinyl cation 6 reveal that cation 6 is 17.8 kcal/mol higher in energy. Activation parameters for fragmentation of (Z)-2-ethyl-1-hexenyl(3,5-bis-trifluoromethylphenyl)iodonium triflate, 17e, were calculated using the Arrhenius
通过链烯基(芳基)碘鎓三氟甲烷磺酸盐的裂解,可以容易地生成乙烯基阳离子。动力学和电子效应由CDCl(3)中的(1)H NMR光谱探测。除碘芳烃外,裂解产物还包括六种烯醇三氟甲磺酸酯异构体。烯醇三氟甲磺酸酯来自三氟甲磺酸根阴离子与起始碘鎓盐的直接反应以及三氟甲磺酸酯与衍生自那些盐的重排仲阳离子的反应。对仲乙烯基阳离子7和伯乙烯基阳离子6之间的理论等离子氢化物转移反应的G2计算表明,阳离子6的能量高17.8 kcal / mol。使用Arrhenius方程计算(Z)-2-乙基-1-己烯基(3,5-双-三氟甲基苯基)碘化三氟甲磺酸盐碎片的活化参数:E(a)= 26.8 kcal / mol,Delta H( ++)= 26。2 kcal / mol,且Delta S(++)= 11.9 cal / mol xK。添加的三氟甲磺酸盐会稍微增加碎片化速率,并且对于大多数β,β-二烷基取代的乙烯基碘鎓