1-[(E)-2-Arylethenyl]-2,2-diphenylcyclopropanes: Kinetics and Mechanism of Rearrangement to Cyclopentenes
作者:Johann Mulzer、Rolf Huisgen、Vladimir Arion、Reiner Sustmann
DOI:10.1002/hlca.201100135
日期:2011.8
measurements for the thermal rearrangement of 2,2‐diphenyl‐1‐[(E)‐styryl]cyclopropane (22a) to 3,4,4‐triphenylcyclopent‐1‐ene (23a) in decalin furnished ΔH=31.0±1.2 kcal mol−1 and ΔS=−6.0±2.6 e.u. The lowering of ΔH≠ by 20 kcal mol−1, compared with the rearrangement of the vinylcyclopropane parent, is ascribed to the stabilization of a transition structure (TS) with allylic diradical character. The racemization
在十氢化萘中将2,2-二苯基-1-[[(E)-苯乙烯基]环丙烷(22a)热重排为3,4,4-三苯基环戊-1-烯(23a)的动力学测量ΔH = 31.0±1.2 kcal mol -1和ΔS = -6.0±2.6 eu与乙烯基环丙烷母体的重排相比,ΔH ≠降低20 kcal mol -1归因于具有烯丙基双自由基的过渡结构(TS)的稳定特点。的外消旋化(+) - (小号) - 22A前进至Δ ħ = 28.2±0.8千卡摩尔-1和Δ小号= −5±2 eu,比重排快150°106倍。合成并表征了另外七个七个1-(2-芳基乙烯基)-2,2-二苯基环丙烷22(E)和(Z)-异构体。(E)化合物在其k rac(在119.4°)和k isom(在159.3°)值中仅显示出适度的取代基影响。缺乏对速率的溶剂依赖性,从而在TS中反对了电荷分离,但是log k rac与log prf的线性关系(即ArH自由基