Retro Diels−Alder Reactions of 5,6-Disubstituted-7-oxabicyclo[2.2.1]hept-2-enes: Experimental and Density Functional Theory Studies
作者:Jason T. Manka、Andrew G. Douglass、Piotr Kaszynski、Andrienne C. Friedli
DOI:10.1021/jo0003091
日期:2000.8.1
Several 5,6-disubstituted-7-oxabicyclo[2.2.1]hept-2-enes (1-4) were synthesized on > or = 0.1 mol scale. The heat-induced retro Diels-Alder (rDA) decomposition of these derivatives was studied by thermal analysis, and the kinetics of the rDA were measured for 4. First-order rate constants (k = 1.91-14.2 x 10(-5) s(-1)), measured at four temperatures between 124 and 150 degrees C, were used to calculate
合成了大于或等于0.1摩尔规模的几个5,6-二取代-7-氧杂双环[2.2.1]庚-2-烯(1-4)。通过热分析研究了这些衍生物的热诱导逆Diels-Alder(rDA)分解,并测量了4个rDA的动力学。一级速率常数(k = 1.91-14.2 x 10(-5)s (-1))在124至150摄氏度之间的四个温度下测量,用于计算Arrhenius激活参数Ea(34.5 +/- 0.5 kcal / mol)和ln A(1.77 +/- 0.03 x 10(4)) 。观察到的活化能比先前对马来酸酐加合物1测得的活化能大得多(达9.5 kcal / mol),这归因于两个亲二烯体的LUMO能量不同。用密度泛函理论(DFT)计算相似化合物5和6对4的活化参数进行建模,得出delH双匕首,deltaG双匕首,deltaS双匕首的定量相关性。发现研究的rDA反应是熵驱动的。