Mechanism, Regioselectivity, and the Kinetics of Phosphine-Catalyzed [3+2] Cycloaddition Reactions of Allenoates and Electron-Deficient Alkenes
作者:Yong Liang、Song Liu、Yuanzhi Xia、Yahong Li、Zhi-Xiang Yu
DOI:10.1002/chem.200701725
日期:2008.5.9
experiments, the detailed mechanism of the phosphine-catalyzed [3+2] cycloaddition reactions of allenoates and electron-deficient alkenes has been investigated. It was found that this reaction includes four consecutive processes: 1) In situ generation of a 1,3-dipole from allenoate and phosphine, 2) stepwise [3+2] cycloaddition, 3) a water-catalyzed [1,2]-hydrogen shift, and 4) elimination of the phosphine catalyst
借助于计算和实验,研究了膦酸酯和烯丙酸酯和缺电子烯烃的[3 + 2]环加成反应的详细机理。发现该反应包括四个连续的过程:1)从脲基甲酸酯和膦原位生成1,3-偶极; 2)逐步[3 + 2]环加成; 3)水催化的[1,2]-氢转移,和4)消除膦催化剂。1,3-偶极子的原位生成是所有亲核膦催化的反应的关键。通过动力学研究,我们发现1,3-偶极子的生成是烯丙酸酯和缺电子烯烃的膦催化的[3 + 2]环加成反应的速率决定步骤。DFT计算和FMO分析表明,在丙二烯中需要一个吸电子基团,以确保在动力学和热力学上生成1,3-偶极子。分子中的原子(AIM)理论用于分析1,3偶极子的稳定性。FMO和AIM理论可以很好地合理化[3 + 2]环加成反应的区域选择性。同位素标记实验与DFT计算相结合表明,应将普遍接受的分子内[1,2]质子位移校正为水催化的[1,2]质子位移。烯丙酸酯和电子缺陷型亚胺的杂[3 + 2]