Using Ring Strain to Control 4π-Electrocyclization Reactions: Torquoselectivity in Ring Closing of Medium-Ring Dienes and Ring Opening of Bicyclic Cyclobutenes
作者:Byron A. Boon、Aaron G. Green、Peng Liu、K. N. Houk、Craig A. Merlic
DOI:10.1021/acs.joc.7b00203
日期:2017.5.5
accomplished via palladium(II)-catalyzed oxidative cyclizations of terminal bis(vinylboronate esters). The reactions generate strained (E,E)-1,3-dienes that undergo spontaneous 4π-electrocyclizations to form bicyclic cyclobutenes. Formation of the cyclobutenes is driven by the strain in the medium-ring (E,E)-1,3-diene intermediate. Thermal ring openings of the cyclobutenes give (Z,Z)-1,3-diene products
应变环二烯的合成是通过钯(II)催化末端双(乙烯基硼酸酯)的氧化环化而完成的。该反应产生应变的(E,E)-1,3-二烯,其经历自发的4π-电环化以形成双环环丁烯。环丁烯的形成是由中环(E,E)-1,3-二烯中间体中的应变驱动的。环丁烯的热环开口给出(Z,Z)-1,3-二烯产物,也是出于热力学原因。DFT计算验证了反应的热力学与动力学控制,并且动力学研究与计算出的能量变化非常吻合。钯(II)催化的氧化均耦合/8π电环化级联反应证明了串联偶联/4π电环化途径的扩展。