Using Ring Strain to Control 4π-Electrocyclization Reactions: Torquoselectivity in Ring Closing of Medium-Ring Dienes and Ring Opening of Bicyclic Cyclobutenes
Using Ring Strain to Control 4π-Electrocyclization Reactions: Torquoselectivity in Ring Closing of Medium-Ring Dienes and Ring Opening of Bicyclic Cyclobutenes
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DOI：
10.1021/acs.joc.7b00203
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发表时间：
2017-05-05
影响因子：
3.6
通讯作者：
Merlic, Craig A.
中科院分区：
文献类型：
--
作者：
Boon, Byron A.;Green, Aaron G.;Merlic, Craig A.
通过钯（II）催化末端乙烯基硼酸酯的氧化环化反应合成了张力环二烯。该反应生成张力（E，E）-1,3-二烯，这些二烯经过自发的4 -电环化形成双环丁烯。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。由于热力学原因，环丁烯的热开环得到（Z，Z）-1,3-二烯产物。DFT计算验证了反应的热力学和动力学控制，动力学研究与计算的能量变化非常吻合。通过钯（II）催化氧化均偶联/8 - pi电环化级联，证明了串联偶联/4 - pi电环化途径的延伸。
Syntheses of strained cyclic dienes were accomplished via palladium(II)-catalyzed oxidative cyclizations of terminal bis(vinylboronate esters). The reactions generate strained (E,E)-1,3-dienes that undergo spontaneous 4 pi-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, again for thermodynamic reasons. DFT calculations verified the thermodynamic versus kinetic control of the reactions, and kinetic studies are in excellent agreement with the calculated energy changes. An extension of the tandem coupling/4 pi-electrocyclization pathway was demonstrated by a palladium(II)-catalyzed oxidative homocoupling/8 pi-electrocyclization cascade.