Enantioselective [2+2] Cycloadditions of Cinnamate Esters: Generalizing Lewis Acid Catalysis of Triplet Energy Transfer
Enantioselective [2+2] Cycloadditions of Cinnamate Esters: Generalizing Lewis Acid Catalysis of Triplet Energy Transfer
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DOI：
10.1021/jacs.9b04643
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发表时间：
2019-06-19
影响因子：
15
通讯作者：
Yoon, Tehshik P.
中科院分区：
文献类型：
--
作者：
Daub, Mary Elisabeth;Jung, Hoimin;Yoon, Tehshik P.
报道了简单肉桂酸酯的对映选择性[2+2]环加成反应，其产物是环丁烷类天然产物可控组装的有用配体。该方法利用了一种助催化体系，其中手性刘易斯酸加速三重态能量从激发态Ir（III）光催化剂转移到肉桂酸酯。计算证据表明，刘易斯酸助催化剂的主要作用是降低底物前线分子轨道的绝对能量，导致敏化剂和底物之间更大的电子耦合，并增加能量转移事件的速率。这些结果表明，刘易斯酸可以对三重态敏化反应具有多种有益作用，影响Dexter能量转移的热力学驱动力和动力学。
We report the enantioselective [2+2] cycloaddition of simple cinnamate esters, the products of which are useful synthons for the controlled assembly of cyclobutane natural products. This method utilizes a cocatalytic system in which a chiral Lewis acid accelerates the transfer of triplet energy from an excited-state Ir(III) photocatalyst to the cinnamate ester. Computational evidence indicates that the principal role of the Lewis acid cocatalyst is to lower the absolute energies of the substrate frontier molecular orbitals, leading to greater electronic coupling between the sensitizer and substrate and increasing the rate of the energy transfer event. These results suggest Lewis acids can have multiple beneficial effects on triplet sensitization reactions, impacting both the thermodynamic driving force and kinetics of Dexter energy transfer.