Visible-Light-Mediated Heterocycle Functionalization via Geometrically Interrupted [2+2] Cycloaddition
Visible-Light-Mediated Heterocycle Functionalization via Geometrically Interrupted [2+2] Cycloaddition
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通过几何中断的可见光介导的杂环官能化 [2 2] 环加成
DOI：
10.1002/ange.202009704
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发表时间：
2020
影响因子：
--
通讯作者：
Popescu M
中科院分区：
文献类型：
--
作者：
Popescu M
[2+2]光环加成是最有价值和研究最深入的光化学过程。在这里，我们证明了用蓝色LED光（440nm）照射含有iriii配合物的N -丙烯基杂环，可以在一系列取代杂环上高效、高产地形成融合γ -内酰胺。量子计算表明，该反应在三重态激发态通过环化产生1,4‐二自由基；系统间交叉优先导致闭合壳层单线态两性离子。由于酰胺取代基的平面性，这在几何上限制了重组生成环丁烷的可能性。原向性移位导致观察到的双环产物可以看作是中断的[2+2]环加成。
The [2+2] photocycloaddition is the most valuable and intensively investigated photochemical process. Here we demonstrate that irradiation of N‐acryloyl heterocycles with blue LED light (440 nm) in the presence of an IrIIIcomplex leads to efficient and high yielding fused γ‐lactam formation across a range of substituted heterocycles. Quantum calculations show that the reaction proceeds via cyclization in the triplet excited state to yield a 1,4‐diradical; intersystem crossing leads preferentially to the closed shell singlet zwitterion. This is geometrically restricted from undergoing recombination to yield a cyclobutane by the planarity of the amide substituent. A prototropic shift leads to the observed bicyclic products in what can be viewed as an interrupted [2+2] cycloaddition.