[6π] 光环化反应生成顺式六氢咔唑-4-酮：底物修饰、机理和范围。
[6π] Photocyclization to cis-Hexahydrocarbazol-4-ones: Substrate Modification, Mechanism, and Scope.
机构信息
Department of Chemistry and Catalysis Research Center (CRC) , Technical University of Munich , Lichtenbergstrasse 4 , 85747 Garching , Germany.
Interdisciplinary Center for Scientific Computing , Ruprecht-Karls University , Im Neuenheimer Feld 205A , 69120 Heidelberg , Germany.
出版信息
J Org Chem. 2019 Feb 1;84(3):1139-1153. doi: 10.1021/acs.joc.8b03144. Epub 2019 Jan 23.
Upon irradiation at λ = 366 nm, tertiary N-alkoxycarbonyl- N-aryl-β-enaminones furnished exclusively the trans-hexahydrocarbazol-4-ones by a conrotatory [6π] photocyclization but epimerized on silica to cis-hexahydrocarbazol-4-ones (14 examples, 44-98% yield). The acceptor substitution on the nitrogen atom enhanced the stability of the cyclized products compared to N-alkyl- N-aryl-β-enaminones reported previously. The mechanism of the [6π] photocyclization was investigated by quenching experiments, deuterium-labeling experiments, and DFT calculations, suggesting a triplet pathway for the conrotatory ring closure followed by a suprafacial [1,4] hydrogen migration.
在 λ = 366nm 的光照下，叔 N-烷氧基羰基-N-芳基-β-烯胺酮通过协同的 [6π] 光环化反应生成了反式-六氢咔唑-4-酮，但在硅胶上异构化为顺式-六氢咔唑-4-酮（14 个例子，44-98%产率）。与之前报道的 N-烷基-N-芳基-β-烯胺酮相比，氮原子上的吸电子取代基增强了环化产物的稳定性。通过猝灭实验、氘标记实验和 DFT 计算研究了 [6π] 光环化的反应机制，表明协同的环闭合是通过三重态途径进行的，随后是顺式[1,4]氢迁移。
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