[6π] photocyclization to cis-hexahydrocarbazol-4-ones

• Verfasst von: Modha, Sachin G. [VerfasserIn]
• Verfasst von: Dreuw, Andreas [VerfasserIn]
• Titel: [6π] photocyclization to cis-hexahydrocarbazol-4-ones
• Titelzusatz: substrate modification, mechanism, and scope
• Verf.angabe: Sachin G. Modha, Alexander Pöthig, Andreas Dreuw, and Thorsten Bach
• E-Jahr: 2019
• Jahr: January 16, 2019
• Umfang: 15 S.
• Fussnoten: Im Text wird pi als griechischer Buchstabe dargestellt ; Gesehen am 20.11.2019
• Titel Quelle: Enthalten in: The journal of organic chemistry
• Ort Quelle: [S.l.] : American Chemical Society, 1936
• Jahr Quelle: 2019
• Band/Heft Quelle: 84(2019), 3, Seite 1139-1153
• ISSN Quelle: 1520-6904
• DOI: doi:10.1021/acs.joc.8b03144
• Datenträger: Online-Ressource
• Sprache: eng
• K10plus-PPN: 1677909153

Abstract

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.