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[6?] Photocyclization to cis-Hexahydrocarbazol-4-ones: Substrate Modification, Mechanism, and Scope.

ABSTRACT: Upon irradiation at ? = 366 nm, tertiary N-alkoxycarbonyl- N-aryl-?-enaminones furnished exclusively the trans-hexahydrocarbazol-4-ones by a conrotatory [6?] 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-?-enaminones reported previously. The mechanism of the [6?] 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.

SUBMITTER: Modha SG

PROVIDER: S-EPMC6362434 | biostudies-literature | 2019 Feb

REPOSITORIES: biostudies-literature

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[6π] Photocyclization to cis-Hexahydrocarbazol-4-ones: Substrate Modification, Mechanism, and Scope.

Modha Sachin G SG Pöthig Alexander A Dreuw Andreas A Bach Thorsten T

The Journal of organic chemistry 20190123 3

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 experimen ...[more]

PMID: 30648858

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