Synthesis of carbazole analogs via Grob fragmentation of norbornyl α-diketones

[Display omitted] •Regioselective synthesis of carbazole analogs is reported.•Cadogan or Pd-catalyzed intramolecular cyclization was employed in the final step.•The reported motifs are present in many carbazole natural products. A regioselective synthesis of carbazole analogs belonging to both the c...

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Bibliographic Details
Published in:Tetrahedron letters 2016-08, Vol.57 (31), p.3449-3452
Main Authors: Sravanthi, Kadavergu, Agrawal, Sumit Kumar, Rao, Chintada Nageswara, Khan, Faiz Ahmed
Format: Article
Language:English
Subjects:
Aromatization
Cadogan cyclization
Carbazoles
Diketones
Fragmentation
Pd-catalyzed cyclization
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Summary:[Display omitted] •Regioselective synthesis of carbazole analogs is reported.•Cadogan or Pd-catalyzed intramolecular cyclization was employed in the final step.•The reported motifs are present in many carbazole natural products. A regioselective synthesis of carbazole analogs belonging to both the categories of natural origin, viz., microorganisms and higher plant source is reported. The synthesis of carbazole derivatives possessing a methylester group at C-1 position has been achieved by Cadogan cyclization of nitro bi-phenyl derivatives, whereas, the carbazole analog possessing a methylester group at C-3 position was synthesized by Buchwald–Hartwig Pd-catalyzed cyclization of amino bi-phenyl derivatives. Suitably substituted bi-phenyl precursors were accessed from norbornyl α-diketones via Grob fragmentation, O-methylation and DBU aromatization reaction sequence. The reported carbazole derivatives possess structural features that are common with many carbazole natural products: mukonine, clausine-L, murrayafoline-A, and their sibling natural products.
ISSN:0040-4039
1873-3581
DOI:10.1016/j.tetlet.2016.06.080