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Diazonamide synthetic studies. Reactivity of N-unsubstituted benzofuro[2,3-b]indolines

Benzofuro[2,3-b]indolines undergo ring opening in the presence of base to generate 3H-indolines. The latter can rearrange into 3-arylindoles through an intramolecular transfer of the methoxycarbonyl moiety from quaternary carbon to oxygen of phenol. The intermediate 3H-indolines can be isolated upon DMAP-catalyzed O-acylation of the phenol moiety with Boc2O.

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Notes

  1. * Isolated compound 11a was converted to N-deprotected indole 8a under thermal conditions (PhMe, 160°C, 30 min)8 to confirm the structural assignment for compound 8a, which was based on the NMR experiments.

  2. * As has been demonstrated by Hassner,9 the reaction of DMAP with Boc2O produces ion pair: N-Boc-pyridinium tert-butoxycarboxylate. The tert-butoxycarboxylate decomposes to CO2 and the strong base tert-butoxide.

References

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We thank European Social Fund (project No. 1DP/1.1.1.2.0/13/APIA/VIAA/006) for financial support of this research. E. Vedejs thanks InnovaBalt project for funding.

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Correspondence to Edgars Suna.

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Published in Khimiya Geterotsiklicheskikh Soedinenii, 2015, 51(7), 613–620

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Mutule, I., Kalnins, T., Vedejs, E. et al. Diazonamide synthetic studies. Reactivity of N-unsubstituted benzofuro[2,3-b]indolines. Chem Heterocycl Comp 51, 613–620 (2015). https://doi.org/10.1007/s10593-015-1749-7

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  • DOI: https://doi.org/10.1007/s10593-015-1749-7

Keywords

  • diazonamide
  • DMAP
  • hemiaminal
  • indole
  • 3H-indoline