Synthesis of 3-fluoro-2-hetarylindoles and 3,3-difluoro-2-hetarylindolines through Lewis acid-catalyzed formation of 3,3-difluoroindolium ions

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Synthesis of 3-fluoro-2-hetarylindoles and 3,3-difluoro-2-hetarylindolines through Lewis acid-catalyzed formation of 3,3-difluoroindolium ions
Title:
Synthesis of 3-fluoro-2-hetarylindoles and 3,3-difluoro-2-hetarylindolines through Lewis acid-catalyzed formation of 3,3-difluoroindolium ions
Journal Title:
European Journal of Organic Chemistry
Keywords:
Publication Date:
08 January 2015
Citation:
Fong, J. Z. M.; Choo, S. S. S.; Richard, J.-A.; Garland, M. V.; Guo, L. F.; Johannes, C. W.; Nguyen, T. M., Synthesis of 3-fluoro-2-hetarylindoles and 3,3-difluoro-2-hetarylindolines through Lewis acid-catalyzed formation of 3,3-difluoroindolium ions. European Journal of Organic Chemistry 2015, 2015 (5), 995-1006.
Abstract:
Synthesis of 3-fluoro-2-hetarylindoles through addition of hetarenes to 3,3-difluoroindolium ions generated in situ by Zn(OTf)2-catalyzed oxazolidine ring opening is described. Indoles, pyrroles and alkyl-substituted furans can be used as hetaryl nucleophiles to afford a range of 3-fluoro-2-hetarylindole products 6 in 56–95 % yields. A diverse array of 3,3-difluorinated 2-hetarylindolines 7 can also be synthesized in 43–84 % yields by a tandem sequential process that involves hetarene nucleophilic addition, HF elimination and fluorocyclization reactions. Our study by 1H NMR and UV/Vis spectroscopy reveals that 3,3-difluorinated 2-hetarylindolines possess interesting substituent-dependent acidochromic properties. UV absorption and fluorescence spectra of selected compounds 6 and 7 are also studied.
License type:
PublisherCopyrights
Funding Info:
This work was funded by the Institute of Chemical and Engineering Sciences (ICES) and Agency for Science, Technology and Research (A*STAR).
Description:
This is the peer reviewed version of the following article: Fong, J. Z. M.; Choo, S. S. S.; Richard, J.-A.; Garland, M. V.; Guo, L. F.; Johannes, C. W.; Nguyen, T. M., Synthesis of 3-fluoro-2-hetarylindoles and 3,3-difluoro-2-hetarylindolines through Lewis acid-catalyzed formation of 3,3-difluoroindolium ions. European Journal of Organic Chemistry 2015, 2015 (5), 995-1006, which has been published in final form at https://dx.doi.org/10.1002/ejoc.201403443. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.
ISSN:
1434-193X
1099-0690
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