Indole synthesis by radical cyclization of o-alkenylphenyl isocyanides and its application to the total synthesis of natural products

Chemical Record : an Official Publication of the Chemical Society of Japan ... [et Al.]
Hidetoshi Tokuyama, Tohru Fukuyama

Abstract

Development of indole synthesis by tin-mediated radical cyclization of o-alkenylphenyl isocyanide is described. Upon heating o-alkenylphenyl isocyanide in the presence of tri-n-butyltin hydride and AIBN, 2-stannyl-3-substituted indole was formed via 5-exo-trig cyclization of the imidoyl radical intermediate. After acidic workup, 3-substituted indoles were isolated. For substrates bearing simple alkyl groups, a substantial amount of tetrahydroquinoline derivatives were generated through 6-endo-trig cyclization. This undesired cyclization was suppressed by using an excess amount (five equivalents based on o-alkenylphenyl isocyanide) of ethanethiol instead of tri-n-butyltin hydride. The 2-stannylindole intermediates proved to be a suitable substrate for Stille coupling, giving 2,3-disubstituted indoles in a one-pot procedure. In addition, the 2-stannylindole intermediates could be converted to 2-iodoindoles by treatment with iodine or N-iodosuccinimide. The 2-iodoindoles thus obtained served as good substrates for Heck reactions, Stille couplings, Suzuki couplings, and palladium-mediated carbonylations, to afford a variety of 2,3-disubstituted indoles. The utility of this protocol was demonstrated by application to synthetic studi...Continue Reading

Citations

Dec 24, 2003·Yakugaku zasshi : Journal of the Pharmaceutical Society of Japan·Hidetoshi Tokuyama
Apr 13, 2017·The Journal of Organic Chemistry·Takahiro SoetaYutaka Ukaji
Feb 24, 2006·Organic & Biomolecular Chemistry·J CampoT Torroba
Dec 20, 2003·Organic & Biomolecular Chemistry·Mateo AlajarínMaría-Mar Ortín
Feb 13, 2016·Organic & Biomolecular Chemistry·Jian LeiQiang Zhu
Jul 5, 2007·Organic & Biomolecular Chemistry·Haruhiko Fuwa, Makoto Sasaki
Nov 6, 2010·Angewandte Chemie·Alexander V Lygin, Armin de Meijere
Oct 30, 2010·Angewandte Chemie·Takayuki YamakawaTohru Fukuyama
Jan 23, 2014·Chemical Record : an Official Publication of the Chemical Society of Japan ... [et Al.]·Takahiro Soeta, Yutaka Ukaji
Apr 11, 2014·Chemical Society Reviews·Giuseppe BartoliMonica Nardi
Apr 19, 2011·Angewandte Chemie·Yuki Han-yaTohru Fukuyama
Mar 23, 2011·Organic & Biomolecular Chemistry·Sara H KyneHiroshi Matsubara
Jul 30, 2014·Organic & Biomolecular Chemistry·Hiroki IwasakiMasayuki Yamashita
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Feb 14, 2012·Organic Letters·Takahiro SoetaYutaka Ukaji
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Oct 3, 2018·Journal of the American Chemical Society·Gabriel Dos Passos GomesIgor V Alabugin
May 24, 2003·Organic Letters·Shinjiro SumiTohru Fukuyama
Dec 19, 2002·Journal of the American Chemical Society·Jennifer L RutherfordStephen L Buchwald
Jan 18, 2008·Journal of the American Chemical Society·Sarah E ReismanJohn L Wood
Nov 30, 2021·Organic Letters·Matthew C LeechKevin Lam

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