Condensation reactions of indole with acetophenones affording mixtures of 3,3-(1-phenylethane-1,1-diyl)bis(1H-indoles) and 1,2,3,4-tetrahydro-3-(1H-indol-3-yl)-1-methyl-1,3-diphenylcyclopent[b]indoles

Wayland E. Noland, Christopher D. Brown, Rodney D. DeKruif, Nicholas P. Lanzatella, Siming M. Gao, Abigail E. Zabronsky, Kenneth J. Tritch

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4 Scopus citations

Abstract

Condensation of indole 1a with eight acetophenones 8a–h in ethanolic HCl afforded the corresponding mixtures of condensation products: 3,3-(1-phenylethane-1,1-diyl)bis(1H-indoles) 11a–h (2:1 condensation of indole:acetophenone, –H2O) and diastereomers of substituted 1,2,3,4-tetrahydro-3-(1H-indol-3-yl)-1-methyl-1,3-diphenylcyclopent[b]indoles 12a–h and 13a–h (2:2 condensation of indole:acetophenone, –2H2O). Each mixture was analyzed by 1H NMR. The use of substituted electron-withdrawing acetophenones favored formation of 2:1 condensation products, whereas the use of substituted electron-donating acetophenones favored formation of 2:2 condensation products. Increased reaction temperature gave higher 2:2 condensation yields, but temperatures above 40 °C were unfavorable, giving complex, tarry mixtures.

Original languageEnglish (US)
Pages (from-to)1755-1765
Number of pages11
JournalSynthetic Communications
Volume48
Issue number14
DOIs
StatePublished - Jul 18 2018

Keywords

  • Acetophenones
  • acid-catalyzed condensation
  • bisindoles
  • cyclopent[b]indoles
  • indole

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