Bromination and azidation reactions of 2-styrylchromones. New syntheses of 4(5)-aryl-5(4)-(2-chromonyl)-1,2,3-triazoles

Artur M.S. Silva, Judite S. Vieira, Cristela M. Brito, José A.S. Cavaleiro, Tamás Patonay, Albert Lévai, José Elguero

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Abstract

The bromination of 2-styrylchromones, bearing electron neutral substituents, with two molar equivalents of piridinium tribromide gave 2-(2-aryl-1,2-dibromoethyl)chromones and 3-bromo-2-(2-aryl-1,2-dibromoethyl) chromones. The presence of electron-donating substituents on their B ring led to a mixture of compounds due to the higher reactivity of their C(2)=C(3) and Cα=Cβ double bonds, whereas the strongly electron-withdrawing group hindered the bromination. The dehydrobromination of 2-(2-aryl-1,2-dibromoethyl)chromones with triethylamine gave a diastereomeric mixture of (E)- and (Z)-2-(α-bromostyryl)chromones. Some novel 4(5)-aryl-5(4)-(2-chromonyl)-1,2,3-triazoles have been obtained from the reactions of 2-(2-aryl-1,2-dibromoethyl)chromones, 2-(α-bromostyryl) chromones, and 2-styrylchromones with sodium azide. The reactions of 2-styrylchromones with sodium azide are more efficient, general, and constitute a one-pot synthetic method of 4(5)-aryl-5(4)-(2-chromonyl)-1,2,3-triazoles allowing the preparation of 1,2,3-triazoles bearing either electron-donating or electron-withdrawing substituents in their aryl ring. The structure of all new compounds was established by extensive NMR spectroscopic studies.

Original languageEnglish
Pages (from-to)293-308
Number of pages16
JournalMonatshefte fur Chemie
Volume135
Issue number3
DOIs
Publication statusPublished - Mar 1 2004

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Keywords

  • 1,2,3-Triazoles
  • 2-Styrylchromones
  • Azidation
  • Bromination
  • Dehydrobromination

ASJC Scopus subject areas

  • Chemistry(all)

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