Substitution vs. addition. Regioselective electro-bromination of benzofuran

Hideo Tanaka, Yusuke Kawakami, Manabu Kuroboshi, Sigeru Torii

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4 Citations (Scopus)

Abstract

Regioselective electro-bromination of benzofuran (2) was achieved successfully by an adequate choice of solvents and bromide salts to afford 5-bromobenzofuran (1), 5,7-dibromobenzofuran (3), and 2,3-dibromo-2,3-dihydrobenzofuran (4), respectively. Upon electrolysis of benzofuran (2) in AcOH/H2O (100/1) containing NH4Br, substitution at the C(5)-position of benzofuran (2) proceeded smoothly to afford 5-bromobenzofuran (1). After passage of totally 4 F/mol of electricity in a similar medium, 5,7-dibromobenzofuran (3) was obtained as a sole product. On the other hand, electrolysis of benzofuran (2) in CH2Cl2/H2O (1/1) and/or AcOH/H2O (10/1) in the presence of either NaBr or NH4Br afforded 2,3-dibromo-2,3-dihydrobenzofuran (4), exclusively.

Original languageEnglish
Pages (from-to)825-831
Number of pages7
JournalHeterocycles
Volume54
Issue number2
Publication statusPublished - Feb 1 2001

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Keywords

  • 2,3-Dibromo-2,3-dihydrobenzofuran
  • 5-Bromobenzofuran
  • Benzofuran
  • Bromination
  • Electrolysis

ASJC Scopus subject areas

  • Organic Chemistry

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