The mechanisms for thermal and photochemical isomerizations of N-substituted 2-halopyrroles: Syntheses of N-substituted 3-halopyrroles

Sung Hyun Park, Hong Joo Ha, Chultaek Lim, Dong Kwon Lim, Kwang Hee Lee, Yong Tae Park

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Halopyrroles, N-substituted 2-halopyrroles were prepared by halogenation of N-substituted pyrroles with NBS, NCS, or surfuryl chloride. N-Substituted 3-halopyrroles were synthesized by acid-catalyzed thermal and photochemical isomerization reactions of N-substituted 2-halopyrroles. Both the thermal and photochemical reactions were acid-catalyzed. For the acid-catalyzed isomerization, a mechanism of [1,3] bromine shift followed by deprotonation is operated. For the acid-catalyzed photoisomerization, an excited triplet state of 2-protonated N-benzyl-2-halopyrrole produces an intermediate N-substituted pyrrole complex with halonium ion which is equilibrated with N-substituted pyrrole plus halonium ion, and then the halonium ion newly adds to 3-position of N-substituted pyrrole followed by deprotonation to afford N-benzyl-3- halopyrrole.

Original languageEnglish
Pages (from-to)1190-1196
Number of pages7
JournalBulletin of the Korean Chemical Society
Volume26
Issue number8
DOIs
Publication statusPublished - 2005 Aug 20

Keywords

  • N-Benzyl-2-halopyrrole
  • N-Benzyl-3-halopyrrole
  • Photochemical isomerization
  • Pyrrole ring complex with bromonium ion
  • Thermal isomerization

ASJC Scopus subject areas

  • Chemistry(all)

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