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http://dx.doi.org/10.5012/bkcs.2005.26.8.1190

The Mechanisms for Thermal and Photochemical Isomerizations of N-Substituted 2-Halopyrroles: Syntheses of N-Substituted 3-Halopyrroles  

Park, Sung-Hyun (Kyungpook National University)
Ha, Hong-Joo (Kyungpook National University)
Lim, Chul-Taek (Kyungpook National University)
Lim, Dong-Kwon (Kyungpook National University)
Lee, Kwang-Hee (Kyungpook National University)
Park, Yong-Tae (Kyungpook National University)
Publication Information
Bulletin of the Korean Chemical Society / v.26, no.8, 2005 , pp. 1190-1196 More about this Journal
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.
Keywords
N -Benzyl-2-halopyrrole; N-Benzyl-3-halopyrrole; Photochemical isomerization; Thermal isomerization; Pyrrole ring complex with bromonium ion;
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