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Type: Artigo de periódico
Title: Formal fusion of a pyrrole ring onto 2-pyridyl and 2-pyrimidyl cations: One-step gas-phase synthesis of indolizine and its derivatives
Author: Sparrapan, R
Mendes, MA
Carvalho, M
Eberlin, MN
Abstract: Two ortho-hetarynium ions, the 2-pyridyl and 2-pyrimidyl cations, react promptly with 1,3-dienes in the gas phase by annulation, formally by fusion, onto the ions of a pyrrole ring. This novel reaction proceeds through an initial polar [4 + 2(+)] cycloaddition across the C=N+ bond, followed by fast ring opening, a [1,4-H] shift, and finally a recyclization that results in a contraction of a six- to a five-membered ring and dissociation by the loss of a methyl radical. For the 2-pyridyl cation. this reaction yields ionized indolizines (pyrrolo[1,2-a]pyridines), while for the 2-pyrimidyl cation, it gives ionized pyrrolo[1,2-a]pyrimidines. The annulation reaction, performed in the rf-only collision quadrupole of a pentaquadrupole (QqQqQ) mass spectrometer, occurs readily with both 1,3-butadiene and isoprene, and is thermodynamically and kinetically favored as predicted by ab initio calculations. Ortho-hetarynium ions and 1,3-dienes provide, therefore, the two building blocks for the efficient one-step gas-phase synthesis of ionized bicyclic pyrrolo[1,2-a]pyridine (indolizine) and pyrrolo[1,2-a] pyrimidine, as well as their analogues and derivatives.
Subject: cycloadditions
ion-molecules reactions
mass spectroscopy
Country: Alemanha
Editor: Wiley-v C H Verlag Gmbh
Citation: Chemistry-a European Journal. Wiley-v C H Verlag Gmbh, v. 6, n. 2, n. 321, n. 326, 2000.
Rights: fechado
Identifier DOI: 10.1002/(SICI)1521-3765(20000117)6:2<321
Date Issue: 2000
Appears in Collections:Unicamp - Artigos e Outros Documentos

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