Artículos de revistas
Formal fusion of a pyrrole ring onto 2-pyridyl and 2-pyrimidyl cations: One-step gas-phase synthesis of indolizine and its derivatives
Registro en:
Chemistry-a European Journal. Wiley-v C H Verlag Gmbh, v. 6, n. 2, n. 321, n. 326, 2000.
0947-6539
WOS:000084931200013
10.1002/(SICI)1521-3765(20000117)6:2<321
Autor
Sparrapan, R
Mendes, MA
Carvalho, M
Eberlin, MN
Institución
Resumen
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. 6 2 321 326