Descrevemos neste trabalho a ação de ácido trifluoroacético, ácido trifluorometanossulfônico e cloreto de alumínio sobre aril azidas orto-substituídas para formar indóis, azepinas e arilaminas com bons rendimentos. As azidas protonadas perdem nitrogênio para formar íons arilnitrênios intermediários que sofrem N-substituição aromática intramolecular. A decomposição ácida de aril azidas é comparada com resultados de termólise tomados da literatura.We describe in this paper the action of trifluoroacetic acid, trifluoromethanesulfonic acid and aluminum chloride upon ortho-substituted aryl azides to form indoles, azepines and arylamines in good yields. The protonated azides lose nitrogen to form arylnitrenium ion intermediates which undergo intramolecular aromatic N-substitution. The acid decomposition of aryl azides is compared with reported thermolyses.
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[triple bond]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.
Enantioselective Synthesis of (R)-(-)-1-Phenylethanolamines Using Baker's Yeast Reduction of Some α-Substituted Methyl Phenyl Ketones. --(BRENELLI, E. C. S.; DE CARVALHO, M.; OKUBO, M. T.; MARQUES, M.; MORAN, P. J. S.; RODRIGUES, J. A. R.; SORRILHA, A. E. P. M.; Indian J. Chem., Sect. B: Org. Chem. Incl. Med. Chem. 31 (1992) 12, 821-823; Inst. Quim., Univ. Estadual Campinas, 13081-970 Campinas, Brazil; EN)
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