R 30 Deoxygenative vs. vicarious nucleophilic substitution of hydrogen in reactions of 1,2,4-triazine 4-oxides with - alpha-halocarbanions [Text] / D. N. Kozhevnikov, V. L. Rusinov, O. N. Chupakhin, M. Makosza, A. Rykowski, E. Wolinska // European Journal of Organic Chemistry. - 2002. - № 8. - P1412-1416 Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): AROMATIC SUBSTITUTION -- NUCLEOPHILIC SUBSTITUTION -- NITROGEN HETEROCYCLES Аннотация: The 3,6-diaryl-1,2,4-triazine 4-oxides 1a-e undergo a nucleophilic substitution of hydrogen with the -halomethyl aryl sulfones 2, 3 and 7 by two alternative pathways: vicarious nucleophilic substitution (VNS) and/or an intramolecular deoxygenative process. The former pathway is found to dominate in the reaction of 1 with bromomethyl tolyl sulfone (7) yielding the 5-tosylmethyl-1,2,4-triazine 4-oxides 6, while the reaction with the chloromethyl aryl sulfones 2 and 3 leads to the 5-arylsulfonylchloromethyl-1,2,4-triazines 4 and 5, respectively, as the products of deoxygenative substitution. The reaction of 6-phenyl-1,2,4-triazine 4-oxide (1f) with the chloromethyl aryl sulfones 2 and 3 proceeds differently. At low temperature (-75 C) the products of the VNS reaction at position 5 (6f and 12f) are formed. At room temperature the 7-chloro-1-hydroxy-3-phenyl-7-(arylsulfonyl)-1,4,5-triazahepta-1,3,6-trienes 10f and 11f are obtained by addition of the carbanions 2 and 3 in the 3-position, followed by the ring opening of the resulting adduct. © Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)???????? |