S 83 Stereoselective hetero-Diels–Alder reaction of 3-nitro-2-trihalomethyl-2H-chromenes with 2,3-dihydrofuran and ethyl vinyl ether under solvent-free conditions [Text] / V. Yu. Korotaev, V. Ya. Sosnovskikh, M. A. Barabanov, E. S. Yasnova, M. A. Ezhikova, M. I. Kodess, P. A. Slepukhin // Tetrahedron. - 2010. - Vol. 66, № 6. - P1404-1409 Рубрики: ХИМИЧЕСКИЕ НАУКИ Аннотация: 3-Nitro-2-trifluoro(trichloro)methyl-2H-chromenes undergo heterodiene cycloaddition to 2,3-dihydrofuran and ethyl vinyl ether under solvent-free conditions producing novel cyclic nitronates with high stereoselectivity and in good yields. 3,6-Dinitro-2-trifluoromethyl-2H-chromene reacts with two molecules of ethyl vinyl ether to give the tandem [4+2]/[3+2] cycloaddition adduct in 48% yield. The stereochemistry of the products was established based on 2D COSY, NOESY, HSQC, and HMBC experiments and an X-ray diffraction study \\\\Expert2\\nbo\\Tetrahedron\\2010, v.66, N 6, p.1404.pdf |