1H and 13C NMR and X-ray studies of 2- and 4-phenyl-6,7-dimethoxy-3methyl-3,4-dihydro-2H-1,3-benzothiazines [1]

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Abstract

The stereochemistry of 2- and 4-phenyl-6,7-dimethoxy-3-methyl-3,4-dihydro-2H-1,3-benzothiazine (2,6) has been studied by 1H, 13C NMR spectroscopy and X-ray diffraction. Crystals of compound 2 (C17H19NO2S) are monoclinic, space group P21/n, with a = 11.428(1), b = 10.048(1), c = 14.161(2) Å, ß = 100.00(1)°, Z = 4, Dc = 1.247 g cm-3. Crystals of 6 are orthorhombic, space group P212121 with a = 7.068(1), b = 10.857(1), c = 20.343(1) Å, Z = 4, Dc = 1.247 g cm-3. The structures are refined to R = 0.041 for 2728 reflections of 2 and R = 0.039 for 1671 reflections of 6. The results unequivocally show that the 3-N-methyl group, and the 4-phenyl group are axial, while the 2-phenyl moiety is equatorial. Comparison are made between conformations of the title compounds and those of the following 1-phenyltetrahydroisoquinolines: unnatural cryptostyline II [2, 3], crypstostyline I [4] and 2-benzyl-1,2,3,4-tetrahydro-6,7-dimethoxy-2-methyl-1-phenyl-isoquinolinium iodide [5].

Original languageEnglish
Pages (from-to)341-354
Number of pages14
JournalJournal of Molecular Structure
Volume145
Issue number3-4
DOIs
Publication statusPublished - júl. 1986

ASJC Scopus subject areas

  • Analytical Chemistry
  • Spectroscopy
  • Organic Chemistry
  • Inorganic Chemistry

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