Chemistry of the phenoxathiins and isosterically related heterocycles. XXX. The crystal and molecular structure of 2‐AZA‐phenoxathiin 2‐oxide: Further evidence in support of the relationship between the 13C‐NMR chemical shift of C‐10a resonance and the molecular dihedral angle

Abstract

AbstractThe synthesis of 2‐azaphenoxathiin 2‐oxide (4) and the total assignment of the 13C‐nmr spectrum is described. Facile assignment was obtained from the assigned spectrum of 2‐azaphenoxathiin with additivities obtained from a comparison of 1‐azaphenoxathiin and its N‐oxide. The crystal structure has also been determined from three dimensional X‐ray diffraction data. The compound crystallizes in the monoclinic space group P21/n with a = 17.50(2)Å, b = 7.147(3)Å, c = 16.044(7)Å, β = 110.60(5) and Z = 8. Intensity data were collected at ‐ 135 ± 2°C on an automatic diffractometer using nickel‐filtered CuKα radiation. The structure was solved by direct methods and was refined by least‐squares techniques to give a final R‐value of 0.045 for all 3831 independent reflections.