Conformational analysis of thiane-1 imides: an x-ray study of thiane-1-tosylimide and diastereoisomeric 2-alkyl- and 4-phenylthiane-1-tosylimides

I. Jalsovszky, Á Kucsman, F. Ruff, T. Koritsánszky, Gy Argay, A. Kálmán

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Abstract

The molecular structures of thiane-1-tosylimide and its cis/trans-2-Me, cis-2-Pri, trans-2-But and cis/trans-4-Ph derivatives have been investigated by X-ray diffraction. The results confirm our earlier 13C NMR assignments of configurations, giving direct evidence for ring geometry and conformational preference of ring substituents. They show that the electron-withdrawing tosylimino group is axial in both thiane-1-tosylimide and cis disubstituted analogues, whilst it is equatorial in trans compounds. The C-substituents are always equatorial. Distortions of chair-shaped thiane rings of sulphilimines are compared with those of cyclic sulphoxides and sulphonium salts, and explained by steric effects. Conformations of 1,2-disubstituted thiane-1-imides are controlled by both syn-axial interaction and steric repulsion between 1-tosylimino and 2-alkyl groups, with the latter being the more significant. The conformation of the exocyclic S-tosylimide part is also compared with that of known acyclic N-arylsulphonyl sulphilimines. Rotations about SIV-N, NSVI and SVICar bonds are discussed and deviations from S-symmetric conformations and "Koch- Moffitt's cases IIa of conjugation" are interpreted in terms of steric effects conjugation, n-σ* type stereoelectronic effects and sulphur(IV)-oxygen interaction; SIVC. SVIN and SVIO bond lengths are discussed on the same basis. The SONsp2 group may substitute SO2 in the case "case-IIa of conjugation" with the aryl group. In antiperiplanar position there exists a maximum interaction between the nitrogen lone pair and the SVIO bond, resulting in a significant shortening of the SVIN bond.

Original languageEnglish
Pages (from-to)165-192
Number of pages28
JournalJournal of Molecular Structure
Volume156
Issue number3-4
DOIs
Publication statusPublished - Feb 1987

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ASJC Scopus subject areas

  • Analytical Chemistry
  • Spectroscopy
  • Organic Chemistry
  • Inorganic Chemistry

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