Conformational analysis of thiolane-1-amides: an x-ray study of thiolane-1-tosylimide and diastereoisomeric 2-alkylthiolane-1-(arylsulphonyl)imides

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

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Abstract

The molecular structures of thiolane-, trans-2-methylthiolane-, trans-2-ethylthiolane- and cis-2-tert-butylthiolane-1-tosylimide and that of cis-2-methylthiolane-1-(p-nitro-phenylsulphonyl)imide were investigated by X-ray diffraction. The results confirmed our earlier 13C-NMR assignments of configurations. Direct evidence was obtained for ring geometry and conformational preference of ring substituents and cyclic sulphilimines were compared with analogous sulphoxides and sulphonium salts. It has been found that the electron-withdrawing and bulky NTs (N-tosyl) group is pseudoaxial in thiolane-1-tosylimide. The conformations of 1,2-disubstituted thiolanes are controlled by steric repulsion between 1-(arylsulphonyl)imino and 2-alkyl groups, which are 1-axial and 2-equatorial in cis derivatives, and 1-endo-isoclina and 2-exo-isoclinal in trans isomers. The 2-tert-butyl group and C4/C5 ring atoms are almost antiperiplanar. In connection with the conformation of the S-tosylimino part, rotations about SIVN, NSVI and SVICar bonds are analysed, and deviations from a SIV-symmetric conformation and "Koch-Moffitt's case IIa of conjugation" are interpreted in terms of steric and stereoelectronic effects. Changes in SIVC, SVIN and SVIO bond lengths are also rationalized.

Original languageEnglish
Pages (from-to)193-212
Number of pages20
JournalJournal of Molecular Structure
Volume156
Issue number3-4
DOIs
Publication statusPublished - Feb 1987

ASJC Scopus subject areas

  • Analytical Chemistry
  • Spectroscopy
  • Organic Chemistry
  • Inorganic Chemistry

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