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1 H, 13 C, 17 O NMR and quantum‐chemical study of the stereochemistry of the sulfoxide and sulfone derivatives of 3‐arylidene‐1‐thioflavan‐4‐one epoxides
Author(s) -
Kovács József,
Tóth Gábor,
Simon András,
Lévai Albert,
Koch Andreas,
Kleinpeter Erich
Publication year - 2003
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1153
Subject(s) - chemistry , conformational isomerism , sulfone , sulfoxide , ab initio , chemical shift , nuclear magnetic resonance spectroscopy , ab initio quantum chemistry methods , computational chemistry , cis–trans isomerism , thiirane , stereochemistry , crystallography , ring (chemistry) , molecule , organic chemistry
The oxidation of the trans,cis ‐( 2 ) and trans,trans ‐epoxides ( 3 ) of differently substituted ( Z )‐3‐arylidene‐1‐thioflavan‐4‐ones ( 1 ) with dimethyldioxirane (DMD) yielded the appropriate sulfoxides ( 4, 5 ) and sulfones ( 6, 7 ). The structures were elucidated by the extensive application of one‐ and two‐dimensional 1 H, 13 C and 17 O NMR spectroscopy. The conformational analysis was achieved by the application of 3 J (C,H) coupling constants, NOESY responses and ab initio calculations. The preferred ground‐state conformers (twisted envelope‐A, twisted envelope‐B for 6 and twisted envelope‐A, envelope‐B for 7 ) were obtained as global minima of the theoretical ab initio MO study and also the examination of the 17 O and 13 C chemical shifts, calculated for the global minima structures of the sulfone isomers by the GIAO method. Analogous results, obtained for the sulfoxide isomers ( 4, 5 ), not only led to the preferred conformers but also gave evidence for the trans arrangement of the 2‐Ph group and the oxygen atom of the SO group. Chemical shift differences between the isomers, sulfoxides and sulfones were corroborated by ab initio calculations of the anisotropic effects of the oxirane ring and the SO and SO 2 groups. Copyright © 2003 John Wiley & Sons, Ltd.