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Conformational analysis of 7‐membered dimethyl cyclic sulphites: 2‐Oxo‐1,3,2‐dioxathiepanes and 3‐oxo‐2,4,3‐dioxathiepins
Author(s) -
Guimaraes Afonso Celso,
de Almeida Paulo Gontijo Veloso,
Baltas Michel,
Cazaux Louis
Publication year - 1983
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/omr.1270211202
Subject(s) - diastereomer , chemistry , twist , stereochemistry , crystallography , series (stratigraphy) , nuclear magnetic resonance spectroscopy , coupling constant , computational chemistry , physics , mathematics , paleontology , geometry , particle physics , biology
2‐Oxo‐1,3,2‐dioxathiepanes and 3‐oxo‐2,4,3‐dioxathiepins, including two series of three diastereoisomers, were synthesized, isolated by HPLC and characterized by 1 H and 13 C NMR spectroscopy. Their conformational behaviour was studied using a computer‐assisted LIS technique and, for c ‐4, t ‐7‐dimethyl‐2‐oxo‐1,3,2‐dioxathiepane, a 400 MHz spectral analysis. Single twist‐chair conformations or an equilibrium between them are the most stable in the dioxathiepane series while chair or twist‐boat forms, or both in equilibrium, are favoured in the dioxathiepin series. Conformations and equilibria are detailed, with and without LSR, taking into account 1 H coupling constants and IR SO stretching frequencies as conformational probes.