Conformational analysis 29: Preparation and1H and13C NMR,FTIR, MS,and crystallographic conformational and configurational study of 3-Oxo-1,3-oxathiane and its monomethyl derivatives |
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Authors: | Kalevi Pihlaja Reijo Sillanpää Martti Dahlqvist Géza Stájer Markku Ahlgren |
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Institution: | (1) Department of Chemistry, University of Joensuu, Joensuu, Finland;(2) Present address: Institute of Pharmaceutical Chemistry, Albert Szent-Györgyi Medical University, Szeged, Hungary;(3) Department of Chemistry, University of Turku, SF-20500 Turku, Finland |
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Abstract: | 3-Oxo-1,3-oxathiane (1) and its monomethyl derivatives were prepared by oxidation of the corresponding 1,3-oxathianes. The structural analysis was carried out by1H and13C NMR, FTIR, and mass spectrometry. At 298 K compound1 was a 1 1 (at 173 K a 3 1) mixture of the SO(ax) and SO(eq) chair forms. The major oxidation products of methyl 1,3-oxathianes attained exclusively the SO(ax), Me(eq) chair forms except that of the 5-methyl derivative, which consisted of 7% of the SO(eq), Me(ax) chair conformation in CDCl3 solution. The minor products of oxidation existed in anancomeric SO(eq), Me(eq) chair conformations. The oxidation of 2-methyl- 1,3-oxathiane, however, led to 3,3-dioxo derivative (6) in addition to thetrans SO(eq)] monoxide. The crystal structures of6 andtrans-3-oxo-5-methyl-1,3-oxathiane were solved by X-ray diffractometry. |
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Keywords: | Conformational analysis X-ray crystallography 3-oxo-1 3-oxathianes |
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