Complexation of Acyclic Dialkyl Sulfoxides with Carboxylic Acids: a Stereochemical Analysis of Deshielding Effects
✍ Scribed by Peter H. Buist; Behnaz Behrouzian
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 469 KB
- Volume
- 34
- Category
- Article
- ISSN
- 0749-1581
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✦ Synopsis
The chemical shifts of the u-sulfinyl hydrogens of acyclic dialkyl sulfoxides (0.04 M CDCl, solutions) were assigned for the first time. Complexation of these compounds with carboxylic acids leads to deshielding of the 'H resonances of only one of the diastereotopic a-sulfinyl hydrogens. The stereochemistry of this deshielding effect was investigated via 'H and 'H NMR using a stereospecifically deuteriated model sulfoxide of known absolute configuration: (9R, lOS)-( 102H, 1 methyl 9-thiastearate S-oxide. Complexation of this compound with 3 equiv. of (S)-( +)a-methoxyphenylacetic acid resulted in a downfield shift of the deuteron resonance and the spin system of the quasi-enantiotopic C-8 hydrogen as monitored by 'H NMR and 'H NMR, respectively. The 'H spin system of the C-10 methine and that of its quasi-enantiotopic counterpart at C-8 were not significantly affected under these conditions as detected by 'H NMR.