3-Oxo-1,3-oxathiolanes—synthesis and stereochemistry

✍ Scribed by Kalevi Pihlaja; Jari Sinkkonen; Géza Stájer

• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: English
• Weight: 132 KB
• Volume: 46
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.2172

✦ Synopsis

Abstract

The compound 3‐oxo‐1,3‐oxathiolane (6) and its cis ‐ and trans ‐ 2‐methyl (7,8), 4‐methyl (9,10), 5‐methyl (11,12) and 2‐p‐nitrophenyl (13,14) derivatives were prepared by oxidizing the corresponding 1,3‐oxathiolanes (1–5) with NaIO~4~ in water. The oxides were purified and their isomers separated using thin layer chromatography. The structural characterization was carried out with ^1^H NMR spectroscopy and molecular modeling. Compounds 8–10, 12, and 14 attain the half‐chair type conformation with O(1) above and C(5) below the plane (HC1), but 6, 7, 11, and 13 are, for steric reasons, the mixtures with the alternative half‐chair (HC2), where O(1) is below and C(5) above this plane. Accordingly, 6 appears based on the values of experimental coupling constants as an 81:19, 7 as a 37:63, 11 as a 33:67 and 13 as a 54:46 mixture of HC1 and HC2, respectively. The relative energies of these conformations, the values of the vicinal H,H‐coupling constants and ^1^H chemical shifts were estimated for compounds 6–12 also by computational methods and they support nicely the conclusions based on experimental data. Copyright © 2008 John Wiley & Sons, Ltd.