1H-, 31P- and 13C-NMR spectra of some 2-arylsulphonylamido-2-thiono-5-methyl-1,3,2-dioxaphospholanes

✍ Scribed by A. Barabás; V. Mureşan; L. Almási

• Publisher: John Wiley and Sons
• Year: 1979
• Tongue: English
• Weight: 512 KB
• Volume: 12
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1270120513

✦ Synopsis

Abstract

Some 2‐arylsulphonylamido‐2‐thiono‐5‐methyl‐1,3,2‐dioxaphospholanes (1), containing two chiral centres, give NMR spectra in which splittings of the ^1^H and ^13^C signals of the 5‐methyl substituent and of the ^31^P signal indicate that they exist in an approximately 70:30% ratio of two racemic mixtures, Z and E respectively, diastereomeric to each other. These splittings were invariably observed for compounds 1a, containing a monosubstituted sulphonylamido group (Y = H) and various substituents at position 4′ of the aryl group, X = H, CH~3~, OCH~3~, F, CI and Br. The methylenic protons in position 4 of the phospholane ring are diastereotopic and therefore magnetically non‐equivalent. Benzene‐induced shifts were measured for the Z isomers of compounds 1a, X = H, F and for compound 1b, containing an N‐disubstituted sulphonylamido group (Y = CH~3~) and X = H; the tentative interpretation of these shifts places the more shielded diastereotopic methylene proton on the same side of the ring as the 5‐methyl substituent. The HP and HH coupling constants indicate that the preferred conformation of the dioxaphospholane ring should be a ‘twisted envelopey’ shape with the 5‐methyl substituent in the equatorial position.