Conformational and configurational study of 1,3-dioxolanes by proton and carbon NMR spectroscopy

✍ Scribed by A. Mucci; L. Schenetti; L. Brasili; L. Malmusi

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 637 KB
• Volume: 33
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1260330303

✦ Synopsis

Abstract

The configurational and conformational properties of six 4‐trimethylammoniummethyl 2,2‐disubstituted 1,3‐dioxolanes were studied using NOE experiments and vicinal coupling constants. Selective 1D NOE experiments proved to be effective tools in the configurational assignment of C‐2 relative to C‐4. The preferred conformation of the dioxolane ring and the exocyclic group at C‐4 was obtained by employing vicinal coupling constants and NOE results. The ^1^H and ^13^C NMR chemical shifts show stereochemically dependent trends. Quantitative analysis of conformer populations was performed using Haasnoot et al's equation. The N^+^(CH~3~)~3~ group was found to be synclinal with respect to the heterocyclic O‐3 atom and points outside the ring. When a phenyl group is present at C‐2, the 4‐CH~2~N^+^— group in a trans relationship to the 2‐phenyl ring was found to occur prevalently in a pseudo‐axial orientation, whereas it was established to be prevalently pseudo‐equatorial when cis with respect to the phenyl ring.