Conformational study of the 4,9-dihetero-(Z,Z)-cyclodeca-1,6-diene ring system; the mono- and di-benzo analogues

✍ Scribed by E. Kleinpeter; J. Hartmann; W. Schroth

• Publisher: John Wiley and Sons
• Year: 1990
• Tongue: English
• Weight: 563 KB
• Volume: 28
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1260280713

✦ Synopsis

Abstract

The dynamic ^1^H and ^13^C NMR spectra of a series of mono‐ and bis‐annelated 4,9‐dihetero‐(Z,Z)‐cyclodeca‐1,6‐dienes were obtained and are discussed with respect to ground‐state conformers and the barriers to ring inversion, and to the restricted rotation about exocyclic partial C,N double bonds. The ten‐membered rings are, with one exception, anancomeric chair conformers and interconvert via a combination of single bond rotations and bond angle bendings. Depending on the heteroatoms present, the series of decreasing barriers to ring inversion S > NH > O was obtained. Benzannelation decreases the free energy of activation of the same dynamic process owing to greater intramolecular transannular H,H interactions.