Compounds with bridgehead nitrogen. 51—The NMR spectra and stereochemistry of the 6-ethylindolizidines
作者:Lee Banting、Trevor A. Crabb、Andrew N. Trethewey
DOI:10.1002/mrc.1260250416
日期:1987.4
1H and 13C NMR spectroscopy showed that both isomers of 6‐ethylindolizidine adopt predominantly the trans‐fused conformation in CDCl3 at 298 K. ΔG 298⊖ for the cis‐⇌tram‐fused conformational equilibrium in indolizidine must accordingly be not less than 2.8 kcal mol−1.
Compounds with bridgehead nitrogen. 62—NMR spectra and stereochemistry of perhydropyrido[1,2-c][1,3]thiazepines and related systems
作者:Trevor A. Crabb、Asadollah Fallah
DOI:10.1002/mrc.1260280509
日期:1990.5
Perhydropyrido[1,2‐c][1,3] thiazepine adopts (CDCl3 solution, 25°C) an equilibrium containing > 98% trans‐fused conformer, in contrast to perhydropyrido[1,2‐c][1,3]oxazepine, which adopts a ca. 74% trans‐fused ⇌ 26% O‐inside‐cis‐fused conformational equilibrium. The cis‐(H‐5a, H‐8)‐8‐ethyl‐substituted derivatives of both systems show increased preference for the S/O inside cis conformations. The related