Various NMR methods have been applied to investigate the ring‐reversal process in the title compounds. In order to measure barriers an exact assignment of proton‐exchange connectivities was required. This assignment was made using phase‐sensitive NOESY and difference NOE and saturation transfer spectroscopies. The barriers for ring reversal were found to differ substantially between compounds 1–3 on one hand (9–10.5 kcal mol−1), and compound 4 on the other (20.2 kcal mol−1). This was rationalized in terms of the different geometries of the ring systems.
ASJC Scopus subject areas
- Chemistry (all)