Proton magnetic resonance studies of cyclic compounds. Part VIII. The conformations of cis- and trans-decahydroquinolines and their acyl derivatives

Abstract

Proton magnetic resonance spectra are in accord with a twin-chair conformation for trans-decahydroquinoline and its acyl derivatives. cis-Decahydroquinoline prefers that twin-chair conformation which allows the nitrogen lone pair to occupy the hindered ‘inside’ position. However, the N-benzoyl, N-benzenesulphonyl, N-carboxyanilide, and N-nitroso-derivatives of cis-decahydroquinoline adopt the alternative twin-chair conformation, thus avoiding the repulsive interaction between the N-substituent, and the C-8 methylene group.