Lythraceous Alkaloids. XIV. Kinetic Equalization of Carbon-13 Nuclear Magnetic Resonance Chemical Shifts in N, O-Dimethyllythranidine, a Cyclophane Bearing Asymmetric Carbon Atoms

Abstract

Temperature-dependent carbon-13 nuclear magnetic resonance (¹³C-NMR) studies have disclosed that the mobile equilibrium in N, O-dimethyllythranidine (1) involves mainly two dynamic processes, which are rotation about the carbon-carbon bond between two phenyl rings and reversal of the piperidine ring. At ambient temperature, ¹³C chemical shift differences due to rotational movement were averaged, while those due to ring flip of piperidine moiety were not. This provides another example of "selective kinetic equalization of chemical shifts."