Cyclic allylamine–enamine systems. Part 7. A theoretical study of the relative energies of isomeric cyclic allylamine–enamine systems
Abstract
The relative energies of a series of isomeric cyclic allylamine–enamine systems have been calculated by MINDO/3 and ab initio MO methods including complete geometry optimisation. The MINDO/3 results are shown to be reliable by comparison with experiment and with the ab initio results. Thus, for a particular pair of N-methyltetrahydropyridine-4-carbaldehyde isomers (12) and (13), both ab initio and MINDO/3 methods give similar optimised geometries and predict the enamine to be more stable than the allylamine by 1.5 and 1.3 kJ mo–1 respectively. This energy difference is predicted to be increased by up to 3 kJ mol–1 in water.