Acyl derivatives of cyclic secondary amines. Part 1. Dipole stabilization of anions: the cumulative effect of two stabilizing groups

Lithiation studies with diacylimidazolidines, diacylhexahydropyrimidines, and triacylhexahydro-1,3,5-triazines indicate that no substantial increase in carbanion stability occurs as a results of the introduction of the second stabilizing group. Relative energies are calculated for three conformers of lithiated diformylimidazolidine, six conformers of lithiated diformylhexahydropyrimidine, and eight conformers of lithiated triformylhexahydro-sym-triazine. For the six-membered rings, conformers with equatorial lithium are always more stable those those with axial lithium. Although equatorial syn-syn conformers (with double O–Li co-ordination) are more stable than equatorial syn-anti, the difference is significantly less than that found between the corresponding syn-anti and (least stable)anti-anti conformers.