Stereochemistry of heterocyclic compounds

Summary The stereochemistry of the reaction of 1-alkyl-4-piperidones with phenyllithium depends not only on steric factors, but also on the character of the nitrogen-attached alkyl group. The effect of alkyl groups is associated with fixation of the direction of the dipole of the nitrogen atom, as a result of which the predominant direction of reaction becomes that for which the free electron pair of the nitrogen and the C-O bond of the enolate ion then arising occupy antiparallel directions.