A heteroannulation process for preparing piperidones and tetrahydropyridones by reacting an appropriately substituted enamine with an acryloyl derivative wherein a leaving group occupies the carbonyl; a process for cleaving a 1-phenylethyl group from an acylated amino group or an heterocyclic nitrogen atom adjacent to a carbonyl group, particularly that on the nitrogen atom of the products of the heteroannulation process, is also provided.