3‐(Allylamino)‐ and 3‐(propargylamino)propanal were converted via the corresponding oximes into nitrile oxides, which readily underwent intramolecular 1,3‐dipolar cycloadditions to furnish a piperidine‐annulated isoxazole or isoxazoline. The annulated isoxazoline was transformed into orthogonally carbamate‐protected cis‐ and trans‐4‐aminopiperidine‐3‐carboxylates, both representing interesting scaffolds for combinatorial chemistry. Through sequences of amidations and deprotections two triply functionalized products were obtained as examples for diversification. After Boc removal, the piperidino‐annulated isoxazole was also subjected to diversifying reactions, such as reductive amination, amidation, and the formation of sulfonamido‐ and ureido‐substituted derivatives.