Substituted tetrahydropyridines and piperidines are common six-membered heterocycles found in biologically active natural products and synthetic pharmaceuticals. [1] One of the most versatile and reliable methods to prepare this class of six-membered heterocycles is the aza-Diels-Alder reaction. [2] Particularly, the recent development of dienamine catalysis [3] has added a powerful dimension to the aza-Diels-Alder reaction, which strongly relies on the formation of the dienamines developed by the groups of Barbas, [4] Jørgensen, [5] and Chen [5] by 1,2-addition of the amine catalyst to enone or enal (Scheme 1). Despite extensive studies and noteworthy