Direct Synthesis of β‑Aminoenals through Reaction of 1,2,3-Triazine with Secondary Amines

Simple and direct nucleophilic addition of secondary amines, including imidazole, to 1,2,3-triazine under mild reaction conditions (THF, 25–65 °C, 12–48 h), requiring no additives, cleanly provides β-aminoenals 4 in good yields (21 examples, 31–79%). The reaction proceeds by amine nucleophilic addition to C4 of the 1,2,3-triazine, in situ loss of N2, and subsequent imine hydrolysis to provide 4.