Mechanistically, aminomalonate and aspartate nucleophiles are presumed to attack Ntriflylpyrimidinium species 9 at C6, analogous to our previously reported observations with hydrazine in the pyrimidine-to-pyrazole transformation (Figure ). Dearomatized adduct 10 could undergo a related 6p electrocyclic ring opening, leading to aza-Zincke imine intermediate 11. Since the aspartate nitrogen atom that initially attacked the pyrimidinium remains the most nucleophilic atom in the molecule, this nitrogen attacks at C2 (favoring a 6-exo-trig over a 4-exotrig cyclization) resulting in ring-closed N-succinyl dihydro-aminopyrimidine intermediate 12.