Aminocatalytic Asymmetric <i>exo</i>-Diels–Alder Reaction with Methiodide Salts of Mannich Bases and 2,4-Dienals to Construct Chiral Spirocycles

An asymmetric <i>exo</i>-Diels–Alder reaction of α-methylene carbonyl compounds, generated in situ from stable methiodide salts of Mannich bases, with 2,4-dienals, has been developed through trienamine activation of a chiral secondary amine. A spectrum of spirocyclanes with high molecular complexity was efficiently constructed in moderate to excellent diastereo- and enantioselectivity