Nafion-H-catalyzed Mukaiyama aldol condensations and hetero Diels–Alder reactions using aldehydes and imines. Part 15: General synthetic methods

Nafion-H catalyzes the Mukaiyama aldol condensation between aromatic aldehydes and the Danishefsky diene whereas the corresponding imines directly undergo hetero Diels–Alder cyclization to form 2,3-dihydro-γ-pyridones. Some chiral acetal derived aldehydes were found to undergo Mukaiyama aldol condensation in the presence of Lewis acids but not with Nafion-H.