Noncovalent Catalysis for Enantioselective Direct Aldol Reaction of 3‐Acetylcoumarins to Pyrazole‐4,5‐diones

The first catalytic enantioselective direct aldol reaction of 3‐acetylcoumarins to pyrazole‐4,5‐diones is reported and shown to proceed through noncovalent substrate activation by a quinine‐derived bifunctional tertiary amino‐amide as the catalyst. The densely functionalized products, consisting of an oxygen‐containing quaternary stereocenter and bearing two biologically relevant heterocycles, are generally obtained in high yields with moderate to excellent enantioselectivities. Organocatalysis: Enantioselective direct aldol reaction of 3‐acetyl‐2H‐chromenes with electrophilic pyrazole‐4,5‐diones has been demonstrated by noncovalent catalysis. The products, comprising an oxygen‐containing quaternary stereogenic center and two biologically important heterocyclic frameworks, were obtained in high yields with moderate to excellent enantioselectivities using a bifunctional tertiary amino‐amide as catalyst.