Enantioselective Diels-Alder Cycloadditions with beta-Substituted Pyrazolidinone Propiolimides

Chiral Lewis acid catalyzed Diels-Alder cycloadditions between beta-substituted pyrazolidinone propiolimides and cyclic dienes have been studied. A catalyst prepared from Sc(OTf)(3) and t-Bu-pybox ligand promotes the formation of enantioenriched diene cycloadducts in moderate to high yield and good enantioselectivity from the reactions of acetylenic dienophiles and cyclic dienes.