C2-Symmetric bipyrrolidines as organocatalysts for asymmetric Diels-Alder reactions

A new class of C2-symmetric 3,3′-dialkoxy-2,2′-bipyrrolidines have been designed and developed for asymmetric organocatalytic Diels-Alder reactions of α,β-unsaturated aldehydes. The bipyrrolidines combined with HClO4 were found to be effective organocatalysts for enantioselective Diels-Alder reactions. The catalysis mode has been demonstrated by NMR and X-ray crystallographic studies for diiminium intermediate.