Scandium(III)‐Zeolites as New Heterogeneous Catalysts for Imino‐Diels–Alder Reactions

This study demonstrates the first zeolite‐catalyzed synthesis of piperidine derivatives, including peptidomimetics and indoloquinolizidine alkaloids. The approach developed utilizes a highly effective one‐pot reaction cascade, through imine formation and imino‐Diels–Alder reactions, promoted by scandium‐loaded zeolites as a heterogeneous catalyst. The methodology described benefits from very low catalyst loadings (≤5 mol % of Sc^III), commercially and readily available starting materials, and mild reaction conditions. Furthermore, the Sc^III‐zeolite catalyst can be readily reused more than 10 times without any loss in efficiency.