Direct Construction of Julolidines via Reductive Annulation of Quinolines and Conjugated Enones by a MOF-Derived Hierarchically Porous Iridium Catalyst

ABSTRACT: Here, we describe the development of a MOF-derived hierarchically porous ZrO2-supported iridium catalyst (Ir-N@HP-mesoZrO2), featuring sufficient accessible catalytic sites even with ultralow iridium loading. Such a catalyst was successfully applied to selective and direct construction of julolidines via catalytic reductive annulation of readily available quinolines and conjugated enones, proceeding with good substrate and functional group compatibility, reusable catalyst, high step and atom efficiency, and easy applicability for the fabrication of functional molecules. The present work opens a door to further develop useful transformations by merging hydrogen transfer-mediated substrate activation with in situ incorporation of a coupling sequence under heterogeneous reductive catalysis.

Automated summary

In this study, a hierarchically porous ZrO2-supported iridium catalyst was developed, which exhibited sufficient catalytic activity even with a low iridium loading. This catalyst was successfully used for the selective and direct construction of julolidines, showing good substrate and functional group compatibility, reusability, high step and atom efficiency, and applicability for the fabrication of functional molecules.