Synthesis of Chiral Covalent Organic Frameworks via Asymmetric Organocatalysis for Heterogeneous Asymmetric Catalysis
Fei Li, Jing‐Lan Kan, Bing‐Jian Yao, Yu‐Bin Dong
Abstract
Abstract A general and efficient organocatalytic asymmetric polymerization approach for the synthesis of chiral covalent organic frameworks (CCOFs) has been developed. With a chiral 2‐methylpyrrolidine catalyst, a series of tris( N ‐salicylideneamine)‐derived β‐ketoenamine‐CCOFs are directly constructed from prochiral aldehyde‐ and primary amine‐monomers. The adopted aminocatalytic asymmetric Schiff‐base condensation herein is performed under ambient conditions with clear green synthetic advantages over the conventional acid‐catalysed solvothermal methods. The obtained β‐ketoenamine‐CCOFs can be further metalated by a solid‐state coordination approach, and the resulting Cu II @CCOFs can highly promote an asymmetric A 3 ‐coupling reaction. Specifically, a Cu II @CCOF@chitosan aerogel was fabricated as a highly efficient fixed‐bed model reactor for scaled‐up catalysis. The concept of aminocatalytic asymmetric polymerization might open a new way for constructing the CCOFs via asymmetric organocatalysis.