Development of a Solvent Knitting Method in Immobilizing Chiral Ferrocene Phosphine Catalysts and Their Application in Asymmetric Reactions

Traditional methods for the immobilization of chiral catalysts typically require time-consuming and complicated premodification steps involving specific functional groups. In this study, we present a straightforward, highly efficient, and universal solvent knitting strategy for immobilizing chiral ferrocene phosphine catalysts, eliminating the need for premodification. This method enables facile control over the structure of heterogeneous Zhaophos catalysts by incorporating various commercially available organic comonomers or silica-based materials. Notably, the incorporation of MCM-41 dramatically increases the Brunauer–Emmett–Teller (BET) surface area by more than 100-fold relative to simple polymerization and generates a predominantly mesoporous polymer network, while the untemplated polymer remains largely macroporous. This structural change results in an over 6-fold improvement in turnover frequency (TOF). The immobilized heterogeneous catalysts demonstrate good performance in the asymmetric hydrogenation of benzoxazinones and quinoxalinones, achieving up to 99% yield and 99% enantiomeric excess (e.e.). The versatility of this solvent knitting strategy is further illustrated by the successful immobilization of four additional chiral ferrocene phosphine catalysts while maintaining their high catalytic activity in asymmetric transformation.