Synthesis, Characterization, And Catalytic Application Of Chiral Pyrrolidine-Triazole Functionalized Materials

Since List et al. firstly reported the asymmetric aldol reaction catalyzed by (L)-proline in 2000, the research on organocatalysis has been flourished, which starts a new chapter in the field of asymmetric catalysis.. However, the use of organocatalysts in large amounts (usually in 20-30%) and the difficulty in recycling the organocatalysts have restricted the wide application of organocatalysis. Heterogenization of organocatalysts is, therefore, of great importance to resolve these problems. Currently, the main strategy for catalyst heterogenization is the grafting method, by which the organocatalysts could be immobilized onto the surface of various solid supports, such as PEG, silica, ionic liquid, DNA, dendrimer and inorganic porous materials (for example, MCM-41). However, the grafting method still has several inherent flaws, for example, inhomogeneous distribution of catalytic moieties, poor catalyst stability and low catalyst loading.In recent years, periodic mesoporous organosilicas (PMO) and conjugated microporous polymers (CMP) have received much attention because of their unique advantages, such as large surface, excellent porous nature, good thermal and chemical stability, and so on. These materials may work as potential support for immobilizing organocatalysts., To the best of our knowledge, however, there has been no reports on constructing functional PMO or CMP materials with organocatalysts through the "bottom-up" strategy, i.e., through self-condensation or cross-coupling reactions.Accordingly, the main task of this thesis was to design and synthesize several PMO and CMP materials, in which certain organocatalyst could be embedded into the porous network via self-condensation or cross-coupling reactions. The synthesized materials were fully characterized by solid-state NMR spectroscopy, elemental analysis, powder X-ray diffraction (XRD), and scanning electron microscopy. Finally, application of these functional materials as heterogeneous catalysts was also exploited.In Chapter I, the research background on organocatalysis and porous materials (PMO and CMP) are introduced. The advantages and disadvantages of organocatalysts and applications of PMO and CMP materials in heterogeneous catalysis are highlighted.In Chapterâ…¡, we report on the synthesis and characterization of chiral PMO materials, which contain the chiral pyrrolidine-triazole-based organocatalysts in the framework. Fristly, two organocatalysts precursors (Precursorâ… and Precursorâ…¡) based on functional pyrrolidine-triazole were synthesized. The chiral PMO were then prepared via self-condensation of these chiral organosilane precursors. The synthesized PMO materials were characterized by powder X-ray diffraction (XRD) and solid-state NMR spectroscopy.In Chapterâ…¢, we report on the synthesis, characterization, functionalization and catalytic application of functional CMP materials, which contain chiral pyrrolidine-triazole-based organocatalysts in the framework. We firstly synthesized the pyrrolidine-triazole-based organocatalyst (Precursorâ…¢), and then constructed several organocatalyst-functionalized CMP materials via Sonogashira-Hagihara cross-coupling reaction. The CMP materials were characterized by solid-state NMR spectroscopy, elemental analysis, infrared spectroscopy, and scanning electron microscopy. Moreover, the catalytic applications of these functional CMP were exploited in the Michael addition of ketones to nitroolefins.