Application Of Titanium-coordinated Hybrid Materials In Organic Synthesis

Nanocatalysis is one of the hot topics in the research field of heterogeneous catalysis. In this dissertation, several organic-inorganic hybrid nano and submicron materials was designed and prepared as well as their catalytic efficiency in chemoselective aerobic oxidation and C-C band formation was investigated. By using above-mentioned materials as catalyst and scavenger, two serials of 1,2,3-thiadiazole-containing heterocyclic derivatives were prepared as potential fungicidal chemicals. This study includes three aspects. Firstly, N-butyl titanate was employed as a bridging reagent to immobilize 4-OH-TEMPO hemisuccinate on mesoporous molecular sieve MCM-41, and the TEMPO functionalized MCM-41 was then used as a catalyst in aerobic oxidation of alcohols to form corresponding carbonyl compounds. The effect of catalyst preparation and oxidation conditions were also investigated. Secondly, protocatechuic aldehyde was anchored on MCM-41 through titanium-coordination to afford aldehyde-functional hybrid material (aldehyde-MCM-41) which could be used as a scavenger in the synthesis of 1,2,3-thiadiazole-containing heterocyclic derivatives. A green oxidation process for the preparation of 4-methyl-1,2,3-thiadiazole-5-aldehyde was developed based on TEMPO-MCM-41 catalyzed aerobic oxidation. Starting from this intermediate, two serials of heterocyclic derivatives were prepared; namely (a) compounds from the cyclic condensation between the Knoevenagel products of 1,2,3-thiadiazole-5-aldehyde and carbonyl-containing active methylene compounds, and (b) aryl hydrazones of 1,2,3-thiadiazole-5-aldehyde. In the synthesis of aryl hydrazones, aldehyde-MCM-41 was employed as a scavenger to remove excess aromatic hydrazines in initiatory purification. Bioassay results indicated that certain compounds in serial (a) showed fungicidal activities to some extent against Phytophthora infestans and Pseudomonas syringae. Thirdly, submicron particles of nicotinic acid-NiCl2 hybrid material were obtained through sol-gel process from biorenewable nicotinic acid and anhydrous nickel chloride. Such catalyst showed a good catalytic activity and recycling performance in the Michael addition of indole to chalcones.