关键词: 聚合型膦配体, Suzuki-Miyaura 偶联反应, 均相催化, 异相循环

A recyclable polymeric phosphorus ligand, PolyBIDIME, and its palladium complexes was designed and introduced to address the high loadings of palladium catalysts in complex Suzuki-Miyaura coupling reaction. PolyBIDIME, a supported BI-DIME ligand on a polyamide chain, was designed as a soluble ligand in organic solvent applicable to homogeneous catalysis, but insoluble or less soluble in certain solvents for easy recovery from reaction conditions. This polymeric phosphorus ligand was designed in order to provide a practical and efficient example of “homogeneous catalysis and heterogeneous recycling in order to achieve a higher turnover number”. PolyBIDIME was synthesized by polymerization of 6-vinyl BIDIME with N-isopropylacrylamide in the presence of AIBN. The structure of the polymeric ligand was well characterized by 1H, 31P NMR, and GPC. The palladium complex of PolyBIDIME was prepared and characterized as Pd(PolyBIDIME)2Cl2, which was applied as the catalyst to the key Suzuki-Miyaura cross-coupling reaction of herbicide rinskor. Under optimized conditions, the Pd-PolyBIDIME catalyst provided high yields of the coupling product, excellent recyclability (10 times), and high total turnover numbers (up to 1,000), showing great potential for industrial applications. The Pd-PolyBIDIME was also applicable as the catalyst to a range of Suzuki-Miyaura couplings, showing great compatibility to steric hindrance and functional groups. Further synthetic applications were demonstrated in the synthesis of herbicides boscalid and fluxapyroxad as Suzuki-Miyaura cross-coupling catalyst, as well as in the synthesis of naproxen as a carbonylation catalyst, showcasing the high potential of Pd-PolyBIDIME as a cross-coupling catalyst in industrial settings. Detailed NMR studies and catalyst weight analysis were conducted to rationalize the catalyst recycling process. Results showed that slight physical loss of the palladium catalyst was confirmed during each run, while partial oxidation of the phosphorus ligand increased gradually after each run, which could be the main reason for the gradual decrease in catalytic efficiency during catalyst recycling.

Key words: polymeric phosphorus ligand, Suzuki-Miyaura coupling, homogeneous catalysis, heterogeneous recycling