The Synthesis Of Palladium Catalysts Supported On MCM-41 Mesoporous Molecular Sieves And Their Application In Preparation Of 2-Fluoro-4-Ethyl-4-Pentyl Terphenyl

Suzuki reaction is one of the most important c-c coupling reactions. The typical catalyst of suzuki reaction is homogeneous catalyst, such as Pd(PPh₃)₄ and Pd(OAc)₂ . These catalysts have high activity, but they are not separated from reactants and not recovered and reused easily. Palladium catalyst supported on heterogeneous carrier can overcome the disadvantages of homogeneous palladium catalyst. The catalyst can be recovered and reused easily after the reaction, whose activity and selectivity are as high as homogeneous palladium catalyst.Three palladium catalysts supported on MCM-41 were prepared by coordinating palladium species and MCM-41. Firstly, MCM-41 was grafting three different ligands respectively, which were diphenylphosphino methanol, acetyl pyridine, and thiophenecarboxaldehyde. And then the functionalized MCM-41 was reacted with PdCl2 or Pd(OAC)₂ through coordination. These catalysts were successfully applied to Suzuki reaction for the preparation of 2′-fluoro-4″-ethyl-4-pentyl terphenyl (2B(F)B5), which is an important intermediate of liquid crystal. The diphosphine palladium(II) complex (MCM-41-2P-Pd (II)) was more activity than another two catalysts. And the type of alkali, solvent, temperature, reaction time and catalyst dosage were investigated. Finally, the yield of 2B(F)B5 was up to 92.5% with optimizing conditions, and the conversion of substrate was still above 85% after the fourth recovered reaction.