Study On The P(?)O And P(?)N Chelated Pd(Ⅱ) Complexes Catalyzed Suzuki Cross-coupling Reaction: Synthesis Of TFT-LCs

Suzuki cross-coupling of aryl bromides with arylboronic acid is one of effective methods to form biphenyl derivatives in organic synthesis. In this thesis, the three series of P, O and P, N bidentate ligands chelated palladium complexes ï¿¡40-46} were designed and synthesized for Suziki cross-coupling reaction. The coupling reaction of aryl bromides with arylboronic acid in the presence of catalytic amount of 40-46 proceeded smoothly under mild reaction conditions (room temperature) with high selectivity and excellent yields, which indicated that the palladium complexes 40-46 are excellent catalysts for Suzuki cross-coupling reactioa Various substrates can be employed in the palladium complexes 40-46 catalyzed coupling reaction, and the new method could be used in industry to prepare biphenyl derivatives. The details are as follows:1. The bidentate P/O ligands were synthesized by improved method under mild reaction conditions in high yields with high purities. The three bidentate P/O palladium complexes, cis-Pd(Ph₂PCH₂COO)₂ (40), cis-Pd(Ph₂PCH₂CH₂COO)₂ (41) and cis-Pd(o-Ph₂PC₆H₄COO)₂ (42), were prepared, and the crystal structure of 40_was elucidated.2. The three bidentate palladium complexes mentioned above were used as catalysts in Suzuki cross-coupling. Liquid crystalline compounds were synthesized via one-step process at room temperature in excellent yields (>90%). These catalysts could be reused for three times without losing their catalytic activities.3. Two bidentate P/O palladium complexes, Pd(Ph₂PCH₂CH₂O)₂ (43) and Pd(Ph₂PCH₂CH(CH₃)O}₂ (44), were synthesized, and their catalytic activities in Suzuki cross-coupling were investigated. The catalyst 44 shows higher catalytic activity than that of 43.4. Two bidentate P/N palladium complexes, [Pd(Ph₂PCH₂CH₂NH₂)₂]Cl₂ (45) and [Pd(Ph₂PCH₂CH₂CH₂NH₂)₂]Cl₂ (46), were synthesized, and their catalytic activities in Suzuki cross-coupling were investigated and the high yields of products were obtained in almost case. Both of the catalysts 45 and 46 show higher catalytic activities than that of bidentate P/O palladium complexes.5. The mechanism of the palladium complex 40 catalyzed Suzuki cross-coupling reaction was discussed. The cause of decomposition of catalyst and appearance of palladium black were studied.