The Synthesis, Characterization Of [N, O] Bidentate Palladium Complexes And Their Applications In Suzuki-Miyaura Coupling Reaction

Pd-catalyzed Suzuki-Miyaura coupling reaction of aryl halides with arylboronic acidshas become one of the most powerful C-C bond forming methods with the advantages ofhigh yields, mild reaction conditions, wide functional groups tolerance and commercialavailability of the diverse arylboronic acids. Its has widely applied in the synthesis ofnatural products, pharmaceuticals, and functional polymer materials.The development of stable and environmentally friendly phosphine-free ligands for thepreparation of biaryls has been intensely investigated in recent years. we have designed andsynthesized a series of α-hydroxyimine ligands, their palladium complexes and a series of[N,O] salicylaldimine ligands in this paper.1.α-imino ketones was synthesized according to the literature method, the α-iminoketones were first treated with trimethylaluminum to form the coordinated complexes insitu, and a chemoselective addition to C=O by methyl group occurred subsequently.α-hydroxyimine ligands were obtained by hydrolysis in high yields. As a result thepalladium complexes C1, C2and C3were prepared with PdCl2and these ligands. Herein, we report the catalytic properties of these precatalysts for the Suzuki-Miyauracross-coupling reaction. the experiments showed that C3exhibited the best catalyticefficiency and C1exhibited minimum. C3also exhibit a very high catalytic activity for thesteric bulks and the rich electronic aryl bromides with arylboronic acids. Using4-methylbromobenzene with phenylboronic acid in the presence of0.01%PdCl2at roomtemperature for2h hours, was obtained93%yield. The experimental results indicate that toform palladium nanoparticles possessing high catalytic activity.2. A series of [N,O] salicylaldimine ligand were synthesized, Our group recentlyinvestigated the effect of ligands using4-chlorobenzaldehyd and phenylboronic acid assubstrates at room temperature, the L10exhibited the best catalytic efficiency for the arylhalides with arylboronic acid coupling reaction. For instance, the coupling reaction of4-methoxy bromobenzene with phenylboronic acid in the presence of0.5%catalytic at60oC,94%yield was obtained after2hours.2-chlorobenzonitrile and4-methylphenylboronic acids provided the key intermediate of Sartan family in the presence of0.5%catalyst at110oC,82%yield was obtained. Significantly, Introduction of an appropriateamount of water in the catalyst system can improve the catalytic activity of the catalyst.The ligands,palladium complexes and biphenyls were confirmed by1HNMR,13CNMR.The Crystal structure of the α-hydroxyimine ligand L3, complexes C1, C2and C3haveexamination by X-ray.