Synthesis Of N, O Bidentate Ligands And Reaction Studies Involved In CC Bond Construction

Biaryls,alkenes and alkynes constitute the key structural motifs in numerous natural products,pharmaceutical intermediates and functional materials.Palladium-catalyzed C-C cross-coupling reactions have been proved to be the most efficient method to synthesize these compounds.Generally,the use of suitable ligand can accelerate the reaction process.Phosphine ligands are widely employed in catalytic reaction due to the high coordination activity.However,the drawbacks are preparative difficulties and instability.Therefore,developing efficient,stable and novel ligands become hot research topic.In this paper,a series of stable and novel N,0-bide'ntate ligands were designed and synthesized,including 2,3-dihydroxybenzaldehyde oxime,2,4-dihydroxybenzaldehyde oxime,2,5-dihydroxybenzaldehyde oxime,2,5-dihydroxyterephtlialaldehyde dioxime,2,4-dihydroxy-5-acetyIacetophenone dioxime and naringenin oxime and hesperetin oxime.These ligands were applied to palladium-catalyzed Suzuki cross-coupling reaction,Heck cross-coupling reaction and Sonogashira cross-coupling reaction,respectively.Firstly,palladium-catalyzed Suzuki cross-coupling in the presence of novel N,O-bidentate ligand was investigated by selecting the reaction conditions including the ligands,the amount of catalyst,solvent,base and temperature.A novel system of PdCI2 as catalyst,2,5-dihydroxyterephthalaldehyde dioxime as ligand to catalyze Suzuki reaction was developed.35 biaryls were synthesized under the optimal conditions.The reaction system was mild,environmentally friendly and efficient.Secondly,palladium-catalyzed Heck cross-coupling reaction in the presence of novel N,O-bidentate ligand was exploited.By specifying conditions,an efficient protocol to the Heck reaction of arylbromides with alkenes was developed in the presence of PdC12 as catalyst and naringenin oxime as ligand in the DMF-H2O.22 alkenes were synthesized in this system.The catalytic system was efficient and have a good group tolerance.Lastly,palladium-catalyzed Sonogashira cross-coupling reaction in the presence of new N,O-bidentate ligand was explored.A new catalytic system of PdCl2 catalyzed Sonogashira cross-coupling reaction was developed in the presence of naringenin oxime as ligand in the MeOH-H20 by screening reaction conditions.17 alkyenes were synthesized using this new system.The method have a good group tolerance and efficient catalytic activity.