| The Suzuki reaction has become one of the most powerful carbon-carbon bond forming methods with the advantages of mild reaction conditions, wide functional groups tolerance, little influnence by steric bulk of substrates, high yields and commercial availability of the diverse arylboronic acids. It has been widely applied in the synthesis of natural products, Pharmaceuticals, and advanced functional materials.Bidentate ligands with the property of hemilability have attracted chemists' research interests and have been widely applied in many palladium-catalyzed transformations. We designed and synthesized a series of P, N-bidentate ligands combined properties of bulky 1-adamantyl group and hemilability of bidentate ligand. The intermediate, o-(diphenylphosphino) benzaldehyde, was firstly synthesized according to literature. Then, the iminophosphine P, N-bidentate ligandâ… was synthesized by schiff base reaction of the intermediate and 1-adamantylamine with yield 83%; In succession, ligandâ…¡was obtained with yield 84% by reduction ofâ… using NaBH4 as reducing reagent. As an electron eletron donating group with steric effect, the methyl group was introduced into the molecule of ligandâ…¡via N-methylation using dimethyl sulfate as methylation reagent, resulting in the formation ofâ…¢in 40% yield.Systemic research of P, N bidentate ligands in palladium-catalyzed Suzuki reaction of aryl chlorides were conducted. The effects of palladium spices, solvents, Pd/P molar ratios and bases were tested.The two catalytic systems that Pd(OAc)2/â… -1,4-Dioxane/H2O-K3PO4·3H2O and Pd(OAc)2/â…¡-Toluene/H2O-NaOH were established. Both of them were efficient for the Suzuki reaction of aryl chlorides with electron withdrawing groups and aryl boronic acids, giving the highest yields of 96% and 100%, respectively. The Suzuki reaction of 4-chlorobenzene with phenylboronic acid was tesed in Pd(OAc)2/â…¢-Toluene/H2O-NaOH catalytic system resulting in 99% yield within 1.5 h. The activities of the ligands related closely with their structure that the active sequence of ligandâ… ,â…¡,â…¢in Pd(OAc)2/ligand-Toluene/H2O-NaOH catalyic system wasâ…¢>â…¡>â… .A seires of Schiff base type of P, N bidentate ligands with biphenyl moieties were also synthesized. The effect of C=N position on the activity of schiff base ligands was investigated in a model reaction of 4-chlorobenzene with phenylboronic acid. The results demonstrated that ligandâ…£-â…¦were unefficient with yield of 15-25% in 6 h with C=N outside the 5-membered ring of the proposed complex formed from the ligand and palladium. On the contrary, ligandâ…§with C=N in the 6-membered ring of the proposed complex formed from the ligand and palladium was efficient with yield 96% within 4 h in Pd(OAc)2/â…§-Toluene/H2O-NaOH.All the ligands synthesized in this paper were characterized by 1H NMR,13C NMR,31P NMR and MS. The crystal structure of ligandâ… ,â…¡,â…¢,â…¤were obtained. All the cross-coupling products were characterised by 1H NMR.
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