Synthesis Of Novel Monodentate Phosphorus Ligands And Their Application In Asymmetric Hydrogenation

Chiral molecules are closely related to people’s lives.Currently,the methods of obtaining chiral molecules include extraction from natural products,kinetic resolution and asymmetric synthesis.Asymmetric synthesis has attracted much attention because of its advantages.In this paper,a novel monophosphine ligand was synthesized from simple and readily available raw materials,and characterized by hydrogen,carbon,phosphorus and mass spectrometry.(1)First of all,we synthesized dendrimers using inexpensive and easily available3,5-dihydroxybenzoic acid,methanol,carbon tetrabromide,benzyl chloride,potassium iodide,potassium carbonate,lithium tetrahydrogenate,etc.as raw materials.Then the dendritic phosphite ligands were synthesized using the synthesized dendrimers,S-BINOL,phosphorus trichloride,etc.as reaction materials.Then,using bromoacetylene,p-hydroxybenzaldehyde,benzylamine,etc.as reaction materials,amines with acetylene bonds were synthesized,and then other amines were reacted with S-BINOL and phosphorus trichloride to synthesize phosphoramidite ester ligands.(2)The dendritic phosphite ligand was applied to Rh-catalyzed asymmetric hydrogenation of α-dehydroamino acid ester substrates.In this kind of reaction substrate,the dendritic phosphite ligand-rhodium catalyst shows a clear "dendritic molecular effect",in which the third-generation dendritic phosphite ligand makes the reaction obtain up to 90.7% Image selectivity and good substrate adaptability.(3)Next,the dendritic phosphite ligand was applied to the rhodium-catalyzed asymmetric hydrogenation of enamide substrates.Through experiments,we found that this type of catalyst does not exist “Dendritic molecular effect” in the asymmetric hydrogenation of enamide substrates,but the reaction obtained an ee value as high as93.5%.(4)A series of monophosphine ligands were applied to the asymmetric hydrogenation of 2-methylquinoline catalyzed by iridium.The dendrimer phosphite ligand-iridium catalyst gave only moderate enantioselectivity and no observation“Dendritic molecular effect”,and the reaction has a strong solvent effect;and with the phosphinamide ester ligand-iridium catalyst,the reaction obtained a higher enantioselectivity(90.3% ee).