Research On The Asymmetric Hydrogenation Of Imine

Asymmetric Hydrogenation is an efficient reduction strategy,which could construct chiral molecules efficiently and this strategy is widely applied.The asymmetric addition reactions between unsaturated compounds and hydrogen molecules are highly efficient,those unsaturated compounds including carbon-oxygen double bonds(C=O),carbon-nitrogen double bonds(C=N)and carbon-carbon double bonds(C=C).This type of reaction can quickly construct chiral structures with high atom economy and improve the synthesis efficiency,which means the industrial production of chiral molecules is promising.The direct products of imine's asymmetric hydrogenation are chiral amine compounds,which plays an important role in the synthetic chemistry.As a result,the asymmetric hydrogenation of imine compound has been widely concerned.Dibenz[c,e]azepines are a class of chiral amine compounds with axial chirality,which are widely applied in the synthetic chemistry.In the existing researches,the catalyst based on chiral bidentate phosphine ligands can asymmetric hydrogenate imines efficiently.Based on such researches,the work mainly concerning obtaining the dibenz[c,e]azepine molecules by asymmetric hydrogenation reduction of imines are carried on.The enantioselectivity of the product obtained by such strategy is up to 97%.This strategy also has extensive compatibility with different substituents.In recent years,Xumu Zhang's group has developed a series of chiral tridentate ligands based on ferrocene.Iridium complexes based on these ligands exhibit excellent enantioselectivity and conversion in asymmetric hydrogenation of simple ketones.Those catalysts are applied to the asymmetric hydrogenation of imines,the required hydrogen pressure of imines' asymmetric hydrogenation is 75 atm,the highest enantioselectivity is 66%.Iridium complexes based on these ligands are inapplicable in imines' asymmetric hydrogenation.This type of catalyst are then applied to the asymmetric hydrogenation of ortho-substituted diaryl ketones.The enantioselectivity of the product is up to 97%,TON is up to 11850.This catalytic system also has extensive compatibility with different substituents.