Study On Asymmetric Alkenylation And Heteroarylation Of Rhodium - Diene - Catalyzed Imines

The transition metal catalyzed asymmetric addition of the C=N bonds of imines has become one of the most effective methods for the asymmetric synthesis of chiral α-branched amines. Especially, significant efforts have devoted to the development of the Rh(Ⅰ)-catalyzed addition of boronic reagents to activated imines is one of the most booming strategies. This dissertation is mainly about two related research projects:the Rh(I)-diene-catalyzed alkenylation and heteroarylation of activated imines.In the first part, we started our research in the Rh(Ⅰ)-diene catalyzed addition of the commerically available alkenyl potassium tetrafluoroborates to activated imines. Based on (3-substituented of the double bond is aliphatic or aryl, two different reaction conditions were developed to achieve the desired products in excellent yields and enantioselectivities. For example, the combination of base/water/temperature for the (3-aliphatic-substituent alkenyl trifluoborates is K3PO4/H2O (10eq)/70℃, while the KF/H2O (55eq)/rt for arylsubstituented ones. In all of the examined examples, high yields and excellent enantioselectivities (97->99%ee) were observed.Next, the Rh(I)-diene catalyzed asymmetric addition of alyklimines with alkenyl potassium tetrafluoroborates were carried out in neutral reaction condition. When the loading of catalysis was increased to5mol%and used MeOH (2eq) as the proton source, the aimed products were generated in good yields and enantioselectivities(up to93%yield and99%ee)。 This is the first successful report on the rhodium-catalyzed alkenylation of alkylimines.In addtion, as a demonstration of the utility of the upper method, the synthesis of natural molecular (-)-aurantioclavine was pursued. A different strategy from the previous method was used, in which the key intermediate was constructed directly by alkenylation of imines derived from the the relevant indole-5-carboxaldehyde, affording an efficient formal synthesis route toward (-)-aurantioclavine.The second part is mainly about the asymmetric heteroarylation of arylimines. The neopentyl glycol boronic esters were used in the3mol%Rh(I)-diene complex catalyzed asymmetric arylation after the optimization of the reaction condition, a series of chiral a-branched amines constituted by thiophene、furan and pyridine were prepared in95-99%yields and97->99%ee. Moreover, because the unique activity of the heteroaryl structure, the deprotection of Ts be realized in93%yield under the Mg/MeOH system after the introduction of Boc-group to tne N-atom.