Asymmetric Catalysis With Azoalkenes

To be regarded as an important synthetic intermediate,azoalkene has been widely used for the synthesis of various achiral hetereocyclic compounds such as pyrroles,pyrozoles and pyrodazines.In recent years,our group has also investigated lots of catalytic asymmetric reactions using azoalkene as key intermediate.In order to extend the applications of azoalkene,we designed kinds of different reactions based on the unique reactivity of azoalkene.My research work are as followed:1)An efficient Cu(Ⅱ)-catalyzed enantioselective inverse-electron-demand aza-Diels-Alder reaction of azoalkenes with enol ethers is reported.This methodology provides a facile entry to biologically important tetrahydropyridazine derivatives in generally good yield with excellent enantioselectivity.2)We have developed a Cu(Ⅰ)/tBu-Box complex catalyzed asymmetric IEDDA reaction of in situ generated azoalkenes with fulvenes.The present methodology offers a directed entry to synthesize bicyclic tetrapyridazine derivatives in exclusive regioselectivity,excellent stereoselectivity and good yield even in a larger scale.3)We have described the Cu(Ⅰ)-catalyzed asymmetric desymmetrization of 1-silylcyclopentadienes with azoalkenes.This is the first example of applying desymmetrization in accessing a-chiral silane motif with high enantiopurity.The target products were obtained in good yield with excellent stereoselectivity.Meanwhile,a plausible reaction mechanism involving an inverse-electron-demand Diels-Alder reaction pathway is proposed based on DFT calculations.4)An unprecedented enantioselective 1,3-dipolar[3+4]cycloaddition of azomethine imines with azoalkenes has been realized,which was efficiently catalyzed by a chiral Cu(Ⅱ)//Bu-Box complex.This strategy provides a facile access to biologically important 1,2,4,5-tetrazepine derivatives in high yield,exclusive regioselectivity and excellent stereoselectivity.Moreover,enantioenriched azomethine imine could be obtained via efficient kinetic resolution using the same approach.5)The first asymmetric 1,3-dipolar[3+4]cycloaddition of nitrones with azoalkenes catalyzed by Cu(Ⅰ)/Phosferrox complex has been developed successfully,affording the biologically important 1,2,4,5-oxatriazepane derivatives in good yield with exclusive regioselectivities and excellent enantioselectivities.