Synthesis Of Benzoxazine Derivatives Based On Electrophilic Trapping Of Zwitterionic Intermediates

As one of the important intermediates in organic synthesis,transition metal carbene has been widely concerned by synthetic chemists.These highly reactive carbene species are capable of special reactivity,which can be used to realize the unusual reactions.Zwitterionic intermediates based on transition metal carbene have become one of the most important transformation of carbene intermediates.Our research group have developed a series of novel multi-component reactions based on the electrophilic trapping of zwitterionic intermediates,which can be used for efficiently constructing structurally diverse compounds.Benzoxazine derivatives are important structural units for the construction of natural products and synthetic drugs.Among these derivatives,4-quaternary carbon-4H-benzoxazine derivatives have showed antitumor biological activity and bactericidal organisms.The electrophilic capture of the zwitterion intermediate provides a powerful tool for efficient construction of heterocyclic compounds.In Chapter 2,we have successfully realized the electrophilic trapping of metal-carbene-induced zwitterionic intermediate generated in situ from2-diazo-2-(2-arylamidophenyl)acetate by using aromatic aldehyde.The reaction provides a novel method for the construction of 4-quaternary carbon-4H-benzoxazine derivatives.This work repents a supplement of our works about electrophilic trapping active zwitterionic intermediate.Moreover,the protocol could be easily scaled up to gram-scale synthesis.An attempt to develop an asymmetric version of the Rh(II)/ Zr* system were also explored,resulted in a moderate enantioselectivity.In Chapter 3,we have successfully realized the electrophilic trapping of metal-carbene-induced zwitterionic intermediate generated in situ from 2-diazo-2-(2-arylamidophenyl)acetate by using nitroolefin by ruthenium(I)and lewis base co-catalyst system.The transformation enriches the construction of 4-quaternary carbon-4H-benzoxazine derivatives by this strategy.