Studies On N-Heterocyclic Carbene Catalyzed Cascade Reaction And Conjugate Umpolung Of Alkynyl Aldehydes

N-heterocyclic carbene catalyzed polarity reversal strategy is widely used to provide unconventional access to various target molecules. According to the type of reactions catalyzed by N-heterocyclic carbene, this dissertation consists of four chapters.Chapter1:The development of N-heterocyclic carbenes in recent years was reviewed. The acyl anion, enolate intermediate and homoenolate equivlents as three typical intermediates generated by N-heterocyclic carbenes were presented.Chapter2:The N-heterocyclic carbene catalyzed cascade epoxide-opening and lactonization reaction was presented in detail. We have provided a more direct and efficient way to construct skeletons of dihyropyrones.Chapter3:The N-heterocyclic carbene catalyzed/Lewis acid mediated conjugate umpolung alkynyl aldehydes for the sysnthesis of butenlides was described in detail. Our strategy demonstrated the success of allenoalte addition reaction.Chapter4:The N-heterocyclic carbene catalyzed highly reigoselective annulation of ynals with isatins. Our work demonstrated two reaction pathway involving Breslow intermediate annulation and allenolate equivalents annulation. The regoselectivity between the two reaction intermediates depending on substrate-dependent control.