The Research On Carbene And Onium Intermediates From Alkynes

Metal carbene intermediates and onium salts have attracted lots of attentions for their reaction varieties.This graduation thesis will mainly focus on our research about the captures of carbene intermediates and onium salts originated from alkynes.Chapter One:In this chapter,the reactions of metal carbenoid and onium salts originated from alkynes and their applications in organic synthesis are summarized.According to the reaction intermediates,four aspects are described as follows:?1?metal carbenoid originated from alkynes;?2?sp² isopyrylium salts originated from alkynes;?3?sp² isoquinolinium salts originated from alkynes;?4?sp³ azonium salts originated from alkynes.Chapter Two:In this chapter,the traditional methods for the synthesis of aziridine compounds were summarized briefly.On the basis of these works,we have developed the new strategy using dirhodium?II?catalyzed cascade reaction of enynones and imines to construct poly-substituted aziridine compounds with excellent diastereoselectivity in mild condition.The key 2-furyl rhodium carbene intermediate which were formed by the cyclization and rearrangement of the enynones was then captured by the imines to afford aziridine products.The the obtained aziridine moiety could serve as 1,3-dipolar to achieve[3+2]cycloaddition with electron-deficient alkynes or diethyl azoatecan and the furan moiety could be used as 4?component to react with benzyne by[4+2]cycloaddition reaction.Furthermore,the one-pot synthesis of five-membered heterocyclic compounds using enynones,imines and diethyl azoatecan were also demonstrated.Chapter Three:In this chapter,the previous works of our group about the capture of pyrylium salts originated from alkynes by transition metal catalyzed were reviewed.As for a further research,we have developed the three components cascade reaction of enynals/enynimines,alkenes and H₂O catalyzed by silver to construct poly-substituted tetrahydronaphthols or Tetrahydronaphthyamines.The preliminary mechanism study suggests the pyrylium intermediate reacts with the olefins by[4+2]cycloaddition reactions to give the bicyclic onium intermediate,then trapped by water to give the final product.When using enynals as reactant,the additive p-nitropyridine N-oxide is crucial,as it may stabilize the bicyclic pyrylium intermediate as a psedu protecting group to form a stable azonium.While in enynimines system,the additive were unnecessary,which may be attributed to the phenyl group in the imines have already play this role.Chapter Four:In the last chapter,different well-developed reaction types involving aryl alkyne with ortho-substituted heteroatoms was introduced.On this basis,we have developed a divergent transformation strategy of N-?but-1-en-2-ynyl?-lactams using silver and palladium as catakysts.The sp³ azonium salts intermediate formed by metal catalyzed cyclization of N-?but-1-en-2-ynyl?-lactams occurred a lactam C-N bond disrupt and undergo different migration pathways.Under silver catalyzed condition,tricyclic indole were afforded by Friedels-Craft reaction of the acyl cation,while cyclic pyrrole compounds were formed through continuous 1,2-migration when palladium catalyzed system.