Studies On Transition Metal-catalyzed Cyclization Of Alkynones And Nitroalkynes

This thesis can be sumarized as two parts:Part I: Styrene as 4?-Component in Zn(II)-Catalyzed Intermolecular DielsAlder/Ene-Tandem ReactionThe Diels-Alder reaction is one of the most useful pericyclic reactions to construct the six-membered carbocyclic compounds.The Diels-Alder reaction typically involves the 4?-electron of the conjugated diene and 2?-electron of the dienophile.In comparison with the conjugated diene,the Diels-Alder reaction using styrene as 4? component is,however,much less developed,in which the unfavorable dearomatization should occur.As a useful C-C forming tool,Ene reaction have attracted much attention.This part we wish to introduce to you a novel the ene in Ene reaction,which could can afford high yields and selectivities at significantly lower temperatures,making the Ene reaction a useful C–C forming tool for the synthesis of complex molecules and natural products.In conclusion,a mild Zn-catalyzed intermolecular Diels-Alder/ene tandem reaction with styrene as 4?-component will be described in this part.The reaction was initiated by a Diels-Alder reaction between 4?–component styrene and dienophile alkynone,followed by an ene reaction with another dienophile,leading to the dihydronaphthalene products in moderate to good yields.The reaction pathway was rationalized by DFT calculations,and the key intermediate was isolated when 2-vinylnaphthalene was used as the 4?–component.This study could not only help to understand the Diels-Alder reaction with styrene as 4?–component,but also provide a general and efficient protocol to synthesize dihydronaphthalene derivatives.Part II: Hg-Catalyzed one-pot synthesis of indole derivatives from the reaction of nitroalkyne and alkyneTransition metal catalyzed cyclization of alkynes containing adjacent nucleophilic centers is considered as a powerful tool to construct complex molecular framework.The nitro group is a very important nucleophile and it can be involved in a variety of redox transformations.Transition metal-catalyzed intramolecular cyclization of nitroalkyne is one of the most simple and convenient routes for the synthesis of isatogens and benzo[c]isoxazole derivatives.We are particularly interested in the selective synthesis the molecule benzo[c]isoxazole,as which is a very useful synthon in organic synthesis when the weak N-O bond was cleaved.5 However,the competition between 5-exo-dig cyclization and 6-endo-dig cyclization was often the major obstacle to realize the selective preparation of isatogens or benzo[c]-isoxazole derivatives.Although great efforts have been made in this regard,it's still a challenge to selectively produce benzo[c]isoxazole from nitroalkynes.In this regard,we wish to report a Hg(II)-catalyzed redox cyclization of nitroalkyne to selectively afford benzo[c]isoxazole and its further application in the synthesis of indole derivatives.In this part,we will describe a Hg(OTf)2-catalyzed 6-endo-dig cyclization of nitroalkyne to produce the corresponding benzo[c]isoxazole in excellent yields with high selectivity.On the basis of this strategy,a one-pot method to synthesize indole derivatives has been developed.In these transformations,two Hg-carbene intermediates were proposed to be involved.We believe this catalytic system may enrich the knowledge of mercury carbene chemistry and also promote the development and application of mercury catalysis.