The Research Of Oxonium Intermediate

The oxonium intermediate is a kind of highly active transient species.In organic synthesis,oxonium chemistry is a powerful tool for efficient transfer of oxygen atoms and construction of heterocyclic compounds.Over the past few decades,chemists had successfully achieved the synthesis of heterocyclic compounds and complex natural products through the continuous research of oxonium chemistry.Alkyones and diketones are important oxonium precursors,which can rapidly generate oxonium intermediates by the activation of transition metals.We devoted to transition-metal catalyzed alkyones or diketones to form the oxonium intermediate.During the research process,efficient generation of oxonium and the construction of polycyclic compounds methods were developed,which provide new ideas for the further study of oxygen transfer and cyclization reactions.This paper mainly carried out the following three parts:(1)Gold-catalyzed ring-expansion through acyl migration to afford furan-fused polycyclic compounds.Ring-expansion reactions represent powerful synthetic strategies for the construction complex cyclic compounds in organic synthesis.we have reported a gold-catalyzed ring-expansion through acyl migration to afford furan-fused polycyclic compounds.Through controls the reaction conditions,the reaction was initiated by the attack of the exocyclic carbonyl group to the activated alkyne,and furan-fused cycloalkanone(sixor seven-membered ring)system was rapidly accessed.The reaction was proposed through consecutive process of ring-fragmentation,protodeauration,aromatization,and Friedel-Crafts reaction.The acylcation species was regarded as the key intermediate for this reaction.This ring-expansion strategy holds the advantages of mild reaction condition and good selectivity,which makes this system very appealing for organic chemists to synthesize different furan-fused polycyclic compounds.(2)Cu(I)-Catalyzed stereoselective synthesis of Z-enol esters via interrupting 1,3-O-transposition reactions.Transition metal-catalyzed(Au,Pt,etc.)intramolecular 1,3-O-transposition of ynones or ynesulfonamides are common reaction modes,proceeding via a four-membered heterocycle delocalized system.We envisioned that the intramolecular 1,3-O-transposition process of ynones could be interrupted by introducing an appropriate external nucleophile and the regulation of the catalyst.Through the screening of the nucleophile and catalyst,we found that the 1,3-O-transposition process could be well inhibited when the carboxylic acid was used as a nucleophile and copper chloride was used as catalyst,and the Z-enol ester could be efficiently constructed.This method is featured with mild reaction conditions and wide substrate scope,providing a convenient synthesis of complex highly functionalized Z-enol esters.Furthermore,Ibuprofen,mycophenolic acid,and other drugs bearing carboxylic acid group could engage in the reaction effectively to afford the desired Z-enol ester products in high yields.(3)Iron/Zinc-catalyzed benzannulation reactions of 2-(2-oxo-alkyl)benzketones leading to naphthalene and isoquinoline derivatives.The naphthalene and isoquinoline derivatives are widely used in pharmaceutical chemistry and material science.Development of efficient methods to synthesize naphthalene and isoquinoline derivatives,especially polysubstituted ones,would be highly valuable in organic synthesis.An efficient method for the synthesis of poly-substituted naphthalene and isoquinoline derivatives via Fe(III)/Zn(II)-catalyzed [4+2] cyclization of 2-(2-oxo-alkyl)benzketones with unsaturated compound are described.For the reaction of diketone with unsaturated compounds(alkenes,alkynes and enols)or the diketone tethered with nitrile group,a sequential intermolecular/intramolecular [4+2] reaction and decarboxylation process occurred to produce poly-substituted naphthalene/isoquinoline products.Furthermore,we can achieve the synthesis of mono-substituted/ disubstituted/tri-substituted/tetra-substituted naphthalenes in different regions by the control of the substrate.