Synthesis Of New High-Functional Furan Derivatives Based On The Conversion Of Silver Carbene

2-Alkenylfurans,4-（furan-2-yl）-3,4-dihydro-2H-pyrrole-2-ones and6-（furan-2-yl）-4H-furo[3,4-c]pyrroles are important heterocyclic compounds.In this thesis,synthetic methods for these heterocyclic compounds are explored.The researches are not only significant in theory,but also possess considerable value in synthetic application.On the basis of the literatures,synthetic approaches to the heterocyclic compounds are planned,and experimental explorations are carried out by us.Reasonable mechanisms for the construction of these heterocyclic compounds are proposed.The thesis is divided into the following four parts.In the first chapter,the synthesis of polysubstituted furan derivatives and the decomposition reactions of iodonium ylides are reviewed.Inthesecondchapter,thesynthesisof tetrasubstituted-2-alkenylfurans is discussed.In silver（I）tetrafluoroborate/dichloromethane/air system,conjugated ketene（ester,amide）first undergoes intramolecular cyclization to form（2-furyl）silver carbene,then subjected to nucleophilic attack by iodonium ylides.Subsequentβ-elimination was performed to construct a new carbon-carbon double bond,providing new tetrasubstituted2-alkenylfuran derivatives.The optimized conditions for the synthesis of tetrasubstituted-2-alkenylfurans were determined as below:10 mol%silver（I）tetrafluoroborate as catalyst,dichloromethane as solvent at-40^oC under air.Under the optimized conditions,the reaction afforded the desired products in 72-96%yields.In the reaction,iodonium ylides played excellent nucleophiles to effectively capture the metal carbene.The cross-coupling reaction of enynones with iodonium ylides has been achieved for the first time.It is worth noting that various tetrasubstituted-2-alkenylfuransbearingtwostrongly electron-withdrawing groups at the same C=C carbon were synthesized based on this new method for the first time.The 2-alkenylfuran derivatives has pharmacological activity and potential application value as organic building blocks.Inthethirdchapter,thesynthesisof4-（furan-2-yl）-3,4-dihydro-2H-pyrrole-2-ones was discussed.Enynones were transformed into（2-furyl）carbene complex under transition metal catalysis,and then the（2-furyl）carbene complex underwent[1+2]cycloaddition with 3-aminoacrylate to provide cyclopropanation intermediate,andsubsequentintramolecularring opening-migration-nucleophilic substitution reaction resulted in the formation of 4-（furan-2-yl）-3,4-dihydro-2H-pyrrole-2-ones.The optimizedconditionsforthesynthesisof4-（furan-2-yl）-3,4-dihydro-2H-pyrrole-2-ones from enynones and3-aminoacrylates were determined as below:10 mol%silver tetrafluoroborate as catalyst,dichloromethane as solvent at-60 ^oC under N₂.Under the optimized conditions,the reaction were suitable for all kinds of enynones and enamine esters,affording the desired products in51-85%yields with excellent regioselectivity.There were many obvious advantages such as mild conditions,cheap starting materials and simple operation.In chapter Four,study on the synthesis of6-（（2,3-dihydrofuran-2-yl）methyl）-4H-furo[3,4-c]pyrrole derivatives was explored.The reaction of（2-furyl）carbene complexes from enynones with4-alkynylisoxazole produced a new kind conjugated alkynyl ketene intermediates with an imine core structure via the N-O bond insert and subsequent intramolecular rearrangement.Finally,intramolecular cyclization and dipolar cycloaddition reactions led to the formation of4H-furan[3,4-c]pyrrole derivatives.The optimal conditions of the reaction were as follows:10 mol%Ag OTf as the catalyst,1,2-dichloroethane as the solvent,and under nitrogen,at-20 ^oC for 1 hour,and then refluxed at 60 ^oC for another 12 hours.Under the optimized conditions,all kinds of enynones and 4-alkynylisoxazoles were suitable for the conversion,providing the desired products in 33-78%yields with excellent regioselectivity.There were some advantages such as high reaction efficiency,simple operation,mild conditions and simple preparation and available starting materials.