Gold-Catalyzed Oxidative Annulation Of Alkynes With Nitrones:Efficient Approaches To Dihydrofuran-3-one And Tetrahydropyran Derivatives

As a cheap and readily available material,alkyne is a useful building block in organic chemistry.In recent years,due to the advantages of high selectivity control and bond-formation efficiency,gold-catalyzed functionalization of alkynes shown broad applications for the preparation of complex organic molecules with structural diversity in modem synthetic organic chemistry.Nitrone can be used not only as a 1,3-dipole.but also as an oxidant in organic synthesis.Nitrones can oxidation alkynes which were activated by gold-complex.The main consequence is the formation of ?-oxo gold carbene and then to forming the functionalized products.Alternatively,formation of vinyl gold intermediate that can directly undergo transformations to giving the functionalized products.In this thesis,we studied the gold catalzyed oxidative annulations of nitrones with homopropargyl alcohols,which form dihydrofuran-3-one and tetrahydropyran derivatives via a-oxo gold carbene pathway and non-carbene pathway,repspectively.The first chapter is the summary of gold-catalyzed functionalization reactions by alkyne oxidation.Also the design of our research project and the main content of this thesis.The second chapter describes a reaction of gold/chiral phosphoric acid cooperative catalysis to form chiral dihydrofuran-3-one derivatives.This chapter presents the first example of asymmetric Mannich-type trapping of gold enolate,which is generated through the gold-catalyzed alkyne oxidation via an ?-oxo gold carbene intermeidate.and could inspire novel discoveries in gold-catalyzed asymmetric alkyne invloved muth-compunent reactions.In the third chapter,inexpensive and readily nitrones and homopropargyl alcohols were used as substrates to form tetrahydropyran derivatives.The proposed reaction mechanism does not involving the ?-oxo gold carbene intermediates.Instead,direct hydrolysis of vinyl gold intermediate occurrs followed by proton deauration.then a[3,3]-sigmatropic rearrangement happens to form indole products through an intramolecular condensation.The indole further gives the tetrahydropyran derivative through the intermolecular condensation with aldehyde.This chapter offers a simple and efficient way to form tetrahydropyran derivatives.