Investigation On Palladium-catalyzed Cyclization And Functionalization Of Alkenes/Alkynes

Palladium-catalyzed cyclization of alkenes/alkynes has always been a popular topic in organic synthesis methodology.With the continuous exploration of scientists,different forms of cyclization have provided more possibilities for total synthesis,medicinal chemistry,and materials chemistry.In recent years,with our increasing concern for green chemistry and the economics of reactions,how to further modify the structure during the process of cyclization to synthesize compounds with special properties has posed higher demands on researchers.In this thesis,a series of highly functionalized furan and isoxazole derivatives were constructed based on alkenes and alkynes as reaction substrate.The cyclization and functionalization of the substrates was achieved by the strategy of carbon nucleophilic metallization as well as nucleophilic palladation.The details are as follows:In chapter 2,based on intramolecular Heck-type reaction,a convenient and efficient strategy to construct functionalized ynones by palladium-catalyzed cascade annulation reaction has been developed.This reaction possesses good functional group compatibility,broad substrate scope,and high atom-and step-economy.Furthermore,this approach could also be extended to direct alkynylation that gave another route to synthesize dihydrobenzofurans.In chapter 3,a Pd-catalyzed cascade cyclization for the synthesis of E-?,?-unsaturated carbonyl compounds with the sequential formation of C-C bonds have been developed.For this strategy,we achieved a true participation of sulfoxonium ylides in the reaction under palladiumcatalyzed system.This method features great efficiency,good functional group tolerance,moderate to excellent yields and typically displays high stereoselectivity.In chapter 4,a palladium-catalyzed cascade cyclization for the assembly of polyfunctionalized isoxazoles derivatives has been accomplished.This new protocol exhibits mild conditions,high efficiency,good functional group tolerance and broad substrate scope.Remarkably,the easy availability of starting materials along with the efficiency of the present strategy provides a new tool for the construction of structurally diverse isoxazole derivatives,becoming a promising application in synthetic and pharmaceutical chemistry.In chapter 5,a palladium-catalyzed ionic liquids-accelerated oxidative cascade annulation/functionalization of acetylinic oximes with unactivated long-chain enols under aerobic conditions was accomplished.The newly developed protocol provides the rapid and straightforward synthetic strategy for the assembly of structurally diverse isoxazoles architectures under mild conditions with high atom-and step-economy and exceptional functional group tolerance.Notably,the ionic liquid acts as not only a solvent in the reaction,but also provides the excess halide ions to eliminate hydrochloride from acetylinic oximes.Moreover,this catalytic system could be recycled up to eight times and reused without significant loss of catalytic activity.