Research On Palladium-Catalyzed Coupling Reaction To Construct Functionalized Heterocycle Compounds

The heterocycles are some of the most important building blocks in organic chemistry. Those mutifs are significant building blocks, which not only exist extensively in pharmaceuticals, agrochemicals, and functional materials, but also serve as useful synthetic intermediates in modern organic synthesis. To this end, transition metal-catalyzed reactions have been used as powerful tools for the preparation of various heterocycles.Palladium-catalyzed reactions continue to be a fantastic research area because of its efficiency in constructing multiple new bonds, including C-C bond and C-X bond. Therefore, Palladium-catalyzed reactions become important methods for natural product and bioactive compounds. In this context, we designed a series of efficient approaches to afford highly functionalized heterocycles in good yields with excellent chemo- and regionselectivity. The details are summarized as following:(1) In chapter 2, we develop a palladium-catalyzed oxidative difunctionalization, with enol ethers and 1,3-dicarbonyl compounds to construct trisubstituted furans. This protocol allows broad substrate scope and affords furan derivatives in good to excellent yields with easily accessible substrates and dioxygen as the sole oxidant.(2) In chapter 3, we develop a method for the synthesis of oxazole derivatives from amides and ketones. The starting materials are simple and readily available, and the reactions are easily operated, thus this strategy can be broadly applied to medical chemistry.(3) In chapter 4, we describe a palladium-catalyzed Heck-type reaction of O-acetyl ketoximes and allylic alcohols to synthesise pyridines. This protocol allows the synthesis of pyridines and azafluorenones in good to excellent yields with tolerance of various functional groups under mild conditions.(4) In chapter 5, we describe a highly regioselective nucleopalladation for the oxidative coupling of internal alkynes with alkenyl alcohols to construct isocoumarin-alkanones. This method has the advantages of mild conditions, good functional group tolerance, and can be performed with unactivated alkenes to afford isocoumarin derivatives by using green and low-costing dioxygen as the sole oxidant.(5) In chapter 6, we develop a protocol for γ-lactones from homoallylic alcohols via palladium(II) catalysis. The protocol affords aryl, alkyl and spiro γ-lactones directly from readily available homoallylic alcohols in good yields with excellent functional group tolerance and chemoselectivities.