Preparation Of Polystyrene-Supported Organoselenium Reagents And Their Applications In Organic Synthesis

In this dissertation, the preparation of polystyrene-supported organoselenium reagents and their applications in organic synthesis were investigated.Firstly, the first solid-phase synthesis of flavonoids was developed, which employs Lewis acid-catalysed 1% cross-linked polystyrene-supported selenium -induced intramolecular cyclization of chalcones, followed by selenoxide syn-elimination cleavage of selenium resins with 30% hydrogen peroxide with good yields and high purities. Several derivatives of flavones were synthesized with good results by the alkylation, sulfonylation, phosphorylation, and glycosidation of polystyrene-supported 4'-hydroxylflavanone and Suzuki coupling reaction of polystyrene-supported 4'-bromoflavanone, and subsequent oxidation-elimination with 30% hydrogen peroxide. Evident advantages of this method are mild reaction conditions, easy operations, odorlessness, good yields, and high purity of the products.Secondly, poly-substituted dihydrofurans and tetrahydrofurans have been synthesized through 1% cross-linked polystyrene-supported selenium-induced intramolecular electrophilic cyclization of a-allyl substituted 1,3-dicarbonyl compounds and y-allyl substituted 1,3-dicarbonyl compounds, followed by selenoxide syn-elimination cleavage of selenium resins with 30% hydrogen peroxide or novel nuclophilic iodine substitution cleavage of selenium resins with sodium iodide and methyl iodide with good yields and high purities. The elimination of hydrogen iodide with DBU and subsequent isomerization with sulfuric acid afforded trisubstituted furans with good yields. And also the resins can be regenerated and reused. In the presence of alcohols, the oxidation with ammonium persulfate, deselenization, substitution and aromatization of selenocyclic enol ethers, easily prepared from a-allyl substituted 1,3-dicarbonyl compounds, afforded trisubstituted furans with good yields.Thirdly, 1% cross-linked polystyrene-supported selenovinyl bromide, easily prepared from 1% cross-linked polystyrene-supported selenenyl bromide with alkynes,reacted with different Grignard reagents using a step-by-step strategy to offord (2T)-l,2-disubstituted ethenes and trisubstituted ethenes in good yields.