Studies On Tetrahydrofuran And Tetrahydropyran Ring-forming Cyclizations

This thesis deals with the BiX3 and FeX3-promoted Prins cyclization of enol ethers in CH2Cl2 and Au (Ⅰ) and Au (Ⅲ)-catalyzed cyclization ofωandδ-hydroxy propargyl alcohols. The thesis consists of three chapters. In the first chapter, the synthetic applications of the Prins cyclization reaction are briefly reviewed. The second and the third Chapters describe my own works which are summarized as follows.(1) The FeX3 and BiX3-catalyzed Prins cyclization of enol ethers. The reagent combination of TMSX and BiX3 (or FeX3) was very effective for the Prins cyclization of enol ethers in CH2Cl2. A small amount of water in the reaction system was required for the reaction to proceed. The reaction was probably catalyzed by Lewis acid-assisted Br(?)nsted acids, which were generated in situ from MX3 and water in the solvent.(2) The gold-catalyzed cyclization ofωandδ-hydroxy propargyl alcohol. We found that when AuCl (PPh3)/AgSbF6 was used as the catalytic system,ωandδ-hydroxy propargyl alcohols mainly react via the Meyer-Schuster rearrangement pathway. On the other hand, the reagent combination of AuCl3/AgSbF6 was more favorable for the TBS-protected co andδ-hydroxy propargyl alcohols to undertake the direct substitution at the propargyl position.