Synthesis And Application Of Novel Chrial Triazolium Salts From L- Phenylalanine

This thesis mainly focuses on the synthesis and application of novel chiral trizolium salts, which were readily synthesized from methyl-L-phenylalaninate. The NHCs were found highly efficient in the annulations of enals with 2-naphthols or phenols providing enantioeriched β-arylsplitomicin or 4-aryl-3,4-dihydrocoumarin respectively.In the first part, a series of triazolium salts were synthesized from commercially available methyl L-phenylalaninate hydrochloride, involving synthesis of lactam with different steric group and the preparation of NHC precursors according to a reported procedure.In the second part, the asymmetric annulation of enals with 2-naphthols catalyzed by the novel chiral NHC was achieved, affording β-arylsplitomicin derivatives with up to 96% ee, which represents the best result in the preparation of these kinds of poducts via NHC catalysis.In the third part, the annulation of enals with phenols was studied. With our novel triazolium salts, various dihydrocoumarins could be obtained in good yields and excellent ee. In addition, the product could be transformed into natural product upon one simple operation.