Study On The Cascade Reaction Of Isochromenylium Salts And Stilbene Derivatives,and The Synthesis Of The Fragments Of Natural Alkaloid Lycopladine D

This thesis contains two parts of research works,including study on the cascade reaction of isochromenyliums with stilbenes and synthesis of the fragment in natural alkaloid Lycopladine D.Isochromenylium tetrafluoroborates(ICTBs),having nonclassical Huckel aromaticity and a electron-deficient system in general,are a unique class of oxa-diene equivalent.Generally,ICTBs can smoothly react with electron-rich olefins to start cascade cationic reactions,providing various complex skeletons.In this thesis,we developed a new type of three-component reaction of isochromenylium tetrafluoroborates with electron-rich stilbenes in acetonitrile,affording benzo[c]-phenanthridine analogues in one pot.This cascade reaction is initiated by an intermolecular oxa[4+2]-cycloaddition,relayed with a nucleophilic addition of acetonitrile,and terminated by an intramolecular Friedel-Crafts reaction,forming multiple new C-C and C-N bonds efficiently.Lycopladine D was isolated from the club moss Lycopodium complanatum in 2006 by Kobayashi's group.Due to its unique polycyclic cage structure,it has attracted considerable attention of synthetic chemists.Based on our retrosynthetic analysis of Lycopladine D,the synthesis of fragment 5 or 50,and explored several methods to achieve the targets,including intramolecular ten-membered ring closure?Claisen condensation,intermolecular Grignard reaction and nucleophilic addition.