Studies On Organocatalysed Asymmetric Michael Addition And Cascade Annulation Of Air-stable Isochromenylium Salts With Bifunctional Styrenes

This thesis contains 4 parts of research works, including:1) Study on asymmetric C-H Oxidation of the a position of carbonyls; 2) organocatalysed asymmetric Michael addition; 3) cascade reaction of stable isochromenylium salts with bifunctional styrenes; and 4) derivatization of the podophyllotoxin frameworks.Since the 20th century, asymmetric catalysis has attracted great attentions to chemists as the most important methodology in modern organic chemistry, and also great progress have been made in this area. Metal catalysis and organocatalysis have been playing more and more important roles in organic syntheses.In the first part, chiral Cu[S,S)-PDP] has been applied to participate in the asymmetric oxygen oxidation of the C-H bond at the a position of a carbonyl. Unfortunately, the product was proven to be racemic under basic conditons. In the second part, a new class of organocatalysts were prepared having a structural motif of C2-symmetrical-type 2,2’-bipyrrolidine mono-N-sulfonamide. The new catalysts were applied to the enantio-and diastereoselective Michael addition of 4H-thiopyran-4-one to a variety of nitroolefins, resulting in the corresponding products with high yields, excellent diastereo-and enantioselectivities (up to 99/1 d.r and 98% ee). Furthermore a representative Michael adduct was proven to be useful for the diversity-oriented synthesis of enantiopure multiring heterocycles through a unique common bicyclic nitrone intermediate.Isochromenyliums are one series of reactive intermediates having unique structures. Owing to existance of oxa diene, electrophile and ylide functionlities in the isochromenyliums, diverse transformations have been demonstrated. Usually, isochromenyliums could be prepared in situ by Bronsted or Lewis acid-catalyzed electrophilic cyclization reaction of o-alkynylbenzaldehyde. We firstly, in 2009, synthesized a number of air-stable crystalline isochromenylium tetrafluoroborates (ICTBs). In the third part, a highly efficient catalyst-free cascade reaction of air-stable isochromenylium tetrafluoroborates (ICTBs) and bi-functional styrenes containing a 1,3-diketone moiety has been developed, affording the corresponding single diastereomeric octahydrophenanthrene derivatives (21 examples, up to 86% yield). A cascade process of [4+2]-cyclization and subsequent intramolecular nucleophilic addition is proposed to generate the three new C-C bonds diastereoselectively in the reactions.In the last part, derivatization of the podophyllotoxin frameworks was studied for biological activity tests.