Synthesis Many Novel Isoquinolin Compounds Via Tandem Reactions

Currently, methodologyical development for rapid access to N-heterocycles withcomplexity and diversity has attracted considerable attention in the studies ofchemical genetics. The tandem reactions have been applied as a powerful approachfor the preparation of biologically and pharmaceutically important N-heterocycliccompounds. Isoquinoline alkaloids are the major important natural alkaloids withdiverse structural skeletons. This dissertation mainly focuses on methodologicaldevelopment for constructions of H-pyrazolo[5,1-a]isoquinoline and isoquinolinecompounds via tandem reactions starting from N’-(2-alkynylbenzylidene)hydrazideand2-alkynylbenzaldoxime.In chapter1, the development of diversity-oriented synthesis (DOS) and itsapplications for construction of natural product-like libraries are introduced.In chapter2, tandem reactions which generate the isoquinoline derivatives aredescribed. Firstly, we described a silver triflate-catalyzed tandem reaction ofN’-(2-alkynylbenzylidene)hydrazide with ketene. The ketene could be generated insitu from acetyl chloride in the presence of a base. This reaction proceeded through6-endo-cyolization,[3+2]cycloaddition, and rearrangement, leading to2,6-diaza-bicyclo[3.2.2]non-6-en-3-one derivatives in moderate to good yields. Furthermore,we described a tandem reaction of2-alkynylbenzaldoxime with ketene. However, toour surprise, an unexpected3,4-disubstituted isoquinoline was obtained.In chapter3, both tandem reactions which generate the H-pyrazolo[5,1-a]isoqui-noline derivatives are described. Firstly, we have investigaeted a silver(I)-rhodium(I)cooperative catalysis in the reaction of N’-(2-alkynylbenzyl-idene)hydrazide with2-vinyloxirane. During the tandem process, multiple bonds are formed andH-pyrazolo[5,1-a]isoquinoline-1-carbaldehydes could be obtained in moderate togood yields under mild conditions. Once more, we described a silvertriflate-catalyzed tandem reaction of N’-(2-alkynylbenzylidene)hydrazide withaminoallenes. The aminoallenes could be generated in situ from propargylic aminesin the presence of a base. The reaction generates functionalized H-pyrazolo[5,1-a]iso-quinoline in good yields and proceeds smoothly under mild conditions. In chapter4, we have presented a general and facile amidation procedure for thesynthesis of1-acylaminoisoquinolines. A diverse substrate scope combined with anoperationally simple procedure makes this reaction a useful methodology. Benzoylchloride-mediated bond-forming reactions are governed by the electronic propertiesof the reaction substrates.