Study On The Heterrocyclic Ketene Aminals As Synthon By Four-Component And Tandem Reactions

Heterocyclic ketene aminals are good synthons in the form of C-C bond and C-Nbond because of its high reactivity. Diketene, which have the structure composed ofexocyclic double bond and4-member ring lactone, is readily ring-opened and thereforefrequently appears to react as β-dicarbonyl compounds with nucleophiles. Newstrategy of organic synthesis-multicomponent reaction and tandem reaction-cansynthesize libraries of compounds with structural complexity and diversity rapidly, byvirtue of their convergence, productivity, ease of execution, and generally high yieldsof products, have become the most enabling synthetic tools in organic synthesis. Thisthesis focus on building new framework of1,8-naphthyridine and imidazo[1,2-a]pyridines from high functional heterocyclic ketene aminals and diketene. This methodis flexible, which includs the advantages of eco-friendly high bond-forming efficiency,in various and oriented synthesis.In this thesis, tetrahydroimidazo[1,2-a]pyridines derivatives unreported in theliteratures have been synthetized with heterocyclic ketene aminals by themulticomponent reactions and tetrahydroimidazo[3,2,1-ij]bezeno[1,8]naphthyridinevia β-(2-chloroaryl)-heterocyclic ketene aminals with tandem reactions in the presenceof Et3N and K2CO3as catalyst. The reaction conditions including solvent, catalyst andmolar ratio were also investigated. The optimal condition of synthetizingtetrahydroimidazo[1,2-a]pyridines was Et3N as catalyst, molar ratio of heterocyclicketene aminals, aromaticaldehydes, dikenete and amines with1:1.2:1.2:1.2andacetonitrile as solvent. The intermediate could not be separated, and then proceededintramolecular cyclization reactions in the presence of K2CO3in DMF to obtain the1,8-naphthyridines in high yields. These reactions were very mild, convenient andeffective.25target compounds (5a–y) and8target compounds (6a–h) weresynthesized.In this reaction, twelve different active sites were involved; five new bonds and two new rings were constructed with all reactants which efficiently utilized via a sequenceof Knoevenagel condensation, aza-ene reaction, cyclization and intramolecularnucleophilic substitution reactions.The structures of all the target compounds were confirmed by IR,1H NMR,13CNMR, and HRMS, and the plausible mechanism was also presented. The unambiguousmolecular structure of5y was determined by X-ray diffraction analysis.