N-Heterocycle Synthesis By Using Propargyl Compounds As Synthons

Transition-metal-catalyzed cycloaddition of unsaturated compounds is oneof the most important reactions to develop the atom-economic synthetic methods.Development of new synthetic methods for N-heterocyclic compounds by usingpropargyl compounds as synthons, involving cycloaddition step, was thepurpose of this dissertation, and one-pot transformation of propargyl compoundswith other synthetic building blocks to develop the synthetic reaction systemsfor the formation of1,2-dihydroquinolines,4-vinyltriazoles and2,5-dimethyl-pyrazines was studied.At first, in the presence of CuCl and CuCl₂, the reaction between anilinesand propargyl alcohols was investigated. It was found that in toluene, thecycloaddition of anilines with propargyl alcohols occurred to afford2,2-disubstituted1,2-dihydroquinolines in mild to high yields. The notableadvantages of the present procedure include easily available starting material,cheap catalyst without addition of any ligand or additive, as well as high-atomefficiency with formation of water as exclusive by-product. It is anenvironmentally friend and facile synthetic protocol for the synthesis of1,2-dihydroquinolines.Secondly, since vinyl-substituted triazole derivatives are a new family ofmonomers, which have been widely applied in the synthesis of functionalpolymers. Therefore, in this dissertation in a combined catalytic system ofCuCl/RuCl₃/TFA, the reaction of azides with propargyl alcohols via cascadedipolar cycloaddition and dehydration to produce the functionalized4-vinyltriazoles has been developed. High regioselectivity of reaction led toefficient formation of1-substituted4-vinyltriazole derivatives, and without thegeneration of1,5-isomers.Finally, one-pot cascade construction of2,5-dimethylpyrazine derivativesby the reaction of aldehydes and propargyl amines in the presence of Au（I）complex was also investigated. The formation of2,5-dimethylpyrazine derivatives was resulted from a domino procedure involving the reactions ofintermolecular hydroamination, intramolecular cyclic hydroamination anddehydration reaction.Although propargyl compounds not only have multiple reactive sites, butalso show high reactivity in most cases, resulting in low selectivity in theorganic transformation. The research work in this dissertation realizes thehighly selective transformation of propargyl compounds as synthons in thesynthesis of1,2-dihydroquinolines,4-vinyltriazoles and2,5-dimethylpyrazinesthrough optimizing the catalyst systems and catalytic reaction conditions. Theobtained results in this dissertation have not only developed the application ofpropargyl alcohols and propargyl amines in the synthesis of nitrogen-containingheterocycles, but also enriched the transformation-type of propargyl compoundsin organic synthesis.