Study On The Synthetic Method And Structural Characterization Of Pyridine And Pyrazole Derivatives

The work in this paper can be seperated in two parts, One was the synthesis of new pyridine derivatives fromβ-keto thioamides, which were used as multifuctional synthons. The other was the synthesis of pyrazole derivatives by enaminones and semicarbazide hydrochloride, which provides a new methodology to construct the pyrazole compounds. Fifty pyridine and pyrazole derivatives were synthesized in this paper, and the structure of all the synthesized compounds were characterized by IR, 1H NMR, MS spectrum and elemental analysis, some of them were further confirmed 13C NMR spectrum. The synthetic methodologies were also discussed.In the first chapter, thioamides and enaminones as very useful synthons in the wide use of organic synthesis were reviewed firstly. Then it was summarized the advantages such as the convenient management, the higher productivity and the diminish of circumstance pollution by using multicomponet reactions (MCRs) and the microwave dielectric heating in organic synthesis.In the second chapter, a sequential one-pot two-step protocol for microwave-assisted synthesis of Hantzsch-type hexa-substituted 1,4-dihydropyridines was introduced. The three-component reactions ofβ-aroylthioamides with aldehydes and acetonitrile derivatives produce the intermediates in situ followed by a S-alkylation to afford hexa-substituted 1,4-dihydropyridines. The reaction presumably proceeds via a Knoevenagel condensation–Michael addition–cyclocondensation–rearrangement–SN2 reaction sequence. Target compounds were obtained in high yields and simply purified by recrystallization. The novel method is complementary to the classical Hantzsch synthesis.In the third chapter, the synthetic method of 3-aryl-1H-pyrazoles by enaminones and semicarbazide hydrochloride was introduced. 3-aryl-1H-pyrazoles were formed by eliminating carboxamide of 5-aryl-1H-pyrazole-1-carboxamide. Target compounds were obtained in high yields and simply purified by recrystallization. The reaction heated by traditional and microwave method was compared in the two chapters, compared with the traditional synthetic method, under the microwave radiation the same products were obtained with shorter reaction time and higher yield.