Study On Synthesis And Photochemical Properties Of1,4-dihydropyrazines

The1,4-dihydropyrazines are anti-aromatic chemicals with8π-electronconjugation and widely used as medicines and biological agents. Based on the reviewof the literatures, the studies on the synthesis of1,4-dihydropyrazines and theirphotochemical properties are the main contents of this dissertation. In order to access aseries of the1,4-dihydropyrazines, the synthetic methods were studied by theinvestigation on the related factors. The photoreaction products were obtained and themechanisms were speculated by the investigation on their photostabilities andphotoreactions. The results will provide the experimental basis for their applications inmedicines and biological agents. It will also promot the research prograss on theirphotooxidations and photocycloadditions.The studies on the synthesis of the1,4-dihydropyrazines were focused on theN,N’-diacyl-1,4-dihydropyrazine and N,N’-diaryl-1,4-dihydropyrazine. The efficientmethods were established by the improvements on the microwave irradiation and theinvestigations on the reaction factors (such as reactents, solvents, catalyst, and so on).New methods of synthesis of the N,N’-diacyl-1,4-dihydropyrazine were based on thereactions of the1,4-diazabutanenes as the starting materials. One was the modificationsof pyrazines obtained from the1,4-diazabutanenes. The other was constructions ofpyrazines by the Hetero-Diels-Alder reactions of1,4-diazabutanenes and dienophiles.The the main influencing factors on the preparation of1,4-dihydropyrazine wasdetermined by the speculating the synthetic mechanisms. The results will be thefoundations for the optimization and scale-up preparation of1,4-dihydropyrazine.The studies on the photochemical properties of the1,4-dihydropyrazines includedthe photostabilities and photoreactions of N,N’-diacyl-1,4-dihydropyrazines and N,N’-diaryl-1,4-dihydropyrazines. The relationships between their spectra characteristics andstructures were investigated by their ultraviolet-visible spectrum. The suitablewavelength of photoreactions was determined by their photostabilities. Thephotoreactions were investigated in solution and in the solid state under the selectedirradiations. In solution, the photoreaction of the1,4-dihydropyrazines were studied onthe influences of solvent, concentration and photosensitizer, and the photoproductswere separated and identified. The photoreaction mechanism of the1,4-dihydropyrazines was speculated to explain the formation of the photoproducts by thespin trapping-ESR. In the solid state, the photoreaction of the1,4-dihydropyrazineswere the [2+2] photocycloaddition by introduction of solid template. The solidtemplates were selected by the method of hot stage microscopy. The cocrystal of1,4-dihydropyrazines and templates were prepared by the mixed solvents evaporation. The[2+2] photocycloaddition products were obtained by irradiation of the cocrystal of1,4-dihydropyrazines and templates. The mechanism of photocycloadditions in solid template was clarified by the data of X-ray single crystal diffractions. The results willprovide the theoretic basis for the synthesis of2,5,8,11-tetraazaasterane.There are43novel compounds in the studies on synthesis and photochemicalproperty of1,4-dihydropyrazines. They are twenty seven1,4-dihydropyrazines andrelated compounds, twelve photooxidation products and four photocycloadditionproducts. All of their structures were identified by1H NMR,13C NMR, HRMS and X-ray diffraction. The photooxidation of1,4-dihydropyrazines in solution and the [2+2]photocycloadditions in solid template were studied systematically in details for the firsttime. The results will be the theoretic and experimental basis for the broad applicationof1,4-dihydropyrazines.