Study On Synthesis And Photochemical Properties Of 1,4-heterocyclohexadienes

1,4-Dihydropyrazines and 4H-1,4-oxazines are two kinds of 1,4-heterocyclo hexadienes which were widely used as medicines, biological agents and electronic materials. The synthesis of 1,4-dihydropyrazines and 4H-1,4-oxazines and their photochemical properties were investigated. The relationships between the structures and photochemical properties and the insights to the phtochemicl reactions are studied in order to amplify the applications of 1,4-dihydropyrazines and 4H-1,4-oxazines.The synthesis of 1,4-dihydropyrazines and 4H-1,4-oxazines. In the synthesis of 4-aryl-1,4-dihydropyrazines (2), the intermediate N,N-bisalkylated anilines (1) were alkylated with anilines using ethyl 2-diazo acetoacetate in a reaction catalyzed by rhodium acetate, the influences of the catalysts and oxygen on the yields of 1 have been studied to obtain the optimal reaction conditions. In the synthesis of 1,4-diaryl-1,4-dihydropyrazines (3), the appropriate conditions were obtained by the investigation of the catalysts and molar ratio of reactants. The feasibility of the Hetero-Diels-Alder reaction of 1,4-diazabutanenes (4) was investigated, and 4 was synthesized by the the condensation ofα-diketones and anilines using the grinding and ultrasounic irradiation method under the solvent-free condition, respectively. The protonic intermediate of 4 was identified to be imidazole hydroperchlorates instead of E-s-cis-E (4) hydroperchlorates. The synthesis of 4H-1,4-oxaziene (9-12) was verified by the condesation of N,N-bis(phenacetyl)anilines (5-8) in the presence of POCl3.The photochemical characters of 1,4-dihydropyrazines and 4H-1,4-oxazines. Ultraviolet-visible spectrum and fluorescence spectrum were used to investigate the relationship between the structures of 1,4-dihydropyrazines (2-3) and 4H-1,4-oxazienes (9-12) and photochemical properties. The wavelength of photochemical reaction was determined by the ultraviolet-visible spectrum and the TLC. The photochemical reactions of 1,4-dihydropyrazines (2-3) and 4H-1,4-oxazienes (9-12) were investigated under the selected irradiation and the photochemical products were separated and identified.There are forty-seven novel compounds in the synthesis and photochemical products of 1,4-dihydropyrazines (2-3) and 4H-1,4-oxazienes (9-12). All of their structures were identified by 1H NMR,13C NMR, IR, MS and X-ray diffraction. The photochemical reactions of 1,4-dihydropyrazines and 4H-1,4-oxazines are studied systematically in details for the first time.