| 1,3,4-oxadiazole is a five-membered heterocyclic compound containing a nitrogen atom and an oxygen atom, the main substitution product of 1,3,4-oxadiazole derivatives are at 2 and 5. Due to the special nature of 1,3,4-oxadiazole molecular structure, its derivatives have broad applications in medicine and materials. In pharmaceutical applications, mainly as follows:pain, blood pressure, diuretic, anti-bacterial, anti-inflammatory, anti-convulsants, anti-tumor, anti-viral, promoting plant growth, etc. Meanwhile,1,3,4-oxadiazole compounds with strong electron-deficient, better luminescent properties and stability, chemical resistance, therefore, In material application, it can be used as the light emitting material, electron transport material, and organic electroluminescent devices. Imidazole have similar chemical structure with 1,3,4-oxadiazole, imidazole is a five-membered aromatic heterocyclic compounds containing two meta nitrogen atom, the same unique structure determines the uniqueness of its nature, so their derivatives have similar applications in medicine and materials. Based on the structure and applications similarity of imidazole and 1,3,4-oxadiazole, they can be incorporated into the same compound, which is expected to be superimposed pharmacophore groups, so that the final imidazo [2,1-b]-1,3,4-oxadiazole derivatives have strong biological activity. Meanwhile, in material applications, it has faster transmission and optical properties, strong chemical stability and thermal stability.This topic designed and synthesized a series of imidazole containing aromatic groups and [2,1-b]-1,3,4-oxadiazole compound. Linking the structure of imidazole and 1,3,4-oxadiazole derivatives, to get a new class of drug molecules, which has a stronger antibacterial activity than any single active group. Specific experiments are divided into the following four areas:(1)Twelve kinds semicarbazones containing aromatic group were synthesized referring to the appropriate literature, with semicarbazide hydrochloride, ethanol, aromatic aldehyde as the raw material.12 kinds of amino-5-substituted-1,3,4-oxadiazole were synthesized, with bromine as catalyst, glacial acetic acid and anhydrous sodium acetate as solvent, the reaction were detect by TLC. Including 2-amino-5-phenyl-1,3,4 oxadiazole,2-amino-5-(4-hydroxyphenyl)-1,3,4-oxadiazole,2-amino-5 (4-methylphenyl)-1,3,4-oxadiazole,2-amino-5-(4-methoxyphenyl)-1,3,4-oxadiazole,2-amino-5-(4-nitrophenyl)-1,3,4-oxadiazole,2-amino-5-(2-nitrophenyl)-1,3,4-oxadiazole,2-amino-5-(3-nitrophenyl)-1,3,4-oxadia-zole,2-amino-5-(4-fluorophenyl)-1,3,4-oxadiazole,12-amino-5-(4-bromophenyl)-1,3,4-oxadiazole,2-amino-5-(4-chlorophenyl)-1,3,4-oxadiazole,2-amino-5-(4-dimethylaminophenyl)-1,3,4-oxadiazole,2-amino-5-phenyl-ene-1,3,4-oxadiazole. The structure of the compounds were identified by IR and elemental analysis.(2) Five kinds ?-bromo-substituted acetophenone were synthesized corresponding reference literature, with bromine, methanol, concentrated hydrochloric acid and 5 kinds of acetophenone as starting material, five kinds ?-bromo-substituted acetophenone including a-bromoaceto-phenone, ?-bromo-hydroxyacetophenone, between a-bromo nitroaceto phenone, ?-bromo methylacetophenone, a-bromo-bromoacetophenone, and the five kinds of compounds were identified by IR and elemental analysis.(3)Sixty kinds of aromatic containing imidazo [2,1-b]-1,3,4-oxadiazole compound were synthesized by liquid phase synthesis and microwave synthesis, with the above obtained 12 kinds of 2-amino-5-substituted-phenyl-1,3,4-oxadiazole,5 kinds of ?-bromo-substituted acetophenone, and ethanol as the raw material. Of which fifty kinds have not been reported so far. Liquid phase synthesis method is a mixture of 2-amino-5-substituted-phenyl-1,3,4-oxadiazole and ?-bromo-substituted acetophenone, with anhydrous ethanol as solvent. With the reaction of 2-amino-5-(4-hydroxyphenyl)-1,3,4-oxadiazole and between ?-bromo- substituted acetophenone as an example, optimum reaction conditions were determined using single factor test, it is:the molar ratio of 2-amino-5-(4-hydroxyphenyl)-1,3,4-oxadiazole and ?-bromo- substituted acetophenone is 1:1.12, the reaction time is 16.5h, the reaction temperature is 78?, the solvent is ethanol. Microwave synthesis is placed 2-amino-5-(4-hydroxyphenyl)-1,3,4-oxadiazole and ?-bromo-sub stituted acetophenones in crucible, using ethanol as solvent.Comparison of these two methods, microwave synthesis method is simple, low equipment requirements, shorter reaction time, simple post-processing and higher yields, environmental protection and so on. Then the 60 kinds of compounds were identified by IR,1H NMR, elemental analysis.(4)Sixty kinds containing 2-substituted phenyl-5-methyl-piperazine-6-substituted phenylimidazo [2,1-b]-1,3,4-oxadiazole were synthesized by liquid phase, with 60 kinds of the aromatic group-containing imidazole obtained above and [2,1-b]-1,3,4-oxadiazole,40% formaldehyde solution, ethanol, and anhydrous piperazine as the raw material. Optimum reaction conditions were determined using single factor test, it is:The molar ratio of aromatic imidazo [2,1-b]-1,3,4-oxadiazole and 40% formaldehyde solution is 1:2.5, the reaction temperature is 80?, reaction time is 8h. Then the 60 kinds of compounds were confirmed by IR,1H NMR, elemental analysis. |
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