3-甲基-5-羟基-1-取代-1 H-吡唑的合成及其光谱性质

Synthesis and spectral properties of 3-methyl-5-hydroxy-1-substituted-1H-pyrazole

以取代羧酸和氨基硫脲为初始原料,经多步反应合成中间体2-肼基-5-取代-1,3,4-噻二唑,再将其与乙酰乙酸乙酯反应,设计合成9个含l,3,4-噻二唑取代基的3-甲基-5-羟基-1-取代-1 H-吡唑类化合物(4a^4i),其中,8个为新化合物.借助IR、NMR、元素分析等技术手段对所合成化合物的结构进行了表征.运用高斯程序对9种化合物中可能存在的异构体的能量进行了理论计算.计算结果表明:化合物以烯醇式结构存在时的能量最低,稳定性最好.此外,通过紫外光谱测试讨论了烯醇式与酮式的互变异构现象及其影响因素.通过荧光光谱测试,发现化合物4c的荧光强度最强,将其对金属阳离子做离子识别筛选实验,其对Cu^(2+)有选择性识别作用.将化合物4c作为Cu^(2+)荧光猝灭型探针,不受其他常见的阳离子干扰,对Cu^(2+)具有较高的选择性响应.

The intermediate 2-hydrazino-5-substituted-1,3,4-thiadiazole was synthesized by a series of reactions with carboxylic acid and thiosemicarbazone as raw materials, and then reacted with ethyl acetoacetate, 3-methyl-5-hydroxy-l-substituted-lH-pyrazole compounds （4a-4i） were synthesized of nine compounds containing the substituent with 1,3,4-thiadiazole, eight of them were new com- pounds. The structures of all the compounds were confirmed by means of infrared spectrum, NMR and elemental analysis. The energies of the isomers in the nine compounds were calculated by Gaussi- an program. The calculated results show that the compounds in the enol structure of the lowest ener- gy,it can be stable existence. In addition, the isomerization phenomena of enol and keto forms and their affect factors were discussed by UV spectroscopy. By using fluorescence spectroscopy,these re- sults suggest that compound 4c had the significant increase of the fluorescence intensity then, in the ion selective screening experiment of metal cations, it was found that it had selective recognition of Cu2＋. The probe 4c was used as a Cu2＋ fluorescence quenching probe, and found that other common cationic did not induce obvious fluorescence change, indicating the high selectivity of the probe 4c to Cu2＋.