5种多取代吡咯的合成

以乙酰乙酸乙酯或丙酰乙酸甲酯(Ⅰ)为起始反应物,在醋酸溶液中发生亚硝化反应可得到相应的肟,肟用锌粉还原为α-胺基羰基化合物后再与1,3-二羰基化合物进行成环缩合反应,合成了5种多吡咯化合物(Ⅳa～Ⅳe)。实验表明,还原和成环缩合的反应条件是影响目标化合物产率的主要因素,该文详细考察了还原和成环缩合反应中锌粉的用量,溶液酸度以及反应温度等条件对产率的影响,确定的最佳反应条件为:n(Zn)∶n(Ⅰ)=(2.7～2.8)∶1.0,pH=4.0～4.5,反应温度95～100℃,在该反应条件下,5种目标化合物的产率可达56%～67%。通过熔点测定、IR和1HNMR等对合成的5种多取代吡咯化合物进行了表征。

Synthesis of Five Polysubstituted Pyrroles

Five polysubstituted pyrroles(Ⅳa～Ⅳe) were synthesized from ethyl acetoacetate or methyl 3-oxopentanoate,which undergoes a nitrosation reaction leading to the formation of hydroximino compounds in acetate acid.Each hydroximino was reduced by zinc powder to give a α-amidocyanogen-carbonyl compound,which then forms the cyclization condensation with 1,3-dimethylcarbonyl.The final target compounds were obtained under the given reaction conditions.The experimental results indicate that the reaction conditions of the reduction and cyclization condensation are the key factor of the influence on the yield of the products.Therefore,the effects of the amount of reducing reagent,the acidity and temperature of the solution on the yield of polysubstituted pyrroles were examined.The optimal reaction conditions were determined:the mole ratio of reductant(zinc powder) to the main reactant(ethyl acetoacetate or methyl 3-oxopentanoate) was(2.7～2.8)∶1.0,pH=4.0～4.5 and the temperature 95～100 ℃.Under the given reaction conditions,the yields of the target products(Ⅳa～Ⅳe) were up to 56%～67%.The five synthesized polysubstituted pyrroles were characterized by melting point measurements,IR and 1HNMR spectroscopy.