β-取代硝基乙烯的合成研究

Synthesis of β-substituted nitroolefins

在NH;Ac的作用下,硝基甲烷分别和各种不同的醛(包括芳香醛、脂肪醛)在HAc溶液中发生Henry反应并消除得到一系列β-取代硝基乙烯化合物(1a~1r),产物结构经;H NMR表征。并以硝基甲烷与4-氟苯甲醛的反应为模型,考察了物料比、反应温度及反应时间对反应的影响,确定最佳反应条件为:物料比n;∶n;=3∶1;反应温度120℃;反应时间2h,在该条件下,(E)-1-氟-4-(2-硝基乙烯)苯(1a)产率达到87.1%。然后,对于β-取代硝基乙烯在Michael加成反应中的应用进行研究发现,在有机碱三乙胺的作用下,1a与乙酰丙酮在室温下发生Michael加成反应得到3-[1-(4-氟苯基)-2-硝基乙基]戊-2,4-二酮(6),产率达到77.4%。

In the presence of ammonium acetate, a series of β-substituted nitroolefin compounds(1a ~1r)through Henry reaction and elimination reaction by using nitromethane and various aldehydes(including aromatic aldehydes and aliphatic aldehydes) as starting materials. The structures of the products were characterized by ~1HNMR. The reaction of nitromethane with 4-fluorobenzaldehyde were used as a model, the effects of material ratio,reaction temperature and time on the reaction were investigated. The optimal reaction conditions were determined as follows: material ratio n;∶n;=3∶1;reaction temperature is 120℃ reaction time is 2 hour. Under these conditions, the yield of(E)-1-fluoro-4-(2-nitrovinyl)benzene(1a) up to 87.1%. Then, the application of β-substituted nitroolefin in Michael addition reaction was studied. It was found that under the action of organic base triethylamine, 3-(1-(4-fluorophenyl)-2-nitroethyl)pentane-2,4-dione(6)was obtained with 77.4% yield by the Michael addition reaction of compound 1a and acetyl acetone at room temperature.