Studies on Trifluoromethyl Ketones. VII. Ene Reaction of Trifluroacetaldehyde and Its Application for Synthesis of Trifluoromethyl Compounds.
摘要:
作为三氟甲基酮烯化反应研究的延伸,我们还研究了三氟乙醛的烯化反应。在路易斯酸(其中二氯化甲基铝的效果最好)存在的情况下,该醛作为一种良好的亲烯烃与各种烯化合物发生反应,但路易斯酸引起的醛聚合往往会降低烯反应的分离产率。使用 Dess Martin 试剂成功地将烯酮反应产物氧化为三氟甲基 β、γ-不饱和酮。烯反应产物还原后再用琼斯试剂氧化,得到饱和的三氟甲基酮。β、γ-不饱和酮在热分解过程中重新排列为 α、β-不饱和酮。得到的这些酮又转化为其他类型的三氟甲基化合物。因此,三氟乙醛的烯化反应为合成多种类型的三氟甲基化合物提供了一种通用方法。在这一衍生过程中,发现三氟甲基的取代基比癸基大得多。
Reaction of trifluoroacetaldehyde ethyl hemiacetal with ene compounds in the presence of a Lewis acid gives a-trifluoromethylated homoallyl alcohols, the same products as those from the ene reaction of trifluoroacetaldehyde, in moderate to good yields. Boron trifluoride etherate was found to be most effective in this reaction. This method eliminated many difficulties encountered on the ene reaction of trifluoroacetaldehyde, which is a gas at room temperature and polymerizes to insoluble polymer in the presence of a Lewis acid. (C) 1999 Elsevier Science S.A. All rights reserved.