Department of Chemistry, Nara University of Education, Takabatake-cho, Nara 630-8528, Japan.
J Org Chem. 2010 Feb 19;75(4):1188-96. doi: 10.1021/jo902430v.
Quinolines are an important class of compounds, and the development of new efficient synthetic strategies for the construction of quinolines is of considerable interest. Zinc triflate catalyzed cyclization of ethenetricarboxylate derivatives with 2-aminobenzaldehydes has been examined. The reaction of ethenetricarboxylate with 2-aminobenzaldehydes in the presence of zinc triflate (0.2 equiv) at 80 degrees C in ClCH(2)CH(2)Cl gave bridged tetrahydroquinoline derivatives in 15-95% yield. On the other hand, the reaction at room temperature in CH(2)Cl(2) gave hydroxy tetrahydroquinoline derivatives in 38-90% yield. Heating the hydroxy tetrahydroquinolines with zinc triflate (0.2 equiv) at 80 degrees C in ClCH(2)CH(2)Cl led to the bridged tetrahydroquinoline derivatives in 75-96% yield. Thermal reaction of the bridged tetrahydroquinolines (180 degrees C) gave indole derivatives regioselectively.
喹啉类化合物是一类重要的化合物，因此开发新的有效合成策略来构建喹啉类化合物具有重要意义。我们考察了三氟甲磺酸锌催化的乙二羧酸酯衍生物与 2-氨基苯甲醛的环化反应。在三氟甲磺酸锌（0.2 当量）存在下，乙二羧酸酯与 2-氨基苯甲醛在 80°C 的 ClCH(2)CH(2)Cl 中反应，得到桥连四氢喹啉衍生物，产率为 15-95%。另一方面，在室温下的 CH(2)Cl(2)中反应，得到羟基四氢喹啉衍生物，产率为 38-90%。将羟基四氢喹啉与三氟甲磺酸锌（0.2 当量）在 80°C 的 ClCH(2)CH(2)Cl 中加热，得到桥连四氢喹啉衍生物，产率为 75-96%。桥连四氢喹啉（180°C）的热反应可以区域选择性地得到吲哚衍生物。
