Department of Applied Chemistry, National Chiao Tung University, Hsinchu 300-10, Taiwan.
Chem Asian J. 2011 Sep 5;6(9):2471-80. doi: 10.1002/asia.201100277. Epub 2011 Jun 30.
A tandem transformation that involves the formation of three bonds and two heterocyclic rings in a one-pot fashion through amino-alkylation of an ionic-liquid-immobilized diamine with keto acids followed by successive double intramolecular cyclizations to afford a tricyclic framework has been explored. This tandem cyclization has been utilized to develop a rapid and efficient method to synthesize various pyrrolo[1,2-a]benzimidazolones and pyrido[1,2-a]benzimidazolones on an ionic-liquid support by using focused microwave irradiation. The application of this tandem cyclization was further extended to the aromatic keto acids to provide isoindolinone-fused benzimidazoles, a structurally heterogeneous library with skeletal diversity. The outcome of the cascade reaction was confirmed by the X-ray crystallographic study of the product directly attached to the ionic-liquid support. Use of the ionic liquid as a soluble support facilitates purification by simple precipitation along with advantages like high loading capacity, homogeneous reaction conditions, and monitoring of the reaction progress by regular conventional spectroscopic methods, whereas application of microwave irradiation greatly accelerates the rate of the reactions.
通过将离子液体固定化二胺与酮酸进行氨烷基化，一锅法形成三个键和两个杂环，随后进行连续的双重分子内环化，从而构建三环骨架，探索了串联转化。这种串联环化已被用于在离子液体载体上使用聚焦微波辐射，快速有效地合成各种吡咯并[1,2-a]苯并咪唑啉酮和吡啶并[1,2-a]苯并咪唑啉酮。这种串联环化的应用进一步扩展到芳香族酮酸，提供了异吲哚啉酮稠合的苯并咪唑，这是一个具有骨架多样性的结构异构库。通过直接连接到离子液体载体的产物的 X 射线晶体学研究证实了级联反应的结果。离子液体作为可溶性载体的使用便于通过简单沉淀进行纯化，同时具有高负载能力、均相反应条件以及通过常规光谱方法监测反应进程的优点，而微波辐射的应用则大大加快了反应速率。
