A new approach for the synthesis of coumarins from siloxy alkynes and salicylaldehydes is disclosed. Unlike the previous benzannulation reactions of siloxy alkynes that all proceed by electron-inversed Diels–Alder mechanism, this process represents a new [4+2] cyclization. In the presence of the superior HNTf2 catalyst, a wide range of coumarins were efficiently synthesized. This process was also extended to the synthesis of 2-quinolones. The polarized electron-rich triple bond might react sequentially with the aldehyde and hydroxy group by polarity switching in the stepwise formation of the C–C and C–O bonds. Control experiments provided insights into the mechanistic understanding.

中文翻译：

---

甲硅烷氧基炔烃和水杨醛[4+2]环化合成香豆素

公开了一种从甲硅烷氧基炔烃和水杨醛合成香豆素的新方法。与之前通过电子反转 Diels-Alder 机制进行的甲硅烷氧基炔烃的苯环化反应不同，该过程代表了一种新的 [4+2] 环化。在优异的 HNTf2 催化剂存在下，可以有效地合成范围广泛的香豆素。该过程还扩展到 2-喹诺酮类药物的合成。在 C-C 和 C-O 键的逐步形成过程中，极化的富电子三键可能会通过极性转换依次与醛和羟基反应。对照实验提供了对机械理解的见解。