A metal-free, TfOH (1.1 equiv)-mediated formal cycloisomerization of easily prepared allene-alkynylbenzenes to give pyrrolidines and cyclopentanes derivatives was developed. This reaction is initiated by the generation of allylic cation from allene, followed by alkyne’s reaction with the allylic cation, to give a vinyl cation, which is finally intercepted by the triflate (TfO) anion. This cycloisomerization can be further tuned to become an acid-mediated intramolecular formal [4+3] cycloaddition by using 10 equiv of TfOH (The excess acid was used to promote the Friedel–Crafts reaction of the acid-mediated cycloisomerization products). The present system can also be applied to synthesized F-incorporated products by using HBF₄ or Me₃OBF₄ as the fluoro source.

中文翻译：

---

TfOH和HBF ₄介导的丙二烯炔基苯的形式环异构化和[4 + 3]环加成

开发了无金属，TfOH（1.1当量）介导的易于制备的烯丙基-炔基苯的正式环异构化反应，得到吡咯烷和环戊烷衍生物。该反应通过从丙二烯生成烯丙基阳离子开始，然后由炔烃与烯丙基阳离子反应，得到乙烯基阳离子，该乙烯基阳离子最终被三氟甲磺酸根（TfO）阴离子拦截。通过使用10当量的TfOH（可以将过量的酸用于促进酸介导的环异构化产物的Friedel-Crafts反应），可以将该环异构化进一步调整为酸介导的分子内形式的[4 + 3]环加成反应。通过使用HBF ₄或Me ₃ OBF ₄作为氟源，本系统还可以应用于合成的掺入F的产物。