Cycloisomerization reactions involving C–P bond formation have been overlooked for the synthesis of P-heterocycles. In this work, we developed a simple, efficient and versatile route to synthesize benzophosphole oxides by reacting ortho-alkynyl secondary phosphine oxides with 5 mol% AgSbF₆. Mechanistic investigations revealed a radical-chain mechanism involving phosphinoyl radicals as key intermediates and rare 5-endo-dig cyclization as a key step, rather than the π-activation of the CC triple bond. The transformation is both efficient and versatile. It effectively complements alternative intermolecular approaches. It works with a wide diversity of substitution patterns (alkynyl, benzo and phosphorus moieties) and enables the exquisite control of regioselectivity. Post-functionalization via direct C–H vinylation of the C2 position is also substantiated.

中文翻译：

---

通过银促进的自由基环异构化有效合成苯并磷氧化物

在 P-杂环的合成中，涉及 C-P 键形成的环异构化反应被忽视。在这项工作中，我们开发了一种简单、高效且通用的路线，通过邻炔基二氧化膦与5 mol% AgSbF ₆反应来合成苯并磷氧化物。机理研究揭示了自由基链机制，涉及膦酰基自由基作为关键中间体和罕见的5-内环化作为关键步骤，而不是CC三键的π-激活。这种转变既高效又灵活。它有效地补充了替代分子间方法。它可与多种取代模式（炔基、苯并和磷部分）配合使用，并能够精确控制区域选择性。还证实了通过C2 位直接 C-H 乙烯基化进行后官能化。