PDF(Pubmed)
Abstract：
The electrophilic activation of various substrates via double or even triple protonation in superacidic media enables reactions with extremely weak nucleophiles. Despite the significant progress in this area, the utility of organophosphorus compounds as superelectrophiles still remains limited. Additionally, the most common superacids require a special care due to their high toxicity, exceptional corrosiveness and moisture sensitivity. Herein, we report the first successful application of the \"Brønsted acid assisted Brønsted acid\" concept for the superelectrophilic activation of 2-hydroxybenzo[e][1,2]oxaphosphinine 2-oxides (phosphacoumarins). The pivotal role is attributed to the tendency of the phosphoryl moiety to form hydrogen-bonded complexes, which enables the formation of dicationic species and increases the electrophilicity of the phosphacoumarin. This unmasks the reactivity of phosphacoumarins towards non-activated aromatics, while requiring only relatively non-benign trifluoroacetic acid as the reaction medium.
摘要：
在超酸性介质中通过双重或甚至三重质子化对各种底物的亲电子活化使得能够与极弱的亲核试剂反应。尽管在这方面取得了重大进展，有机磷化合物作为超亲电物质的用途仍然有限。此外,最常见的超强酸由于其高毒性而需要特别小心，特殊的腐蚀性和湿度敏感性。在这里，我们报告了“布朗斯台德酸辅助布朗斯台德酸”概念首次成功应用于2-羟基苯并[e][1,2]氧杂膦胺2-氧化物（磷酸香豆素）的超亲脂性活化。关键作用归因于磷酰基部分形成氢键复合物的趋势，这使得能够形成双阳离子物种并增加磷香豆素的亲电性。这揭示了磷香豆素对非活化芳烃的反应性，而仅需要相对非良性的三氟乙酸作为反应介质。
