The gold(I)‐catalyzed intramolecular hydroarylation of o‐ethynylarylphosphonium salt 1 gave phosphepinium 2 or phosphinium salt 3. The use of methylphosphonium salt instead of phosphine chalcogenide is key to success for the intramolecular hydroarylation. The substrate with 2‐methoxyphenyl group at the alkyne position preferentially provided seven‐membered phosphacycle 2, while that with a hydrogen did six‐membered phosphacycle 3. Theoretical calculations revealed that the activation energy of 6‐exo‐dig cyclization in the substrate with the aryl group increased due to the steric repulsion of the two aryl rings. Furthermore, the Wittig‐type reaction of phosphepinium salt 2 a afforded methyl‐substituted phosphepin oxide 4 a via the elimination of an aryl group.

中文翻译：

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金（I）催化的邻乙炔基芳基Salt盐的分子内氢化反应导致七元和六元磷酸环的形成

金（I）催化的邻乙炔基芳基salt盐1的分子内氢芳基化反应生成了磷pin 2或or 3。使用甲基phosph盐代替膦硫属化物是成功进行分子内氢芳基化的关键。在炔基位置具有2-甲氧基苯基的底物优先提供七元的磷环2，而具有氢的底物优先提供六元的磷环3。理论计算表明，由于两个芳基环的空间排斥作用，带有芳基的底物中6-exo-dig环化的活化能增加。此外，磷pin盐的Wittig型反应2，得到甲基取代phosphepin氧化物4经由消除的芳基。