Reduction of 2‐benzyl‐1‐mesityl‐5,7‐dimethyl‐2,3‐dihydrophosphindole 1‐oxide (2‐O), which was prepared by catalytic addition of dimesitylphosphane oxide across phenylacetylene via dimesityl‐phenylethenylphosphane oxide (1), with excess of trichlorosilane in toluene yielded 2‐benzyl‐1‐mesityl‐5,7‐dimethyl‐2,3‐dihydrophosphindole (2). Straightforward oxidation of 2 with sulfur and selenium in toluene at 110 °C allowed the isolation of crystalline colorless 2‐benzyl‐1‐mesityl‐5,7‐dimethyl‐2,3‐dihydrophosphindole 1‐sulfide (2‐S) and 1‐selenide (2‐Se). The hindered rotation of the P‐bound mesityl group around the P–C bond is indicative of significant intramolecular steric strain. Despite this strain, the P–E bond lengths (E = S, Se) lie in expected ranges.

中文翻译：

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立体阻碍的2,3-二氢磷吲哚及其硫属元素化物

还原2-苄基-1-间甲苯基-1,5,7-二甲基-2,3-二氢磷吲哚1-氧化物（2-O），这是通过经由二苯甲基-苯基乙烯基膦氧化物（1）在苯乙炔上催化加成二苯甲基膦氧化物制备的（1），用过量的三氯硅烷在甲苯中制得2-苄基-1-甲磺酰基-5,7-二甲基-2,3-二氢磷吲哚（2）。在110°C下用硫和硒在甲苯中直接将2氧化，可以分离出结晶的无色结晶2-苄基-1-甲磺酰基-5,7-二甲基-2,3-二氢磷吲哚1-硫化物（2-S）和1-硒化物（2 Se）。P结合的异氰酸酯基团围绕P–C键的旋转受阻表明存在明显的分子内空间应变。尽管有这种压力，PE键的长度（E = S，Se）仍在预期范围内。