研究室工作進展 May. 5th, 2019

發表于 2019-05-05

Direct Functionalization of White Phosphorus to

Cyclotetraphosphanes: Selective Formation of Four P−C Bonds

Shanshan Du,^§Jimin Yang,^§ Jingyuan Hu, Zhengqi Chai, Gen Luo, Yi Luo,*

Wen-Xiong Zhang,* and Zhenfeng Xi

J. Am. Chem. Soc. 2019, 141, 6843–6847. (^§Equal Contribution)

The functionalization of white phosphorus (P₄) through direct P−C bond formation has been a continuous interest because of the chlorine-free synthesis of organophosphorus compounds. Since the first report of P−C bond formation by reaction of organolithium with P₄ in 1963, continuous efforts have been made in order to convert P₄ into organophosphorus compounds directly. Although the conversions of P₄ to various [M_xP_y]_n complexes have gained great achievements, the direct formation of organophosphorus compounds from P₄ are rare. In fact, making organophosphorus compounds through direct P−C bond formation from P₄ generally suffers from: i) high electrophilic reactivity of the P₄ tetrahedron, ii) the low selectivity for the P−P bond rupture after the first P−P bond cleavage, and iii) the low conversion efficiency of the phosphorus atoms in P₄. Thus, the controllable and atom-efficient functionalization of P₄ to construct directly organophosphorus or polyphosphorus compounds is highly desirable.

The ate-complexes of aluminacyclopentadienes react with P₄ selectively affording the cyclotetraphosphanes featuring four newly formed P−C bonds and a planar square cyclo-P₄ ring. DFT calculations show that the conversion of tetrahedral P₄ to planar cyclo-P₄ moiety undergoes through an unexpected 1,1-P-insertion/D-A reaction/isomerization cascade process. The reaction of these complexes with iodomethane or p-benzoquinone can afford the P-methylation product and the metal-free cyclotetraphosphane, respectively. This work shows a promising synthetic route to the cyclotetraphosphanes starting from P₄ and throws a light on the functionalization of P₄ to organophosphorus compounds.

亮點介紹

白磷活化直接合成有機膦化合物具有十分重要的科學意義，該過程避免了工業合成中常用的PCl₃等劇毒化合物以及産生的廢酸等污染問題。近三十年來，白磷活化的研究一直被人們所關注并取得了一些進展。但到目前為止，該研究領域仍然存在許多挑戰性問題：1）反應選擇性低，産物不可控；2）合成有機膦的效率低且研究匮乏；3）機理研究匮乏；4）f區金屬活化白磷的研究匮乏。因此，由白磷直接高效、高選擇性地合成有機膦化合物就十分重要與必要。

2016年，我們利用丁二烯基橋聯的雙锂試劑與白磷直接反應，在溫和的條件下，首次實現了從白磷直接高效高選擇性合成磷雜環戊二烯基锂的方法（Angew. Chem. Int. Ed. 2016, 55, 9187–9190.）。2017年，我們利用稀土金屬雜環戊二烯同時作為雙親核試劑與雙烯體試劑，通過白磷的[3+1]-碎片化反應，分離和表征了磷雜環戊二烯基锂和第一例稀土金屬cyclo-P₃化合物（Angew. Chem. Int. Ed. 2017, 56, 15886–15890.）。2018年，我們詳細研究了磷雜戊二烯基锂的固體聚集态結構，其可以為單體、二聚體、配位聚合物等多種形式（Organometallics 2018, 37, 2018–2022.）。2019年，我們分離并表征了四種磷锂簇合物，其分别為Li₃(THF)₆P₇、Li₄(THF)₁₀P₁₄、Li₂(THF)₆P₁₆和Li₄(THF)₁₃P₂₆（Chin. J. Chem. 2019, 37, 71–75.）。

最近，我們研究了鋁雜環戊二烯促進的白磷活化。鋁雜環戊二烯與白磷反應可以高選擇性、高收率地得到含鋁的cyclo-P₄化合物，其同時構建了四根P−C鍵，具有一個規整的平面正方形cyclo-P₄結構。理論計算表明該反應經曆了一個1,1-P-插入、D−A反應、異構化的串聯反應機理。該化合物與碘甲烷反應可以得到P-甲基化的季鏻鹽化合物，與對苯醌反應可以得到不含金屬的四磷雜環丁烷衍生物。這是目前合成四磷雜環丁烷最高效的方法，也為白磷活化直接合成有機膦化合物提供了一種新思路。