Calder Ethan D E, Male Louise, Jupp Andrew R
School of Chemistry, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.
Dalton Trans. 2024 Sep 18;53(36):15032-15039. doi: 10.1039/d4dt02248c.
Heterocycles containing both phosphorus and nitrogen have seen increasing use in recent years in luminescent materials, coordination chemistry and as building blocks for inorganic polymers, yet their chemistry is currently dominated by five- and six-membered derivatives. Seven-membered P/N heterocycles are comparatively scarce and lack general, high yielding syntheses. Here, we explore the synthesis and characterisation of 1,2,5-diazaphosphepines from azophosphines. The mechanism has been probed in detail with both computational and experimental studies supporting a stepwise mechanism to form a five-membered ring, and subsequent ring expansion to the diazaphosphepine. Regioselective synthesis of five- and seven-membered rings is possible using asymmetric alkynes. The Lewis acidic borane B(CF) could either catalyse the formation of the seven-membered ring (Pr derivative) or trap out a key intermediate a frustrated Lewis pair (FLP) mechanism (Bu derivative).
近年来，同时含有磷和氮的杂环在发光材料、配位化学以及作为无机聚合物的结构单元方面的应用越来越广泛，然而它们的化学性质目前主要由五元及六元衍生物主导。七元磷/氮杂环相对较少，且缺乏通用的、高产率的合成方法。在此，我们探索了由偶氮膦合成1,2,5 - 二氮杂磷庚因的方法及表征。通过计算和实验研究详细探究了其机理，这两种研究均支持形成五元环的逐步机理以及随后向二氮杂磷庚因的扩环过程。使用不对称炔烃可以实现五元环和七元环的区域选择性合成。路易斯酸性硼烷B(CF) 既可以催化七元环（Pr衍生物）的形成，也可以通过受阻路易斯酸碱对（FLP）机理捕获关键中间体（Bu衍生物）。
