Tetrazarsoles--a new class of binary arsenic-nitrogen heterocycles.
Tetrazarsoles--a new class of binary arsenic-nitrogen heterocycles.
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四扎索——一类新的二元砷氮杂环化合物。
DOI：
10.1002/anie.200704367
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发表时间：
2008
影响因子：
--
通讯作者：
A. Villinger
中科院分区：
文献类型：
--
作者：
A. Schulz;A. Villinger
以（Me_3Si）_2N_2N（SiMe_3）PCl_2 [2]和GaCl_3为原料，在温和条件下通过GaCl_3辅助的[3+ 2]环加成反应合成了三氮杂二磷杂茂[1].二元氮杂磷杂环戊二烯的第二个例子是四氮杂磷杂环戊二烯[3]，它是在Me 3SiN 3与Mes* N= PCl（Mes*= 2，4，6-tBu 3C 6 H2）的反应中形成的，同样由GaCl 3催化。两个反应仅在添加GaCl 3时成功，因为GaCl 3触发Me 3SiCl的消除并且通过加合物形成在反应序列的末端动力学稳定杂环（两个反应的产率均大于95%）。据我们所知，二元五元砷氮杂环组成的只有这两个元素还不知道，因此，我们试图应用GaCl 3辅助的[3+ 2]环加成砷物种。[4a]类似于氮杂磷杂茂的合成，有两条路线似乎是有希望的：1）（Me 3Si）2NH 4 N（Me 3Si）AsCl 2与GaCl 3的反应，然而，在有趣的固有Cl/甲基交换之后，其导致（ClSiMe 2）2NH 4 N（SiMe 3）AsMe 2。[4b]2）利用“伪装的”动力学稳定的亚氨基阿烷，得到高产率的所需的四唑胂（方案1）。在这里，我们提供了一个有趣的扩展GaCl 3辅助的正式[3+ 2]环加成砷的化学，这导致了第一个二元砷氮五元杂环，一个tetrazarsole的隔离。我们首先研究了环二砷杂二氮烷（1）和它的单体亚氨基砷烷（2;方案1）之间的平衡，通过随温度变化的1H NMR光谱。二聚体首先由Burford等人描述，作者推测其可逆解离。[5]白色结晶二聚体1容易溶解在CH 2Cl 2中，但最初无色的溶液缓慢地变成红色，即单体物质的颜色。为了获得二聚体-单体平衡的热化学数据，在233和298 K之间收集1H NMR光谱，得到单体化焓的值为2.2 kJ mol/L。[6a]A在298 K下发现二聚体/单体比为1：1.7，对应于自由焓ΔG8= Δ G2。6 kJ molybdenum 1.根据1H和13 C NMR研究，如果在408 ℃下将一当量的Me 3SiN 3（相对于单体）和随后的一当量的GaCl 3加入到1和2的平衡中，则单体的红色立即消失，并形成一种新的无色物质。事实上，反应的结束（新物质的完全形成）可以利用不同的颜色滴定。
Triazadiphosphole [1] was recently prepared from (Me3Si) 2NÀ N (SiMe3) PCl2 [2] and GaCl3 under mild conditions in a formal GaCl3-assisted [3+ 2] cycloaddition. The second example of a binary azaphosphole, the tetrazaphosphole,[3] was formed in the reaction of Me3SiN3 with Mes* N= PCl (Mes*= 2, 4, 6-tBu3C6H2), again catalyzed by GaCl3. Both reactions only succeed when GaCl3 is added, because GaCl3 triggers the elimination of Me3SiCl and kinetically stabilizes the heterocycle at the end of the reaction sequence by adduct formation (yields for both reactions are greater than 95%). To our knowledge, binary five-membered arsenic–nitrogen heterocycles composed of only these two elements are not yet known, and hence we tried to apply the GaCl3-assisted [3+ 2] cycloaddition to the arsenic species.[4a] In analogy to the azaphosphole synthesis, two routes seemed promising: 1) The reaction of (Me3Si) 2NÀN (Me3Si) AsCl2 with GaCl3, which, however, led to (ClSiMe2) 2NÀN (SiMe3) AsMe2, after an intriguing intrinsic Cl/methyl exchange.[4b] 2) Utilization of “disguised” kinetically stabilized iminoarsanes that give high yields of the desired tetrazarsole (Scheme1). Herein, we provide an interesting extension of the GaCl3-assisted formal [3+ 2] cycloaddition to the chemistry of arsenic, which led to the isolation of the first binary arsenic–nitrogen five-membered heterocycle, a tetrazarsole. We started with an investigation of the equilibrium between cyclic diarsadiazane (1) and its monomer, the iminoarsane (2; Scheme 1), by means of temperature-dependent 1H NMR spectroscopy. The dimer was first described by Burford et al., and the authors speculated on its reversible dissociation.[5] The white crystalline dimer 1 readily dissolves in CH2Cl2, but the initially colorless solution slowly turns red, the color of the monomeric species. To derive thermochemical data for the dimer–monomer equilibrium, 1H NMR spectra were collected between 233 and 298 K, yielding a value of 2.2 kJmolÀ1 for the enthalpy of monomerization.[6a]A dimer/monomer ratio of 1: 1.7 was found at 298K, corresponding to a free enthalpy ΔG8= À2. 6 kJ molÀ1. If one equivalent of Me3SiN3 (relative to the monomer) and subsequently one equivalent of GaCl3 are added at À408C to 1 and 2 in equilibrium, the red color of the monomer immediately disappears, and one new colorless species is formed, according to 1H and 13C NMR studies. Indeed, the end of the reaction (complete formation of the new species) can be titrated utilizing the distinct color