The catalytic activity of zinc(II) compounds was exploited in the nucleophilic addition of amines to nitriles to form amidines. The reaction systems comprised a Zn(II) starting material [Zn(quin)₂(H₂O)] (quin⁻ = quinaldinate, an anion of quinaldinic acid), secondary cyclic amine, acetonitrile, and in some cases, methanol. Amines with additional heteroatoms in the ring (thiomorpholine, piperazine) or ring substituents (piperidine derivatives, piperazine derivatives) with different steric and electronic effects were used. The aim of the study was to determine how the nature of the amine affects the formation of amidines. Different types of Zn(II) products were obtained: mono- or diamine complexes, amidine complexes, and also an ionic compound with a protonated amine. In one case, the amidine itself crystallized. A Zn(II) complex with acetamidine was also obtained. Acetamidine was formed from acetonitrile and ammonia, which most likely originated from the hydrolysis of acetonitrile under harsh reaction conditions. The hydrolysis could terminate at the acetamide step, which was confirmed by the isolation of a cocrystal containing acetamide. In the case of piperazine (pz), a polymeric compound with the composition [Zn(quin)₂(pz)]_n was isolated regardless of the reaction conditions. The same coordination polymer was also observed to form in 1-methylpiperazine, 1-ethylpiperazine, and 1-acetylpiperazine reaction systems, containing piperazine as an inherent impurity. This was unambiguously confirmed by the crystal structure of a cocrystal, [Zn(quin)₂(1-Acpz)₂]·[Zn(quin)₂(pz)]_n·4CH₃CN, which formed in the 1-acetylpiperazine (1-Acpz) reaction system.

中文翻译：

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哌啶和哌嗪类似物的作用：锌 (II) 介导的脒形成

利用锌( II )化合物的催化活性将胺与腈进行亲核加成形成脒。反应系统包含Zn( II )起始材料[Zn(quin) ₂ (H ₂ O)]（quin ^- =喹哪啶酸根，喹哪啶酸的阴离子）、仲环胺、乙腈，以及在一些情况下的甲醇。使用环上具有额外杂原子的胺（硫代吗啉、哌嗪）或具有不同空间和电子效应的环取代基（哌啶衍生物、哌嗪衍生物）。该研究的目的是确定胺的性质如何影响脒的形成。获得了不同类型的 Zn( II ) 产品：单胺或二胺络合物、脒络合物以及具有质子化胺的离子化合物。在一种情况下，脒本身结晶。还获得了与乙脒的Zn( II )络合物。乙脒是由乙腈和氨形成的，很可能源自乙腈在恶劣的反应条件下水解。水解可以在乙酰胺步骤终止，这通过含有乙酰胺的共晶的分离得到证实。在哌嗪(pz)的情况下，无论反应条件如何，都分离出组成为[Zn(quin) ₂ (pz)] _n的聚合化合物。在含有哌嗪作为固有杂质的 1-甲基哌嗪、1-乙基哌嗪和 1-乙酰基哌嗪反应体系中也观察到形成相同的配位聚合物。共晶 [Zn(quin) ₂ (1-Acpz) ₂ ]·[Zn(quin) ₂ (pz)] _n ·4CH ₃ CN的晶体结构明确证实了这一点，该共晶在 1-乙酰基哌嗪 ( 1-Acpz)反应体系。