While investigating a 1,1′-thiocarbonyldiimidazole (TCDI)-mediated coupling in the synthesis of an aryl isothiocyanate, imidazole autocatalysis was observed. Although reported for 1,1′-carbonyldiimidazole (CDI), imidazole autocatalysis with TCDI has not been described. In this study, we explore the mechanism of imidazole autocatalysis in TCDI-mediated couplings of aniline. Notably, acids and non-nucleophilic bases were not shown to catalyze this reaction, suggesting that imidazole autocatalysis occurs via an alternative mechanism. We propose that imidazole acts as a nucleophilic catalyst leading to a more reactive cationic TCDI species. Inverse first-order kinetics with respect to imidazole anion and rapid equilibration with deuterated imidazole resulting in the release of free imidazole from TCDI support this conclusion. Increased catalytic activity with several known nucleophilic catalysts was observed, further supporting the role of imidazole as a nucleophilic catalyst. A density functional theory (DFT)-based computational model was constructed to identify other potential nucleophilic catalysts in this reaction. This model was successful in identifying several classes of nucleophilic catalysts that proved to be even more reactive catalysts for TCDI-mediated couplings of aniline compared to imidazole.

中文翻译：

---

1,1'-硫代羰基二咪唑介导的苯胺偶联咪唑自催化机理研究

在研究芳基异硫氰酸酯合成中 1,1'-硫代羰基二咪唑 (TCDI) 介导的偶联时，观察到咪唑自催化作用。尽管报道了 1,1'-羰基二咪唑 (CDI)，但尚未描述 TCDI 的咪唑自催化作用。在本研究中，我们探讨了 TCDI 介导的苯胺偶联中咪唑自催化的机制。值得注意的是，酸和非亲核碱并未显示出催化该反应，这表明咪唑自催化是通过替代机制发生的。我们建议咪唑充当亲核催化剂，产生更具反应性的阳离子 TCDI 物质。咪唑阴离子的逆一级动力学和与氘代咪唑的快速平衡导致从 TCDI 释放游离咪唑支持了这一结论。观察到几种已知的亲核催化剂的催化活性增加，进一步支持了咪唑作为亲核催化剂的作用。构建了基于密度泛函理论（DFT）的计算模型来识别该反应中其他潜在的亲核催化剂。该模型成功地识别了几类亲核催化剂，事实证明，与咪唑相比，这些催化剂对于 TCDI 介导的苯胺偶联反应活性更高。