We have discovered that the dba ligand in the commonly used Pd₂(dba)₃·CHCl₃ cross-coupling pre-catalyst is susceptible to bis-arylation when used in the presence of aryl iodides. The in situ formed dbaAr₂ ligands result in Pd-species with altered catalytic activity. In the case of study, the room temperature C3 arylation of benzo[b]thiophenes with aryl iodides, we have observed a marked catalyst deactivation when dba is arylated with electron-deficient aryl iodides, accounting for the poor yields obtained in the C3 arylation reactions with these aryl iodides. Based on these studies, we report a new catalytic system, employing a dba-free Pd catalyst, which allows for the first time the direct C3 arylation of benzo[b]thiophenes with electron-deficient aryl iodides at room temperature.

中文翻译：

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反应监测揭示了Pd ₂（dba）_3的中毒机理并指导催化剂的选择

我们已经发现，当在芳基碘化物存在下使用时，常用的Pd ₂（dba）₃ ·CHCl ₃交联预催化剂中的dba配体易于双芳基化。在原位形成dbaAr ₂配体导致的Pd-物种与改变的催化活性。在研究的情况下，室温下苯并[ b]的C3芳基化]噻吩与芳基碘化物的反应，我们发现当dba与缺电子的芳基碘化物进行芳基化时，催化剂会明显失活，这说明在这些芳基碘化物的C3芳基化反应中收率低。基于这些研究，我们报告了一种新的催化体系，该体系采用不含dba的Pd催化剂，这首次允许在室温下苯并[ b ]噻吩与缺电子的芳基碘化物直接进行C3芳基化。