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Reaction monitoring reveals poisoning mechanism of Pd₂(dba)₃ and guides catalyst selection

Author:
Colletto, Chiara, Burés, Jordi, Larrosa, Igor
Source:
Chemical communications 2017 v.53 no.96 pp. 12890-12893
ISSN:
1364-548X
Subject:
ambient temperature, arylation, catalysts, catalytic activity, chloroform, cross-coupling reactions, ligands, monitoring, organoiodine compounds, palladium, thiophenes
Abstract:
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.
Agid:
6397008