Oxidative Addition of Haloheteroarenes to Palladium(0): Concerted versus SN Ar-Type Mechanism
Bert U W Maes1, Stefan Verbeeck, Tom Verhelst
1Organic Synthesis, Department of Chemistry, University of Antwerp, 2020 Antwerpen (Belgium). bert.maes@uantwerpen.be.
Abstract:
The kinetics of the oxidative additions of haloheteroarenes HetX (X=I, Br, Cl) to [Pd(0) (PPh3 )2 ] (generated from [Pd(0) (PPh3 )4 ]) have been investigated in THF and DMF and the rate constants have been determined. In contrast to the generally accepted concerted mechanism, Hammett plots obtained for substituted 2-halopyridines and solvent effects reveal a reaction mechanism dependent on the halide X of HetX: an unprecedented SN Ar-type mechanism for X=Br or Cl and a classical concerted mechanism for X=I. These results are supported by DFT studies.
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