Details

Autor(en) / Beteiligte

• Zhou, Edouard
• Chourreu, Pablo
• Lefèvre, Nicolas
• Ahr, Mathieu
• Rousseau, Lidie
• Herrero, Christian
• Gayon, Eric
• Cahiez, Gérard
• Lefèvre, Guillaume

Titel

Mechanistic Facets of the Competition between Cross-Coupling and Homocoupling in Supporting Ligand-Free Iron-Mediated Aryl–Aryl Bond Formations

Ist Teil von

• ACS Organic & Inorganic Au, 2022-08, Vol.2 (4), p.359-369

Ort / Verlag

American Chemical Society

Erscheinungsjahr

2022

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• In the context of cross-coupling chemistry, the competition between the cross-coupling path itself and the oxidative homocoupling of the nucleophile is a classic issue. In that case, the electrophilic partner acts as a sacrificial oxidant. We investigate in this report the factors governing the cross- versus homocoupling distribution using aryl nucleophiles ArMgBr and (hetero)­aryl electrophiles Ar′Cl in the presence of an iron catalyst. When electron-deficient electrophiles are used, a key transient heteroleptic [Ar2Ar′FeII]− complex is formed. DFT calculations show that an asynchronous two-electron reductive elimination follows, which governs the selective evolution of the system toward either a cross- or homocoupling product. Proficiency of the cross-coupling reductive elimination strongly depends on both π-accepting and σ-donating effects of the FeII-ligated Ar′ ring. The reactivity trends discussed in this article rely on two-electron elementary steps, which are in contrast with the usually described tendencies in iron-mediated oxidative homocouplings which involve single-electron transfers. The results are probed by paramagnetic 1H NMR spectroscopy, experimental kinetics data, and DFT calculations.