Cobalt-Catalyzed C(sp2)–CN Bond Activation: Cross-Electrophile Coupling for Biaryl Formation and Mechanistic Insight

Céline Dorval (1) , Maxime Tricoire (1) , Jeanne-Marie Begouin (1) , Vincent Gandon (1, 2) , Corinne Gosmini (1)

1 LCM - Laboratoire de chimie moléculaire
2 ICMMO - Institut de Chimie Moléculaire et des Matériaux d'Orsay

Herein, we report a cross-electrophile coupling of benzonitrile derivatives and aryl halides with a simple cobalt-based catalytic system under mild conditions to form biaryl compounds. Even though the cobalt catalyst is able to activate the C(sp 2)−CN bond alone, the use of the AlMe 3 Lewis acid enhances the reactivity of benzonitriles and improves the cross-selectivity with barely any influence on the functional group compatibility. X-ray structure determination of an original low-valent cobalt species combined with catalytic and stoichiometric reactions reveals a catalytically active cobalt(I) species toward the aryl halide partner. On the other hand, experimental insights, including cyclic voltammetry experiments, suggest the involvement of a cobalt complex of a lower oxidation state to activate the benzonitrile derivative. Finally, density functional theory calculations support the proposed mechanistic cycle involving two low-valent cobalt species of different oxidation states to perform the reaction.

Mots clés: cobalt; catalysis; benzonitriles; reductive cross-coupling; biaryl; cross-electrophile coupling

Domaines: Catalyse

Céline Dorval, Maxime Tricoire, Jeanne-Marie Begouin, Vincent Gandon, Corinne Gosmini. Cobalt-Catalyzed C(sp2)–CN Bond Activation: Cross-Electrophile Coupling for Biaryl Formation and Mechanistic Insight. ACS Catalysis, 2020, 10 (21), pp.12819 - 12827. ⟨10.1021/acscatal.0c03903⟩. ⟨hal-03026541⟩