Nickel-Catalyzed Cross-Coupling of Aryl Chlorides with Aryl Grignard Reagents

Abstract

Dedicated to Professor Wilhelm Keim on the occasion of his 65th birthdayThe Grignard cross-coupling mediated by nickel and palladium catalysts [1, 2] represents a useful synthetic approach to biaryls, terphenyls, and oligoaryls which are important

Nickel(II) complexes with bifunctional phosphine–imidazolium ligands and their catalytic activity in the Kumada–Corriu coupling reaction

“…Amongst them is a very efficient Pd-imidazolium chloride precatalyst described by Huang et al [59], though this system required the use of relatively elevated temperatures. The only known examples involving nickel-N-heterocyclic carbene systems are complexes A, reported by Bö hm et al in [21]. These systems are able to couple aryl chlorides with aryl Grignard reagents at room temperature and in very good yields [21].…”

“…The only known examples involving nickel-N-heterocyclic carbene systems are complexes A, reported by Bö hm et al in [21]. These systems are able to couple aryl chlorides with aryl Grignard reagents at room temperature and in very good yields [21]. To date, no catalyst bearing a bifunctional ligand with a N-heterocyclic carbene has been tested in the Kumada-Corriu reaction.…”

“…It seems, however, that this system is much more active than previously appreciated and looks very promising for future catalytic applications. [21] Further studies in our laboratory will be devoted to further optimizing it.…”

Protonation of N-heterocyclic carbene ligand coordinated to copper(I): Coordination mode of imidazolium cation as a function of counterion as determined by solid-state structures

“…Thus, the aromatic carbons are asymmetrically bound with the more sterically encumbered carbon (C8, ortho to i Pr substituent) exhibiting a longer Cu-C bond than C7, which is meta to the i Pr substituent. A search of the Cambridge Structural Database (CSD) reveals several examples of Cu(I) complexes with g 2 -coordinated arene ligands with the Cu-C bond distances of the coordinated arene carbons varied from 2.072 to 2.455 Å with an average distance of 2.17 Å [29][30][31][32][33][34][35][36][37][38][39]. The imidazolium cation is oriented to hydrogen-bond with an uncoordinated oxygen of the terminal triflate ligand with the distance between the imidazolium proton (between N1 and N2) and triflate oxygen of 2.22 Å .…”

Nickel‐Catalyzed Cross‐Coupling Reactions

“…In these cases, appropriate selection of the ligand for the nickel catalysts is essential. Sterically demanding N-heterocyclic carbenes [34], hindered alkylphosphines [34], and dialkylphosphine sulfides [35] were chosen to be used as effective ligands (entries 1-3 in Table 2.1). In contrast, the corresponding palladium-catalyzed reactions with a N-heterocyclic carbene ligand require a higher temperature (80 C) [36], but this may lead to problems of selectivity.…”