Suzuki-Miyaura Reactions Catalyzed by C2-Symmetric Pd-Multi-Dentate N-Heterocyclic Carbene Complexes

Abstract

Suzuki-Miyaura coupling reactions are promoted by Pd complexes ligated with C2-symmetric multi-dentate N-heterocyclic carbenes derived in situ from Pd(OAc)2 and imidazolium salts. Good to excellent yields were obtained for aryl bromides as substrates. Turnover numbers of up to 105 could be achieved with 5 × 10−4 mol% of Pd(OAc)2/1 × 10−3 mol% NHC precatalyst in 24 h.

C(acyl)–C(sp2) and C(sp2)–C(sp2) Suzuki–Miyaura cross-coupling reactions using nitrile-functionalized NHC palladium complexes

“…In other reports, the authors mentioned that unidentified structures were detected in some catalytic reactions. 11 We also observed the undesired product and we found that this occurs when using aqueous solvents. In aqueous solvents, the benzoyl chloride converts the benzoic acid and thus directly affects the reaction efficiency.…”

“… 10 They control metal ions by blocking the reactive sites of the metal ion and preventing them from entering into their normal (and in many cases undesirable) reactions. As coordination flexibility in hybrid ligands can have a profound effect on catalytic performance, 11 we were interested in effect of NHC structure and nitrile group on catalytic activities. So, the azolium salts (benzothiazolium, benzimidazolium, imidazolium) containing 2-nitrile substituted benzyl groups and not nitrile group were prepared.…”