Negishi cross-coupling reactions catalyzed by an aminophosphine-based nickel system: A reliable and general applicable reaction protocol for the high-yielding synthesis of biaryls

摘要

Treatment of NMP solutions of NiCl_2 with 1,1′,1″- (phosphanetriyl)tripiperidine (≈2.05 equiv), dissolved in THF, in air at 25°C forms a highly active catalytic system for the cross-coupling of a large variety of electronically activated, non-activated, deactivated, and ortho-substituted, heterocyclic, and functionalized aryl bromides and aryl chlorides with diarylzinc reagents. Very high levels of conversion and yields were obtained within 2 h at 60°C in the presence of only 0.1 mol% of catalyst (based on nickel) and thus at catalyst loadings far lower than typically reported for nickel-catalyzed versions of the Negishi reaction. Various aryl halides-which may contain trifluoromethyl groups, fluorides, or other functional groups such as acetals, ketones, ethers, esters, lactones, amides, imines, anilines, alkenes, pyridines, quinolines, and pyrimidines-were successfully converted into the corresponding biaryls. Electronic and steric variations are tolerated in both reaction partners. Experimental observations indicate that a molecular (Ni~I/Ni~(III)) mechanism is operative.