Nickel Bromide Catalyzed Ligand‐Free and Activator‐less Suzuki Coupling Reactions

Abstract

AbstractReadily available and inexpensive bromide salt based on earth‐abundant nickel has been used to catalyze the Suzuki coupling of a variety of aryl halides (ca. 37 examples) in high yields under ambient conditions with good functional group tolerance. The reactivity of various aryl halides follows the corresponding C−X (X=I, Br and Cl) bond strength in the order Ar−I>Ar−Br>Ar−Cl. EPR analysis, mercury‐drop experiments and reactions with radical scavenger such as TEMPO point to the involvement of well‐defined molecular species that operate via a Ni(0)/Ni(II) catalytic cycle where oxidative addition of the aryl halide to Ni(0) is likely to be the rate‐determining‐step (RDS). For the first time, valuable new polycyclic aromatic hydrocarbons (PAHs) with exciting photophysical properties have been synthesized (ca. 23 examples) via a Ni(II) catalyzed multi‐fold Suzuki coupling.