achieved by Ru(II)−carboxylate‐catalyzed reaction with aryl bromides in water, whereas meta‐substituted phenylpyrimidines selectively led to monoarylation. The reaction is strongly accelerated under microwave irradiation, and is compatible with various functional groups on both coupling partners. As established from Hammett plots, electron‐withdrawinggroups on the pyrimidine substrates facilitate the