A series of hexa(heteroaryl)benzenes were synthesized by the Ru(II)-carboxylate-catalyzed multiple C-H activation of benzenes carrying pyridyl, pyrimidyl, or pyrazolyl directing groups using N-heteroaryl bromides as coupling partners. The reactions proceeded with high selectivity under microwave irradiation in water. Iterative penta-arylation could be implemented via activation of C-H bonds of generated intermediates by cascade chelation assistance of in situ installed pyridyl groups. This strategy provides multidentate ligands for selective complexation of transition metals and potential building of photoredox systems.
Efficient diarylation of ortho‐C−H bonds of 2‐arylpyrimidines was 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‐withdrawing groups on the pyrimidine substrates facilitate the arylation, while both, electron‐withdrawing and electron‐donating groups on the aryl bromides lead to a faster reaction. The C−H functionalization of 2‐arylpyrimidines with heteroaryl halides provides potential multidentate ligands.
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