Palladium‐Catalyzed Regioselective C−H Arylation of 4‐Azaindazole at C3, C5 and C7 Positions.

Direct and site‐selective C5 and C7 palladium‐catalyzed C−H arylations of 4‐azaindazole N‐oxide have been achieved. A bidentate ligand and Pd(OAc)2 catalyst in toluene promoted the activation of C5 position, while a phosphine ligand and PdCl2 catalyst in DMA directed the arylation at C7 position. Using this new method, the synthesis of C5, C7‐diarylated 4‐azaindazole N‐oxides as well as the C3, C5, C7‐triarylated 4‐azaindazoles was achieved towards future medicinal compounds development. [ABSTRACT FROM AUTHOR]