An efficient Ir(III)-catalyzed C-H activation and annulations of aryloxime with α-diazocarbonyl compounds has been developed for the synthesis of substituted isoquinoline N-oxides. The reaction proceeds under mild atmospheric conditions, without any external oxidants and releases N2 and H2O as the byproducts. In addition, synthetic applications of the N-oxide products have been established by performing further functionalization. An interesting dimeric iridacyclic complex allied through a bis-silver carboxylate bridge has been isolated that efficiently catalyzed the reaction.