Deep Eutectic Solvent–Mediated Ionic Cascades: Direct Access to Azaindazoles and Related Fused Heterocycles from Diverse N‐Arenes

We report a sustainable strategy for the direct C–H functionalization of pyridines, quinolines, isoquinolines, quinoxalines, pyrimidine, and pyrazine to access N‐aryl‐7‐azaindazoles and related fused azaheterocycles. N‐Heteroarene ylides, generated from readily available corresponding precursors, react with aryl diazonium tetrafluoroborates in the presence of DABCO through an ionic cascade of nucleophilic substitution, intramolecular S N Ar, electrocyclization, and rearomatization. Deep eutectic solvents (DES) serve as efficient and green media, stabilizing diazonium salts, mitigating safety concerns, and enabling these transformations under mild conditions at 60°C with broad substrate scope. This protocol establishes DES as a safe and environmentally benign platform for heteroarene editing and late‐stage diversification of drug‐like molecules. Downstream functionalization of the final azaindazoles was demonstrated. Some of the final compounds demonstrated moderate antibacterial activity against antibiotic‐resistant gram‐ve bacteria.