Microwave‐Assisted Copper‐Mediated One‐Pot Sequential Synthesis of Quinolino[3,4‐ b ]quinoxalines

An efficient microwave‐assisted one‐pot protocol has been developed for the synthesis of 6‐aryl/heteroarylquinolino[3,4‐ ‍b ]quinoxaline derivatives. The method involves a CuI‐mediated tandem annulation of 2‐(2‐bromophenyl)quinoxalines with aryl and heteroaryl aldehydes, using TMSN 3 as the nitrogen source. The transformation proceeds rapidly under microwave irradiation, delivering the desired products in moderate‐to‐excellent yields (up to 91%) with broad substrate scope. Further, benzyl alcohols (with TBHP) also serve as viable precursors under identical conditions to afford 6‐aryl/heteroaryl‐quinolino[3,4‐ b ]quinoxaline derivatives. Notably, the protocol eliminates the requirement for a stoichiometric amount of reducing agent used in the earlier protocol. It can be extended to gram‐scale synthesis with a remarkably reduced reaction time. Mechanistic investigations, supported by control experiments, ESI‐HRMS analysis, and DFT calculations, provide insight into the reaction pathway. This approach offers a rapid, practical, and scalable route to quinolino[3,4‐ b ]quinoxaline frameworks of potential medicinal relevance.