DBU‐Mediated [4+2] Cyclization of Sulfoxonium Ylides and o‐Phenylenediamines for Quinoxaline Synthesis

A novel method for the synthesis of quinoxalines from o‐phenylenediamines and sulfoxonium ylides, mediated by DBU (1,8‐Diazabicyclo[5.4.0]undec‐7‐ene), is presented. This method does not require metal catalysts or oxidants, making it economical and environmentally friendly, while exhibiting excellent functional group tolerance. Mechanistic studies suggest that DBU facilitates the reaction through nucleophilic attack on sulfoxonium ylides. Gram‐scale synthesis and various cross‐reactions further highlight the advantages of this strategy.