DBU‐Catalyzed [3+3] and [3+2] Annulation Reactions of Azomethine Ylides with α‐Diazocarbonyls as N‐Terminal Electrophiles: Modular, Atom‐Economical Access to 1,2,4‐Triazine and 1,2,4‐Triazole Derivatives

The DBU‐catalyzed [3+3] and [3+2] cyclization reactions of azomethine ylides with α‐diazocarbonyls as N‐terminal electrophiles have been developed. These reactions involve a sequential intermolecular nucleophilic addition/intramolecular cyclization/oxidation procedure. By the assembly of readily available starting materials, these transformations offer novel, highly efficient one‐pot syntheses of various functionalized 1,2,4‐triazine and 1,2,4‐triazole derivatives in an atom‐economical manner under ambient and metal‐free conditions in a high regio‐ and diastereoselective manner.