A simple one pot synthesis of condensed 1,2,4‐triazines by using the tandem aN‐SNipso and SNH‐SNipsa reactions

A new synthetic approach to condensed 1,2,4‐triazines based on using the tandem A_N‐S_N^ipso and S_N^H‐S_N^ipso reactions has been developed. 5‐Methoxy‐3‐penyl‐1,2,4‐triazine and its N₁‐methyl quaternary salt were found to react with C,N‐, C,O‐ and N,N'‐bifunctional nucleophiles (m‐phenylenediamine, resor‐cinol, semicarbazide and ureas) into triazacarbazoles, benzofuro[2,3‐e][1,2,4]‐triazines, and 6‐azapurine derivatives. In all cases nucleophiles attack first the unsubstituted C‐6 carbon of the triazine ring, while the final stage is replacement of the methoxy group affording cyclization products.