Selective ring closure to substituted pyrido[1,2-b]-as-triazinium salt

Article abstract of DOI:10.1016/S0040-4020(01)86594-7

Reaction of arylglyoxal with 1,2-diaminopyridinium salt 1 under acidic conditions afforded 2-aryl-pyrido[1,2-b]-as-triazinium salt 9 selectively, whereas cyclization of the same dioxo compound with 1-amino-2-iminopyridine 5 under neutral conditions - due