Fused Pyridines by a Tandem Aza‐Wittig/Heterocyclization Strategy: Synthesis of 1,2,4‐Triazolo[1,5‐a]pyridines and Pyrido[1,2‐b][1,2,4]triazines.

The iminophosphorane 1-amino-6-(triphenylphosphoranylideneamino)-2-oxo-4-phenyl-1,2-dihydro-pyridine-3,5-dicarbonitrile 2 prepared from 1,6-diaminopyridine 1 reacts with heterocumulenes such as carbon disulfide and phenylisocyanate, and with acid chlorides, acid anhydrides and haloketones to give directly the title compounds in an one-pot aza-Wittig / heterocyclic-ring closure process with good yields.