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

摘要

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.