A general [3+2+1] annulation strategy for the preparation of pyridine N-oxides

[GRAPHICS] Stabilized ketone, aldehyde, and ester enolates react with vinamidinium hexafluorophosphate salts and hydroxylamine hydrochloride to give access to the corresponding pyridine N-oxides, The annulation reactions proceed in good to excellent yields with vinamidinium salts with a range of beta -substituents (R-3 = halo, aryl, nitro, trifluoromethyl).