Synthesis of N-(iminyl)pyridinium salts from hydrazones by the Zincke reaction

N -(Iminyl)pyridinium salts are a rare and poorly explored class of pyridine derivatives. In this work, we propose a method for the synthesis of these compounds from methyl nicotinate and hydrazones of aromatic ketones. The method involves N -arylation of pyridine with 2,4-dinitrophenol tosylate and subsequent reaction of the arylpyridinium salt with the amino group of N -unsubstituted hydrazones (the Zincke reaction).