Synthesis of some N‐[pyridyl(phenyl)carbonylamino]‐alkyl‐1,2,3,6‐tetrahydropyridines

Alkyl substituted 2,4‐dinitrophenylpyridinium chlorides 3 are formed by the nucleophilic substitution of 1‐chloro‐2,4‐dinitrobenzene with alkyl pyridines. Reaction of pyridyl acid hydrazides or benzoyl hydrazides 4 with the pyridinium chlorides 3 furnish the isolable 2,4‐dinitroanilino derivatives 5 which undergo hydrolysis when refluxed in water: p ‐dioxane mixture (1:4 v/v) to yield the pyridinium ylides 6 . Sodium borohydride reduction of 6 in absolute ethanol at 0° for 4 hours result the formation of the title compounds 7 in moderate to excellent yields.