Synthesis and insecticidal activity of some 1,3,4-oxadiazoles derived from 2-chloropyridine-5-acetic acid

The synthesis of a number of 1,3,4-oxadiazoles 6a-e is described. 2-Chloropyridine-5-acetic acid 3 is prepared starling from easily available 2-chloro-5-chloromethylpyridine 1, via 2-chloro-5-cyanomethylpyridine 2. Esterfication of 3 with methanol in the presence of H 2 SO 4 gives the corresponding methyl ester 4. Hydrazinolysis of 4 with hydrazine hydrate affords 2-chloropyridine-5-acetic acid hydrazide 5. Hydrazide 5 on reacting with aroyl chlorides in the presence of POCl 3 yields 2-chloro-5-(5-aryl-1,3,4-oxadiazol-2-yl)methylpyridines 6a-e.