New routes to 1,3,4‐oxadiazoles, 1,3,4‐oxadiazolopyridines, and pyridopyridazines

Ethyl (5‐cyanomethyl‐1,3,4‐oxadiazol‐2‐yl)acetate (4) could be prepared by condensing cyanoacetohydrazide (2) with diethyl monoimidic malonate (1). The reactivity of 4 towards a variety of electrophilic reagents is reported. The reaction of 1 with 2‐amino‐1‐propene‐1,1,3‐tricarbonitrile gives the pyridine 12 which is converted into pyridopyridazine 13 on coupling with benzenediazonium chloride.