In addition, Bayat et al. explained the efficient synthesis of novel spiroindenopyridazine-4H-pyran derivatives, where they used ninhydrin 131, cyanoacetohydrazide 1, malononitrile , and various cyclic CH-acids 132a-j as substrates to synthesize the target compounds 133a-j (Scheme 46). The presence of the carbonyl and amino groups led to the formation of five membered rings with three heteroatoms. Thus, it has been reported that 5-cyanomethyl-1,2,4-triazole 137 can be formed by heating cyanoacetohydrazide 1 with formamide for several hours on a steam bath, followed by cooling and dilution with ethyl alcohols as shown in Scheme 48. Moreover, treatment of cyanoacetohydrazide 1 with ethyl β-ethoxy-βaminomethylene acetate 138 gave a product which had been interpreted as ethyl (5-cyanomethyl -1,3,4-oxadiazol-2-yl)acetate 139. A mechanistic pathway for its formation was suggested (Scheme 49). This synthetic approach was applied in the synthesis of hitherto undocumented title compound as exemplified in Scheme 52. Where, the stirring of 2chlorobenzoyl chloride 149 with ammonium thiocyanate in dry acetonitrile yielded the 2-chlorobenzoyl isothiocyanate 150, in situ cyanoacetohydrazide 1 was supplied on the later under stirring at ambient temperature, succeeded by refluxing of the engendered 2-chloro-N-(2-(2-cyanoacetyl)hydrazine-1-carbonothioyl)benzamide 151 in glacial acetic acid to generate 1,3,4-thiadiazole derivative 152 (Scheme 52) . It is noteworthy that Allam and Nawwar conducted the synthesis of cyanomethyloxadiazole-spiroindoline 157. They concluded that the condensation product of cyanoacetohydrazide 1 with isatin 21 could be cyclized in acidic medium to yield the oxadiazolo-2-spiroindoline structure 157 (Scheme 55) 76 . There are some reactions in which cyanoacetohydrazide behaves as a Hydrazine, meaning that the NH and NH 2 active centers are involved in these reactions . One of the well known approaches for the synthesis of substituted pyrazoles is the condensation of 1,3-bidentate reagents such as β-diketones and βketoesters with cyanoacetohydrazide in acidic medium .