It is noteworthy that the treatment of compound 191 with cyanoacetohydrazide 1 in boiling DMF yielded pyrazole derivative 192, which is the final product 192, as demonstrated in Scheme 65. Moreover, the reaction of compound 191 with cyanoacetohydrazide 1 was conducted in glacial acetic acid and resulted in pyrazolo [3,4-b]pyridine derivative 194. Also, compound 194 was also generated authentically from the reaction of compound 191 with 5-amino-2,4-dihydro-3Hpyrazol-3-one 193, in boiling DMF containing piperidine (Scheme 65). Recently, it has been reported that, cyanoacetohydrazide 1 reacted via its cyano, amido and hydrazino groups with the ketene dithio-acetal derivative 216, and the isolated product was identified as the 2-methylthio-3-methoxycarbonyl-5aminopyrazolo[2,3-a]pyrimidin-7-one 217. A mechanistic pathway for this product formation was suggested as follow (Scheme 73): 100 In anaology, Napoles et al. synthesized pyrazolo [1,5-a]pyrimidines 218 from cyanoacetohydrazide 1 and push-pull systems. Beginning with cyanoacetohydrazide 1 and cinnamonitrile derivatives 82 in DMF, the target compounds could be generated in only one step, but with low yield, because of the formation of multiple byproducts. Furthermore, when the reactions of polarized ethylenes with other nucleophiles are conducted, two steps are necessary, and the reaction mixture must be heated for a few hours. Hypothetically, the presence of the appropriate reactive centerin, the ketene-S,S-acetals and 1,3-dithiethanes used as push-pull systems, facilitates the necessary intramolecular cyclizations after the initial nucleophilic attack of the cyanoacetohydrazide 1 (Scheme 74) 101 . When the hydrazones 219 (obtained from the reaction of cyanoacetohydrazide 1 with the corresponding aldehyde) were refluxed in glacial acetic acid, new products were isolated which have been identified as the condensed pyrazoles 222 . The formation of these products is assumed to proceed through a reaction involving the nucleophilic (CH 2 ) and the electrophilic (C=N) centers to afford the intermediates, 220 which subsequently cyanoacetylated at its nitrogen nucleophilic center by its open form hydrazone and finally self-cyclized via the CN and NH groups to form the final isolabie product 222 102 as shown in Scheme 75. The synthesis of Hydrazide hydrazone 230 was reported from the reaction of cyanoacetyl-hydrazone, which, in turn, was prepared via the reaction of cyanoacetyl hydrazide 1 with aldehydes, and acetyl acetone 104 e.g. 2chloroquinoline-3-carbaldehyde 228. Also, the reaction of 228 with cyanoacetyl hydrazide 1 yielded the formation of N'-((2-chloroquinolin-3-yl) methylene)-2cyanoacetohydrazide 229, which reacted with acetyl acetone in refluxed ethanol to produce 105 230 (Scheme 77). Moreover, Hadi illustrated 108 the synthesis of [1,2,4]triazolo [1,5-a]pyridines via concerted reactions between 2′-cinnamoyl-2-cyanoacetohydrazide and αcyanocinna-monitriles. At first, through the reaction of cyanoacetohydrazide 1 with 3-phenylpropenoyl chloride 234 at 0 °C, the corresponding N-substituted 2cyanoacetohydrazides 235 were formed. Then, reaction of compound 235 with αsubstituted cinnamonitriles 67 and piperidine in alcoholic solution resulted in 6exo-dig cyclization to produce the intermediate N-cinnamoylamino-3,4-dihydro-2pyridones 236. After that, subsequent 5-exo-trig cyclization by attack of the primary amino group on the lower reactive amide carbonyl group resulted in the [1,2,4]triazolo [1,5-a]pyridones that were separated as piperidinium salts due to the high acidity of the ring proton, in moderate to good yield. Furthermore, production of the piperidinium salt in the triazolo [1,5-a]pyridinone is due to the stability of the anions, originating from charge delocalization in the two fused heterocyclic rings, triazolo nitrogens, and the pyridone oxygen in compounds 237. Lastly, the neutral compounds 238 could be generated from the piperidinium salt 237 by treatment with hydrochloric acid (Scheme 79) 108 . Four reactive centers from cyanoacetohydrazide 1 may be involved in heterocyclic synthesis as observed in the following reaction. The condensed αiminocoumarin 247 was obtained when the α-cyanoacetylsalicylaldehyde hydrazone 219a was refluxed in glacial acetic acid (Scheme 82), the reaction is assumed to proceed by the same mechanistic pathway disscussed before .