الفهرس 
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Abstract
<This part presents the aim and the rational upon which the newly synthesized compounds were designed.
It includes the bases on which the pyridine derivatives were synthesized (schemes A, B, C, D).
Scheme A involves the the preparation of 3-cyano-2,6¬dimethylpyridin-2-one I VIa condensation of acetylacetone with cyanoacetamide.
The pyridin-2-one I was converted by POCI3 to the corresponding 2¬chloropyridine analogue II, which was reacted, independently, with certain amines, hydrazine hydrate and thiourea to afford the 2-N-substituted aminopyridine IlIa-i, the pyrazolopyridine derivative IV, and the pyridin-2¬thione V, respectively.
Scheme B involves reactions of 3-amino pyrazolopyridine IV, separately, with some aldhydes, pheny lisocyanate and its thio analouge, certain acid derivatives, 1,3-dicarbonyl compounds (EAA, AA) and NaNOz/HCI to afford the corresponding arylideneimines Vla-f, urea and thiourea derivatives ofpyrazolopyridine VIIa,b the pyrazolopyridine amides Vllla,h the pyridopyrazolopyrimidines IXa,b and finally the pyridopyrazolotriazine Xa,b.
Scheme C includes alkylation of pyridin-2-thione derivative V to give the corresponding 2-alkylthio analogues XIIa-c. It also involves condensation of V with formalin/ certain lOry amines to afford the pyridothiadiazine derivatives Xllla-f. Condensation of pyridin-2-thione derivative V with chloroacetic acid and certain aldhydes in a mixture of acetic acid and acetic anhydride gave the thiazolopyridine derivatives Xla-f.
On the other hand, reaction of pyridin-2-thione derivative V with ethyl bromoactate gave the respective 2-ethoxy-carbonylmethyl thio pyridine analogue XIIc, which was subsequently converted to the thienopyridine derivatives XIV and XV via reaction with NaOEtiEtOH and NHzNHz.
Scheme D involves the following reactions:
1- Reaction of the tI1ienopyridine-2-carboxyhydrazide XV with certain aldhydes to give the corresponding arylidenehydrazides XVla-f.