الفهرس 
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Abstract
The reactivity of 3-substituted-6,8-dimethylchromones 1-5 was investigated towards selected nucleophiles namely; 3-amino-1,2,4-triazole, 2-aminobenzimidazole, 7-chloro-4-hydrazinoquinoline and 5,6-diphenyl-3-hydrazino-1,2,4-triazine. These nucleophiles were allowed to react with 6,8-dimethylchromone-3-carboxaldehyde (1) through condensation with the aldehyde group with opening of γ–pyrone ring. Reactions of the current nucleophile with 6,8-dimethylchromone-3-carbonitrile (2) and 6,8-dimethylchromone-3-carboxylic acid (3) occur via attack at position 2 in both compounds followed by cycloaddition onto the nitrile function (in case of carbonitrile 2) or decarboxylation and cyclocondensation with the carbonyl group (in case of carboxylic acid 3). The current nucleophilic reagents reacted with simple condensation products 4 and 5, in boiling dioxane, through nucleophilic addition at the exocyclic double bond followed by addition at the C≡N group. Reactions of carbonitrile 2 with cyanoacetohydrazide, malononitrile dimer, and isomeric cyclohexanediones led to a diversity of coumarins and chromones fused nitrogen heterocyclic systems. Also, 1-ethyl-4-hydroxyquinolin-2(1H)-one (39) and 6-ethyl-4-hydroxypyrano[3,2-c]quinoline-2,5(6H)-dione (40) are chemical equivalent toward carbonitrile 2 leading to benzo[h]chromeno[2,3-b][1,6]naphthyridine derivative 41. Structures of the new synthesized products were deduced on the basis of their analytical and spectral data.