Reactivity of some 3‐substituted‐6,8‐dimethylchromones toward some nucleophilic reagents

The reactivity of 3-substituted-6,8-dimethylchromone derivatives 1-5 was investigated toward selected nucleophilic reagents 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 giving compounds 6, 7, 10, and 11. Reactions 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 vinyl bond followed by addition at the CN group giving 6,8-dimethylchromone linked various heterocyclic systems 20-27.