Chemical Reactivity of 1H-Benzimidazol-2-ylacetonitrile and Dimedone toward Simple Condensates Derived from 3-Formylchromone

Abstract

The chemical reactivity of 1H-benzimidazol-2-ylacetonitrile and dimedone was investigated towards some simple condensates (1a-d and 2a-c) obtained from condensation reaction of 3-formylchromone with some active methylene compounds. Mainly, the used nucleophiles undergo nucleophilic addition at the olefinic carbon with concomitant cycloaddition or cyclocondensation. Chromonylacrylonitrile 1a reacted with 1H-benzimidazol-2-ylacetonitrile through γ-pyrone ring opening followed by cyclocondensation giving pyrido[1,2-a]benzimidazole derivative 5. The simple condensates 2b and 2c showed similar behavior towards 1H-benzimidazol-2-ylacetonitrile and dimedone leading to the same products which are identical with those obtained from 3-formylchromone with the same reagents. Structures of the new synthesized products were established based on elemental analysis and spectral data.

Synthesis and characterization of the novel heteroannulated chromeno[2,3‐d]pyrimidines and chromeno[2,3‐d][1,3]thiazolo[3,2‐a] pyrimidines

“…Reactions of chromone-3-carboxaldehyde with bifunctional nucleophiles usually proceeds via condensation with the aldehyde function followed by γ-pyrone ring opening [27][28][29]. Meanwhile, all other 3-substituted chromones the reaction preferentially occurs through nucleophilic attack at C-2 position followed by cycloaddition of cyclocondensation [30][31][32][33][34]. In our previous work, treatment of 6,8-dibromo-7-hydroxychromone-3-carbo xaldehyde (1) with hydroxylamine hydrochloride in ethanolic sodium hydroxide solution (1%) afforded 2-amino-6,8-dibromo-7-hydroxychromone-3-carboxamide…”