Ring Opening and Recyclization Reactions of 3‐Nitrochromone with Some Nucleophilic Reagents

Abstract

The chemical reactivity of 3‐nitrochromone (1) was studied towards some nucleophilic reagents. Reaction of 3‐nitrochromone (1) with some carbon nucleophiles revealed existence of ring‐opening ring‐closure reactions, and the mode of cyclization depends on the nucleophile used. Treatment of 3‐nitrochromone (1) with malononitrile and ethyl cyanoacetate produced benzoxocinone derivatives 2 and 3, respectively. Boiling compound 1 with cyanoacetamide and 2‐aminoprop‐1‐ene‐1,1,3‐tricarbonitrile afforded pyridine derivatives 4 and 5, respectively. Reaction of compound 1 with 1H‐benzimidazol‐2‐ylacetonitrile, 5‐amino‐2,4‐dihydro‐3H‐pyrazol‐3‐one, and dimedone led to pyrido[1,2‐a]benzimidazole 6, pyrazolo[3,4‐b]pyridine 7, and chromenone 8, respectively. Treating 3‐nitrochromone (1) with heterocyclic amines gave enaminones 11 and 12 via nucleophilic attack at C‐2 position with ring opening. The structures of the newly synthesized products were deduced on the basis of their analytical 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…”

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

“…The chemical behavior of chromones is extensively different depending on the substituent present at position 3 17–19 . 3‐Substituted chromones reacted with binucleophilic reagents giving a diversity of heterocyclic systems 20–22 . In some cases, the presence of methyl groups in the benzo‐rings alter the reactivity of substituted chromones toward some nucleophilic reagents 23–25 .…”

Construction, characterization, and antimicrobial evaluation of the novel heteroannulated chromeno[2′′,3′′:6′,5′]pyrido[2′,3′‐d] [1,3] thiazolo[3,2‐a]pyrimidines

“…[21][22][23][24] The presence of electron withdrawing substituents in position 3 of the chromone moiety activate the C-2 position toward nucleophilic reagents providing a diversity of products based on the functional group at position 3 as well as the used nucleophile. [25][26][27][28][29][30] The current work is directed to synthesis a new series of annulated chromenopyridothiazolopyrimidines and investigate their antimicrobial activity.…”