Ring Opening Ring Closure Reactions with 3-Substituted Chromones under Nucleophilic Conditions

El‐Sawy

et al. 2016

The chemical reactivity of 4,9‐dimethoxy‐5‐oxo‐5H‐furo[3,2‐g]chromene‐6‐carboxaldehyde (6‐formylkhellin) (1) was studied toward a diversity of nitrogen nucleophilic reagents. Reaction of carboxaldehyde 1 with some primary amines and heterocyclic amines afforded the corresponding Schiff bases. Also, the reactivity of carboxaldehyde 1 was studied toward some hydrazine derivatives, namely 7‐chloro‐4‐hydrazinoquinoline, 3‐hydrazino‐5,6‐diphenyl‐1,2,4‐triazine, N4‐phenylthiosemicarbazide, and S‐benzyldithiocarbazate. 6‐Formylkhellin (1) underwent ring transformation upon treatment with hydroxylamine hydrochloride producing 5‐hydroxy‐4,9‐dimethoxy‐7‐oxo‐7H‐furo[3,2‐g]chromene‐6‐carbonitrile (22). Some pyrimidine, [1,2,4]triazolo[4,3‐a]pyrimidine, tetrazolo[1,5‐a]pyrimidine, and diazepine derivatives linked benzofuran were efficiently synthesized. Reaction of carboxaldehyde 1 with a variety of 1,4‐binucleophiles produced furochromone‐fused benzodiazepine, pyridotriazepine, benzoxazepine, and benzothiazepine derivatives. Some unsymmetrical thiocarbohydrazones were also synthesized. Structures of the new synthesized products were deduced on the basis of their analytical and spectral data.

Section: Resultsmentioning

confidence: 99%

Chemical Reactivity of 4,9‐Dimethoxy‐5‐oxo‐5H‐furo[3,2‐g]chromene‐6‐Carboxaldehyde Toward Some Nucleophilic Reagents

El‐Gohary

El‐Sawy

et al. 2016

“…3‐Substituted chromones bearing electron withdrawing groups at position 3 revealed a diversity of transformations upon treatment with nucleophilic reagents . In continuation to our aforementioned work related to γ‐pyrone ring opening followed by ring closure , the present work aims to study the ring opening ring closure reactions of 6,8‐dimethylchromone‐3‐carbonitrile with some nuclophilic reagents under different reaction conditions.…”

Section: Introductionmentioning

confidence: 92%

Heteroannulated Coumarins and Chromones from Chemical Transformations of 6,8‐Dimethylchromone‐3‐carbonitrile

Badran

Hashiem

2018

A novel series of heterocyclic systems fused coumarins and chromones were efficiently synthesized from chemical transformations of 6,8-dimethylchromone-3-carbonitrile (1) with a variety of carbon nucleophilic reagents. Ring opening ring closure reactions of carbonitrile 1 with cyanoacetohydrazide, malononitrile dimer (2-aminoprop-1-ene-1,1,3-tricarbonitrile), and isomeric cyclohexanediones led to a diversity of coumarins and chromones fused nitrogen heterocyclic systems. Also, 1-ethyl-4-hydroxyquinolin-2(1H)-one (13) and 6-ethyl-4-hydroxypyrano[3,2-c]quinoline-2,5(6H)-dione (14) are chemical equivalent towards carbonitrile 1 leading to benzo [h]chromeno[2,3-b][1, 6] naphthyridine derivative 15. Structures of the new synthesized products were deduced on the basis of their analytical and spectral data.Scheme 3. Reaction of compound 5 with malononitrile dimer. Scheme 2. Reaction of carbonitrile 1 with malononitrile dimer. Scheme 4. Condensation of carbonitrile 1 and compound 5 with cyclohexane-1,2-dione. Scheme 5. Condensation of carbonitrile 1 with 1,3-cyclohexanedione. Scheme 6. The suggested mechanism for the formation of compound 11. Scheme 7. Condensation of carbonitrile 1 and compound 5 with cyclohexane-1,4-dione. Scheme 8. Formation of benzo[h]chromeno[2,3-b][1,6]naphthyridine derivative 15. DMF, dimethylformamide.

“…Recently, enaminone derivatives represent a good source for synthesis of a diversity of 3‐substituted chromones 14–16 . 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 .…”

Section: Introductionmentioning

confidence: 99%

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

Badran

El‐Gohary

et al. 2020

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.