Studies on the Chemical Transformations of Simple Condensates Derived from 3-Formylchromone under Nucleophilic Conditions

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.

Section: Resultsmentioning

confidence: 99%

“…Also, reacting compounds 4 and 5 with 5,6‐diphenyl‐3‐hydrazino‐1,2,4‐triazine ( 9 ) in boiling ethanol gave triazinylpyrazole derivative 11 (the same melting point and coidentical spectral data) (Scheme 9). 32 …”

Section: Resultsmentioning

confidence: 99%

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

Badran

et al. 2020

“…The solid obtained was filtered off and crystallized from methanol to give compound 23 as yellow crystals. Yield {5-[(6-Hydroxy-4,7-dimethoxy-1-benzofuran-5-yl)carbonyl] 2-methylpyrimidine (24).…”

Section: Methodsmentioning

confidence: 99%

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

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.

“…This domino‐transformation usually involves initial nucleophilic addition on the 2‐position of the chromone skeleton with subsequent γ‐pyrone ring opening followed by the formation of new heterocyclic systems. These types of transformations are facilitated by the electron‐withdrawing group present at the 3‐position .…”

Section: Introductionmentioning

confidence: 99%

Studies on the Chemical Reactions of Some 3‐Substituted‐6,8‐dimethylchromones with Nucleophilic Reagents

Badran

et al. 2018

A variety of 3‐substituted‐6,8‐dimethylchromones have been synthesized and characterized. The chemical reactivity of 3‐substituted‐6,8‐dimethylchromones was studied towards some nucleophiles, namely, S‐benzyldithiocarbazate, o‐phenylenediamine, and cyanoacetamide, and a diversity of products were efficiently synthesized. Reactions of 3‐substituted‐6,8‐dimethylchromones (except 3‐formyl‐6,8‐dimethylchromone), with nucleophilic reagents, usually proceed through nucleophilic attack at C‐2 position followed by different types of heterocyclization depending on the functional group present at C‐3 position. Structures of the newly synthesized products have been established based on elemental analysis and spectral data.