Studies on the Chemical Reactivity of 6,8‐dibromo‐7‐hydroxychromone‐3‐carboxaldehyde Towards Some Nitrogen Nucleophilic Reagents

Abstract

The chemical reactivity of 6,8‐dibromo‐7‐hydroxychromone‐3‐carboxaldehyde (1) was studied towards some nitrogen nucleophilic reagents such as heterocyclic amines, 1,2‐N,N‐binucleophiles, 1,2‐N,O‐binucleophiles, 1,3‐N,N‐binucleophiles, 1,4‐N,N‐binucleophiles, 1,4‐N,O‐binucleophiles, and 1,4‐N,S‐binucleophiles under different reaction conditions.

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

“…On the other hand, condensation of carboxaldehyde 1 with o ‐phenylenediamine in boiling ethanol proceeds in a different mechanism leading to the polyfused furo[3′,2′:6,7]chromeno[2,3‐ e ]benzo[ b ][1,4]diazepin‐5(12 H )‐one 28 (Scheme ) . The mass spectrum of compound 28 showed the molecular ion peak at m / z 362 corresponding to its molecular formula weight (C 20 H 14 N 2 O 5 ) and supports the identity of the structure.…”

“…Condensation of carboxaldehyde 1 with semicarbazide hydrochloride in aqueous ethanol afforded the corresponding semicarbazone derivative 33 . Intramolecular oxidative cyclization of semicarbazone 33 using bromine in acetic acid and freshly fused sodium acetate produced 6‐(5‐amino‐1,3,4‐oxadiazol‐2‐yl)‐4,9‐dimethoxy‐5 H ‐furo[3,2‐ g ]chromen‐5‐one ( 34 ) (Scheme ). The 1 H‐NMR spectrum of oxadiazole derivative 34 showed characteristic singlet at δ 8.47 assigned to H‐7, as well as D 2 O exchangeable signal at δ 9.34 attributed to the NH 2 protons.…”

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

“…Repeating the previous reaction under reflux for 2 h furnished the annulated benzochromenodiazepine derivative 11 as pale yellow crystals, via the formation of compound 10 followed by elimination of two molecules of water with subsequent dehydrogenation (Scheme ) . In this reaction, the orange crystals formed after 1 min was dissolved under reflux, indicating the formation of compound 11 throughout compound 10 (as isolable intermediate).…”

Synthesis and Chemical Reactivity of the Novel 4‐Hydroxy‐6‐methyl‐2,5‐dioxo‐5,6‐dihydro‐2H‐pyrano[3,2‐c]quinoline‐3‐carboxaldehyde

“…Intramolecular oxidative cyclization of semicarbazone 17 with bromine in acetic acid and freshly fused sodium acetate produced 3‐(5‐amino‐1,3,4‐oxadiazol‐2‐yl)‐pyrano[3,2‐ c ]quinoline ( 19 ) (Scheme ) . Also, oxidative cyclization of thiosemicarbazone 18 using ferric chloride in aqueous dioxane afforded 3‐(5‐amino‐1,3,4‐thiadiazol‐2‐yl)‐pyrano[3,2‐ c ]quinoline ( 20 ) (Scheme ) .…”

“…Likewise, condensation of carboxaldehyde 4 with benzohydrazide and pyridine‐3‐carbohydrazide yielded the corresponding hydrazones 21 and 22 , which upon intramolecular oxidative cyclization afforded 3‐[5‐(phenyl/pyridin‐3‐yl)‐1,3,4‐oxadiazol‐2‐yl]‐2 H ‐pyrano[3,2‐ c ]quinoline‐2,5(6 H )‐diones 23 and 24 , respectively (Scheme ) . The mass spectra of compounds 23 and 24 recorded their molecular ion peaks at m/z 387 and 388, respectively.…”