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

Abstract

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.

Synthesis, Characterization and Antimicrobial and Anticancer Evaluations of Some Novel Heteroannulated Difuro[3,2-c:3′,2′-g]Chromenes

“…Meanwhile, three distinctive singlet signals were observed in the 1 H NMR spectrum of compound 5 at δ 1.03 (2CH 3 ), 2.74 (CH 2 ) and 2.92 (CH 2 ). 13 reaction of 4,9-dimethoxy-5-oxo-5H-furo[3,2-g]chromene-6-carboxaldehyde (1) with hydroxylamine hydrochloride in aqueous ethanol yielded carbonitrile derivative 2 which, upon treatment with chloroacetone, yielded the target precursor 3, as shown in Figure 1 [23,24]. The present research aimed to employ compound 3 as a precursor to form a novel category of polyfused systems through reactions with a diversity of active methylene nucleophiles as well as evaluate their antimicrobial and anticancer efficiency.…”

Heterocyclizations of β-alkoxy, β-diaminoalkyl, and related β-functionalized enones (enals) with NCN-binucleophiles

“…In particular, fivemembered dienone 73 reacts with benzamidine to form 5,5'-bis(2-hydroxyethyl)pyrimidine in low yield, while the six-membered homolog 74 was converted to 5.5'-bis(2hydroxypropyl)pyrimidine in 67% yield alongside with formation of a monoheterocyclization product (Scheme 29). 3-Formylchromone 75 is known to react via recyclization with amidines [166][167][168][169], guanidines [166,168,170,171], thiourea [171], 2-methylisothiourea [172], carbonohydrazonic diamides [173] to give pyrimidines decorated with the salicylic moiety or the corresponding cyclic fused hemiacetal products [172,174] (Scheme 30). Moreover, the reactions of 3-formylchromone with amidoximes were used for the instant preparation of pyrimidine-N-oxides [175][176][177][178].…”