(searched for: doi:10.5155/eurjchem.1.3.195-199.91)
Russian Chemical Bulletin, Volume 70, pp 1011-1045; doi:10.1007/s11172-021-3183-6
The review is focused on recent developments of chemistry of synthetic analogs of natural compounds, isoflavone and homoisoflavone. The possible synthetic strategies to access heterocyclic analogs of these compounds starting from readily available 3-formylchromone and its derivatives (3-cyanochromone, 2-amino-3-formylchromone) and products of its condensation with simplest C- and N-nucleophiles are discussed. The structural features of the reaction products that depend on the nature of the reaction medium, structure of the starting compounds, and reagent ratio are considered. Particular attention is given to the application of the modern strategies of organic synthesis, namely green chemistry approaches, click reactions, domino reactions, etc. Examples of compounds of this group most promising for clinical application due to wide and pronounced pharmacological effects are given.
Polycyclic Aromatic Compounds pp 1-16; doi:10.1080/10406638.2021.1886125
A newer, convenient and efficient approach has been designed for the diverse synthesis of 2-amino-4H-pyranoquinolines and achieved by a one-pot three-component reaction of aromatic aldehydes with ethyl cyanoacetate/malononitrile and 8-hydroxyquinoline catalyzed by β-cyclodextrin as a reusable supramolecular catalyst in an aqueous medium under ultrasound irradiation. Target products were synthesized in a tandem process, which meets their requirements of pharmaceutical chemistry. Graphical Abstract
Journal of Molecular Structure, Volume 1226; doi:10.1016/j.molstruc.2020.129358
6-Ethyl-4-hydroxy-2,5-dioxo-5,6-dihydro-2H-pyrano[3,2-c]quinoline-3-carboxaldehyde (HL) was synthesized as a ligand and subject to chelate with Cu(II) ion of different anions (AcO–, NO3–, SO42–ClO4–, Cl– and Br–) in presence and absence of auxiliary ligands (L′); N,O-donor; or N,N-donor such as 8-hydroxyquinoline, 1,10-phenanthroline and 2,2′-bipyridyl. The obtained results revealed that the ligand behaves as a neutral/monoanionic bidentate, forming chelates with molar ratio 1:1, (M:L). The metal complexes were fully characterized by analytical and spectral techniques in addition to thermal, magnetic susceptibility and conductivity measurements. The metal complexes displayed square planar and octahedral geometrical arrangements depending on the nature of the anion. The ligand and its complexes were screened for their antimicrobial activity against Gram–positive bacteria which are Staphylococcus aureus and Bacillus subtilis, Gram–negative bacteria which are Escherichia coli and Salmonella typhimurium, yeast (Candida albicans) and fungus (Aspergillus fumigatus). The antitumor activity of the HL ligand and its Cu(II) complexes were examined against Ehrlich Ascites Carcinoma cell line (EAC) from ascetic fluid of the female Swiss albino mice. To explore the most probable structure and the nature of bonding of HL ligand to metal ions; semi-emperical (PM3) calculations were achieved in gas phase. All theoretically possible structural data of the free ligand (HL) and its complexes have been correlated with the experimental data to explore the most probable structure.
European Journal of Organic Chemistry, Volume 2020, pp 525-538; doi:10.1002/ejoc.201901605
Recent advances of β ‐keto acids were summarized as five categories according to their triggered mechanisms: (1) decarboxylative enolate nucleophiles; (2) addition without decarboxylation; (3) electrophilic acids; (4) nucleophilic acids; (5) electrophilic ketones. We hope this review will promote future research in this area.
Journal of Heterocyclic Chemistry; doi:10.1002/jhet.3440
The novel 6‐ethyl‐4‐hydroxy‐2,5‐dioxo‐5,6‐dihydro‐2H‐pyrano[3,2‐c]quinoline‐3‐carboxaldehyde (2) was efficiently synthesized from Vilsmeier–Haack formylation of 3‐(1‐ethy1‐4‐hydroxy‐2‐oxo‐(1H)‐quinolin‐3‐yl)‐3‐oxopropanoic acid (1). The aldehyde 2 was allowed to react with some nitrogen nucleophiles producing a variety of hydrazones 3–7. Reaction of aldehyde 2 with hydrazine hydrate and hydroxylamine hydrochloride afforded pyrazole and isoxazole annulated pyrano[3,2‐c]quinoline‐2,5(6H)‐dione, respectively. The reactivity of aldehyde 2 was examined toward some active methylene nitrile, namely, malononitrile, ethyl cyanoacetate, and cyanoacetamide leading to 2‐iminopyrano[2′,3′:4,5]pyrano[3,2‐c]quinolines 10–12, respectively. Also, some novel pyrazolo[4″,3″:5′,6′]pyrano[2′,3′:4,5]pyrano[3,2‐c]quinolines (13, 14) and thiazolo[5″,4″:5′,6′]pyrano[2′,3′:4,5]pyrano[3,2‐c]quinolines (15, 16) were synthesized. Structures of the new synthesized products were deduced on the basis of their analytical and spectral data.
Journal of Heterocyclic Chemistry, Volume 55, pp 2834-2843; doi:10.1002/jhet.3353
Vilsmeier–Haack formylation of 3‐(4‐hydroxy‐1‐methy1‐2‐oxo‐(1H)‐quinolin‐3‐yl)‐3‐oxopropanoic acid (2) produced the novel 4‐hydroxy‐6‐methyl‐2,5‐dioxo‐5,6‐dihydro‐2H‐pyrano[3,2‐c]quinoline‐3‐carboxaldehyde (4). The chemical reactivity of carboxaldehyde 4 with a diversity of nitrogen nucleophilic reagents was studied, and a variety of products were obtained. Some 1,3,4‐oxadiazolyl/1,3,4‐thiadiazolyl/benzothiazolyl linked pyrano[3,2‐c]quinoline‐2,5(6H)‐dione were efficiently synthesized. Structures of the new synthesized products were deduced on the basis of their analytical and spectral data.
HETEROCYCLES, Volume 91; doi:10.3987/rev-15-824
Synthetic Communications, Volume 44, pp 3470-3482; doi:10.1080/00397911.2014.949775
Vilsmeier–Haack formylation of 3-acetyl-1-methyl-4-hydroxyquinolin-2(1H)-one (2) produced the novel 6-methyl-4,5-dioxo-5,6-dihydro-4H-pyrano[3,2-c]quinoline-3-carboxaldehyde (3). Reactions of carboxaldehyde 3 with a diversity of nucleophilic reagents were studied and a variety of products were obtained via ring-opening, ring-closing (RORC) sequence. Also, some novel heteroannulated pyrano[3,2-c]quinolines were prepared. Structures of the new synthesized products were deduced on the basis of their analytical and spectral data.
European Journal of Chemistry, Volume 4; doi:10.5155/eurjchem.4.3.311-328.815
This review covers the chemical reactivity of 3-formylchromones towards condensation reactions with a variety of carbon and nitrogen nucleophiles. Some chromone derivatives linked a variety of heterocyclic systems were prepared from the direct condensation of 3-formylchromones with heterocyclic compounds containing active methylene groups. A diverse number of fused heterocyclic systems were prepared from the reaction of 3-formylchromones with some bifunctional nucleophiles, these reactions mainly proceed via condensation with the aldehydic function followed by nucleophilic attack at C-2 position of the chromone moiety.
HETEROCYCLES, Volume 87; doi:10.3987/com-13-12709
Molecules, Volume 17, pp 13856-13863; doi:10.3390/molecules171213856
A series of 4-aryl-6-methyl-3,4-dihydro-2H-pyrano[3,2-c]quinolin-2,5(6H)-diones were synthesized via the three-component reactions of aromatic aldehydes, 4-hydroxy-1-methylquinolin-2(1H)-one, and Meldrum’s acid catalyzed by L-proline. The structures of the products were identified by spectroscopic analysis. A mechanism for this three-component reaction catalyzed by L-proline was proposed.
Journal of Heterocyclic Chemistry, Volume 49, pp 1269-1289; doi:10.1002/jhet.906
The present review covers the methods developed for the synthesis of different pyrano[3,2‐c]quinolinones as well as the chemical reactivity of these compounds towards various types of chemical reactions.