Angular methoxy-substituted furo- and pyranoquinolinones as blockers of the voltage-gated potassium channel Kv1.3

Synthesis of Naphtho[1',2':4,5]furo[3,2-b]pyridinones via Ir(III)-Catalyzed C6/C5 Dual C-H Functionalization of N-Pyridyl-2-pyridones with Diazonaphthalen-2(1H)-ones

Presented herein is an unprecedented synthesis of naphtho[1',2':4,5]furo[3,2-b]pyridinones via Ir(III)-catalyzed C6/C5 dual C-H functionalization of N-pyridyl-2-pyridones with diazonaphthalen-2(1H)-ones. This protocol forms C-C and C-O bonds in one pot in which diazonaphthalen-2(1H)-ones serve as bifunctional reagents, providing both alkyl and aryloxy sources. To the best of our knowledge, this is the first example of an Ir(III)-catalyzed synthesis of the title compounds by using diazonaphthalen-2(1H)-ones as bifunctional substrates. Notably, this method features operational simplicity, good functional group tolerance, high efficiency, and high atom economy.

Aryl glyoxal: a prime synthetic equivalent for multicomponent reactions in the designing of oxygen heterocycles

The category of bifunctional building blocks overrides many others because of their fascinating wide applicability in synthetic chemistry. Aryl glyoxal is one of the key molecules that has been extensively used in heterocyclic chemistry to afford nearly all types of five- and six-membered heterocycles, which are the structural constituents of many natural products. The multicomponent reaction is a practical strategy to utilize this wonderful moiety with different types of starting materials to obtain numerous diverse oxygen heterocycles. This review covers the advancement of aryl glyoxal as a prime synthetic equivalent in recent years for the synthesis of oxygen heterocycles.

Synthesis of pyrano[3,2-c]quinolones and furo[3,2-c]quinolones via acid-catalyzed tandem reaction of 4-hydroxy-1-methylquinolin-2(1H)-one and propargylic alcohols

Two acid-catalyzed tandem reactions between 4-hydroxy-1-methylquinolin-2(1H)-one and propargylic alcohols are described. Depending mainly on the propargylic alcohol used, these tandem reactions proceed via either a Friedel–Crafts-type allenylation followed by 6-endo-dig cyclization sequence to form pyrano[3,2-c]quinolones or a Friedel–Crafts-type alkylation and 5-exo-dig ring closure sequence to afford furo[3,2-c]quinolones in moderate-to-high yields. The pyrano[3,2-c]quinolones products could be further transformed to tetracyclic 4,9-dihydro-5H-cyclopenta[lmn]phenanthridin-5-one derivatives.

Two acid-catalyzed tandem reactions between 4-hydroxy-1-methylquinolin-2(1H)-one and propargylic alcohols are described.

Sequential condensation/biannulation reactions of β-(2-aminophenyl)-α,β-ynones with 1,3-dicarbonyls

A divergent domino condensation/biannulation reaction of β-(2-aminophenyl) α,β-ynones with 1,3-dicarbonyls to construct a polycyclic 4H-pyrano[3,4-c]quinoline core has been developed. The p-TsOH·H2O catalyzed reaction of β-(2-aminophenyl) α,β-ynones with β-ketoesters in ethanol proceeds with good to excellent yields to provide a simple and effective method for the synthesis of functionalized 4H-pyrano[3,4-c]quinolinones. Further elaboration of these latter derivatives with an excess of 20% NH4OH in EtOH at 50 °C helps achieve the synthesis of the perlodinine analogues benzo[c][2,7]naphthyridin-4(3H)-one derivatives in high yields. Moreover, the p-TsOH·H2O mediated reaction of β-(2-aminophenyl) α,β-ynones with β-di-ketones leads to the formation of a variety of structurally diverse 4H-pyrano[3,4-c]quinoline polycyclic ketals by the incorporation of an alcohol solvent molecule in a cascade fashion.

Ring expansion and ring opening of 3-halooxindoles with N-alkoxycarbonyl-O-tosylhydroxylamines for divergent access to 4-aminoquinolin-2-ones and N-Cbz-N’-arylureas

The reaction of N-alkoxycarbonyl-O-tosylhydroxylamines with indol-2-ones in situ generated from 3-halooxindoles has been developed for divergently accessing 4-aminoquinolin-2-ones and N-Cbz-N’-arylureas in good to excellent yields.

Furo[3,2-c]coumarins carrying carbon substituents at C-2 and/or C-3. Isolation, biological activity, synthesis and reaction mechanisms

The isolation, biological activity and synthesis of natural furo[3,2-c]coumarins are presented, covering mainly the developments in the last 35 years. The most relevant approaches toward the synthesis of 2-substituted, 3-substituted and 2,3-disubstituted heterocycles are also discussed, with emphasis on the efficiency of the processes and their mechanisms.

Site-Selective Double and Tetracyclization Routes to Fused Polyheterocyclic Structures by Pd-Catalyzed Carbonylation Reactions

In this contribution, we report novel palladium-catalyzed carbonylative cascade approaches to highly functionalized polyheterocyclic structures. The Pd-catalyzed carbonylative process involves the regioselective insertion of one to three CO molecules and the sequential ordered formation of up to eight new bonds (one C–O, two C–C, five C–N). The exclusive formation of six-membered heterocycles is elucidated by detailed modeling studies.

Synthesis of 2-aroylfuro[3,2-c]quinolines from quinolone-based chalcones and evaluation of their antioxidant and anticholinesterase activities

A series of 2-aroylfuro[3,2-c]quinolines 2a–e was synthetized from quinolone-based chalcones 1a–e. When R = ortho-OH, an unexpected compound 3 was also obtained. Compounds, 2a and 2c, showed significant inhibition of acetylcholinesterase enzyme.

Efficient syntheses and antimicrobial activities of new thiophene containing pyranone and quinolinone derivatives using manganese(iii) acetate: the effect of thiophene on ring closure–opening reactions

The syntheses, spectroscopic properties, and antimicrobial activities of new pyranones and quinoline-based dihydrofurans accompanied by 3-alkenyl-substituted structures were investigated.

Iodine mediated in situ generation of R-Se–I: application towards the construction of pyrano[4,3-b]quinoline heterocycles and fluorescence properties

Iodine mediated in situ generation of R-Se–I and its application towards the construction of pyrano[4,3-b]quinolin-1-one derivatives.

Stereoselective synthesis of natural product inspired carbohydrate fused pyrano[3,2-c]quinolones as antiproliferative agents

Design and efficient synthesis of new carbohydrate fused pyrano[3,2-c]quinolone derivatives and their submicromolar anticancer activity.

Indium-Catalyzed Intramolecular Hydroamidation of Alkynes: An Exo-Dig Cyclization for the Synthesis of Pyranoquinolines through Post-Transformational Reaction

An efficient approach for the synthesis of pyranoquinolines through the indium-catalyzed activation of alkynes is reported. Intramolecular hydroamidation of alkynes can proceed through alkyne activation by indium(III) and then 6-exo-dig cyclization, leading to a fused pyran ring with high selectivity, high atom economy, and good to excellent yields. The cyclization was accomplished through the oxygen, not the nitrogen, of the amide functional group.

An efficient one-pot approach for the regio- and diastereoselective synthesis of trans-dihydrofuran derivatives: cytotoxicity and DNA-binding studies

A facile one-pot, three component strategy has been developed for the construction oftrans-2,3-dihydrofuran derivatives. All the synthesized compounds have been evaluated for their cytotoxic activity.

FeCl3/ZnI2-Catalyzed regioselective synthesis of angularly fused furans

The FeCl₃/ZnI₂-catalyzed synthesis of angularly fused furans by intermolecular coupling between enols and alkynes has been developed in ambient air.

Pyrano[4,3-b]quinolines library generation via iodocyclization and palladium-catalyzed coupling reactions

Synthesis of a 80-member library of novel pyrano[4,3-b]quinolines in solution-phase is reported. The key intermediate, 4-iodopyrano[4,3-b]quinolines were synthesized by the electrophilic iodocyclization of corresponding ortho-alkynyl aldehydes in good to excellent yields under mild reaction conditions. Subsequently a diverse set of libraries was generated by employing palladium-catalyzed Suzuki-Miyaura, Heck, and Sonogashira coupling reactions on 4-iodopyrano[4,3-b]quinolines. In this way, a series of structurally different and biologically interesting molecules were obtained. Some of the selected compounds were screened against 3D7 strains of Plasmodium falciparum for antimalarial activity. Suzuki coupling products 6{3} and 6{21} and Heck coupling product 8{12} exhibit promising antimalarial activity.

A Pd-catalyzed heteroannulation approach to 2,3-disubstituted furo[3,2-c]coumarins

The Pd-catalyzed cyclofunctionalization of 3-alkynyl-4-methoxycoumarins with aryl halides resulted in the selective formation of 3-arylfuro[3,2-c]coumarins in lieu of the expected regioisomeric 3-arylfuro[2,3-b]chromones. A mechanism involving the linear to angular rearrangement of a Pd-containing furan intermediate was proposed.

4-Phenoxybutoxy-substituted heterocycles--a structure-activity relationship study of blockers of the lymphocyte potassium channel Kv1.3

The voltage-gated potassium channel Kv1.3 constitutes an attractive pharmacological target for the treatment of effector memory T cell-mediated autoimmune diseases such as multiple sclerosis and psoriasis. Using 5-methoxypsoralen (5-MOP, 1), a compound isolated from Ruta graveolens, as a template we previously synthesized 5-(4-phenoxybutoxy)psoralen (PAP-1, 2) which inhibits Kv1.3 with an IC(50) of 2nM. Since PAP-1 is more than 1000-fold more potent than 5-MOP, we here investigated whether attaching a 4-phenoxybutoxy side chain to other heterocyclic systems would also produce potent Kv1.3 blockers. While 4-phenoxybutoxy-substituted quinolines, quinazolines and phenanthrenes were inactive, 4-phenoxybutoxy-substituted quinolinones, furoquinolines, coumarins or furochromones inhibited Kv1.3 with IC(50)s of 150 nM to 10 microM in whole-cell patch-clamp experiments. Our most potent new compound is 4-(4-phenoxybutoxy)-7H-furo[3,2-g]chromene-7-thione (73, IC(50) 17 nM), in which the carbonyl oxygen of PAP-1 is replaced by sulfur. Taken together, our results demonstrate that the psoralen system is a crucial part of the pharmacophore of phenoxyalkoxypsoralen-type Kv1.3 blockers.

Microwave-assisted one-pot synthesis of some new furo[2,3-b]quinolines using potassium carbonate under solvent-free conditions

A rapid, solvent-free microwave-assisted method has been developed for the synthesis of novel furo quinolines. The title compounds were achieved by the reaction between corresponding 2-hydroxy-3-formyl-quinolines (1a–1c) with chloroacetamide, ethylchloroacetate, and phenacylbromide in specially designed microwave (MW) oven for organic synthesis in unsealed borosil vessel in presence of potassium carbonate. In this method, isolation is accomplished by just treating the reaction mixture with water, and products were obtained in high yield. Hence, this method was found to be very effective and ecofriendly. The structure of the newly synthesized compounds has been evaluated on the basis of analytical, IR, 1H NMR, and mass spectral data.Key words: furoquinoline, microwave irradiation, potassium carbonate, solvent-free conditions.

A New Efficient Synthesis of Pyranoquinolines from 1-Acetyl N-Aryl Cyclopentanecarboxamides

A new efficient synthesis of pyrano[2,3-b]quinoline derivatives is developed via the H2SO4-mediated tandem cyclization/ring-opening/recyclization reaction of readily available 1-acetyl N-aryl cyclopentanecarboxamides, during which a novel ring-cleavage fashion of the cyclopentane unit is involved and possible mechanisms are discussed.

Novel synthesis of 7-fluoro-8-(trifluoromethyl)- 1H-1,6-naphthyridin-4-one derivatives: intermolecular cyclization of an N-silyl-1-azaallyl anion with perfluoroalkene and subsequent intramolecular skeletal transformation of the resulting pentasubstituted pyridines

In this study, fluorine-containing pentasubstituted pyridine derivatives 9a-m were prepared regioselectively in good yields by the intermolecular cyclization of a variety of N-silyl-1-azaallylic anion intermediates 7, which were generated from a functionalized silane 5 and an aromatic/aliphatic nitrile 6 with perfluoroalkene 8. Also, 7-fluoro-8-(trifluoromethyl)-1H-1,6-naphthyridin-4-one derivatives 11a-k were synthesized in excellent yields by the subsequent base-promoted intramolecular skeletal transformation of the resulting pyridine derivatives 10a-k.