Superelectrophilic activation of N-aryl amides of 3-arylpropynoic acids: synthesis of quinolin-2(1H)-one derivatives

The superelectrophilic activation of N-aryl amides of 3-arylpropynoic acids by Bronsted superacids (CF₃SO₃H, HSO₃F) or strong Lewis acids AlX₃ (X=Cl, Br) results in the formation of 4-aryl quinolin-2(1H)-ones in quantitative yields. The vinyl triflates or vinyl chlorides may be formed as additional reaction products. The investigated amides in reactions with benzene give 4,4-diaryl 3,4-dihydroquinolin-2-(1H)-ones under the superelectrophilic activation. 4-Aryl quinolin-2(1H)-ones in POCl₃ are converted into 4-aryl 2-chloroquinolines. 4-Fluorophenyl-4-phenyl 3,4-dihydroquinolin-2-(1H)-one give N-formylation products in a yield of 79% under the Vilsmeier–Haack reaction conditions.     

The rearrangement of 1H,1′H-spiro[quinoline-4,2′-quinoxaline]-2,3′ (3H,4′H)-diones – a new and efficient method for the synthesis of 4-(benzimidazol-2-yl)quinolin-2(1H)-ones

A new and highly efficient method for the synthesis of 4-(benzimidazol-2-yl)quinolin-2(1H)-ones via the rearrangement of spiroquinoxalinones in moderate-to-excellent yields has been developed. The rearrangement represents a facile approach to medicinally important biheterocyclic compounds. Compared to other methods, the present protocol has a number of advantages such as – cost-effectiveness, avoidance of difficult of access quinolin-2-one and benzimidazole derivatives as reaction partners, and easy accessibility of starting materials, making it a highly practical approach to access various 4-(benzimidazol-2-yl)quinolin-2(1H)-ones.     

Preparation of 2-aminosubstituted 3H-imidazo[4,5-c]quinolin-4(5H)-ones by palladium-assisted internal biaryl coupling reaction

Representatives of the 3H-imidazo[4,5-c]quinolin-4(5H)-ones have shown interesting biological activity. We have found 2-aminosubstituted 3H-imidazo[4,5-c]quinolin-4(5H)-one as a potent dipeptidyl peptidase 4 inhibitor. However effective synthesis of this nucleus with various substituents at the 6-9-positions has not been reported. We report herein the development of a novel and efficient synthesis of 2-aminosubstituted 3H-imidazo[4,5-c]quinolin-4(5H)-ones by palladium-assisted internal biaryl coupling reaction. Our optimization of the reaction conditions revealed that the most important factors for this reaction are use of silver carbonate as a base and high reaction temperature.     

Synthesis and photochromism of a series of new 2-unsubstituted 3-(2-benzylbenzoyl)quinolin-4(1H)-ones

Synthesis and characterization of a series of new 2-unsubstituted 3-(2-benzylbenzoyl)quinolin-4(1H)-ones is described. In addition to their potential biological activity, these compounds exhibit photoreversible photochromic properties in anaerobic conditions. Using the 1 and 2D NMR techniques we demonstrated that the coloration occurred owing to the formation of fluorescent 5a,6-dihydrobenzo[b]acridin-(5H)-ones. The photoreaction is stereoselective and the S,R-isomers are the major products (83%) whereas the S,S-isomers are the minor (6%). In addition, the irreversible formation of two oxidation products, 3-(2-benzoylbenzoyl)quinolin-4(1H)-ones, and acridin-12(5H)-one derivatives was observed in the presence of air.     

Synthesis of furo[2,3-b]pyridin-4(7H)-ones and related quinolinone via Brønsted acid-promoted cyclisation of alkynes

N-Alkyl-4-alkoxy-3-alkynylpyridin-2(1H)-ones readily undergo acid-promoted 5-endo-heteroannulation to furopyridinium intermediates that are dealkylated in situ to provide the corresponding furo[2,3-b]pyridin-4(7H)-ones. The same strategy applies to the formation of furo[2,3-b]quinolin-4(9H)-ones. In the case of Me₃Si-substituted alkynes, hydration of the triple bond was observed.     

Palladium-catalyzed Suzuki-Miyaura couplings of potassium aryl trifluoroborates with 4-tosyloxycoumarins or 4-tosyloxyquinolin-2(1H)-one

Pd(PPh₃)₄ catalyzed Suzuki-Miyaura cross-coupling reactions of 4-tosyloxycoumarins or 4-tosyloxyquinolin-2(1H)-one with various potassium aryl trifluoroborates afforded the corresponding 4-substituted coumarins or 4-substituted quinolin-2(1H)-ones in good to excellent yield.     

A novel entry to cyclopenta[b]quinolines via thermal ring-expansion of (2-aminophenyl)-ethynyl-substituted squaric acid derivatives

Substituted cyclopenta[b]quinolin-1-ones were prepared by thermal ring-expansion of substituted N-Boc protected 4-(2-aminophenylethynyl)-4-hydroxy-2-cyclobuten-1-ones forming the corresponding 2-aminophenylmethylidene substituted 4-cyclopentene-1,3-diones. Deprotection of the amine resulted in spontaneous condensation giving cyclopenta[b]quinolin-1-ones. Sodium borohydride reduction of these products produced cyclopenta[b]quinolin-1-ols.     

The first synthesis of dihydro-3H-pyrido[2,3-b][1,4]diazepinols and a new alternative approach for diazepinone analogues

The first synthesis of a series of 2-aryl(heteroaryl)-4-trifluoromethyl-4,5-dihydro-3H-pyrido[2,3-b][1,4]diazepin-4-ols, where aryl = C₆H₅, 4-FC₆H₄, 4-ClC₆H₄, 4-BrC₆H₄, 4-CH₃C₆H₄, 4-OCH₃C₆H₄, 4,4′-biphenyl, 1-naphthyl and heteroaryl = 2-thienyl, 2-furyl obtained from the direct cyclocondensation reaction of 4-methoxy-1,1,1-trifluoroalk-3-en-2-ones with 2,3-diaminopyridine in 54-71% yield, is reported. Another alternative and efficient route for the synthesis of a series of 2-aryl(heteroaryl)-3H-pyrido[2,3-b][1,4]diazepin-4(5H)-ones from the reaction 4-methoxy-1,1,1-trichloroalk-3-en-2-ones with 2,3-diaminopyridine, in 54-70% yield, is also reported.     

A novel one-pot synthesis of 2-arylpyrazoloquinolinone derivatives

Two regioisomers of 2-arylpyrazolo[3,4-c]quinolin-4(5H)-ones and 2-arylpyrazolo[4,3-c]quinolin-4(5H)-ones were synthesized by utilizing 3-arylsydnones, ethyl 3-bromopropynoate, and 2-aminophenylboronic acid pinacol ester in presence of catalytic agent Pd(PPh₃)₄. This efficient one-pot synthesis methodology involved 1,3-dipolar cycloaddition, Suzuki coupling reaction, and intramolecular cyclization three sequence steps.     

A new approach to the synthesis of 4-(N-aryl)carbamoylmethyl-4,5-dihydropyridazin-3(2H)-ones

Reaction of N-aryl substituted maleimides with aliphatic ketazines leads to the formation of 4,5-dihydropyridazin-3(2H)-ones in moderate yields. The reaction proceeds through 1,4-addition of an azine to the maleimide double bond, as confirmed by separation of the corresponding adducts in some cases, which are then converted into 4,5-dihydropyridazin-3(2H)-ones. In addition, the solid-state synthesis of 4,5-dihydropyridazin-3(2H)-ones is demonstrated for the first time.     

The reaction of 2-(1-hydropolyfluoro-1-alkenyl)-4H-3,1-benzoxin-4-ones with dinucleophilic reagents: a convenient route to fluoroalkylated nitrogen-containing tricyclic compounds

The reactions of 2-(1-hydropolyfluoro-1-alkenyl)-4H-3,1-benzoxin-4-ones (2) with hydrazine hydrate and phenyl hydrazine were investigated. The reaction of 2 with hydrazine hydrate in ethanol under reflux condition readily gave 2-fluoroalkyl-4H-pyrazolo[5,1-b]quinazolin-9-ones (3) in high yields. The reaction of 2 with phenyl hydrazine, however, resulted in the formation of 2-(2-phenyl-5-fluoroalkyl-2H-pyrazol-3-yl) benzoic acids (7). Further treatment of 7 with PPA gave 1-phenyl-4,9-dihydro-3-fluoroalkyl-1H-pyrozolo[3,4-b]quinolin-4-ones (4) in 65-80% overall yields.     

Cascade Transformations of 1-R-Ethynyl-9,10-anthraquinones with Amidines: Expanding Access to Isoaporphinoid Alkaloids

The interaction of acetamidine and phenylamidine with peri-R-ethynyl-9,10-anthraquinones in refluxing n-butanol leads to the formation of cascade transformations products: addition/elimination/cyclization―2-R-7H-dibenzo[de,h]quinolin-7-ones and(or) 2-R-3-aroyl-7H-dibenzo[de,h]quinolin-7-ones. The anti-inflammatory and antitumor properties of the new 2-R-7H-dibenzo[de,h]quinolin-7-ones were investigated in vivo, in vitro, and in silico. The synthesized compounds exhibit high anti-inflammatory activity at dose 20 mg/kg (intraperitoneal injection) in the models of exudative (histamine-induced) and immunogenic (concanavalin A-induced) inflammation. Molecular docking data demonstrate that quinolinones can potentially intercalate into DNA similarly to the antitumor drug doxorubicin.     

Transaminations of enaminones:A Synthesis of tricyclic,N-aryl, 1,2,3-triazole-fused pyridones

1-Phenylmethyl- and 1-(4-methoxyphenylmethyl)-5-chloro-1,2,3-triazole-4-carbonyl chlorides acylated the pyrrolidine enamines of cyclopentanone and cyclohexanone, and the resulting enaminones underwent transaminations with aryl amines under acidic conditions. The products then cyclized under basic conditions to linearly fused, tricyclic 3-phenylmethyl- and 3-(4-methoxyphenylmethyl)-4-aryl-8-oxo-4,5,6,7-tetrahydrocyclopenta[6]-1,2,3-triazolo[4,5-e]pyridines, and to 5,6,7,8-tetrahydro-4-aryl-3H-1,2,3-triazolo[4,5-b]quinolin-9(4H)-ones. Similar transaminations afforded the related 8-phenyl- and 8-(3-chlorophenyl)-1,5,7,8-tetrahydro-1-(phenylmethyl)-4H-thieno[3,4-e]-1,2,3-triazolo[4,5-b]pyridin-4-ones. Phase-transfer and catalytic hydrogenolyses of some of these intermediates furnished 4-aryl-8-oxo-4,5,6,7-tetrahydrocyclopenta[b]-1,2,3-triazolo[4,5-e]pyridines and 4-aryl-5,6,7,8-tetrahydro-3H,2,3-triazolo[4,5-b]quinoline-9-(4H)-ones. The 3-(4-methoxyphenylmethyl)-4-aryl intermediates were sterically crowded. Two protons from the methoxyphenylmethylphenylmethylgroups were dramatically shielded because of anisotropic effects exerted by the 4-aryl substituents.     

Reaction of 3-aminoquinoline-2,4-diones with isothiocyanic acid—an easy pathway to thioxo derivatives of imidazo[1,5-c]quinazolin-5-ones and imidazo[4,5-c]quinolin-4-ones

3-Amino-1H,3H-quinoline-2,4-diones react with thiourea or potassium thiocyanate in boiling acetic acid to give novel 2,3-dihydro-3-thioxoimidazo[1,5-c]quinazolin-5(6H)-ones in high yields. However, if the starting compounds are substituted with a benzyl group at position 3, a C-debenzylation proceeds to give 2,3-dihydro-2-thioxo-1H-imidazo[4,5-c]quinolin-4(5H)-ones. According to a proposed reaction mechanism, a molecular rearrangement of the primarily formed mono-substituted thiourea takes place. All compounds were characterized by ¹H, ¹³C and ¹⁵N NMR and IR spectroscopy as well as by mass spectrometry.     

Regioselective functionalization of quinolin-4(1H)-ones via sequential palladium-catalyzed reactions

A practical and general synthesis of 1,3,6-trisubstituted quinolin-4(1H)-ones starting from 1-alkyl-6-bromo-3-iodoquinolin-4(1H)-one is described, based on regioselective sequential palladium-catalyzed cross-coupling reactions, namely Suzuki-Miyaura, Sonogashira and aminocarbonylation reactions, under microwave irradiation. Good substrate generality, ease of execution and practicability make this method exploitable for the generation of libraries of chemically diverse 4-quinolones.     

CAN-promoted, diastereoselective synthesis of fused 2,3-dihydrofurans and their transformation into tetrahydroindoles

The reaction between 1,3-cyclohexanediones and chalcones (or their vinilogs) in the presence of 2.5 equiv of cerium(IV) ammonium nitrate afforded trans-2-arylcarbonyl-3-aryl (or styryl)-2,3,6,7-tetrahydrobenzofuran-4(5H)-ones in good to excellent yields and in high diastereoselectivities. The method was also extended to the preparation of derivatives of the 5,6-dihydro-2H-cyclopenta[b]furan-4(3H)-one system. The fused 2,3-dihydrofuran derivatives were transformed into 1-alkyl-2-acyl-3-aryl-6,7-dihydroindole-4(5H)-ones by 2,3-dehydrogenation followed by reaction with primary amines. The direct reaction of the tetrahydrobenzofuran-4(5H)-one compounds derived from dimedone with amines gave 1-alkyl-2-alkylimino-3-aryl-6,7-dihydroindole-4(5H)-ones, while starting materials derived from 1,3-cyclohexanedione underwent an unprecedented 2-deacylation reaction and gave 1-alkyl-3-aryl-6,7-dihydroindole-4(5H)-ones.     

Transition-metal-free insertion of benzyl bromides into 2-(1H-benzo[d]imidazol-1-yl)benzaldehyde: One-pot switchable syntheses of benzo[4,5]imidazo[1,2-a]quinolin-5(7H)-ones and 3-arylquinolin-4-ones mediated by base

A transition-metal-free insertion of benzyl group between aldehyde and imidazole of 2-(1H-benzo[d]imidazol-1-yl)benzaldehyde was achieved for the first time. Two diverse sets of quinolin-4-one derivatives: benzo[4,5]imidazo[1,2-a]quinolin-5(7H)-ones (2) and 3-arylquinolin-4-ones (3) were synthesized based on identical starting materials 2-(1H-benzo[d]imidazol-1-yl)benzaldehydes (1) and benzyl bromides. In the preparations, two key intermediates I and II were involved and might be synthesized in situ through the reaction of an intra-Breslow intermediate with benzyl bromide via an enol attack in the presence of base or a NHC-based enamine attack in the absence of base, respectively, in which the intra-Breslow intermediate might function as a nucleophilic reagent by following two novel different pathways.     

Reaction of 3-phenyl-3-aminoquinoline-2,4-diones with isothiocyanates. Facile access to novel spiro-linked 2-thioxoimidazolidine-oxindoles and imidazoline-2-thiones

3-Phenyl-3-amino-1H,3H-quinoline-2,4-diones (1) react with alkyl or aryl isothiocyanates to give novel 9b-hydroxy-3a-phenyl-1,2,3,3a-tetrahydro-2-thioxo-5H-imidazo[4,5-c]quinolin-4(9bH)-ones in high yields. These compounds rearrange in boiling acetic acid or concentrated hydrochloric acid to give novel 5-phenyl-2-thioxospiro[4H-imidazol-4,3′-[3H]indol]-2′(1′H,3H)-ones, 5-hydroxy-5-phenyl-2-thioxospiro[imidazolidine-4,3′-[3H]indol]-2′-ones and (2-methylaminophenyl)-5-phenyl-1H-imidazole-2(3H)-thiones. All compounds were characterized by their ¹H, ¹³C, IR and MS data, and in some cases also by ¹⁵N NMR data. The structures and compositions of four compounds were confirmed by single crystal X-ray diffraction.     

One-pot synthesis of quinolin-2-(1H)-ones via tandem Ugi-Knoevenagel condensations

A new application of the Ugi reaction in the synthesis of heterocyclic compounds is described. Substituted quinolin-2-(1H)-ones are formed in one-pot sequential Ugi four-component condensation and intramolecular Knoevenagel cyclization between o-acylanilines, aldehydes, malonic or tosylacetic acids and cyclohexyl isocyanide.     

Microwave-assisted multistep synthesis of functionalized 4-arylquinolin-2(1H)-ones using palladium-catalyzed cross-coupling chemistry

[reaction: see text] Biologically active 4-aryl-3-alkenyl-substituted quinolin-2(1H)-ones have been synthesized in a short and concise manner employing readily available 4-hydroxyquinolin-2(1H)-ones as intermediates. Key steps in the synthesis include the derivatization of the quinolin-2(1H)-one cores using palladium-catalyzed Suzuki and Heck reactions, installing the 4-aryl and 3-alkenyl substituents. All synthetic transformations (six steps) required for the synthesis of the desired target quinolin-2(1H)-one were carried out using controlled microwave-assisted organic synthesis.