KOH/DMSO: A basic suspension for transition metal-free Tandem synthesis of 2,3-dihydroquinazolin-4(1H)-ones

A novel protocol for the synthesis of 2,3-dihydroquinazolin-4(1H)-ones from 2-aminobenzamides and aldehyde derivatives catalyzed by KOH/DMSO suspension has been developed. The present transition metal free methodology is operationally simple, scalable and varieties of 2,3-dihydroquinazolin-4(1H)-one derivatives were obtained in good to excellent yields in short reaction times.     

Brønsted acidic ionic liquids catalyze the preparation of 2,3-dihydroquinazolin-4(1H)-one derivatives

A simple and facile method for the green synthesis of 2,3-dihydroquinazolin-4(1H)-one derivatives by direct three-component cyclo-condensation of isatoic anhydride, ammonium acetate (or primary amines), and arylaldehydes using different Brønsted acidic ionic liquids, for example 2-pyrrolidonium hydrogensulfate ([hnmp][HSO₄]), N-methyl-2-pyrrolidonium hydrogensulfate ([NMP][HSO₄]), and N-methyl-2-pyrrolidonium dihydrogenphosphate ([NMP][H₂PO₄]), as reusable catalysts under solvent-free conditions is described. In addition, reaction of anthranilamide and arylaldehydes for synthesis of 2,3-dihydroquinazolin-4(1H)-one derivatives was investigated.     

A facile and rapid access towards the synthesis of 2,3-dihydroquinazolin-4(1H)-ones

An efficient synthetic route for 2,3-dihydroquinazolin-4(1H)-ones using 2-morpholinoethanesulfonic acid as a potential and new organocatalyst is described. The developed synthetic protocol represents a novel and very simple route for the preparation of 2,3-dihydroquinazolin-4(1H)-one derivatives. In addition, microwave irradiation technique is successfully implemented for carrying out the reactions in shorter reaction times.     

Synthesis and characterization of VO–vanillin complex immobilized on MCM-41 and its facile catalytic application in the sulfoxidation reaction,and synthesis of 2,3-dihydroquinazolin-4(1H)-ones and disulfides in green media

In this work, a vanillin complex is immobilized onto MCM-41 and characterized by FT-IR, X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, thermogravimetric analysis, and BET techniques. This supported Schiff base complex was found to be an efficient and recoverable catalyst for the chemoselective oxidation of sulfides into sulfoxides and thiols into their corresponding disulfides (using hydrogen peroxide as a green oxidant) and also a suitable catalyst for the preparation of 2,3-dihydroquinazolin-4(1H)-one derivatives in water at 90°C. Using this protocol, we show that a variety of disulfides, sulfoxides, and 2,3-dihydroquinazolin-4(1H)-one derivatives can be synthesized in green conditions. The catalyst can be recovered and recycled for further reactions without appreciable loss of catalytic performance.     

Convenient and Scalable Synthesis of 2,3-Dihydroquinazolin-4(1H)-one Derivatives and Their Anticancer Activities

An efficient and mild InBr₃-catalyzed approach to synthesize 2,3-dihydroquinazolin-4(1H)-one derivatives (3a–3aa) has been developed. Notably, all the products were isolated by recrystallization and the reaction is accessible on a gram scale. Moreover, the reactions only require 10–60 min. All the synthesized compounds were evaluated for their in vitro anticancer activity against four human cancer cell lines.     

Facile,catalyst-free,microwave-assisted access toward the synthesis of 2-aryl/alkyl-3-(1H-benzo[d]imidazol-2-yl)-2, 3-dihydroquinazolin-4(1H)-ones

An efficient, catalyst-free, microwave-assisted approach has been developed for the synthesis of 2-aryl/alkyl-3-(1H-benzo[d]imidazol-2-yl)-2,3-dihydroquinazolin-4(1H)-one derivatives by condensing 2-aminobenzamides with various aliphatic, aromatic, and heterocyclic aldehydes. This catalyst-free approach exhibited good functional group compatibility and produced the desired products in good to excellent yields in just 10–20?min. This approach can be seen as a better alternative of the metal-catalyzed protocols used for the synthesis of this class of compounds. The formation of desired compound has also been confirmed by X-ray analysis.     

Urea/Thiourea as Ammonia Surrogate: A Catalyst-Free Synthesis of 2-Substituted 2,3-Dihydroquinazolin-4(1H)-ones/Quinazoline-4(3H)-ones

Urea/thiourea have been identified as an effective ammonia surrogate in the construction of quinazolin-4(3H)-one ring. This strategy afforded a simple and catalyst-free synthesis of 2-substituted 2,3-dihydroquinazolin-4(1H)-ones and quinazolin-4(3H)-ones via the reaction of isatoic anhydride and aryl aldehydes in the presence of urea or thiourea in ethanol. The reaction proceeded well to afford the quinazolin-4(3H)-one or its dihydro derivative, depending on the nature of carbonyl compounds employed.     

Facile and One-Pot Synthesis of 1,2-Dihydroquinazolin-4(3H)-ones via Tandem Intramolecular Pinner/Dimroth Rearrangement

An efficient synthetic method for the preparation of quinazolin-4-one derivatives was designed. The facile condensation of aromatic o-aminonitriles with aromatic aldehydes catalyzed by Lewis acid give 1,2-dihydroquinazolin-4(3H)-ones in moderate to good yields under refluxing dimethylformamide.     

Metal-Free,Photoredox-Catalyzed Synthesis of Quinazolin-4(3H)-ones and Benzo[4,5]imidazo[1,2-c]quinazolines Using Trialkylamines as Alkyl Synthon

Highly functionalized quinazolin-4(3H)-ones were synthesized from reactions of N-aryl-2-aminobenzamides with trialkylamines under photocatalytic conditions by using eosin Y (EY) as a catalyst. The reaction proceeds under mild conditions in aqueous acetonitrile and has a broad substrate scope. Mechanistic studies disclosed the electron-donor nature of the intermediate 2,3-dihydroquinazolin-4(1H)-one ( 3’ ) in the photocatalytic cycle to afford the 2,3-disubstituted-quinazolin-4(3H)-ones ( 3 ). This methodology has been extended to synthesize benzo [4,5] imidazole[1,2-c] quinazolines and 3 aa on a large scale. Furthermore, the synthesis of potent central nervous system depressant (CNS) drug molecules such as methaqualone ( 3 la ) and mecloqualone ( 3 pa ) was also achieved successfully.     

Synthesis of 2-aryl-2,3-dihydroquinazolin-4(1<Emphasis Type="Italic">H</Emphasis>)-ones using boric acid-functionalized MCM-41 as a novel heterogeneous catalyst under solvent-free condition

Ordered mesoporous silica material MCM-41 with covalently anchored boric acid groups located inside the mesochannels has been utilized as an acid catalyst for the ‘green’ synthesis of 2-aryl-2,3-dihydroquinazolin-4(1H)-one derivatives under solvent-free condition. This novel synthetic method offers advantages, such as excellent yields, simple reaction procedure, short reaction times and mild reaction conditions.     

Heterocycles structurally influenced by a side chain. X. Effect of temperature and side chain on the imine-enamine tautomerism in the quinoxalinone and pyridopyrazinone systems

3-(1-Benzoyl)ethyl-1H-pyrido[2,3-b]pyrazin-2-one ( 7 ), 3-(1-ethoxycarbonyl)ethyl-1H-pyrido[2,3-b]-pyrazin-2-one ( 8 ), and 3-(1-benzoyl)ethyl-1H-quinoxalin-2-one ( 9 ) exist only in the imine form due to the steric effect of the methyl substituent. As regards the imine-enamine tautomerism, 3-(β-carbonylmethylene) derivatives of 1,2-dihydro-4H-pyrido[2,3-b]pyrazin-3-one such as 12 and 15–18 gradually change from the enamine form to the imine form with elevated temperatures; however, 3-(carbonylmethylene) derivatives of 3,4-dihydro-1H-pyrido[2,3-b]pyrazin-2-one such as 10, 19 and 20 show little temperature effect. 2-Phenacylidene-1,2-dihydro-4H-pyrido[3,4-b]pyrazin-3-one ( 21 ) and 3-phenacylidene-3,4-dihydro-1H-pyrido[3,4-b]pyrazin-2-one ( 22 ), which exist in the enamine form, show no temperature effect.     

Electrochemical utilization of methanol and methanol-d4 as a C1 source to access（deuterated） 2,3-dihydroquinazolin-4（1H）-one

Herein, an electrocatalytic protocol for the synthesis of 2,3-dihydroquinazolin-4(1H)-one has been disclosed. Methanol is activated and utilized as the C1 source to cyclize with 2-aminobenzamides.This cyclization reaction proceeds conveniently(room temperature and air atmosphere) without any homogeneous metal catalysts, external oxidants, or bases. A wide variety of N,N-disubstituted 2,3-dihydroquinazolin-4(1H)-ones are obtained via this approach. Moreover, when methanol-d4is used, a deuterated ...     

Dodecanoyl isothiocyanate and N′-(2-cyanoacetyl) dodecanehydrazide as precursors for the synthesis of different heterocyclic compounds with interesting antioxidant and antitumor activity

Dodecanoyl isothiocyanate 1 was utilized for the construction of thioureido, 2-thioxo-2,3-dihydroquinazolin-4(1H)-one, benzo[d]-1,3-thiazin-4(H)-one and 3-amino quinazolin-4(3H)-one derivatives 2, 3, 4, and 5 respectively. However, N′-(2-cyanoacetyl) dodecanehydrazide 6 was also used as a key starting material for the construction of a variety of new pyrazolone, pyrazole, thiadiazole, pyridazine, chromeno[2,3-c]pyrazole, and dithiolane derivatives 7, 9, 12, 15, 18, and 20, respectively. The newly synthesized compounds were characterized by elemental analyses and spectral data (IR, ¹H NMR, and mass spectra). Some of the newly synthesized compounds bearing heterocyclic moieties were tested for antioxidant activity as reflected in their ability to inhibit oxidation in rat brain and kidney homogenates using 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) inhibition. Also, in vitro anticancer activity was examined using the standard (3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide) (MTT) method against a panel of two human tumor cell lines namely; hepatocellular carcinoma HepG2 and mammary gland breast cancer MCF-7. Compounds 12 and 16b exhibited the highest activities as antioxidant and antitumor agents. Meanwhile, compounds 7 and 20 showed moderate activities and the rest of the tested compounds showed weak activities.     

Eco-friendly rapid synthesis of 3-substituted-2-thioxo-2,3-dihydroquinazolin-4(1H)-ones in choline chloride based deep eutectic solvent

A series of 3-substituted-2-thioxo-2,3-dihydroquinazolin-4(1H)-ones and 6-iodo-3-substituted-2-thioxo-2,3-dihydroquinazolin-4(1H)-ones were synthesized in choline chloride/urea deep eutectic solvent. Substituted 2-mercapto-4(3H)-quinazolinones were synthesized from anthranilic acid or 5-iodoanthranilic acid and appropriate isothiocyanates in good to excellent yields. Isolation of final product was easy and required no further purification. Synthesis of these compounds was rapid, selective, and catalyst free, while preparation of deep eutectic solvent was easy, components are readily available, cheap, and environmentally friendly.     

Synthesis of 2,3-dihydroquinazolin-4(1H)-ones from anthranilamide and ketones over Hβ zeolite in aqueous media*

The synthesis of 2,3-dihydroquinazolin-4(1H)-ones by cyclocondensation of anthranilamide with ketones in aqueous media using Hβ zeolite is reported. The scope of the reaction was explored by various ketones such as aromatic, aliphatic and cyclic ketones. Based on the preliminary mechanistic results, a tentative mechanism for the formation of 2,3-dihydroquinazolin-4(1H)-ones using zeolite catalyst (Hβ) is predicted. The reusability study, large-scale experiment and water as solvent showed significant benefits of this catalytic protocol in comparing to earlier methods.     

Synthesis of [1]benzothienonaphthyridines

3-Chlorobenzo[b]thiophene-2-carbonyl chloride reacted readily with 2-amino-, 3-amino-, or 4-aminopyridine to give the corresponding amides. Photocyclization of the amides afforded the following lactams: [1]ben-zothieno[2,3-c][1,5]naphthyridin-6(5H)-one ( 14 ), [1]benzothieno[2,3-c][1,6]naphthyridin-6(5H)-one ( 7 ), [1]benzo-thieno[2,3-c][1,7]naphthyridin-6(5H)-one ( 11 ), and [1]benzothieno[2,3-c][1,8]naphthyridin-6(5H)-one ( 3 ). These lactams have been converted to other derivatives including in two instances the unsubstituted ring system.     

β-Alanine-functionalized magnetic graphene oxide quantum dots: an efficient and recyclable heterogeneous basic catalyst for the synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-dione and 2,3-dihydroquinazolin-4(1H)-one derivatives

In this research, we report a novel synthesis of magnetic β-alanine-functionalized-graphene oxide quantum dots Fe₃O₄@GOQDs-N-(β-alanine) as a recyclable and eco-friendly heterogeneous nanocatalyst. The catalytic efficiency of these nanosheets was explored as a basic catalyst for a one-pot three-component synthesis of various 1H-pyrazolo[1,2-b]phthalazine-5,10-dione and 2,3-dihydroquinazolin-4(1H)-one derivatives. The reactions proceeded smoothly under mild and green conditions to afford the respected products in excellent yields. The structure of this newly fabricated catalyst was successfully confirmed by different analytical techniques such as Fourier transform infrared spectroscopy, X-ray diffraction, field emission-scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, vibrating sample magnetometry, and thermogravimetric analysis. The stability and recyclability of the catalyst were examined by performing the model reaction in six consecutive runs. The recovered catalyst from the first run was directly used for the next runs with no significant loss of catalytic activity.     

Rh(III)-Catalyzed Oxidative Annulation of 2-Arylquinoxalines with Cyclic 2-Diazo-1,3-diketones by C−H Bond Activation

Rh(III)-catalyzed C−H bond annulation of 2-arylquinoxalines with cyclic 2-diazo-1,3-diketones has been accomplished for the first time to synthesize a novel series of 2,3-dihydrodibenzo[a,c]phenazin-4(1H)-one frameworks by means of carbene insertion followed by condensation. The reaction proceeds through the C−H bond activation and functionalization of 2-arylquinoxalines using Rh(III)/AgSbF₆ complex to produce highly substituted 2,3-dihydrodibenzo[a,c]phenazin-4(1H)-one and benzo[5,6][1,2,4]thiadiazino[2,3-f]phenanthridin-5(6H)-one-10,10-dioxide derivatives in good to excellent yields.     

Halogenation of Imidazo[4,5-<Emphasis Type="Italic">b</Emphasis>]pyridin-2-one Derivatives

Chlorination and bromination of 2,3-dihydro-1H-imidazo[4,5-b]pyridin-2-one and its N-methyl-substituted derivatives in acetic acid at 90–95°C leads to formation of the corresponding 5,6-dichloro(dibromo)-2,3-dihydro-1H-imidazo[4,5-b]pyridin-2-ones. Iodination of the same substrates with ICl under analogous conditions yields 6-iodo derivatives. Chlorination of 6-iodo-1,3-dimethyl-2,3-dihydro-1H-imidazo[4,5-b]pyridin-2-one is accompanied by replacement of the iodine atom by chlorine with formation of 5,6-dichloro-1,3-dimethyl-2,3-dihydro-1H-imidazo[4,5-b]pyridin-2-one. Bromination of 6-bromo- and 6-chloro-2,3-dihydro-1H-imidazo[4,5-b]pyridin-2-ones gives 5,6-dibromo- and 5-bromo-6-chloro-2,3-dihydro-1H-imidazo[4,5-b]pyridin-2-ones, respectively.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 4, 2005, pp. 586–589.Original Russian Text Copyright © 2005 by Yutilov, Lopatinskaya, Smolyar, Gres’ko.     

Efficient one-pot synthesis of 2,3-dihydroquinazolin-4(1H)-ones from aromatic aldehydes and their one-pot oxidation to quinazolin-4(3H)-ones catalyzed by Bi(NO3)3·5H2O: Investigating the role of the catalyst

An efficient and novel synthesis of 2,3-disubstituted 2,3-dihydroquinazolin-4(1H)-ones via one-pot, three-component reaction of isatoic anhydride, primary amines and aromatic aldehydes catalyzed by Bi(NO₃)₃·5H₂O under solvent-free conditions is described. Oxidation of these 2,3-dihydroquinazolin-4(1H)-ones to their quinazolin-4(3H)-ones was also successfully performed in the presence of Bi(NO₃)₃·5H₂O. This new method has the advantages of convenient manipulation, short reaction times, excellent yields, very easy work-up, and the use of commercially available, low cost and relatively non-toxic catalyst. The role of Bi(NO₃)₃·5H₂O was also investigated in these transformations.