A facile vanadium-catalyzed aerobic oxidative synthesis of quinazolinones from 2-aminobenzamides with aldehydes or alcohols

Substrate- and reagent-dependent selective annulation of amidines and 2-tert-amino benzaldehydes

Herein, we present an efficient and substrate/reagent-dependent annulation of amidines with 2-tert-amino benzaldehydes. When N-alkyl benzimidamides are employed, amidines undergo self-annulation to generate a hydrotriazine skeleton. In contrast, N-aryl benzimidamides yield quinazolines/hydroquinazolines under similar conditions. Additionally, the coupling of 2-tert-amino benzaldehydes with amidines under basic conditions yields 1,3,5-triazine derivatives.

Symmetrical Bis-Hydrazone Ligand-Based Binuclear Oxido/Dioxido-Vanadium(IV/V) Complexes: Synthesis, Reactivity, and Catalytic Applications for the Synthesis of Biologically Potent 2-Phenylquinazolin-4-(3H)-ones

Symmetrical bis(hydrazone)-based ligands, H4dar(bhz)2 (I), H4dar(fah)2 (II), H4dar(nah)2 (III), and H4dar(inh)2 (IV) obtained from 4,6-diacetylresorcinol (H2dar) and different hydrazides [benzoylhydrazide (Hbhz), isonicotinoylhydrazide (Hinh), nicotinoylhydrazide (Hnah), and 2-furoylhydrazide (Hfah)], were used to prepare potassium salts of binuclear cis-[VVO2]+ complexes, {K(H2O)2}2[(VVO2)2dar(bhz)2] (1), {K(H2O)2}2[(VVO2)2dar(fah)2] (2), {K(H2O)2}2[(VVO2)2dar(nah)2] (3), and {K(H2O)2}2[(VVO2)2dar(inh)2] (4), and binuclear [VIVO]2+ complexes, [{VIVO(MeOH)}2dar(bhz)2] (5), [{VIVO(MeOH)}2dar(fah)2] (6), [{VIVO(MeOH)}2dar(nah)2] (7), and [{VIVO(MeOH)}2dar(inh)2] (8). In the presence of warm MeOH/DMSO (4:1), 3 changed to {K(H2O)2}[(VVO2)2Hdar(nah)2]·DMSO (3a·DMSO). Single crystal XRD studies of 1 and 3a confirm a binuclear structure along with a distorted square pyramidal geometry of each vanadium center where bis{ONO(2-)} ligands coordinate through phenolate-O, azomethine-N, and enolate-O atoms of each unit. While growing crystals of 6 in EtOH, part of it oxidizes and gives [{VVO(OEt)}2dar(fah)2] (9) along with powdery 6. Complex 9 has a distorted octahedral structure. These complexes were used as catalysts for the synthesis of biologically important 2-phenylquinazolin-4-(3H)-ones having different aryl aldehydes, and they all show excellent catalytic performance (up to 97% yield) in less reaction time and low temperature, in the presence of 70% aqueous TBHP/30% aqueous H2O2 as a greener oxidant. Generally, these complexes perform better than their mononuclear analogues. Spectroscopy, DFT studies, and isolated intermediates have helped in proposing a suitable reaction mechanism for the catalytic reaction.

Facile Ru-catalysed synthesis of quinazolin-4(3H)-ones by tandem cyclization of 2-nitrobenzonitrile and alcohol derivatives under air

We have developed an efficient approach for the first Ru-catalysed synthesis of 2-arylquinazolin-4(3H)-ones from 2-nitrobenzonitriles and alcohols. This method features a broad substrate scope, high yields, and functional group tolerance and does not require any oxidant or reductant, allowing for simple, practical and sustainable synthesis.

Polyoxometalate-Based Metal-Organic Frameworks with Both Proton Acid and Multioxidative Active Sites: Highly Efficient Catalytic Synthesis of Quinazolinones

Quinazolinone derivatives are an important class of pharmaceutical and pesticide intermediates, which are generally synthesized starting with the condensation reaction between aldehydes and 2-aminobenzamide to obtain corresponding intermediates and then oxidized to obtain the products. Although some catalysts have been developed currently for the synthesis of quinazolinone derivatives, their catalytic efficiency is relatively low because only the oxidative catalytic sites of the catalyst have been focused on. Herein, we synthesized three new polyoxometalate-based metal-organic frameworks, [CuI4(4,4'-bipy)7(Hn-1PMo12-nVnO40)]·2H2O (n = 1-3), which were formed by coordinating a Cu(I)-bipy complex with different Keggin-type phosphomolybdic acids. An important feature of these compounds is that they possess proton and multioxidative active sites [Cu(I) center and V(V) center]; thus, we applied them to the catalytic synthesis of quinazolinone derivatives. The results indicate that compound 3 has an excellent catalytic activity. Based on density functional theory calculations, it is speculated that protons participate in the aldehyde amine condensation reaction, which changes the reaction pathway and reduces the activation energy from 55.1 to 31.4 kcal/mol, thereby increasing the reaction rate significantly. Interestingly, Raman spectra and electron paramagnetic resonance measurements indicate the presence of CuIIOO• and •O2- during the oxidative dehydrogenation process, which facilitates the rapid consumption of 2-phenyl-2,3-dihydroquinazolin-4(1H)-one intermediates, thereby promoting the chemical reaction to move toward the positive direction. Thanks to the synergistic effect of multicatalytic sites, compound 3 achieved highly efficient catalytic synthesis of quinazolinones with 99% yield in 1 h.

Designing a new method for growing metal-organic framework (MOF) on MOF: synthesis, characterization and catalytic applications

Metal-organic frameworks as a unique class of high-surface-area materials have gained considerable attention due to their characteristic properties. In this perspective, herein, we report an eco-friendly and inexpensive route for the synthesis of 4(3H)-quinazolinones using magnetically separable core-shell-like bimetallic Fe₃O₄-MAA@Co-MOF@Cu-MOF NPs as environmentally-friendly heterogeneous catalysts. To the best of our knowledge, this is the first example of the integration of two different types of MOFs, which contain two different metal ions (Co²⁺ in the core and Cu²⁺ in the shell) using an external ligand. Our study not only introduces a novel nanostructured catalyst for the organic reaction but also presents a new strategy for the combination of two MOFs in one particle at the nanometer level. To survey the structural and compositional features of the synthesized nanocatalyst, a variety of spectroscopic and microscopic techniques including FT-IR, XRD, BET, TEM, HR-TEM, FE-SEM, EDX, EDX-mapping, TGA, VSM, and ICP-OES were employed. The combination of magnetic Co-MOF with Cu-MOF leads to achieving unique structural and compositional properties for Fe₃O₄-MAA@Co-MOF@Cu-MOF NPs with a particle size of 20-70 nm, mesostructure, and relatively large specific surface area (236.16 m² g^-1). The as-prepared nanostructured catalyst can be an excellent environment catalyst for the synthesis of a wide library of 4(3H)-quinazolinones derivatives, including electron-donating and electron-withdrawing aromatic, heteroaromatic, and aliphatic compounds under solvent-free conditions much better than the parent precursors. Moreover, by investigating the longevity of the nanocatalyst, the conclusion could be derived that the aforesaid nanocatalyst is stable under reaction conditions and could be recycled for at least seven recycle runs without a discernible decrease in its catalytic activity.

Room temperature ligand-free Cu2O-H2O2 catalyzed tandem oxidative synthesis of quinazoline-4(3H)-one and quinazoline derivatives

An efficient and simple copper catalytic system has been developed for the synthesis of medicinally important 2-substituted quinazoline-4(3H)-ones from 2-aminobenzonitrile and benzyl alcohol derivatives and additionally 2-substituted quinazolines from 2-aminobenzylamine and benzaldehyde derivatives. Mild oxidant H₂O₂ was utilized, providing excellent product yields. The molecular structure of one of the compounds was substantiated through SC-XRD. The versatility of the protocol was demonstrated through gram-scale syntheses.

Facile One-Pot Synthesis of Functionalized Quinoline-Fused Fluorescent Dihydro/Spiro-quinazolinone Derivatives

A facile and efficient method has been developed for the synthesis of quinoline-fused fluorescent dihydro/spiro-quinazolinones. A plausible mechanism involving an acid-mediated enaminone intermediate is provided. The reaction proceeded using p-toluene sulfonic acid as a green promoter. The methodology was successful in synthesizing various quinoline-appended spiro-quinazolinones 4a-o. The synthetic utility of compounds 4a-o was demonstrated by synthesizing compounds 6a-d via Suzuki coupling as a key reaction. Significantly, the π-π* electronic transition of compounds 4c and 4k showed a blue shift. The molar extinction coefficient (ε), Stoke's shift (Δu̅), and quantum yield (Φ^f)_c were calculated for these derivatives (4c and 4k).

Straightforward synthesis of quinazolin-4(3H)-ones via visible light-induced condensation cyclization

A green, simple and efficient method is developed for the synthesis of quinazolin-4(3H)-ones via visible light-induced condensation cyclization of 2-aminobenzamides and aldehydes under visible light irradiation. The reaction proceeds using fluorescein as a photocatalyst in the presence of TBHP without the need for a metal catalyst. In addition, this reaction tolerates a broad scope of substrates and could afford a variety of desirable products in good to excellent yields. Thus, the present synthetic method provides a straightforward strategy for the synthesis of quinazolin-4(3H)-ones.

Ammonium Formate-Pd/C as a New Reducing System for 1,2,4-Oxadiazoles. Synthesis of Guanidine Derivatives and Reductive Rearrangement to Quinazolin-4-Ones with Potential Anti-Diabetic Activity

1,2,4-Oxadiazole is a heterocycle with wide reactivity and many useful applications. The reactive O-N bond is usually reduced using molecular hydrogen to obtain amidine derivatives. NH4CO2H-Pd/C is here demonstrated as a new system for the O-N reduction, allowing us to obtain differently substituted acylamidine, acylguanidine and diacylguanidine derivatives. The proposed system is also effective for the achievement of a reductive rearrangement of 5-(2'-aminophenyl)-1,2,4-oxadiazoles into 1-alkylquinazolin-4(1H)-ones. The alkaloid glycosine was also obtained with this method. The obtained compounds were preliminarily tested for their biological activity in terms of their cytotoxicity, induced oxidative stress, α-glucosidase and DPP4 inhibition, showing potential application as anti-diabetics.

A magnetically retrievable copper ionic liquid nanocatalyst for cyclooxidative synthesis of 2-phenylquinazolin-4(3H)-ones

In the present work, we report the design and fabrication of a copper-containing ionic liquid supported magnetic nanocatalyst via a convenient and straightforward synthetic approach for the formation of 2-phenylquinazolin-4(3H)-ones using o-aminobenzamide and benzaldehydes as the reaction partners. The successful formation and properties of the as-prepared catalyst have been thoroughly investigated using diverse physico-chemical techniques including FT-IR, XRD, FE-SEM, TEM, ICP, VSM, BET and TGA. Using this nanocatalytic system, a variety of 2-phenylquinazolin-4(3H)-ones are synthesized in excellent yields with operational ease and short reaction times in an environmentally preferable solvent under open air and without using any external oxidizing agent. Besides, the catalyst possessed facile magnetic recoverability and remarkable reusability for six consecutive runs without any appreciable decrease in the catalytic efficiency.

Improved, gram-scale synthesis of sildenafil in water using arylacetic acid as the acyl source in the pyrazolo[4,3-d]pyrimidin-7-one ring formation

An improved, gram-scale synthesis of the blockbuster drug sildenafil, used for the treatment of male erectile dysfunction, has been developed.

An efficient transition-metal-free route to quinazolin-4(3H)-ones via 2-aminobenzamides and thiols

An efficient approach to quinazolin-4(3H)-ones was developed by a one-pot intermolecular annulation reaction of o-amino benzamides and thiols.

Recent advances in sustainable synthesis of N-heterocycles following acceptorless dehydrogenative coupling protocol using alcohols

In this review, we have summarized various aspects of homogeneous and heterogeneously catalyzed recent advancements in the synthesis of heterocycles following the ADC approach.

Visible-light induced copper(i)-catalyzed oxidative cyclization of o-aminobenzamides with methanol and ethanol via HAT

The use of the in situ generated ligand-copper superoxo complex absorbing light energy to activate the alpha C(sp³)-H of MeOH and EtOH via the hydrogen atom transfer (HAT) process for the synthesis of quinazolinones by oxidative cyclization of alcohols with o-aminobenzamide has been investigated. The synthetic utility of this protocol offers an efficient synthesis of a quinazolinone intermediate for erlotinb (anti-cancer agent) and 30 examples were reported.

An Aqueous Facile Synthesis of 2,3-Dihydroquinazolin-4(1H)-One Derivatives by Reverse Zinc Oxide Micelles as Nanoreactor

A green synthetic protocol has been developed for the efficient preparation of 2,3-dihydroquinazolin−4(1H)-one derivatives with excellent yield in aqueous media. Reverse zinc oxide micelles catalyzed the reactions efficiently and selectively as the hallow nanoreactor. Moreover, the catalyst was reusable without significant loss of catalytic efficiency. The notable advantages of the procedure are high yields and mild reaction conditions, simple operation, nonchromatographic purification, environmentally friendly and good versatile substrates.

ortho-Naphthoquinone-catalyzed aerobic oxidation of amines to fused pyrimidin-4(3H)-ones: a convergent synthetic route to bouchardatine and sildenafil

A facile access to fused pyrimidin-4(3H)-one derivatives has been established by using the metal-free ortho-naphthoquinone-catalyzed aerobic cross-coupling reactions of amines. The utilization of two readily available amines allowed a direct coupling strategy to quinazolinone natural product, bouchardatine, as well as sildenafil (Viagra™) in a highly convergent manner.

Fused pyrimidin-4(3H)-one derivatives have been accessed by using the ortho-naphthoquinone-catalyzed aerobic cross-coupling reactions of amines.

Efficient Synthesis of Quinazolinones by Transition-Metal-Free Direct Aerobic Oxidative Cascade Annulation of Alcohols with o-Aminoarylnitriles

A mild and atom-economic method was developed for direct and efficient synthesis of quinazolinones through a transition-metal-free aerobic oxidative cascade annulation reaction of widely available o-aminoarylnitriles and alcohols. Air could be employed as an effective oxidant under mild conditions, generating water as the only byproduct. Possibly owing to the "cesium effect", the water-soluble base CsOH was found to be crucial in all key steps of the reaction mechanism. Because a wide range of substrates can be used to prepare substituted quinazolinones without contamination by transition-metal residues, this method may be of interest for application in pharmaceutical synthesis. Possible reaction paths were also proposed according to control reactions.

Copper-catalyzed tandem oxidative synthesis of quinazolinones from 2-aminobenzonitriles and benzyl alcohols

A highly efficient, one-pot Cu(OAc)₂/Cs₂CO₃-catalyzed protocol for the aerobic oxidative synthesis of quinazolinones from readily available benzyl alcohols and 2-aminobenzonitriles with molecular oxygen as the terminal oxidant has been successfully developed.

Tandem synthesis of quinazolinone scaffolds from 2-aminobenzonitriles using aliphatic alcohol–water system

Functionalized bipyridine based Ru(II) complex catalyzed tandem synthesis of quinazolinones from 2-aminobenzonitriles is reported here utilizing aliphatic alcohol–water system.

Bismuth-Catalyzed Synthesis of 2-Substituted Quinazolinones

The bismuth-catalyzed oxidative condensation of aldehydes with 2-aminobenzamide under aerobic conditions is reported using ethanol as the solvent. Good to excellent isolated yields (68-95%) of the corresponding 2-substituted quinazolinones were obtained under mild reaction conditions with excellent functional group tolerance. The quinazolinones were further functionalized to afford N-allylated quinazolinones, 2-aminopyridine derivatives, and annulated polyheterocyclic compounds via transition-metal catalyzed reactions.

Redox supramolecular self-assemblies nonlinearly enhance fluorescence to identify cancer cells

Based on the nonlinear fluorescence enhancement, our H2O2 induced supramolecular self-assembly reveals a H2O2 threshold among multiple cancer and normal cells. Oxidative elimination restores an intramolecular hydrogen bond which can planarize the molecule to generate a fluorophore. The planarization enhances the intermolecular π-π stacking to promote self-assembly.

Highly Selective Oxidation of Ethyl Lactate to Ethyl Pyruvate Catalyzed by Mesoporous Vanadia-Titania

The direct oxidative dehydrogenation of lactates with molecular oxygen is a “greener” alternative for producing pyruvates. Here we report a one-pot synthesis of mesoporous vanadia–titania (VTN), acting as highly efficient and recyclable catalysts for the conversion of ethyl lactate to ethyl pyruvate. These VTN materials feature high surface areas, large pore volumes, and high densities of isolated vanadium species, which can expose the active sites and facilitate the mass transport. In comparison to homogeneous vanadium complexes and VO_x/TiO₂ prepared by impregnation, the meso-VTN catalysts showed superior activity, selectivity, and stability in the aerobic oxidation of ethyl lactate to ethyl pyruvate. We also studied the effect of various vanadium precursors, which revealed that the vanadium-induced phase transition of meso-VTN from anatase to rutile depends strongly on the vanadium precursor. NH₄VO₃ was found to be the optimal vanadium precursor, forming more monomeric vanadium species. V⁴⁺ as the major valence state was incorporated into the lattice of the NH₄VO₃-derived VTN material, yielding more V⁴⁺–O–Ti bonds in the anatase-dominant structure. In situ DRIFT spectroscopy and density functional theory calculations show that V⁴⁺–O–Ti bonds are responsible for the dissociation of ethyl lactate over VTN catalysts and for further activation of the deprotonation of β-hydrogen. Molecular oxygen can replenish the surface oxygen to regenerate the V⁴⁺–O–Ti bonds.

Palladium-catalyzed oxidative CC bond cleavage with molecular oxygen: one-pot synthesis of quinazolinones from 2-amino benzamides and alkenes

Palladium-catalyzed oxidative cleavage/cyclization has been disclosed for the concise synthesis of various quinazolinone derivatives from readily available 2-aminobenzamides and terminal alkenes with excellent functional group tolerance.