Palladium-catalyzed cyclocarbonylation of o-iodoanilines with heterocumulenes: regioselective preparation of 4(3H)-quinazolinone derivatives

One-pot Synthesis of 2,3-disubstituted-4(3H)-quinazolinone from o-aminobenzoic Acid and DMF Derivatives using Imidazole Hydrochloride as a Promoter

As a novel and environmentally friendly Brönsted acid, imidazole hydrochloride was used to promote the synthesis of 2,3-disubstituted-4(3H)-quinazolinone from o-aminobenzoic acid and DMF derivatives. The essence of this reaction is a multicomponent reaction, which constructs multiple chemical bonds between different components through the transamidation of imidazole hydrochloride. This protocol showed a wide range of functional group tolerance, and a series of quinazolinones were synthesized in low to moderate yields without metal catalysts, oxidants or other additives.

Supported Palladium-Catalyzed Tandem Synthesis of 2-(Alkylamino/amino)-3-arylquinazolin-4(3H)-ones Employing CO Source

Herein, we demonstrated heterogeneous and recyclable polystyrene-supported palladium (Pd@PS) nanoparticles (NPs) catalyzed tandem addition and intramolecular aminocarbonylative cyclization approach for the synthesis of potentially bioactive 2-(alkylamino/amino)-3-arylquinazolin-4(3H)-one analogues from 2-iodophenylcarbodiimides employing amines as nucleophiles and oxalic acid as an ex-situ CO alternative. Various cyclic/acyclic primary and secondary amines were employed and selectively produced substituted 2-(alkylamino)-3-arylquinazolin-4(3H)-ones in good to excellent yields. In addition, we extended the developed strategy to fix two ammonium carbamate and oxalic acid as gaseous NH₃ and CO sources respectively, for the synthesis of 2-amino-3-arylquinazolin-4(3H)-one derivatives. Furthermore, gram scale applicability, diverse substrate scope and high recyclability of the Pd@PS catalyst were the major achievements of the developed protocol.

Metal-Free N-H/C-H Carbonylation by Phenyl Isocyanate: Divergent Synthesis of Six-Membered N-Heterocycles

We disclose a method using phenyl isocyanate to synthesize carbonyl-containing N-heterocycles. The metal-free novel approach for both N-H and C-H carbonylation processes was successfully refined, delivering a range of synthetically valuable derivatives of quinazoline-2,4(1H,3H)-dione, 2H-benzo[e] [1,2,4] thiadiazin-3(4H)-one 1,1-dioxide, and pyrrolo[1,2-a] quinoxalin-4(5H)-one. The protocol features broad substrates with diverse reactions suitable for excellent yields, mild conditions, and good functional group compatibility. Moreover, the applicability of the reaction was characterized by gram-scale synthesis and synthetic transformations for drug molecules.

I2/TBHP mediated domino synthesis of 2-(2,4-dioxo-1,4-dihydroquinazolin-3(2H)-yl)-N-aryl/alkyl benzamides and evaluation of their anticancer and docking studies

A novel I2/TBHP mediated domino synthesis of 2-(2,4-dioxo-1,4-dihydroquinazolin-3(2H)-yl)-N-phenyl benzamides by reaction of isatins with o-amino N-aryl/alkyl benzamides was described. This was the first application of o-amino N-aryl/alkyl benzamides participating in oxidative rearrangement with isatins for synthesis of desired products. The synthesized compounds contained amide and quinazoline units and their combination resulted in molecular hybridization of two important pharmacophores. In this study, the synthesized compounds 3a-r were screened for cytotoxicity against four cancer cell lines A549, DU145, B16-F10, and HepG2 and also non-cancerous cell line CHO-K1. The compounds 3c, 3l and 3o gave promising results. The in silico molecular docking studies (PDB ID 1N37) also validated the anticancer activity of these compounds showing good binding affinity with target DNA and by acting as DNA intercalators.

Preparation of quinazolinones using biosynthesized silver nanoparticles

A silver nanocatalyst has been used as an effective catalyst for the preparation of quinazolinones under reflux conditions in ethanol. The catalyst was characterized by UV-VIS, FT-IR, XRD, SEM and EDS. Amongst the many benefits of this method are atom economy, reusability of the catalyst, low catalyst loading, applicability to a wide range of substrates, high yields of products, environmental friendliness and easy separation of products. Silver nanoparticles (Ag NPs) were prepared using Echium amoenum extract. The structures of the prepared quinazolinones were fully characterized by 1H and 13C NMR, FT-IR spectra and elemental analysis.

Application of Deep Eutectic Solvents in the Synthesis of Substituted 2-Mercaptoquinazolin-4(3H)-Ones: A Comparison of Selected Green Chemistry Methods

In this study, deep eutectic solvents (DESs) were used as green and eco-friendly media for the synthesis of substituted 2-mercaptoquinazolin-4(3H)-ones from different anthranilic acids and aliphatic or aromatic isothiocyanates. A model reaction on anthranilic acid and phenyl isothiocyanate was performed in 20 choline chloride-based DESs at 80 °C to find the best solvent. Based on the product yield, choline chloride:urea (1:2) DES was found to be the most effective, while DESs acted both as solvents and catalysts. Desired compounds were prepared with moderate to good yields using stirring, microwave-assisted, and ultrasound-assisted synthesis. Significantly, higher yields were obtained with mixing and ultrasonication (16-76%), while microwave-induced synthesis showed lower effectiveness (13-49%). The specific contribution of this research is the use of DESs in combination with the above-mentioned green techniques for the synthesis of a wide range of derivatives. The structures of the synthesized compounds were confirmed by 1H and 13C NMR spectroscopy.

Cyclocondensation of Anthranilamide with Aldehydes on Gallium-Containing MCM-22 Zeolite Materials

A gallium-containing MCM-22 (Mobil Composition of Matter No. 22) zeolite material was prepared using a simple hydrothermal method. Fourier transform infrared spectroscopy analysis and powder X-ray diffraction provide evidence of the formation of a pure MCM-22 phase framework and an MWW (MCM-tWenty-tWo) structure. Scanning electron microscopy images showed a uniform spherical shape, interpenetrating the platelet structure and a uniform particle size of approximately 6 μm. ⁷¹Ga nuclear magnetic resonance studies confirmed the presence of gallium in both the tetrahedral framework and the octahedral extra-framework environment. From the sorption studies, the presence of strong acidic sites and the microporous nature of the material were evident. The resultant Ga-MCM-22 material showed an excellent isolated yield of 95% in the synthesis of 2,3-dihydroquinazolin-4(1H)-ones by cyclocondensation of anthranilamide with aldehydes in ethanol. The scope of the reaction was further explored by employing various cyclic, aromatic, and aliphatic aldehydes with anthranilamide. The results provide a very good yield (85-95%). A significant advantage of the developed protocol includes high yield, use of a green solvent, and easy removal of the catalyst through filtration within a short reaction time.

Computational determination of the mechanism of the Pd-catalyzed formation of isatoic anhydrides from o-haloanilines, CO, and CO2

The palladium-catalyzed annulation of o-haloanilines with carbon monoxide (CO) and carbon dioxide (CO₂), discovered by Wen-Zhen Zhang and co-workers, provides a convenient method to synthesize isatoic anhydrides. We explored the mechanism of this reaction, particularly the order of the reaction of CO and CO₂ and the effect of the base, using density functional theory (DFT) calculations (ωB97X-D and M06). It was found that the base-assisted N-H bond activation through a concerted metalation-deprotonation (CMD) mechanism is a requisite for carboxylation, and the carboxylation proceeds via the nucleophilic attack of the (Pd)NH nitrogen on CO₂. The results show that carbonylation occurs prior to carboxylation, because the facile and exergonic carbonylation greatly decreases the energies of the following intermediates and transition states. The mechanistic exploration of the alternative pathways (e.g., mono-carbonylation and carboxylation) and the comparison with the annulation mechanism of the o-iodobenzylamine substrate further demonstrate the perfect cooperation of CO and CO₂ in constructing an anhydride moiety for o-haloanilines.

Carbodiimide-based synthesis of N-heterocycles: moving from two classical reactive sites to chemical bond breaking/forming reaction

Carbodiimides are a unique class of heterocumulene compounds that display distinctive chemical properties. The rich chemistry of carbodiimides has drawn increasing attention from chemists in recent years and has made them exceedingly useful compounds in modern organic chemistry, especially in the synthesis of N-heterocycles. This review has outlined the extensive application of carbodiimides in the synthesis of N-heterocycles from the 1980s to today. A wide range of reactions for the synthesis of various types of N-heterocyclic systems (three-, four-, five-, six-, seven-, larger-membered and fused heterocycles) have been developed on the basis of carbodiimides and their derivatives.

Palladium-catalyzed three-component carbonylative synthesis of 2-(trifluoromethyl)quinazolin-4(3H)-ones from trifluoroacetimidoyl chlorides and amines

An efficient and practical approach for the synthesis of 2-(trifluoromethyl)quinazolin-4(3H)-ones through palladium-catalyzed three-component carbonylative reaction has been developed.

"On-Water" Synthesis of Quinazolinones and Dihydroquinazolinones Starting from o-Bromobenzonitrile

A versatile and practical “on-water” protocol was newly developed to synthesize quinazolinones using o-bromobenzonitrile as a novel starting material. Studies have found that air as well as water plays an important role in synthesis of quinazolinones. Further investigation indicated that dihydroquinazolinones can be prepared with this protocol under the protection of N₂. The protocol can be extended to other substrates and various quinazolinones and dihydroquinazolinones were obtained. o-Bromobenzamide, o-aminobenzonitrile, and o-aminobenzamide were also evaluated as starting materials, and the results further proved the versatility of this protocol, especially towards dihydroquinazolinones.

Palladium-Catalyzed Incorporation of Two C1 Building Blocks: The Reaction of Atmospheric CO2 and Isocyanides with 2-Iodoanilines Leading to the Synthesis of Quinazoline-2,4(1H,3H)-diones

A Pd-catalyzed insertion and cycloaddition of CO₂ and isocyanide into 2-iodoanilines under atmospheric pressure has been developed and affords quinazoline-2,4(1H,3H)-diones through the formation of new C-C, C-O, and C-N bonds under mild conditions. This reaction provides a new and practical method not only for the construction of quinazoline-2,4(1H,3H)-diones but also for the efficient utilization of carbon dioxide.

One-pot three-component selective synthesis of isoindolo[2,1-a]quinazoline derivatives via a palladium-catalyzed cascade cyclocondensation/cyclocarbonylation sequence

A practical and highly efficient procedure for the selective preparation of 6,6a-dihydroisoindolo[2,1-a]quinazoline-5,11-diones through a palladium-catalyzed one-pot three-component cascade reaction of 2-aminobenzamides with 2-bromobenzaldehydes and carbon monoxide under atmospheric pressure has been developed. This cascade reaction, in which four new C-C/C-N bonds and two new rings are simultaneously constructed, is triggered by a cyclocondensation of 2-aminobenzamides with 2-bromobenzaldehydes, followed by a Pd-catalyzed cyclocarbonylation of the in situ formed 2,3-dihydroquinazolin-4(1H)-ones with CO (1 atm). Compared with the existing methods, the present protocol has the advantages of readily available starting materials, broad substrate scope, structural diversity of products, and free of high-pressure equipment.

Synthesis of Cu-catalysed quinazolinones using a Csp3–H functionalisation/cyclisation strategy

A series of 2,3-disubstituted-4(3H)-quinazolinones were synthesised via a copper-catalysed C_sp3–H functionalisation/cyclisation of 2-amino-N,N-dialkylbenzamides.

One-Step Synthesis of 2-Chloropyrimidin-4-ol Derivatives: An Unusual Reactivity of Thiophosgene

A novel, high-yielding, one-step synthesis of 2-chloroquinazolin-4-ols and analogous bicycles from 2-aminoamides using thiophosgene is described. The scope of the reaction includes aminothioamides, amino acids, and fused heterocycle derivatives, furnishing quinazolines, oxazinones, and substituted fused pyrimidine bicycles, respectively. On the basis of observed results with substituted analogues, a mechanism for this transformation is thought to occur via an isothiocyanate intermediate followed by an unexpected chemoselective reaction of thiophosgene on the thiol intermediate.

Synthesis of quinazolines and quinazolinones via palladium-mediated approach

Quinazoline derivatives have drawn attention in the field of heterocyclic chemistry because of their unique skeleton and interesting biological applications. This review summarizes the recent palladium-catalyzed reactions used to construct quinazoline and its related 4(3H)-quinazolinone analogues. The mechanisms of some Pd-catalyzed reactions are also discussed.

Aqueous hydrotrope: an efficient and reusable medium for a green one-pot, diversity-oriented synthesis of quinazolinone derivatives

A library of quinazolinones was prepared by the one-pot three-component reaction of isatoic anhydride, ammonium salts/amines, and various electrophiles using aqueous hydrotropic solution as an efficient, economical, reusable, and green medium giving good to excellent yields of products in very short time. The method offers a versatile way for the development of diversity-oriented synthesis of quinazolinones.

Pd/C as an efficient heterogeneous catalyst for carbonylative four-component synthesis of 4(3H)-quinazolinones

A relatively mild, operationally simple, phosphine-free and recyclable catalytic system for the carbonylative synthesis of 4(3H)-quinazolinones with 2-iodoanilines, trimethyl orthoformate, and amines as the substrates has been developed.

Palladium-catalyzed oxidative carbonylation of hydrazides: synthesis of 1,3,4-oxadiazol-2(3H)-ones

A novel palladium-catalyzed oxidative carbonylation reaction was developed via the carbon monoxide insertions between the amine group and the carbonyl group to realize the intramolecular cyclization, which provides efficient access to 1,3,4-oxadiazol-2(3H)-ones with a wide range of substrates under mild conditions, resulting in good to excellent yields.

One-pot synthesis of 2-amino-4(3H)-quinazolinones via ring-opening of isatoic anhydride and palladium-catalyzed oxidative isocyanide-insertion

An efficient and practical two-step process has been developed for the synthesis of 2-amino-4(3H)-quinazolinones via ring-opening of isatoic anhydride and palladium-catalyzed oxidative isocyanide-insertion in one pot. This regioselective procedure could construct a wide range of 2-amino-4(3H)-quinazolinones in moderate to excellent yields. Furthermore, the methodology also had distinct advantages of easily accessible starting materials and operational simplicity.