Novel Stereo-Induction Pattern in Pudovik Addition/Phospha-Brook Rearrangement Towards Chiral Trisubstituted Allenes

Despite the significance of chiral allene skeletons in catalysis, organic synthesis and medicinal chemistry et al., there is a scarcity of reports on axially chiral allenyl phosphorus compounds. Here, we disclosed an efficient and straightforward cascade reaction between ethynyl ketones and phosphine oxides, resulting in a broad array of trisubstituted allenes incorporating a phosphorus moiety in high yields with excellent stereoselectivities facilitated by peptide-mimic phosphonium salt (PPS) catalysis, Additionally, comprehensive series of mechanistic experiments have been conducted to elucidate that this cascade reaction proceeds via an asymmetric Pudovik addition reaction followed by a subsequent phospha-Brook rearrangement that occurs concomitantly with kinetic resolution, representing a stereospecific rearrangement and protonation process facilitating central-to-axial chirality transfer in a cascade manner. We anticipate that our research will pave the way for a promising exploration of novel stereo-induction pattern in the Pudovik addition/phospha-Brook rearrangement cascade reaction.

Unveiling the Untapped Potential of Bertagnini's Salts in Microwave-Assisted Synthesis of Quinazolinones

Microwave-assisted organic synthesis (MAOS) has emerged as a transformative technique in organic chemistry, significantly enhancing the speed, efficiency, and selectivity of chemical reactions. In our research, we have employed microwave irradiation to expedite the synthesis of quinazolinones, using water as an eco-friendly solvent and thereby adhering to the principles of green chemistry. Notably, the purification of the product was achieved without the need for column chromatography, thus streamlining the process. A key innovation in our approach is using aldehyde bisulfite adducts (Bertagnini's salts) as solid surrogates of aldehydes. Bertagnini's salts offer several advantages over free aldehydes, including enhanced stability, easier purification, and improved reactivity. Green metrics and Eco-Scale score calculations confirmed the sustainability of this approach, indicating a reduction in waste generation and enhanced sustainability outcomes. This methodology facilitates the synthesis of a diverse array of compounds, offering substantial contributions to the field, with potential for widespread applications in pharmaceutical research and beyond.

The Synthesis and Biological Evaluation of 2-(1H-Indol-3-yl)quinazolin-4(3H)-One Derivatives

The treatment of many bacterial diseases remains a significant problem due to the increasing antibiotic resistance of their infectious agents. Among others, this is related to Staphylococcus aureus, especially methicillin-resistant S. aureus (MRSA) and Mycobacterium tuberculosis. In the present article, we report on antibacterial compounds with activity against both S. aureus and MRSA. A straightforward approach to 2-(1H-indol-3-yl)quinazolin-4(3H)-one and their analogues was developed. Their structural and functional relationships were also considered. The antimicrobial activity of the synthesized compounds against Mycobacterium tuberculosis H₃₇Rv, S. aureus ATCC 25923, MRSA ATCC 43300, Candida albicans ATCC 10231, and their role in the inhibition of the biofilm formation of S. aureus were reported. 2-(5-Iodo-1H-indol-3-yl)quinazolin-4(3H)-one (3k) showed a low minimum inhibitory concentration (MIC) of 0.98 μg/mL against MRSA. The synthesized compounds were assessed via molecular docking for their ability to bind long RSH (RelA/SpoT homolog) proteins using mycobacterial and streptococcal (p)ppGpp synthetase structures as models. The cytotoxic activity of some synthesized compounds was studied. Compounds 3c, f, g, k, r, and 3z displayed significant antiproliferative activities against all the cancer cell lines tested. Indolylquinazolinones 3b, 3e, and 3g showed a preferential suppression of the growth of rapidly dividing A549 cells compared to slower growing fibroblasts of non-tumor etiology.

Tandem C-C/C-N Bond Formation via Rh(III)-Catalyzed α-Fluoroalkenylation and Sequential Annulation of 2-Arylquinazolinones and gem-Difluorostyrenes

An efficient method of Rh(III)-catalyzed coupling reaction between 2-arylquinazolinones and gem-difluorostyrenes has been developed. In this work, two diverse structures of monofluoroalkenes and isoindolo[1,2-b]quinazolin-10(12H)-one derivatives were respectively synthesized by controlling the amount of additives (Ca(OH)₂ and AgNTf₂) to achieve controlled stepwise breaking of the C-F bonds of gem-difluorostyrenes. This reaction has the characteristics of a wide range of substrates and good functional group tolerance. Meanwhile, several control experiments were conducted and a plausible mechanism was proposed.

Tandem Reduction, Ammonolysis, Condensation, and Deamination Reaction for Synthesis of Benzothiadiazines and 1-(Phenylsulfonyl)-1H-benzimidazoles

A novel route for a SnCl₂-promoted tandem reduction, ammonolysis, condensation, and deamination reaction which uses nitrile and 2-nitro-N-phenylbenzenesulfonamide/N-(2-nitrophenyl)benzenesulfonamide to synthesize derivatives of benzothiadiazine/1-(phenylsulfonyl)-1H-benzimidazole has been developed. The method features convenient operation and good functional group tolerance. In addition, it employs unsensitive and inexpensive SnCl₂/i-PrOH as the reaction reagent and provides a direct approach for the synthesis of pharmaceutically important targets.

Recent advances and prospects in the organocatalytic synthesis of quinazolinones

Quinazolinone, a bicyclic compound, comprises a pyrimidine ring fused at 4´ and 8´ positions with a benzene ring and constitutes a substantial class of nitrogen-containing heterocyclic compounds on account of their frequent existence in the key fragments of many natural alkaloids and pharmaceutically active components. Consequently, tremendous efforts have been subjected to the elegant construction of these compounds and have recently received immense interest in synthetic and medicinal chemistry. The domain of synthetic organic chemistry has grown significantly over the past few decades for the construction of highly functionalized therapeutically potential complex molecular structures with the aid of small organic molecules by replacing transition-metal catalysis. The rapid access to this heterocycle by means of organocatalytic strategy has provided new alternatives from the viewpoint of synthetic and green chemistry. In this review article, we have demonstrated a clear presentation of the recent organocatalytic synthesis of quinazolinones of potential therapeutic interests and covered the literature from 2015 to date. In addition to these, a clear presentation and understanding of the mechanistic aspects, features, and limitations of the developed reaction methodologies have been highlighted.

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.

Photocatalyst-free visible-light-promoted quinazolinone synthesis at room temperature utilizing aldehydes generated in situ via C[double bond, length as m-dash]C bond cleavage

This is the first report on a facile tandem route for synthesizing quinazolinones at room temperature from various aminobenzamides and in situ-generated aldehydes. The latter was formed via C[double bond, length as m-dash]C bond cleavage, and the overall reaction proceeded using molecular oxygen as a clean oxidant in the absence of a photocatalyst. Visible light, which was indispensable for the entire course of the reaction, played multiple roles. It initially cleaved styrene to an aldehyde, then facilitated its cyclization with an o-substituted aniline, and finally promoted the dehydrogenation of the cyclized intermediate. The previous step provided the feedstock for the next step in the reaction, thereby preventing volatilization, oxidation, and polymerization of the aldehyde. Thus, the overall process is simple, environmentally benign, and economically feasible.

CuII-Catalyzed Coupling with Two Ynone Units by Selective Triple and Sigma C-C and C-H Bond Cleavages

We report a new copper-catalyzed [2 + 2 + 1] annulation process through the selective cleavage of sigma and triple C-C and C-H bonds using two ynone units. This new methodology involves breaking multiple chemical bonds in a single operation, including C≡C, C-C, C-H, and N-O. These high-value adducts lead to a diverse collection of synthetically challenging trisubstituted indolizines by the simultaneous engagement of different bond-breaking events and show excellent fluorescence in green aqueous solutions.

C-C Bond Cleavage Initiated Cascade Reaction of β-Enaminones: One-Pot Synthesis of 5-Hydroxy-1H-pyrrol-2(5H)-ones

An unprecedented C(CO)-C(Ar) bond cleavage of β-enaminones has been realized under mild and transition-metal-free conditions. The cascade transformation based on this C-C bond cleavage involves 1,3-O/C migration and aerobic hydroxylation and leads to various 5-hydroxy-1H-pyrrol-2(5H)-ones with broad functional group tolerance. The application of this methodology has been showcased by preparing 5-alkoxy-1H-pyrrol-2(5H)-one derivatives and a pyrrolo[2,1-a]isoquinolin-3-one derivative.

Recent advances in cyclization reactions of isatins or thioisatins via C–N or C–S bond cleavage

This review summarizes recent developments on cyclization reactions induced by the C–N or C–S bond cleavage of isatins or thioisatins in the last 5 years, which produce fused products instead of spiro compounds.

Rhodium(iii)-catalyzed annulation of 3-arylquinazolinones with alkynes via double C–H activation: an efficient route for quinolino[2,1-b]quinazolinones

An effective method for the synthesis of quinolino[2,1-b]quinazolinones has been described.

Switchable and efficient conversion of 2-amido-aryl oxazolines to quinazolin-4(3H)-ones and N-(2-chloroethyl)benzamides

Switchable chemoselective conversion of 2-amido-aryl oxazolines to quinazolin-4(3H)-ones or N-(2-chloroethyl)benzamides is achieved.

Base-promoted Lewis acid catalyzed synthesis of quinazoline derivatives

A one-pot protocol has been developed for the synthesis of quinazolinones from amide-oxazolines with TsCl via a cyclic 1,3-azaoxonium intermediate and 6π electron cyclization in the presence of a Lewis acid and base. The process is operationally simple and has a broad substrate scope. This method provides a unique strategy for the construction of quinazolinones.

Synthesis of quinazoin-4-ones through an acid ion exchange resin mediated cascade reaction

An interesting cascade reaction of N-(2-(4,5-dihydrooxazol-2-yl)phenyl)benzamide in the presence of an acid ion exchange resin is described. In this reaction, a range of substrates bearing various substituent groups are well compatible. This work provides a green and atom-economical alternative approach for the synthesis of quinazolin-4-ones in good yields.

Rh(iii)-catalyzed, hydrazine-directed C–H functionalization with 1-alkynylcyclobutanols: a new strategy for 1H-indazoles

Rh(iii)-catalyzed coupling of phenylhydrazines with 1-alkynylcyclobutanols was realized through a hydrazine-directed C–H functionalization and [4+1] annulation pathway.

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.

Synthesis of 3-(2-quinolyl) chromones from ynones and quinoline N-oxides via tandem reactions under transition metal- and additive-free conditions

The synthesis of 3-(2-quinolyl) chromones from ynones and quinoline N-oxides via a sequential [3+2] cycloaddition/ring-opening/O-arylation reaction under transition metal- and additive-free conditions is reported.

Ruthenium(ii)-catalyzed chemoselective deacylative annulation of 1,3-diones with sulfoxonium ylides via C-C bond activation

The first successful example of deacylative annulation of 1,3-diones with sulfoxonium ylides was achieved through Ru(ii)-catalyzed C-C bond activation. The excellent chemoselectivity and broad substrate scope render this method a practical and versatile approach for the preparation of (hetero)aryl and alkenyl substituted furans, which are valuable units in many biologically active compounds and functional materials. A preliminary mechanistic study reveals that this process involves a deacylative α-ruthenation to generate key alkyl Ru(ii) intermediates with the release of a benzoic acid fragment.

Quinazolinone Synthesis through Base-Promoted SNAr Reaction of ortho-Fluorobenzamides with Amides Followed by Cyclization

A transition-metal-free synthesis of quinazolin-4-ones by Cs2CO3-promoted SNAr reaction of ortho-fluorobenzamides with amides followed by cyclization in dimethyl sulfoxide has been developed. The present procedure can provide efficient synthetic methods for the formation of both 2-substituted and 2,3-disubstituted quinazolin-4-one rings depending on the use of easily available starting materials and an efficient, one-pot protocol for the synthesis of the marketed drug product of methaqualone.

Discovery of Quinazolin-4(3 H)-ones as NLRP3 Inflammasome Inhibitors: Computational Design, Metal-Free Synthesis, and in Vitro Biological Evaluation

NLRP3 inflammasome is an important therapeutic target for a number of human diseases. Herein, computationally designed series of quinazolin-4(3 H)-ones were synthesized using iodine-catalyzed coupling of arylalkynes (or styrenes) with O-aminobenzamides. The key event in this transformation involves the oxidative cleavage of the C-C triple/double bond and the release of formaldehyde. The reaction relies on the C-N bond formation along with the C-C bond cleavage under metal-free conditions. The nitro-substituted quinazolin-4(3 H)-one 2k inhibited NLRP3 inflammasome (IC₅₀ 5 μM) via the suppression of IL-1β release from ATP-stimulated J774A.1 cells.

Metal-Free Method for Direct Synthesis of Functionalized β-Ketoenamines

A new method for direct synthesis of β-ketoenamines was developed by a BF₃·OEt₂-catalyzed cyclization of 1-iodoalkyne and α-keto acid followed by an amine-mediated ring-opening in one pot. Its metal-free conditions allowed the easy synthesis of those products bearing the transition metal-sensitive functional groups. Its three-component process achieved wide range of functionalized products.

An effective preparation of both 1,3-diketones and nitriles from alkynones with oximes as hydroxide sources

An effective phosphine-catalyzed protocol has been established for the syntheses of 1,3-diketones and nitriles from alkynones with oximes as hydroxide surrogates. This method features the use of a phosphine catalyst, compatibility with various functional groups and ambient temperature, which makes this approach very practical. A plausible mechanism was proposed.

Construction of pyrazolone analogues via rhodium-catalyzed C–H activation from pyrazolones and non-activated free allyl alcohols

Highly efficient rhodium(iii) catalysis was developed for obtaining structurally divergent pyrazolone analogues from pyrazolones and non-activated free allyl alcohols.

High acidity cellulose sulfuric acid from sulfur trioxide: a highly efficient catalyst for the one step synthesis of xanthene and dihydroquinazolinone derivatives

A cellulose sulfonate catalyst (HS-cellulose sulfonate) with high stability, excellent catalytic activity and high acidity value (about 1.55 mmol g⁻¹) was successfully prepared by SO₃ gas phase sulfonation. The basic morphology and nanostructure of the catalyst were determined by HRTEM, XRD, IR, TG, etc. In addition, the catalyst was applied to the catalytic reaction of a dihydroquinazolinone derivative and a xanthene compound, and very valuable results were obtained. The development and preparation of cellulose sulfonate catalysts provide a good approach for the development and application of cellulose, and also an important application of green organic catalytic synthesis methodology.

The HS-cellulose sulfonate catalysed green and efficient one-step synthesis of xanthene and dihydroquinazolinone derivatives.