Copper-Catalyzed Synthesis of 2-Arylquinazolinones from 2-Arylindoles with Amines or Ammoniums

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.

Urea-rich porous organic polymer as a hydrogen bond catalyst for Knoevenagel condensation reaction and synthesis of 2,3-dihydroquinazolin-4(1H)-ones

In this research, a new urea-rich porous organic polymer (urea-rich POP) as a hydrogen bond catalyst was synthesized via a solvothermal method. The physiochemical properties of the synthesized urea-rich POP were investigated by using different analyses like Fourier transform infrared (FT-IR) spectroscopy, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), derivative thermogravimetry (DTG), energy-dispersive X-ray spectroscopy (EDS), elemental mapping analysis, X-ray diffraction analysis (XRD) and Brunauer-Emmett-Teller (BET) techniques. The preparation of urea-rich POP provides an efficacious platform for designing unique hydrogen bond catalytic systems. Accordingly, urea-rich POP, due to the existence of several urea moieties as hydrogen bond sites, has excellent performance as a catalyst for the Knoevenagel condensation reaction and multi-component synthesis of 2,3-dihydroquinazolin-4(1H)-ones.

Forced degradation study of baricitinib and structural characterization of its degradation impurities by high-resolution mass spectrometry and nuclear magnetic resonance spectroscopy

RATIONALE

Baricitinib (BARI), an inhibitor of Janus kinases 1 and 2 (JAK 1/2), is used for the treatment of rheumatoid arthritis and COVID-19. The present study focuses on establishing the forced degradation behavior of BARI under different degradation conditions (hydrolysis, oxidation, and photolysis) following International Council for Harmonization (ICH) guidelines of Q1A (R2)-Stability testing of new drug substances and products and Q1B-Photostability testing of new drug substances and products. This study helps in monitoring the quality and safety of BARI and its product development.

METHODS

Prior to conducting the study, the in silico degradation profile of BARI was predicted by Zeneth. Reversed-phase high-performance liquid chromatography employing a gradient program was used for the identification and separation of degradation impurities with an InertSustain C8 column (4.6 × 250 mm, 5 μm). The mobile phases used were 10 mM ammonium formate (pH 2.89) and acetonitrile. High-resolution mass spectrometry (HRMS) was used for the structural elucidation of the degradation impurities.

RESULTS

BARI was labile to hydrolytic (acidic, basic, and neutral) and photolytic degradation conditions which yielded 10 new degradation impurities and it was stable under oxidative (H2 O2 ) conditions. The separated degradation impurities were characterized by HRMS and the respective degradation pathways were proposed. The generated information helped to propose a mechanism for the formation of the degradation impurities. Additionally, one-dimensional and two-dimensional nuclear magnetic resonance spectroscopy were used for the characterization of two major degradation impurities.

CONCLUSION

The forced degradation study of BARI was carried out in accordance with ICH Q1A and Q1B guidelines, which resulted in the formation of 10 new degradation impurities. In our analysis, three degradation impurities were matching with the Zeneth predictions. In silico tools, DEREK Nexus® and SARAH Nexus®, were used for predicting the toxicity and mutagenicity of BARI and its degradation impurities. Overall, this study sheds light on BARI's safety monitoring and storage circumstances.

Three-Component Ring-Expansion Reaction of Indoles Leading to Synthesis of Pyrrolo[2,3-c]quinolines

Herein, we have developed an atom- and step-economic three-component cascade reaction that enables a modular platform for the synthesis of pyrrolo[2,3-c]quinoline compounds through ring-expansion/cyclization by way of novel N1-C2 cleavage of indoles. The metal-free catalytic system exhibits a broad functional group tolerance.

Palladium-Catalyzed Tandem Nucleophilic Addition/C-H Functionalization of Anilines and Bromoalkynes for the Synthesis of 2-Phenylindoles

A novel and efficient palladium-catalyzed annulation of anilines with bromoalkynes for the synthesis of 2-phenylindoles has been described. This approach features excellent regio- and stereoselectivities and good functional group tolerance. Preliminary mechanistic studies indicate that anilines undergo anti-nucleophilic addition to bromoalkynes to generate (Z)-N-(2-bromo-1-phenylvinyl) anilines, followed by sequential C-H functionalization to deliver different substituted 2-phenylindoles. This method provides potential applications for the construction of various biologically active compounds.

Synthesis of benzo[b][1,5]diazocin-6(5H)-one derivatives via the Cu-catalysed oxidative cyclization of 2-aryl-1H-indoles with 1,1-enediamines

A novel protocol for the synthesis of highly functionalized benzo[b][1,5]diazocin-6(5H)-one derivatives (BDCOs, 4 and 5) from 2-aryl-1H-indoles and 1,1-enediamines was developed via a complex cascade of reactions including regioselective free radical oxidation, the 1,2-addition of imine, imine-enamine tautomerization, intramolecular cyclization, and ring expansion. The cascade reaction was enabled by refluxing a mixture of two substrates in the presence of di-tert-butyl peroxide (DTBP) as an oxidant and anhydrous CuI as a catalyst in toluene under argon protection. Consequently, a series of BDCOs (4 and 5) were synthesized with high regioselectivity in good yield. This protocol can be used for the synthesis of functionalized BDCOs via a one-pot oxidative annulation reaction rather than a multi-step reaction, which is suitable for both combinatorial and parallel syntheses of BDCOs.

Late-stage diversification of indole skeletons through nitrogen atom insertion

Compared with peripheral late-stage transformations mainly focusing on carbon-hydrogen functionalizations, reliable strategies to directly edit the core skeleton of pharmaceutical lead compounds still remain scarce despite the recent flurry of activity in this area. Herein, we report the skeletal editing of indoles through nitrogen atom insertion, accessing the corresponding quinazoline or quinoxaline bioisosteres by trapping of an electrophilic nitrene species generated from ammonium carbamate and hypervalent iodine. This reactivity relies on the strategic use of a silyl group as a labile protecting group that can facilitate subsequent product release. The utility of this highly functional group-compatible methodology in the context of late-stage skeletal editing of several commercial drugs is demonstrated.

Indole Editing Enabled by HFIP-Mediated Ring-Switch Reactions of 3-Amino-2-Hydroxyindolines

This work reports the novel reactivity of hemiaminal as a precursor for indole editing at the multi-site. The HFIP-promoted indole editing of indoline hemiaminals affords 2-arylindoles through a ring-switch sequence. The key to success of this transformation is to use a cyclic hemiaminal as an α-amino aldehyde surrogate under transient tautomeric control. This transformation features mild reaction conditions and good yields with broad functional group tolerance. The utility of this transformation is presented through the one-pot protocol and the synthesis of isocryptolepine.

Rhodium(III)-Catalyzed Synthesis of Quinazolin-4(3H)-ones with N-Methoxyamides as Synthesis Reagents

A practical method to synthesize quinoxalinones via intra/intermolecular amination using rhodium as the catalyst was developed. A wide variety of quinoxalinones were prepared from N-methoxybenzamides in moderate to excellent yields. Gram-scale reactions were also achieved, highlighting the synthetic importance of this new transformation.

Brønsted-Acid-Promoted Selective C2-N1 Ring-Expansion Reaction of Indoles toward Cyclopenta[b]quinolines

A novel Brønsted-acid-promoted selective C2-N1 ring-expansion reaction of indoles has been developed that provides a rapid and efficient protocol for the preparation of fused quinolines. A variety of corresponding quinolines were obtained in high yields. Controlled experiments revealed that C2-spiroindolenines might be intermediates of this C2-N1 ring-expansion reaction. The notable advantages of this process include excellent yields, good functional group tolerance, and operational simplicity.

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.

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.

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.

α-Hydroxy acid as an aldehyde surrogate: metal-free synthesis of pyrrolo[1,2-a]quinoxalines, quinazolinones, and other N-heterocycles via decarboxylative oxidative annulation reaction

A metal-free and efficient procedure for the synthesis of pyrrolo[1,2-a]quinoxalines, quinazolinones, and indolo[1,2-a]quinoxaline has been developed. The key features of our method include the in situ generation of aldehyde from α-hydroxy acid in the presence of TBHP (tert-butyl hydrogen peroxide), and further condensation with various amines, followed by intramolecular cyclization and subsequent oxidation to afford the corresponding quinoxalines, quinazolinones derivatives in moderate to high yields.

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.

Copper-mediated synthesis of quinazolin-4(3H)-ones from N-(quinolin-8-yl)benzamide and amidine hydrochlorides

An efficient copper-mediated tandem C(sp²)–H amination to provide quinazolinones from N-(quinolin-8-yl)benzamide and amidine hydrochlorides has been developed.

Visible-light-induced oxidative ring expansion of indoles with amidines

An efficient and mild visible-light-enabled reaction involving the oxidative ring expansion of indoles with amidines in the aqueous phase at room temperature is developed.

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.

A straightforward TBHP-mediated synthesis of 2-amidobenzoic acids from 2-arylindoles and their antimicrobial activity

Synthesis of 2-amidobenzoic acids has been achieved through TBHP-mediated oxidative ring opening of 2-arylindoles. The synthesized compounds have been evaluated for their antimicrobial activity.

Copper-catalyzed synthesis of 2,3-disubstituted quinazolin-4(3H)-ones from benzyl-substituted anthranilamides

An efficient, practical approach to the copper-catalyzed synthesis of 2,3-disubstituted quinazolin-4(3H)-one derivatives is described. The preparation involves treatment of benzyl amines with benzyl anthranilamides in the presence of Cu(OAc)2 and tetra-n-butylammonium bromide (TBAB).

"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.

Solvent-Dependent Copper-Catalyzed Indolyl C3-Oxygenation and N1-Cyclization Reactions: Selective Synthesis of 3 H-Indol-3-ones and Indolo[1,2- c]quinazolines

A simple and practical procedure for the selective preparation of 3 H-indol-3-one and indolo[1,2- c]quinazoline derivatives through copper-catalyzed aerobic oxygenation and intramolecular cyclization reactions of 2-(2-amidoaryl)-1 H-indoles in the presence of acid has been disclosed. Interestingly, the reaction outcomes are exclusively dependent on the reaction medium employed. With DMF as the solvent, the amide moiety of indole substrates could act as an auxiliary to enable the indole's oxygenation reaction with molecular oxygen from air as the oxidant to give 3 H-indol-3-one derivatives in a highly selective manner. On the other hand, when the reactions were performed in 1,4-dioxane, the amide moiety switched to participate in an intramolecular indolyl N1-cyclization to afford indolo[1,2- c]quinazolines as the predominating products.

Cooperation of copper and dioxygen for the site-selective construction of benzo[1,5]diazocin-6(5H)-ones from indoles and enaminone analogues

A new route for the preparation of benzo[1,5]diazocines from indoles and enaminone analogues is described.

Efficient synthesis of 2-arylquinazolin-4-amines via a copper-catalyzed diazidation and ring expansion cascade of 2-arylindoles

Copper-catalyzed synthesis of 2-arylquinazolin-4-amines from readily available 2-arylindoles and TMSN₃ has been developed.

Palladium-catalyzed tandem addition/cyclization in aqueous medium: synthesis of 2-arylindoles

Pd-catalyzed tandem reaction of potassium aryltrifluoroborates with nitriles for the synthesis of 2-arylindoles in aqueous medium.

Copper-catalyzed construction of eight-membered rings via oxidative ring expansion and intermolecular cyclization sequencing of indoles with amidines: efficient synthesis of benzo[1,3,5]triazocin-6(5H)-ones

Novel and efficient synthesis of eight-membered nitrogen heterocycles in one pot by copper-catalyzed oxidative ring expansion and intermolecular cyclization sequencing of indoles with amidines has been described.

Preparation, characterization and catalytic application of nano-Fe3O4-DOPA-SnO2 having high TON and TOF for non-toxic and sustainable synthesis of dihydroquinazolinone derivatives

A novel class of heterogeneous magnetically separable nano catalysts was designed by encapsulating SnO₂ on nano-Fe₃O₄-DOPA. And is applied for the synthesis of dihydroquinazolinone derivatives.