Camphorsulfonic Acid Catalyzed One-Pot Three-Component Reaction for the Synthesis of Fused Quinoline and Benzoquinoline Derivatives

Recent advancement in the synthesis of quinoline derivatives via multicomponent reactions

The synthesis of quinoline derivatives through multicomponent reactions (MCRs) has emerged as an efficient and versatile strategy in organic synthesis. MCRs offer the advantage of constructing complex molecular architectures in a single step, utilising multiple starting materials in a convergent manner. This review provides an overview of recent advancements in the field of quinoline synthesis via MCRs. Various MCRs, such as the Povarov reaction, the Gewald reaction, and the Ugi reaction have been successfully employed for the synthesis of diverse quinoline scaffolds. These methodologies not only showcase high atom economy but also allow the incorporation of structural diversity into the final products. The versatility of MCRs enables the introduction of functional groups and substitution patterns tailored to specific applications. This review highlights the significance of quinoline derivatives in medicinal chemistry, materials science, and other interdisciplinary areas. The continuous innovation and development of novel MCR-based approaches for quinoline synthesis hold great promise for the rapid and efficient generation of valuable compounds with a wide range of biological and physicochemical properties.

One-Step Synthesis of 7-Bromobenzo[c]chromeno[4,3,2-gh]phenanthridines through a Sequential Bromination/Cyclization/Aromatization Reaction Using N-Bromosuccinimide (NBS)

Herein, metal- and oxidant-free synthesis of 7-bromobenzo[c]chromeno[4,3,2-gh]phenanthridines is reported using N-bromosuccinimide. Sequential regioselective bromination, intramolecular ring cyclization, and aromatization reactions occur in a single step through a successive radical-catalyzed pathway. The mechanistic pathway for the cyclization is supported by a DFT study. Selective bromination in the fully aromatic skeleton is accomplished without involving additional aromatic electrophilic ring bromination. As a synthetic application, the Suzuki coupling reaction of compound 5a with boronic acid is reported to get compound 8a. Aggregation-induced emission of one of the synthesized compounds (5h) is also investigated in THF/hexane solvent along with concentration-dependent emission spectroscopy.

Recent advances on synthesis and biological activities of C-17 aza-heterocycle derived steroids

Steroids modification for improving their biological activities is one of the most efficient and fruitful methods to develop novel medicines. Steroids with aza-heterocycles attaching to the C-17 owing various biological activities have received great attentions and some of the compounds are developed successfully as drugs. In this review, the research of the syntheses and biological activities of steroids bearing various aza-heterocycles published in the last 8 years is assembled, and some important structure-activity relationships (SARs) of active compounds are presented. According to the analysis of the literatures and our experiences in this field, the potential of aza-heterocyclic steroids as medicinal drugs is proposed.

Study and application of graphene oxide in the synthesis of 2,3-disubstituted quinolines via a Povarov multicomponent reaction and subsequent oxidation

The carbocatalyzed synthesis of 2,3-disubstituted quinolines is disclosed. This process involved a three-component Povarov reaction of anilines, aldehydes and electron-enriched enol ethers, which gave the substrate for the subsequent oxidation. Graphene oxide (GO) was exploited as a heterogeneous, metal-free and sustainable catalyst for both transformations. The multicomponent reaction proceeded under simple and mild reaction conditions, exhibited good functional group tolerance, and could be easily scaled up to the gram level. A selection of tetrahydroquinolines obtained was subsequently aromatized to quinolines. The multistep synthesis could also be performed as a one-pot procedure. Investigation of the real active sites of GO was carried out by performing control experiments and a by full characterization of the carbon material by X-ray photoelectron spectroscopy (XPS) and solid-state nuclear magnetic resonance (ssNMR).

DMSO-assisted environmentally benign synthesis of benzo[c]-chromeno[4,3,2-gh]phenanthridines by remote oxidative hetero cross-coupling cyclization and aromatization reaction

An unprecedented metal-free and catalyst-free synthesis of benzo[c]chromeno[4,3,2-gh]phenanthridine derivatives, a class of 1,6-diheterophenalenoid heterocycle, is reported for the first time. The oxidative cross-coupling reaction for the remote cyclization is achieved through the in situ generated o-quinone methide intermediate followed by an electrocyclic ring closure reaction. The aromatization of the cyclohexane ring is achieved by sequential H shift, hydroxylation, and elimination reaction. DMSO-assisted concomitant cyclization and aromatization reactions are also disclosed for the first time.

A Review on Metal-Organic Frameworks as Congenial Heterogeneous Catalysts for Potential Organic Transformations

Metal-organic frameworks (MOFs) have emerged as versatile candidates of interest in heterogeneous catalysis. Recent research and developments with MOFs positively endorse their role as catalysts in generating invaluable organic compounds. To harness the full potential of MOFs in value-added organic transformation, a comprehensive look at how these materials are likely to involve in the catalytic processes is essential. Mainstays of MOFs such as metal nodes, linkers, encapsulation materials, and enveloped structures tend to produce capable catalytic active sites that offer solutions to reduce human efforts in developing new organic reactions. The main advantages of choosing MOFs as reusable catalysts are the flexible and robust skeleton, regular porosity, high pore volume, and accessible synthesis accompanied with cost-effectiveness. As hosts for active metals, sole MOFs, modified MOFs, and MOFs have made remarkable advances as solid catalysts. The extensive exploration of the MOFs possibly led to their fast adoption in fabricating new biological molecules such as pyridines, quinolines, quinazolinones, imines, and their derivatives. This review covers the varied MOFs and their catalytic properties in facilitating the selective formation of the product organic moieties and interprets MOF’s property responsible for their elegant performance.

Regioselective synthetic approach for key precursors of 6-aryl benzo[c]phenanthridin-10-ol derivatives: A useful compound for selective chromogenic recognition of fluoride

A regioselective synthetic strategy for 6-aryl-8,9-dihydro-benzo[c]phenanthridine-10(7H)-ones (4) is accomplished using a one-pot four-component reaction by fine-tuning of reaction temperature. DMSO is excellently used as a reactant-cum-solvent to introduce carbonyl functionality...

An environmentally benign regioselective synthesis of 2-benzyl-4-arylquinoline derivatives using aryl amines, styrene oxides and aryl acetylenes

A novel and an expedient metal- and solvent-free synthesis of a wide variety of 2-benzyl-4-arylquinoline derivatives is described from readily available aryl amines, styrene oxides and aryl acetylenes in the presence of 10 mol% molecular iodine. This domino reaction occurs under metal- and solvent-free conditions at 120 °C, which avoids the usage of metal catalyst and as a consequence generation of metal waste. The salient features of this methodology are the use of simple starting materials, ease of handling, high regioselectivity, shorter reaction time, atom-economical, step-economical, the formation of one C-N and two C-C bonds and a wide range of functional groups tolerance.

Metal-free synthesis of quinoline-2,4-dicarboxylate derivatives using aryl amines and acetylenedicarboxylates through a pseudo three-component reaction

An efficient, useful and one-pot protocol for the synthesis of quinoline-2,4-dicarboxylate scaffolds is accomplished from aryl amines and dimethyl/diethyl acetylenedicarboxylates using 20 mol% molecular iodine as a catalyst in acetonitrile at 80 °C. In addition, the mechanistic explanation for the formation of the desired products is disclosed. The pivotal role of molecular iodine in the formation of the major products, diester quinoline derivatives, and the minor product, triesters, in two cases is described in the mechanism. The notable advantages of this method are non-involvement of a metal catalyst, avoiding of metal contamination in the final product as well as waste generation, use of a low cost and eco-friendly catalyst, ease of handling, high regioselectivity, shorter reaction time, the formation of one C-N and two C-C bonds and a broad substrate scope with good yields.

Benzoquinoline Derivatives: A Straightforward and Efficient Route to Antibacterial and Antifungal Agents

We report here the design, synthesis, experimental and in silico evaluation of the antibacterial and antifungal activity of some new benzo[f]quinoline derivatives. Two classes of benzo[f]quinolinium derivatives—(benzo[f]quinolinium salts (BQS) and pyrrolobenzo[f]quinolinium cycloadducts (PBQC)—were designed and obtained in two steps via a direct and facile procedure: quaternization followed by a cycloaddition reaction. The synthesized compounds were characterized by elemental and spectral analysis (FT-IR, ¹H-NMR, ¹³C-NMR). The antimicrobial assay reveals that the BQS salts have an excellent quasi-nonselective antifungal activity against the fungus Candida albicans (some of them higher that the control drug nystatin) and very good antibacterial activity against the Gram positive bacterium Staphylococcus aureus. The PBQC compounds are inactive. Analysis of the biological data reveals interesting SAR correlations in the benzo[f]quinolinium series of compounds. The in silico studies furnished important data concerning the pharmacodynamics, pharmacokinetics and ADMET parameters of the BQS salts. Studies of the interaction of each BQS salt 3a–o with ATP synthase in the formed complex, reveal that salts 3j, 3i, and 3n have the best fit in a complex with ATP synthase. Study of the interaction of each BQS salt 3a-o with TOPO II in the formed complex reveals that salts 3j and 3n have the best-fit in complex with TOPO II. The in silico ADMET studies reveal that the BQS salts have excellent drug-like properties, including a low toxicity profile. Overall, the experimental and in silico studies indicate that compounds 3e and 3f (from the aliphatic series), respectively, and 3i, 3j and 3n (from the aromatic series), are promising leading drug candidates.

Copper(ii) triflate catalyzed three-component reaction for the synthesis of 2,3-diarylquinoline derivatives using aryl amines, aryl aldehydes and styrene oxides

An efficient and expedient synthetic protocol is reported for the synthesis of 2,3-diarylquinoline derivatives from readily available aryl amines, aryl aldehydes and styrene oxides using 10 mol% copper(ii) triflate by employing three-component reaction.

Dissecting pharmacological effects of chloroquine in cancer treatment: interference with inflammatory signaling pathways

Chloroquines are 4-aminoquinoline-based drugs mainly used to treat malaria. At pharmacological concentrations, they have significant effects on tissue homeostasis, targeting diverse signaling pathways in mammalian cells. A key target pathway is autophagy, which regulates macromolecule turnover in the cell. In addition to affecting cellular metabolism and bioenergetic flow equilibrium, autophagy plays a pivotal role at the interface between inflammation and cancer progression. Chloroquines consequently have critical effects in tissue metabolic activity and importantly, in key functions of the immune system. In this article, we will review the work addressing the role of chloroquines in the homeostasis of mammalian tissue, and the potential strengths and weaknesses concerning their use in cancer therapy.

Choline Chloride-Based Deep Eutectic Systems in Sequential Friedländer Reaction and Palladium-Catalyzed sp3 CH Functionalization of Methyl Ketones

A volatile organic solvent-free and choline chloride (ChCl)-based deep eutectic system (DES)-mediated sp³-CH functionalization of acetophenones 1 with benzyl alcohols 2 to the corresponding α, β-saturated ketones 3 is accounted for. The domino dehydrogenation-aldol condensation (hydrogenation borrowing concept) has been successfully attempted with palladium-tetrakis(triphenylphosphine) [Pd(PPh₃)₄] catalyst-xantphos ligand combination. Furthermore, a sequential Friedländer reaction of 2-aminobenzophenone 4 and palladium-catalyzed α-alkylation of the quinolinyl methyl ketone with benzyl alcohols 2 in ChCl-based DES have been successfully investigated. The C-C bond formation through sp³-CH functionalization involves a wide scope of the substrates, high atom efficiency, chemoselectivity, and environmentally friendly strategy.

Synthesis of indole-cycloalkyl[b]pyridine hybrids via a four-component six-step tandem process

The one-pot four-component reaction of 3-(1H-indol-3-yl)-3-oxopropanenitriles, aromatic aldehydes, cycloalkanones and ammonium acetate occurred via a six-step tandem Knoevenagel condensation–nucleophilic addition to carbonyl–Michael addition–N-cyclization–elimination–air oxidation sequence to afford structurally intriguing indole–cycloalkyl[b]pyridine-3-carbonitrile hybrid heterocycles in excellent yields.

Substrate selective synthesis of indole, tetrahydroquinoline and quinoline derivatives via intramolecular addition of hydrazones and imines

A transition-metal-free, substrate selective synthesis of 2,3-diaryl indoles, 4-hydrazono-tetrahydroquinolines and substituted quinolines has been developed.