Copper(II) catalyzed expeditious synthesis of furoquinoxalines through a one-pot three-component coupling strategy

Unraveling the access to the regioselective synthesis of highly functionalized pyranopyrazoles using an ionic liquid catalyst

An efficient and green strategy for the regioselective synthesis of highly functionalized pyranopyrazole via one-pot condensation of 3-methyl-1-phenyl-5-pyrazolone or EAA and hydrazine hydrate, substituted aromatic aldehydes with NMSM [(E)-N-Methyl-1-(methylthio)-2-nitro-ethenamine] in the existence of IL [(EMIM)Ac] as catalyst with solvent-free condition (SFC) is described. This domino protocol produces biologically substantial heterocycles through Knoevenagel condensation proceeded by Michael addition and O-cyclization with an eradication of methanethiol group, which create the one stereo-center and creation of "C-C, C-N, C-O, C=C, C=N, bonds." The final product is produced by exceptionally easy filtering after the reaction mass was triturated with ethanol. The strategy's noteworthy features include the use of biodegradable IL catalyst, excellent to exceptional yield with rapid reaction times, applicability to a wide range of substrate, clear reaction profile, and straightforward workup process.

Porous Organic Polymer Supported Nano Ruthenium Catalysts for Cascade Aromatization of Quinoxalin-2(1H)-one and C-H Annulation with Alkynes

Selective C-H annulation with alkynes is one of the most useful tools to synthesize heterocycles. Herein, we developed novel porous organic polymers supported ruthenium (POPs-Ru) as highly efficient catalysts for cascade aromatization of quinoxalin-2(1H)-one and C-H annulation with alkynes. Both terminal and internal alkynes were successfully transferred to furo[2,3-b]quinoxaline derivatives with good functional group tolerance and high regioselectivity by using POPs-Ru catalysts. Furthermore, the catalyst exhibited high activity and could be reused at least five times without obvious deactivation of this coupling reaction. This study offers an important platform for the immobilization of molecular metal catalysts for C-H functionalization.

Copper Catalyzed Synthesis of Heterocyclic Molecules via C-N and C-O Bond Formation under Microwaves: A Mini-Review

Heterocyclic moieties play a significant role in the field of drug discovery. C-N and C-O bond formation reactions are the primary synthetic sequence for the generation of heterocyclic molecules. The generation of C-N and C-O bonds involves the use of mostly Pd or Cu catalysts although other transition metal catalyst's are also involved. However, in C-N and C-O bond formation reactions, several problems were faced such as catalytic systems containing costly ligands, lack of substrate scope, lots of waste generation, and high temperature conditions. So it is imperative to uncover new eco-friendly synthetic strategies. In view of enormous drawbacks, it is important to develop an alternate microwave-assisted synthesis of heterocycles via C-N and C-O bond formation, which provides a short reaction time, tolerance for functional groups, and less waste production. Numerous chemical reactions have been accelerated using microwave irradiation which provides a cleaner reaction profile, lower energy consumption, and higher yields. This review article highlights a comprehensive overview on the potential application of microwave assisted synthetic routes for the synthesis of diverse heterocycles via mechanistic pathways covering the year ranges from 2014 to 2023, along with possible biological interests.

Bromine-Promoted One-Pot Furo[b]annulation and α-C(sp2)-Thiomethylation Cascade of (E)-3-Styrylquinoxalin-2(1H)-ones with Dimethyl Sulfoxide

A new process has been developed for the bromine-promoted sequential (sp²)C = (sp²)C bond functionalization of (E)-3-styrylquinoxalin-2(1H)-ones and furo[b]annulation via the 5-exo-cyclization in dimethyl sulfoxide (DMSO). The reaction represents a novel strategy for the synthesis of 2-aryl-3-(methylthio)furo[2,3-b]quinoxalines and involves 3-(1,2-dibromo-2-arylethyl)quinoxalin-2(1H)-ones and 2-arylfuro[2,3-b]quinoxalines as key intermediates. Furthermore, DMSO was converted to dimethyl sulfide in situ, which served as the methylthiolation reagent in the reaction. This protocol constitutes an efficient and convenient method for the annulation and methylthiolation of (E)-3-styrylquinoxalin-2(1H)-ones bearing a wide range of functional groups in high yields at room temperature.

Convenient synthesis of benzothiazinoisoindol-11-ones and benzoindenothiazin-11-ones, and antimicrobial testing thereof

Benzo[5,6][1,4]thiazino[3,4-a]isoindol-11-ones 5a-t and benzo[b]indeno[1,2-e][1,4]thiazin-11(10aH)-ones 6a-e were synthesized conveniently via cyclocondensation of 2-bromo-2-(2/3-substitutedphenyl)-1H-indene-1,3(2H)-diones and 2-aminobenzenethiols in freshly dried ethanol with 70-85% yields. The synthesized derivatives were well characterized by employing different spectral techniques (FTIR, ¹H & ¹³C NMR and HRMS) and X-ray crystallographic analysis. Further, all the reported compounds were tested for their antibacterial and antifungal activities using Ciprofloxacin and Fluconazole as standard drugs, respectively. The results of antimicrobial evaluation revealed that compounds 5o and 5t displayed remarkable inhibitory activity against B. subtilis, S. aureus, P. aeruginosa and A. niger with MIC values in the range of 0.0141-0.0283 µmol/mL, whereas 5j was found active against E. coli and C. albicans with MIC values of 0.0286 µmol/mL and 0.0143 µmol/mL, respectively. Additionally, among all the benzo[b]indeno[1,2-e][1,4]thiazin-11(10aH)-ones, 6c exhibited excellent inhibition against all the tested bacterial and fungal strains with MIC values ranging from 0.0143 to 0.1145 µmol/mL. Structure activity relationships were also established for all the tested benzo[5,6][1,4]thiazino[3,4-a]isoindol-11-ones 5a-t.

Synthesis and characterization of Fe3O4@Sal@Cu as a novel, efficient and heterogeneous catalyst and its application in the synthesis of 2-amino-4H-chromenes

This research paper presents the synthesis and characterization of the magnetic nanoparticle, Fe₃O₄@Sal@Cu, [Fe₃O₄@Si-CH₂-CH₂-CH₂-NH-NH-CO-N=CH-(2-HO-C₆H₄-)@Cu] as a green and retrievable catalyst. This catalyst was characterized by FTIR, XRD, EDX and TGA analyses. In addition, the catalytic activity of this new catalyst was investigated for the synthesis of 2-amino 4H-chromenes by producing good-to-excellent yields under mild reaction conditions. The other advantages of the developed nanocatalyst are its ecofriendliness, being easy to handle, high reusability and being magnetically separable. The synthesis of some new derivatives of 2-amino-4H-chromenes in the presence of this nanocatalyst is also reported.

Para toluenesulfonic acid-catalyzed one-pot, three-component synthesis of benzo[5,6]chromeno[3,2-c]quinoline compounds in aqueous medium

A new series of benzo[5,6]chromeno[3,2-c]quinoline derivatives were successfully synthesized using various arylglyoxal monohydrates, quinoline-2,4-dione, and β-naphthol in H2O:EtOH (2:1) as a green solvent in the presence of catalytic amounts p-toluenesulfonic acid as a mild catalyst under reflux conditions with high yields (83–92%). The reaction conditions were optimized in different solvents at variable thermal conditions, and the optimized reaction condition for this synthesis has been reported. The structures of all new products were defined by 1H-NMR, 13C-NMR, FT-IR, mass spectral data, and HRMS.

Biradical o-iminobenzosemiquinonato(1-) complexes of nickel(ii): catalytic activity in three-component coupling of aldehydes, amines and alkynes

The six-coordinated bis-o-iminosemiquinone complex, NiL2 BIS, in which LBIS is the o-iminosemiquinone 1-electron oxidized form of the tridentate o-aminophenol benzoxazole-based ligand H2LBAP, was synthesized and characterized. The crystal structure of the complex reveals octahedral geometry with a NiN4O2 coordination sphere in which Ni(ii) has been surrounded by two tridentate LBIS ligands. This compound exhibits (S Ni = 1) with both spin and orbital contribution to the magnetic moment and antiferromagnetic coupling between two electrons on two LBIS ligands which results in a triplet spin ground state (S = 1). The electronic transitions and the electrochemical behavior of this open-shell molecule are presented here, based on experimental observations and theoretical calculations. The electrochemical behavior of NiL2 BIS was investigated by cyclic voltammetry and indicates ligand-centered redox processes. Three-component coupling of aldehydes, amines and alkynes (A3-coupling) was studied in the presence of the NiL2 BIS complex, and the previously reported four-coordinated bis-o-iminosemiquinone NiL2 NIS. Furthermore, among these two o-iminobenzosemiquinonato(1-) complexes of Ni(ii) (NiL2 NIS and NiL2 BIS), NiL2 NIS was found to be an efficient catalyst in A3-coupling at 85 °C under solvent-free conditions and can be recovered and reused for several cycles with a small decrease in activity.

Recent Advances in Microwave-Assisted Copper-Catalyzed Cross-Coupling Reactions

Cross-coupling reactions furnishing carbon–carbon (C–C) and carbon–heteroatom (C–X) bond is one of the most challenging tasks in organic syntheses. The early developed reaction protocols by Ullmann, Ullman–Goldberg, Cadiot–Chodkiewicz, Castro–Stephens, and Corey–House, utilizing elemental copper or its salts as catalyst have, for decades, attracted and inspired scientists. However, these reactions were suffering from the range of functional groups tolerated as well as severely restricted by the harsh reaction conditions often required high temperatures (150–200 °C) for extended reaction time. Enormous efforts have been paid to develop and achieve more sustainable reaction conditions by applying the microwave irradiation. The use of controlled microwave heating dramatically reduces the time required and therefore resulting in increase in the yield as well as the efficiency of the reaction. This review is mainly focuses on the recent advances and applications of copper catalyzed cross-coupling generation of carbon–carbon and carbon–heteroatom bond under microwave technology.

Arylacetylenes as two-carbon synthons: synthesis of eight-membered rings via C[triple bond, length as m-dash]C bond cleavage

The first synthesis of eight-membered N-containing heterocycles by oxidative bicyclization/ring extension of arylacetylenes and aryl amines has been achieved. This protocol uses arylacetylene as an unusual two-carbon synthon by incorporating the two parts of the cracked C[triple bond, length as m-dash]C bond into the final product, which provides a new method for using arylacetylenes as two-carbon synthons and further enriches C[triple bond, length as m-dash]C bond cleavage methodology. Moreover, this multi-component reaction can provide diverse fused elegant eight-membered N-heterocycles under mild conditions with wide substrate scopes.

Copper-Catalyzed, Ceric Ammonium Nitrate Mediated N-Arylation of Amines

Cu-Catalyzed, ligand and base free cross-coupling of aryl boronic acids with primary and secondary amines has been reported. This 'Chan-Evans-Lam' reaction has revealed that at room temperature, catalytic copper(II) acetate and ceric ammonium nitrate (CAN) as an oxidant, N-arylation can result in an effective C-N bond formation. This air stable, practical, robust protocol enables a variety of functional group tolerance on both boronic acid and amine partners.

Catalyst free, C-3 functionalization of imidazo[1,2-a]pyridines to rapidly access new chemical space for drug discovery efforts

Multicomponent reactions (MCRs) are robust tools for the rapid synthesis of complex, small molecule libraries for use in drug discovery and development. By utilizing MCR chemistry, we developed a protocol to functionalize the C-3 position of imidazo[1,2-a]pyridine through a three component, decarboxylation reaction involving imidazo[1,2-a]pyridine, glyoxalic acid, and boronic acid.

Cu(OTf)2 loaded protonated trititanate nanotubes catalyzed reaction: a facile method for the synthesis of furo[2,3-b]quinoxalines

An efficient method is developed for the synthesis of furo[2,3-b]quinoxalines via one-pot three-component reaction of o-phenylenediamine, ethylglyoxalate and phenylacetylenes.

In(OTf)3 assisted synthesis of β-carboline C-3 tethered imidazo[1,2-a]azine derivatives

Synthesis of β-carboline based natural products and synthetic derivatives is one of the frontier areas of research owing to their medicinal properties.

Aldehyde–alkyne–amine (A3) coupling catalyzed by a highly efficient dicopper complex

A dicopper(i) complex was developed as highly efficient catalyst for A³ coupling reactions, which led to the formation of propargylamines.