Multicomponent reactions and ionic liquids: a perfect synergy for eco-compatible heterocyclic synthesis

Divergent synthesis of dual 1,4-dihydropyridines with different substituted patterns from enaminones and aldehydes through domino reactions

A concise and efficient protocol for the regioselective synthesis of dual 1,4-dihydropyridines with several substituted patterns has been developed from a cascade cyclization of enaminones and aldehydes in different media (EtOH/CH₃CN). The one-pot cascade reaction involves at least five reactive sites and generates multiple C–C and C–N bonds. The established protocol explores the chemistry of enaminones by employing their three reactive sites. The method has several advantages including mild conditions, operational simplicity, and high bond-forming efficiency. It may offer promise in a variety of biochemical applications.

A concise and efficient protocol for the regioselective synthesis of dual 1,4-dihydropyridines with several substituted patterns has been developed from a cascade cyclization of enaminones and aldehydes in different media (EtOH/CH₃CN).

1,3-Di-n-butylimidazolium tribromide [BBim]Br3: An efficient recyclable catalyst mediated synthesis of N-substituted azepines and their biological evaluation-interaction study with human serum albumin

A majority of previously reported methods suffer from insufficient yields as well as more complicated experimental procedures, a smaller amount of isolated yields involving time-consuming and tiresome work-up with the use of metal catalyst and restricted scope of substrates. To overcome these issues, an environmentally benign, ionic liquid endorsed multi-component protocol to N-substituted azepines has been exploited by means of coupling aromatic amines, dimethyl/diethyl acetylene dicarboxylate, 2,5-dimethoxytetrahydrofuran using 1,3-Di-n-butylimidazolium tribromide [BBim]Br₃. The catalyst can be recycled and reused for subsequent reactions. The reactivated ionic liquid could be further reused twice as an accelerator All the synthesized compounds were further screened for their antimicrobial properties against three gram positive, four gram negative, and five fungal strains with chloromycin, norflaxacin, and fluconazole as reference drugs. Most of the tested compounds presented significant potency, especially, compound 4e displayed significant antibacterial activity (MIC=1-16μg/mL) whereas compound 4k showed momentous antifungal efficacy (MIC=2-32μg/mL). In addition binding behavior of compound 4e was investigated by binding study between calf thymus DNA and compound 4e by UV-Visible absorption spectroscopy and further research about HSA interactions were carried out. The observed wavelength showed a constancy thus revealing the occurrence of non-covalent π-π stacking interactions of compound 4e and HSA.

Synergy Effects in the Chemical Synthesis and Extensions of Multicomponent Reactions (MCRs)-The Low Energy Way to Ultra-Short Syntheses of Tailor-Made Molecules

Several novel methods, catalysts and reagents have been developed to improve organic synthesis. Synergistic effects between reactions, reagents and catalysts can lead to minor heats of reaction and occur as an inherent result of multicomponent reactions (MCRs) and their extensions. They enable syntheses to be performed at a low energy level and the number of synthesis steps to be drastically reduced in comparison with ‘classical’ two-component reactions, fulfilling the rules of Green Chemistry. The very high potential for variability, diversity and complexity of MCRs additionally generates an extremely diverse range of products, thus bringing us closer to the aim of being able to produce tailor-made and extremely low-cost materials, drugs and compound libraries.

Organic superbase derived ionic liquids based on the TFSI anion: synthesis, characterization, and electrochemical properties

Five organic superbase derived ionic liquids based on the TFSI anion were designed and synthesized, and their application as green electrolytes in super-capacitors was also evaluated.

Ionic liquids are not innocent in Pd catalysis. C–H arylation of thiazolium and imidazolium ionic liquids with aryl halides

The ionic liquids bearing an aromatic vinylic C–H moiety are not innocent during Pd-catalyzed cross-coupling reactions of aryl halides. Palladium-catalyzed direct C–H arylation of thiazolium and imidazolium ionic liquids took place to give arylated ionic liquids.

Task-specific acidic ionic liquid-catalyzed efficient synthesis of β-enaminolactones from alkynoates and β-amino alcohols

An efficient task-specific acidic ionic liquid-catalyzed straightforward synthesis of β-enaminolactones has been demonstrated.

Novel iron doped calcium oxalates as promising heterogeneous catalysts for one-pot multi-component synthesis of pyranopyrazoles

The co-precipitation method using a surface modifier, glutamic acid was employed in the design of iron doped calcium oxalates (Fe-CaOx).

Synthesis of highly substituted dihydro-2-oxopyrroles using Fe3O4@nano-cellulose–OPO3H as a novel bio-based magnetic nanocatalyst

A green and environmentally friendly approach for the synthesis of dihydro-2-oxopyrrole derivatives was developed using Fe₃O₄@nano-cellulose–OPO₃H as a novel bio-based magnetic nanocatalyst.

Sn(ii)-Mediated facile approach for the synthesis of 2-aryl-2H-indazole-3-phosphonates and their anticancer activities

The efficient synthesis of 2-aryl-2H-indazole-3-phosphonates has been achieved successfully via a SnCl₂·2H₂O mediated one-pot method.

1,3,5-Tris(2-hydroxyethyl)isocyanurate functionalized graphene oxide: a novel and efficient nanocatalyst for the one-pot synthesis of 3,4-dihydropyrimidin-2(1H)-ones

The preparation and characterization of a novel 1,3,5-tris(2-hydroxyethyl)isocyanurate functionalized graphene oxide (GO–THEIC) nanomaterial and its catalytic application for the Biginelli reaction are described.

A new paradigm for designing ring construction strategies for green organic synthesis: implications for the discovery of multicomponent reactions to build molecules containing a single ring

A new way of developing novel synthesis strategies for the construction of monocyclic rings found in organic molecules is presented. The method is based on the visual application of integer partitioning to chemical structures. Two problems are addressed: (1) the determination of the total number of possible ways to construct a given ring by 2-, 3-, and 4-component couplings; and (2) the systematic enumeration of those possibilities. The results of the method are illustrated using cyclohexanone, pyrazole, and the Biginelli adduct as target ring systems with a view to discover new and greener strategies for their construction using multicomponent reactions. The application of the method is also extended to various heterocycles found in many natural products and pharmaceuticals.

Synthesis of Aminoindolizidines through the Chemoselective and Diastereoselective Catalytic Hydrogenation of Indolizines

Indolizidines are bioactive heterocyclic compounds of great potential normally prepared following multistep routes. However, to the best of our knowledge, the synthesis of 1-aminoindolizidines has never been reported. Herein, 1-(dialkylamino)-3-substituted indolizidines have been straightforwardly synthesized using an atom-economic protocol that involves a copper-catalyzed three-component synthesis of indolizines followed by heterogeneous catalytic hydrogenation. The latter was found to be chemoselective using platinum(IV) oxide as the catalyst at 3.7 atm, providing the aminoindolizidines in modest-to-high yields (35-95%) and high diastereoselectivity (92:8 to >99:1). It has been experimentally demonstrated that the hydrogenation occurs through the intermediate 5,6,7,8-tetrahydroindolizine, which contains a pyrrole moiety. Moreover, the diastereomerically pure 1-(dibenzylamino)-3-substituted indolizidines could be further transformed into the corresponding monobenzylated or fully debenzylated aminoindolizidines by selective hydrogenolysis catalyzed by Pt/C or Pd/C, respectively, under ambient conditions.

One-Pot Three-Component Synthesis of 2-Imino-1,3-Thiazolines on Soluble Ionic Liquid Support

An efficient one-pot, three-component synthesis of 2-imino-1,3-thiazolidines and 2-imino-1,3-thiazolines using ionic liquid-tethered 2-aminobenzimidazoles was reported. The protocol includes reaction of ionic liquid attached 2-aminobenzimidazoles with isothiocyanates to afford isothioureas, followed by its base induced inter and intramolecular nucleophilic displacement reactions with 1,2-dichloroethane (EDC) which results in thiazolidine ring formation. In the next to the last step, the ionic liquid support was removed by methanolysis to deliver 2-imino-1,3-thiazolidines, which were sequentially oxidized with manganese(III) triacetate to yield 2-imino-1,3-thiazolines. The salient feature of this method is the use of 1,2-dichloroethane as a synthetic equivalent for α-haloketone to avoid the use of toxic halogenating reagents.

An efficient one-pot synthesis of thiochromeno[3,4-d]pyrimidines derivatives: Inducing ROS dependent antibacterial and anti-biofilm activities

An efficient synthesis of thiochromeno[3,4-d]pyrimidine derivatives has been achieved successfully via a one-pot three-component reaction of thiochrome-4-one, aromatic aldehyde and thiourea in the presence of 1-butyl-3-methyl imidazolium hydrogen sulphate [Bmim]HSO4. This new protocol has the advantages of environmental friendliness, high yields, short reaction times, and convenient operation. Furthermore, among all the tested derivatives, compounds 4b and 4c exhibited promising antibacterial, minimum bactericidal concentration and anti-biofilm activities against Staphylococcus aureus MTCC 96, Staphylococcus aureus MLS16 MTCC 2940 and Bacillus subtilis MTCC 121. The compound 4c also showed promising intracellular ROS accumulation in Staphylococcus aureus MLS16 MTCC 2940 comparable to that of ciprofloxacin resulting in apoptotic cell death of the bacterium.

Ionic Liquid Promoted Diazenylation of N-Heterocyclic Compounds with Aryltriazenes under Mild Conditions

An efficient, mild, and metal-free approach to direct diazenylation of N-heterocyclic compounds with aryltriazenes using Brønsted ionic liquid as a promoter has been developed for the first time. Many N-heterocyclic azo compounds were synthesized in good to excellent yields at room temperature under an open atmosphere. Notably, the promoter 1,3-bis(4-sulfobutyl)-1H-imidazol-3-ium hydrogen sulfate could be conveniently recycled and reused with the same efficacies for at least four cycles.