Synthesis of new low-viscous sulfonic acid-functionalized ionic liquid and its application as a Brönsted liquid acid catalyst for the one-pot mechanosynthesis of 4H-pyrans through the ball milling process

Ni-Unsymmetrical Salen Complex-Catalyzed One-Pot Multicomponent Reactions for Efficient Synthesis of Biologically Active 2-Amino-3-cyano-4H-pyrans

In this report, four new Ni(II)-unsymmetrical salen complexes, [NiL1-4], were prepared by refluxing Ni(Ac)2·4H2O with unsymmetrical salen ligands, H2L1-4. All of the synthesized ligands and complexes were characterized by various physicochemical methods. Also, the solid-state structures of [NiL1], [NiL2], and [NiL4] were defined through single-crystal X-ray diffraction methods. The catalytic potential of [NiL1-4] was investigated by economic and environmentally friendly one-pot-three-component reactions (using reagent: 1,3-dicarbonyls, malononitrile, benzaldehyde, or its derivatives) for the synthesis of biologically active 2-amino-3-cyano-4H-pyran derivatives (total 16 derivatives). After optimization of the reaction conditions, this new synthetic protocol by taking Ni(II)-unsymmetrical salen complexes as catalysts shows excellent conversion with a maximum yield of up to 98% of the effective catalytic products within 1 h of reaction time. In addition, it was observed that the aromatic aldehyde containing an electron-withdrawing group as a ring substituent shows better conversion (up to 98%), and the electron-donating group substituent shows similar or less conversion compared to benzaldehyde under the optimized reaction conditions. From the comparison of results between all these Ni complexes, it was found that the efficiency of the catalytic performance follows the order [NiL1] > [NiL3] > [NiL2] > [NiL4]. A possible reaction pathway was predicted and established through UV-vis spectroscopy. Intermediate II proposed in the reaction pathway was also trapped and characterized through 1H and 13C NMR.

Nanostructure of Locally Concentrated Ionic Liquids in the Bulk and at Graphite and Gold Electrodes

The physical properties of ionic liquids (ILs) have led to intense research interest, but for many applications, high viscosity is problematic. Mixing the IL with a diluent that lowers viscosity offers a solution if the favorable IL physical properties are not compromised. Here we show that mixing an IL or IL electrolyte (ILE, an IL with dissolved metal ions) with a nonsolvating fluorous diluent produces a low viscosity mixture in which the local ion arrangements, and therefore key physical properties, are retained or enhanced. The locally concentrated ionic liquids (LCILs) examined are 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (HMIM TFSI), 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate (HMIM FAP), or 1-butyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate (BMIM FAP) mixed with 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (TFTFE) at 2:1, 1:1, and 1:2 (w/w) IL:TFTFE, as well as the locally concentrated ILEs (LCILEs) formed from 2:1 (w/w) HMIM TFSI-TFTFE with 0.25, 0.5, and 0.75 m lithium bis(trifluoromethylsulfonyl)imide (LiTFSI). Rheology and conductivity measurements reveal that the added TFTFE significantly reduces viscosity and increases ionic conductivity, and cyclic voltammetry (CV) reveals minimal reductions in electrochemical windows on gold and carbon electrodes. This is explained by the small- and wide-angle X-ray scattering (S/WAXS) and atomic force microscopy (AFM) data, which show that the local ion nanostructures are largely retained in LCILs and LCILEs in bulk and at gold and graphite electrodes for all potentials investigated.

Novel Pyridinium Based Ionic Liquid Promoter for Aqueous Knoevenagel Condensation: Green and Efficient Synthesis of New Derivatives with Their Anticancer Evaluation

Herein, a distinctive dihydroxy ionic liquid ([Py-2OH]OAc) was straightforwardly assembled from the sonication of pyridine with 2-chloropropane-1,3-diol by employing sodium acetate as an ion exchanger. The efficiency of the ([Py-2OH]OAc as a promoter for the sono-synthesis of a novel library of condensed products through DABCO-catalyzed Knoevenagel condensation process of adequate active cyclic methylenes and ninhydrin was next investigated using ultimate greener conditions. All of the reactions studied went cleanly and smoothly, and the resulting Knoevenagel condensation compounds were recovered in high yields without detecting the aldol intermediates in the end products. Compared to traditional strategies, the suggested approach has numerous advantages including mild reaction conditions with no by-products, eco-friendly solvent, outstanding performance in many green metrics, and usability in gram-scale synthesis. The reusability of the ionic liquid was also studied, with an overall retrieved yield of around 97% for seven consecutive runs without any substantial reduction in the performance. The novel obtained compounds were further assessed for their in vitro antitumor potential toward three human tumor cell lines: Colo-205 (colon cancer), MCF-7 (breast cancer), and A549 (lung cancer) by employing the MTT assay, and the findings were evaluated with the reference Doxorubicin. The results demonstrated that the majority of the developed products had potent activities at very low doses. Compounds comprising rhodanine (5) or chromane (12) moieties exhibited the most promising cytotoxic effects toward three cell lines, particularly rhodanine carboxylic acid derivative (5c), showing superior cytotoxic effects against the investigated cell lines compared to the reference drug. Furthermore, automated docking simulation studies were also performed to support the results obtained.

The liquid phase of 4,4'-trimethylenedipiperidine: a safe and greener dual-task agent for clean and facile synthesis of coumarin derivatives

A practical and facile synthesis of various coumarin derivatives was conducted using a liquid phase of 4,4'-trimethylenedipiperidine as a safe and greener dual-task reagent under catalyst-free and solvent-free conditions. This reagent is a commercially available solid and can be handled easily, having a liquid phase over a vast temperature range, high thermal stability, low toxicity, and good solubility in green solvents such as water and ethanol. It is worth mentioning that 4,4'-trimethylenedipiperidine could be completely recovered and regenerated after a simple process. The current method has other merits, including (a) minimizing the use of high-risk and toxic reagents and solvents; (b) the use of a secure and recoverable medium-organocatalyst instead of metal-based catalysts, (c) avoid tedious processes, harsh conditions, and a multi-step process for the preparation of catalysts, (d) transform phenol and salicyladehyde derivatives into the corresponding coumarin derivatives in good to high yields, (e) minimize hazardous waste generation. TMDP could be easily recovered and reused several times with no change in its activity. Furthermore, the current work demonstrated that the liquid phase of 4,4'-trimethylenedipiperidine can be a promising medium in organic reaction at higher temperatures due to its broad liquid range temperature, thermal stability, acceptor/donor hydrogen bond property, and other unique merits. New methodology for the synthesis of coumarines using liquid phase of TMDP under mild conditions.

New Approaches for the Synthesis of Heterocyclic Compounds Corporating Benzo[d]imidazole as Anticancer Agents, Tyrosine, Pim-1 Kinases Inhibitions and their PAINS Evaluations

BACKGROUND

Benzo[d]imidazoles are highly biologically active, in addition, they are considered as a class of heterocyclic compounds with many pharmaceutical applications.

OBJECTIVE

We are aiming in this work to synthesize target molecules that possess not only anti-tumor activities but also kinase inhibitors. The target molecules were obtained starting from the benzo[d]imidazole derivatives followed by their heterocyclization reactions to produce anticancer target molecules.

METHODS

The 1-(1H-benzo[d]imidazol-2-yl)propan-2-one (3) and the ethyl 2-(1H-benzo[d]imidazol-2- yl)acetate (16) were used as the key starting material which reacted with salicylaldehyde to give the corresponding benzo[4,5]imidazo[1,2-a]quinoline derivatives. On the other hand, both of them were reacted with different reagents to give thiophene, pyran and benzo[4,5]imidazo[1,2-c]pyrimidine derivatives. The synthesized compounds were evaluated against the six cancer cell lines A549, HT-29, MKN-45, U87MG, SMMC-7721, and H460 together with inhibitions toward tyrosine kinases, c-Met kinase and prostate cancer cell line PC-3 using the standard MTT assay in vitro, with foretinib as the positive control.

RESULTS

Most of the synthesized compounds exhibited high inhibitions toward the tested cancer cell lines. In addition, tyrosine and Pim-1 kinases inhibitions were performed for the most active compounds where the variation of substituent through the aryl ring and heterocyclic ring afforded compounds with high activities. Our analysis showed that there is a strong correlation between the structure of the compound and the substituents of target molecules.

CONCLUSION

Our present research proved that the synthesized heterocyclic compounds with varieties of substituents have a strong impact on the activity of compounds. The evaluations through different cell lines and tyrosine kinases indicated that the compounds were the excellent candidates as anticancer agents. This could encourage doing further research within this field for the building of compounds with high inhibitions.

Synthesis and characterization of a new acid molten salt and the study of its thermal behavior and catalytic activity in Fischer esterification

A new acid molten salt was synthesized and characterized, and employed in Fischer esterification.

Synthesis, Characterisation, and Determination of Physical Properties of New Two-Protonic Acid Ionic Liquid and its Catalytic Application in the Esterification

A new ionic liquid was synthesised, and its chemical structure was elucidated by FT-IR, 1D NMR, 2D NMR, and mass analyses. Some physical properties, thermal behaviour, and thermal stability of this ionic liquid were investigated. The formation of a two-protonic acid salt namely 4,4′-trimethylene-N,N′-dipiperidinium sulfate instead of 4,4′-trimethylene-N,N′-dipiperidinium hydrogensulfate was evidenced by NMR analyses. The catalytic activity of this ionic liquid was demonstrated in the esterification reaction of n-butanol and glacial acetic acid under different conditions. The desired acetate was obtained in 62–88% yield without using a Dean–Stark apparatus under optimal conditions of 10 mol-% of the ionic liquid, an alcohol to glacial acetic acid mole ratio of 1.3:1.0, a temperature of 75–100°C, and a reaction time of 4h. α-Tocopherol (α-TCP), a highly efficient form of vitamin E, was also treated with glacial acetic acid in the presence of the ionic liquid, and O-acetyl-α-tocopherol (Ac-TCP) was obtained in 88.4% yield. The separation of esters was conducted during workup without the utilisation of high-cost column chromatography. The residue and ionic liquid were used in subsequent runs after the extraction of desired products. The ionic liquid exhibited high catalytic activity even after five runs with no significant change in its chemical structure and catalytic efficiency.

[TBP]2SO4 ionic liquid catalyst for 4MCR of pyridazinoindazole, indazolophthalazine and pyrazolophthalazine derivatives

Tetrabutyl phosphonium sulfate ([TBP]₂SO₄), as novel room-temperature ionic liquid (RTIL), was synthesized by a simple cost-effective method, characterized by ¹H, ¹³C, ³¹P NMR and FT-IR spectrophotometry. The newly prepared catalyst was used as an efficient catalyst in some four multicomponent reactions (4MCRs) e. g., to synthesis pyridazino[1,2-a]indazole, indazolo[2,1-b]phthalazine and pyrazolo[1,2-b]phthalazine. This green method has several advantages such as short reaction time, using simple methods to prepare catalysts and products, easy operation and high efficiency of products. In addition, the catalyst can be easily recovered and reused several times with reduced average activity.

Facile and green synthesis of a series of dihydro-[1,2,4]triazolo[1,5-a]pyrimidine scaffolds

This work presents a new catalytic application of 4,4′-trimethylenedipiperidine for the efficient synthesis of a series of dihydro-[1,2,4] triazolo[1,5-a]pyrimidines. According to the principles of green chemistry, the reaction was performed (a) in a solvent mixture comprised of water and ethanol (1:1 v/v) at reflux temperature and (b) solvent-free grinding in a mortar by a pestle. The organocatalyst could be reused up to 10 runs, and no reduction of catalytic activity was detected. A variety of substituted dihydro-[1,2,4] triazolo[1,5-a]pyrimidines were obtained in good to excellent yields under eco-friendly conditions. 4,4′-Trimethylenedipiperidine is commercially available and easy to handle, and it also shows high thermal stability and good solubility in water. This work revealed that this organocatalyst, a hydrogen bond donor to active carbonyl groups and simultaneously a Lewis base through the nitrogen atom of second piperidine moiety, could play a vital role in the promotion of the one-pot multi-component reactions. The main merits of the current methodology include short reaction time, wide substrate scope, use of a metal-free catalyst and green solvents, and simple work-up process. Furthermore, this organocatalyst can be an alternative to piperidine for organic transformations.

Application of nitrogen-rich porous organic polymer for the solid-phase synthesis of 2-amino-4H-benzo[b]pyran scaffolds using ball milling process

This paper presents the efficient synthesis of 2-amino-4H-benzo[b]pyrans using mesoporous poly-melamine-formaldehyde as a polymeric heterogeneous catalyst. According to the principals of green chemistry, the reaction was performed by the planetary ball milling process at ambient and neat conditions. The heterogeneous catalyst could be reused up to five runs with no reducing of catalytic efficiency. A variety of substituted 2-amino-4H-benzo[b]pyrans were obtained in good to excellent yields under eco-friendly conditions. Other advantages of the current methodology include short reaction time, wide substrate-scope, and use of a metal-free polymeric catalyst. Also, the current method avoids the use of hazardous reagents and solvents, tedious workup and multi-step purification. This work revealed that porous organic polymers containing Lewis base sites having acceptor-donner hydrogen bonding functional groups, and high porosity could play a vital role in the promotion of the one-pot multicomponent reactions in the solid-phase synthesis.

1H,4H-Piperazine-diium Dichlorosulfonate: Structure Elucidation and its Dual Solvent–Catalyst Activity for the Synthesis of New Dihydro-[1,2,4]triazolo[1,5-a]pyrimidine Scaffolds

A new ionic liquid containing a 1H,4H-piperazine-diium ring and chlorosulfonate as a 1,4-dicationic core and counter ion, respectively, was designed and synthesised. The structure elucidation of this ionic liquid was conducted by 1D and 2D NMR, FT-IR, Raman, and mass spectrum analysis. The physical properties of this ionic liquid were determined and reported. Furthermore, the dual solvent–catalyst activity of piperazine-1,4-diium dichlorosulfonate was investigated for the synthesis of new dihydro[1,2,4]triazolo[1,5-a]pyrimidines through a one-pot three-component reaction. The ionic liquid was retrieved and reused several times without reducing its catalytic efficiency.