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In the present manuscript, we easily synthesized three different types of ionic liquid supported 3-quinuclidinone organocatalysts such as [PyAmEQ][BF4] (Py-CATALYST-1), [PyAmEQ][PF6] (Py-CATALYST-2), and [PyAmEQ][NTf2] (Py-CATALYST-3). After performing the careful characterization of the above catalysts with sophisticated analytical techniques, we utilized them as a catalyst to study the passive Morita-Baylis-Hillman reaction. The corresponding Morita-Baylis-Hillman adducts were easily isolated, followed by the simple ether extraction method. Moreover, the above protocol also promoted low catalyst loading, short reaction time, wide substrate scope, easy product, and catalyst recycling. We easily recycled the catalytic system for 5 runs with no noticeable loss in the chemical yield. Additionally, Py-CATALYST-3 was also used to prepare biologically active materials, i.e., N-((E,3S,4R)-5-benzylidene-tetrahydro-4-hydroxy-6-oxo- 2H-pyran-3-yl) palmitamide derivatives.

Background: The present method is facile and effective for the synthesis of N-substituted 5-aryl-4-benzoyl-3-hydroxy-3-pyrrolin-2-one derivatives which are obtained by one-pot threecomponent condensation reactions of aromatic aldehydes, primary amines and ethyl benzoylpyruvate in the presence of a novel homogeneous catalyst including acidic pyridinium inner salt (PIS) at 50°C in ethanol and water mixture as solvent. Methods: 5-Aryl-4-benzoyl-3-hydroxy-3-pyrrolin-2-ones were synthesized through a one-pot three- -component tandem formation of Schiff base cyclo condensation reaction of aromatic aldehydes, primary amines and ethyl benzoylpyruvate in the presence of 10 mol% of acidic pyridinium inner salt as a catalyst under aqueous ethanol medium at 50°C. All obtained structures were confirmed by their elemental analysis data and IR, 1H NMR and 13C NMR spectroscopy. Results: Three-component synthesis of 5-aryl-4-benzoyl-3-hydroxy-3-pyrrolin-2-ones catalyzed by acidic pyridinium inner salt with aromatic aldehydes, primary amines and ethyl benzoylpyruvate in aqueous ethanol medium at 50°C was prepared. The achieved derivatives (eight entries) were well synthesized in excellent yields. Conclusion: We found acidic pyridinium inner salt as a proper catalyst for this method. A catalyst’s novelty is excellent catalytic activity, easy separation of the reaction mixture by washing with cold water and reusability of the catalyst for six consecutive periods without disrupting the activity of this catalyst system.

Excited-state intramolecular proton transfer (ESIPT) dyes typically show strong solid-state emission, but faint fluorescence intensity is observed in the solution state owing to detrimental molecular motions. This article investigates the influence of direct (hetero)arylation on the optical properties of 2-(2'-hydroxyphenyl)benzoxazole ESIPT emitters. The synthesis of two series of ESIPT emitters bearing substituted neutral or charged aryl, thiophene, or pyridine rings is reported herein along with full photophysical studies in solution and solid states, demonstrating the dual solution-/solid-state emission behavior. Depending on the nature of substitution, several excited-state dynamics are observed: quantitative or partially frustrated ESIPT process or deprotonation of the excited species. Protonation studies revealed that pyridine substitution triggered a strong increase of quantum yield in the solution state for the protonated species owing to favorable quinoidal stabilization. These attractive features led to the development of a second series of dyes with alkyl or aryl pyridinium moieties showing strong tunable solution/solid fluorescence intensity. For each series, ab initio calculations helped rationalize and ascertain their behavior in the excited state and the nature of the emission observed by the experimental results.

We have developed a deaminative-decarboxylative protocol to form new carbon(sp3 )-carbon(sp3 ) bonds from activated amines and carboxylic acids. Amines and carboxylic acids are ubiquitous building blocks, available in broad chemical diversity and at lower cost than typical C-C coupling partners. To leverage amines and acids for C-C coupling, we developed a reductive nickel-catalyzed cross-coupling utilizing building block activation as pyridinium salts and redox-active esters, respectively. Miniaturized high-throughput experimentation studies were critical to our reaction optimization, with subtle experimental changes such as order of reagent addition, composition of a binary solvent system, and ligand identity having a significant impact on reaction performance. The developed protocol is used in the late-stage diversification of pharmaceuticals while more than one thousand systematically captured and machine-readable reaction datapoints are reposited.

A sterically strained ionic Bronsted pair complex obtained from a sterically bulky base 2,4,6-tri-tert-butylpyridine and hydrochloric acid imbues unusual reactivity to the anionic chloride. The complete shielding of the cationic [N-H]+ by the bulky ortho-tert-butyl groups weakens the possible hydrogen-bonding interactions with the chloride anion, and the [N-H]+···Cl- distance is unusually longer (3.10 A). This results in strained/frustrated electrostatic interactions between the ion-pair, thus infusing an increased reactivity in both of the ions, which results in the activation of a third molecule like thiol via hydrogen-bonding. This intriguing weak interaction-based reactivity has been utilized to develop an organocatalytic synthesis of 2-deoxy-β-thioglycosides from glycals. While the 1H NMR studies showcase the diamagnetic activation of thiols in the presence of the catalyst, the electron paramagnetic resonance (EPR) studies reveal the generation of a radical species that suggests a possible frustrated radical pair catalysis. Besides, IR spectroscopic studies explain the intriguing influence of size/charge density of the anion on the solvation-insusceptible, cationic [TTBPyH]+ and on the observed reactivity.

In this mini review, we highlight some key work from the last 2 years where ionic polymers have been used as a catalyst to convert CO2 into cyclic carbonates. Emerging ionic polymers reported for this catalytic application include materials such as poly(ionic liquid)s (PILs), ionic porous organic polymers (iPOPs) or ionic covalent organic frameworks (iCOFs) among others. All these organic materials share in common the ionic moiety cations such as imidazolium, pyridinium, viologen, ammonium, phosphonium, and guanidinium, and anions such as halides, [BF4]–, [PF6]–, and [Tf2N]–. The mechanistic aspects and efficiency of the CO2 conversion reaction and the polymer design including functional groups and porosity are discussed in detail. This review should provide valuable information for researchers to design new polymers for important catalysis applications.

The azomethine ylides are generally used in 1,3-dipolar cycloadditions with various dipolarophiles. In this work, a new and diverse route has been developed for the azomethine ylides, for synthesis of novel pyrrole derivatives. The azomethine ylide, produced via C–H activation of unreactive C(sp3)–H bond of 2-methylquinoline, by molecular iodine, in the presence of pyridine. Herein, we represent novel pyrrole derivatives, synthesized from the reaction of pyridinium ylide with olefins, which formed via a reaction of isatin, dialkyl acetylenedicarboxylate derivatives and pyridine as a base in moderate to excellent yields. Various features of this cyclization, discussed.

Three-component condensation of in situ generated pyridinium aroylmethylides with isatins or aromatic aldehydes and cyclic 1,3-dicarbonyl compounds gave a series of condensed 2-aroyl-2,3-dihydrofurans. The reaction proceeds diastereoselectively and represents a cascade process involving the Knoevenagel condensation, the carbo-Michael reaction, and intramolecular nucleophilic substitution. The possibility of reductive rearrangement of spirocyclic furanyl-substituted oxindole into a pyran derivative by the action of zinc in acetic acid was shown.

In this contribution we report on the synthesis, characterization and application of water‐soluble zinc(II) phthalocyanines, which are decorated with four or eight umbelliferone moieties for photodynamic therapy (PDT). These compounds are linked peripherally to zinc(II) phthalocyanine by a triethylene glycol linker attached to pyridines, leading to cationic pyridinium units, able to increase the water solubility of the system. Beside their photophysical properties they were analyzed concerning their cellular distribution in human hepatocyte carcinoma (HepG2) cells as well as their phototoxicity towards HepG2 cells, Gram‐positive (S. aureus strain 3150/12 and B. subtilis strain DB104) and Gram‐negative bacteria (E. coli strain UTI89 and E. coli strain Nissle 1917). At low light doses and concentrations, they exhibit superb antimicrobial activity against Gram‐positive bacteria as well as anti‐tumor activity against HepG2. They are even capable to inactivate Gram‐negative bacteria, whereas the dark toxicity remains low. These unique water‐soluble compounds can be regarded as all‐in‐one type photosensitizers with broad applications ranges in the future., Presented here are umbelliferone substituted water‐soluble zinc(II) phthalocyanines, which are able to inactivate efficiently Gram‐positive and Gram‐negative bacteria and are also active against HepG2 cancer cells. The compounds were investigated concerning their phototoxicity as well as their photophysical properties and their aggregation behavior.

Herein, we present a metal-free visible-light-induced eosin-y-catalyzed deaminative strategy for the sequential alkylation/cyclization of N-methacryloyl-2-phenylbenzoimidazoles with alkyl amine-derived Katritzky salts, which provides an efficient avenue for the construction of various benzo[4,5]imidazo[2,1-a]isoquinolin-6(5H)-one derivatives in moderate to excellent yields under mild reaction conditions. The key enabling feature of this novel reaction includes utilization of redox-active pyridinium salts from abundant and inexpensive primary amine feedstocks that were converted into alkyl radicals via C-N bond scission and subsequent alkylation/cyclization with N-methacryloyl-2-phenylbenzoimidazoles by the formation of two new C-C bonds. In addition, we implemented this protocol for a variety of amino acids, affording the products in moderate yields. Moreover, the novel, environmentally benign batch protocol was further carried out in a continuous-flow regime by utilizing a perfluoroalkoxy alkane tubing microreactor under optimized reaction conditions with a blue light-emitting diode light source, enabling excellent yields and a shorter reaction time (19 min) versus the long reaction time (16 h) of the batch reaction. The reaction displays excellent functional group tolerance, easy operation, scalability, mild reaction conditions, and broad synthetic utility.

Methyl groups can imbue valuable properties in organic molecules, often leading to enhanced bioactivity. To enable efficient installation of methyl groups on simple building blocks and in late-stage functionalization, a nickel-catalyzed reductive coupling of secondary Katritzky alkylpyridinium salts with methyl iodide was developed. When coupled with formation of the pyridinium salt from an alkyl amine, this method allows amino groups to be readily transformed into methyl groups with broad functional group and heterocycle tolerance.

Blue light-emitting diode-mediated environmentally sustainable three component reactions among pyridine/isoquinoline 1/2, aryl diazoesters 3, and acrylic ester/3-alkenyl oxindoles 5/6 provide various dihydroindolizines 7 to 9 in excellent yield. The principle of the strategy is photolytic generation of nitrogen ylides from N-heteroarenes and aryl diazoesters and their subsequent [3 + 2] cycloaddition reaction with dipolarophiles. Detailed mechanistic analysis of the transformation through control experiments establishes this strategy as the foundation for the photolytic multicomponent reaction.

Herein, novel magnetic nanoparticles with pyridinium bridges namely Fe3O4@SiO2@PCLH-TFA through a multi-step pathway were designed and synthesized. The desired catalyst and its corresponding precursors were characterized with different techniques such as Fourier transform infrared (FT-IR) spectroscopy, 1H NMR, 13C NMR, Mass spectroscopy, energy dispersive X-ray (EDX) analysis, thermogravimetric/derivative thermogravimetry (TG/DTG) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM). In addition, the catalytic application of the prepared catalyst in the synthesis of new series of triarylpyridines bearing sulfonate and sulfonamide moieties via a cooperative vinylogous anomeric-based oxidation was highlighted. The current trend revealed that the mentioned catalyst shows high recoverability in the reported synthesis.

A nickel-catalyzed deaminative cyanation of Katritzky pyridinium salts has been developed. When it is coupled with formation of the pyridinium salt from primary amines, this method enables alkyl amines to be converted to alkyl nitriles. A less toxic cyanide reagent, Zn(CN)2, is utilized, and diverse functional groups and heterocycles are tolerated. The method also enables a one-carbon homologation of alkyl amines via reduction of the nitrile products, in addition to many other potential transformations of the versatile nitrile group.

The Ir-catalyzed asymmetric hydrogenation of cyclic pyridinium salts is presented as a new strategy for the convenient and efficient synthesis of chiral indolizidines. The asymmetric hydrogenation of cyclic pyridinium salts derived from 2-(2-acylphenyl)pyridines proceeded smoothly in the presence of [Ir(cod)Cl]2 and (R)-DM-SegPhos to provide the desired chiral 7,8-benzoindolizidines 6 in high to excellent yields with moderate enantioselectivity (up to 86:14 er) and excellent diastereoselectivity (>20:1 dr). The enantiomeric purity of 6j was increased to 92:8 through recrystallization.

An organophotoredox-catalyzed decarboxylative cross-coupling between azole nucleophiles and aliphatic carboxylic acid-derived redox-active esters is demonstrated. This protocol efficiently installs various tertiary or secondary alkyl fragments onto the nitrogen atom of azole nucleophiles under mild and transition-metal-free conditions. The pyridinium additive successfully inhibits the formation of elimination byproducts from the carbocation intermediate. This reaction is applicable to the synthesis of a protein-degrader-like molecule containing an azole and a thalidomide.

Syntheses of push–pull substituted non-symmetric bis(thienyl)ethenes (BTEs) possessing a central perfluorocyclopentene core are described. The substituent effects of anisole, phenole, and phenolate as well as pyridine, pyridinium, and N-methylpyridinium substituents, joined through their 3- or 4-positions to the central BTE core, respectively, cover the range from very strongly electron-donating [σ(4-phenolate)=−1.00] to extremely strongly electron-withdrawing [σ(pyridinium-4-yl)=+2.57] in the title mesomeric betaines. The different isomers possessing 4-yl/4-yl, 4-yl/3-yl and 3-yl/3-yl substituents represent different combinations of conjugated and cross-conjugated partial structures and cause different spectroscopic properties. In addition, through-space conjugation between the 2- and 2′-position of the thiophenes can be observed which circumvents the charge-separation of through-bond cross-conjugation. The BTE possessing the push–pull chromophore consisting of 3-anisole and 4-pyridinium substituents (24) displays the best extinction coefficients within the series of compounds described here (ϵ=33.8/15.7 L/mol ⋅ cm), while the mesomeric betaine possessing an N-methylpyridinium-4-yl and a 4-phenolate substituent (29) displays considerable bathochromic shifts to λmax=724 nm in its closed form.

A new family of N2O-type hydrazine-containing bipyrrole boron complexes has been developed via a one-pot condensation of formylisoindole, hydrazine, and various organoboronic acids. Because of the conformation-restricted coplanar structure and the axial-substituted aryl groups, these novel dyes show deep-red absorption, bright near-infrared (NIR) fluorescence in both solution and solid states, and good solubility in organic solvents. The derivative with pyridinium ions also has been synthesized as an NIR mitochondrially targetable fluorescent probe.

A library of trans-4,5-dihydrofuran-3-carbonitriles was synthesized in a diastereoselective manner in good yields by the three-component reaction of β-ketonitriles, carbonyl- and semistabilized pyridinium ylide precursors, and aldehydes in the presence of piperidine. This one-pot transformation generates two C-C and one C-O bond and proceeds through a cascade Knoevenagel condensation, a Michael addition, and intramolecular SN2 cyclization. Formation of cyclopropanecarbonitrile derivatives, which in some cases were obtained as major products, was found to be a competing reaction. The use of arylglyoxals changes regioselectivity and leads to 2-hydroxy-2H-pyran-5-carbonitriles.

Three-component condensation of in situ generated pyridinium acyl methylides with aromatic aldehydes and 4-hydroxythiocoumarin led to a series of 2-acyl-2,3-dihydro-4H-thiochromeno[4,3-b]furan-4-ones. The reaction proceeds diastereoselectively with the formation of trans-isomers and represents a cascade process involving the Knoevenagel condensation, carbo-Michael reaction, and intramolecular nucleophilic substitution. The subsequent redox rearrangement of 2-acyl-2,3-dihydro-4H-thiochromeno[4,3-b]furan-4-ones by the action of Zn and ZrCl4 grants access to 4H,5H-thiochromeno[4,3-b]pyran-5-ones.

A novel good water-soluble macrocycle containing two pyridinium moieties was synthesized in high yield. It could form 1:1 complexes with neutral guests containing naphthalene or phenyl units in water. The water-soluble macrocycle can selectively encapsulate naphthalene to form a 1:1 complex over a variety of polycyclic aromatic hydrocarbons.

A single-step approach is reported for the preparation of nitrones from benzyl halides and nitrosoarenes via pyridinium ylides, utilizing 4-dimethylaminopyridine (DMAP) catalyst and mild reaction conditions (Li2CO3, dimethylacetamide, and room temperature). The reaction provides both keto- and aldonitrones in high yields with a wide scope for benzyl halides and nitrosoarenes. In the same reaction system, 2-methyl-2-nitrosopropane, which does not have an aryl group, also affords the corresponding N-tert-butyl nitrones from primary benzyl bromides that have an electron-withdrawing group. As an application of the reaction, methyl 2-bromo-2-phenylacetate was used to prepare the corresponding isoxazolidine by a sequential one-pot synthesis.

A [3 + 2]-annulation of gem-difluoroalkenes and pyridinium ylides was developed employing ambient air as the sole oxidant in an open-vessel manner, affording a series of multifunctionalized 2-fluor...

Two N-methylpyridinium compounds and analogous N-protonated salts of 2- and 2,7-substituted 4-pyridyl-pyrene compounds were synthesised and their crystal structures, photophysical properties both in solution and in the solid state, electrochemical and spectroelectrochemical properties were studied. Upon methylation or protonation, the emission maxima are significantly bathochromically shifted compared to the neutral compounds, although the absorption maxima remain almost unchanged. As a result, the cationic compounds show very large apparent Stokes shifts of up to 7200 cm−1. The N-methylpyridinium compounds have a single reduction at ca. −1.5 V vs. Fc/Fc+ in MeCN. While the reduction process was reversible for the 2,7-disubstituted compound, it was irreversible for the mono-substituted one. Experimental findings are complemented by DFT and TD-DFT calculations. Furthermore, the N-methylpyridinium compounds show strong interactions with calf thymus (ct)-DNA, presumably by intercalation, which paves the way for further applications of these multi-functional compounds as potential DNA-bioactive agents. © 2020 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH

The oxide system TiO2–SiO2 as well as a TiO2–SiO2/lignin system have been obtained by the sol–gel synthesis method and applied as supports in Supported Ionic Liquid Phase (SILP) materials. In total 24 SILP systems were obtained with ionic liquids containing imidazolium, pyridinium, phosphonium or sulfonic cations and bis(trifluoromethylsulfonyl)imide or methylsulfate anions, and homogeneous complexes of rhodium or platinum as the active phase. The supports and catalytic materials were subjected to thorough characterization by elemental analysis, XRD, SEM-EDX, IR, and TGA, and their particle size distribution and porous properties were assessed. The new SILP materials were used in hydrosilylation of 1-octene with 1,1,1,3,5,5,5-heptamethyltrisiloxane. The effectiveness of hydrosilylation reaction catalyzed by the obtained SILP materials for the polar and nonpolar reagents was assessed. All the catalytically active materials were proved to be easy to isolate and reuse, and the best SILP systems have been shown to be active in 10 or more subsequent catalytic cycles.

Indolizines and pyrazolo[1,5-a]pyridines were prepared via [3 + 2]-cycloaddition of pyridinium ylides to 1-chloro-2-nitrostyrenes. The synthesized molecules were evaluated for antiproliferative activities against a BE(2)-C neuroblastoma cell line with several compounds decreasing the viability of cancer cells. Indolizine 9db showed higher potency than that of all-trans-retinoic acid, an approved cancer drug. Mechanistically, it was found to inhibit tubulin polymerization and it is thus proposed that the discovered chemistry can be exploited for the development of novel microtubule-targeting anticancer agents.

A novel method utilising sodium cation templation between a pyridinium bridged calix[4]diquinone macrocycle and a pyridine-N-oxide functionalised macrocycle precursor motif is used for the construction of a mechanically interlocked ion-pair binding [2]catenane. The heteroditopic [2]catenane binding mode is elucidated by single-crystal X-ray crystallography with the alkali–metal sodium cation-chloride halide-anion bound in an unprecedented ‘macrocycle separated’ ion-pair configuration.

Two reaction modes of 1-sulfonyl-1,2,3-triazoles and pyridinium 1,4-zwitterionic thiolates were described. Pyrido[1,2-a]pyrazine derivatives were obtained in moderate yields when 4-OEt substituted triazoles were employed in reactions, and 1,4-thiazine derivatives were synthesized when 4-NPhth substituted triazoles were employed. The mechanism may involve a sulfur migration via an addition/elimination process which has never been reported in the previous pyridinium 1,4-zwitterionic thiolate related works.

An efficient two-step approach to 2-fluoroallyl amines was developed that involves the synthesis of (2-fluoroallyl)pyridinium tetrafluoroborates from readily available gem-bromofluorocyclopropanes and the application of the former as novel and stable 2-fluoroallyl electrophiles for Pd-catalyzed allylic substitution

A new stable pyridinium 1,5-zwitterion, generated from azadiene and 4-dimethylaminopyridine, was isolated for the first time. According to DFT calculations, the stability of this species was attributed to be the polarization effect on the exocyclic double bond. The reaction of pyridinium 1,5-zwitterion with isatin-derived α-(trifluoromethyl)imine was regulated by experimental temperature. The umpolung [4 + 3] annulation with isatin-derived α-(trifluoromethyl)imine was reported for the first time at 20 °C in CH3CN. In contrast, the formal Michael addition occurred when performing the reaction at reflux. Compared to the oxygen and methylene analogues, a sulfur atom changed the reaction mode from the umpolung [4 + 3] to the classical [3 + 2] annulation.

Spiro-indolizidine scaffolds are attractive structural motifs in natural alkaloids and pharmaceuticals. Herein, we described a highly stereoselective dearomative [3 + 2] cycloaddition between cyclic pyridinium ylides and nitroolefins. A novel type of cyclic pyridinium salts, which bear an electron-withdrawing group on the pyridine ring, have been developed as the ylide precusors and successfully applied in this cyclization. This protocol features a series of advantages inculding broad substrate scope, mild conditions, short reaction time and high level of yield and stereoselectivity, thus providing a concise and efficient method for the construction of spiro-indolizidine scaffolds.

Conjugated porous polymers are emerging as a new class of polymeric materials with substantial unique properties. Although versatile synthetic strategies have been developed, the search for a sustainable and reliable approach is still extremely desirable for achieving new polymeric species according to the demands for environmental benignity and biocompatibility. Here, we present the synthesis of a new family of olefin-linked conjugated porous polymers by the Knoevenagel condensation of a key monomer 1,1′,6,6′-tetramethyl-[3,3′-bipyridine]-1,1′-diium iodide (TMBPI) with different aryl aldehyde derivatives. In such a strategy, the methyl groups of pyridinium moieties were facile to be activated under organic base catalysis without any metal additives, and they subsequently undergo nucleophilic addition to form aldehyde groups. The resulting carbon–carbon double bond-linked porous polymers feature π-extended rigid networks, ultra-high chemical stability, and high surface areas with micro-/meso-channels, which were completely revealed by optical spectra, solid-state 13C NMR, FT-IR, thermogravimetry, XPS and nitrogen adsorption/desorption analyses. In addition, the unique highly charged skeletons of the as-prepared porous polymers make them well dispersed in some polar solvents, showing large zeta potentials (up to ζ = 16 ± 2.8 mV). Accordingly, such cationic porous polymers enable impeding bacterial growth, exhibiting good antibacterial properties against Gram-negative bacteria (e.g. E. coli).

Hydrogen-bonded (H-bonded) macrocycles that recognize cationic and/or anionic species via non-covalent interactions have found a variety of applications in separation, catalysis, analysis and creation of functional molecules. One of the major challenges in this aspect is to manipulate their dynamic associations in the recognition events for applications. In this study, we report a novel supramolecular strategy using a ditopic H-bonded amide macrocycle that is capable of controlling the binding process in response to external stimulus due to its assembly-and-disassembly-induced anion binding. The presence of an incorporated pyridinium moiety provides the host with a strong tendency to self-associate into 1D interlocked aggregates via intermolecular hydrogen bonds, pi–pi stacking and cation–π interaction, as indicated by the X-ray single-crystal structure analysis. A switchable ensemble is realized through adjusting the intermolecular interaction associated with both the anionic and cationic sites through changing the temperature and introducing a guest. In solution, macrocycle aggregation blocks anion binding but is disrupted upon addition of EMIMBF4, thereby enabling the opening of the anion binding site. A catalytic reaction with bromodiphenylmethane as the substrate reacting with methanol reveals a greatly enhanced yield (over 40% increase) by heating and adding a guest with respect to the case with low temperature, demonstrating the potential of the supramolecular element constructed from H-bonded macrocycles for controllable catalysis.

The structure of Candida rugosa lipase can be affected by solvents used in the enzymatic reactions. Using molecular dynamics simulation as a tool to study the Candida rugosa lipase structure, we studied the effect of various solvent systems, such as water, water-methanol, and water-methanol-ionic liquid. These solvent systems have been chosen because lipase is able to function in both aqueous and non-aqueous medium. In this study, pyridinium (Py)-based ionic liquids were selected as co-solvent. The MD simulation was run for 50 nanoseconds for each solvent system at 328 K. In the case of water-methanol-ionic liquids solvent systems, the total number of the ionic liquids added were varied: 222, 444, and 888 molecules. Water was used as the reference solvent system. The structure of Candida rugosa lipase in water-methanol system significantly changed from the initial structure as indicated by the RMSD value, which was about 6.4 Å after 50 ns simulation. This value was relatively higher compared to the other water-methanol solvent system containing ionic liquid as co-solvent, which were 2.43 Å for 4Py-Br, 2.1 Å for 8Py-Br, 3.37 Å for 4Py-BF4 and 3.49 Å for 8Py-BF4 respectively. Further analysis by calculating the root mean square fluctuation (RMSF) of each lipase residue found that the presence of ionic liquids could reduce changes in the enzyme structure. This happened because the anion component of the ionic liquid interacts relatively more strongly with residues on the surface of the protein as compared to methanol, thereby lowering the possibility of methanol to come into contact with the protein.

The discovery and optimization of a reaction between 2-chloropyridines and 2H-azirines producing imidazo[1,2-a]pyridines is described. The treatment of 2H-azirines with triflic anhydride (Tf2O) forms an electrophilic 1-trifloyl-aziridin-2-yl triflate species which, when reacted in situ with 2-halopyridines, generates transient pyridinium salts. These salts were treated in the same pot with triethylamine (Et3N), leading to the selective formation of C3-substituted imidazo[1,2-a]pyridines, an heterocyclic moiety commonly found in medicinal chemistry leads and drugs. Thorough optimization of the activation/cyclization resulted in yields ranging from 15 to 85% for a variety of substituted heterocycles.

A Michael-initiated ring-closure reaction of pyridinium salts with arylidene oxindoles has been developed. A wide range of aryl-substituted spirocyclopropane oxindoles has been achieved in moderate to good yields (41–99%). This efficient strategy exhibits good functional group compatibility and may serve as an attractive method for the synthesis of diverse cyclopropanes.

With a tandem DMAP-catalyzed reaction between o-AQM, in which it is generated in situ from propargylic amine, and acyl carbene surrogate (from pyridinium ylide), a variety of polyarylated chromenes are assembled in good yields. This process does not require transition-metal catalyst and exhibits easy manipulation of the arene group and good functional group compatibility, particularly the -Br group which can be further transformed to other functionalities by cross-coupling reactions. The modular feature of o-AQM substrates and the simple operation procedures add further advantages to this synthetic method.

In this work, four novel, high fixation reactive dyes containing cationic groups were synthesized using m-aminophenyltrimethylammonium salt or 4-(ethylsulfurate sulfonyl) aniline as the diazo component, 3-(N,N-diethylamino) acetanilide or 3′-aminoacetanilide as the coupling component and m-aminophenyltrimethylammonium salt or N-(2-aminoethyl) pyridinium chloride as the cationic group. The synthesized dyes containing multiple cationic groups were characterized by FT-IR and 1H-NMR spectroscopy. The spectral properties were measured by UV-Vis absorption spectroscopy. Compared with conventional reactive dyes containing cationic groups, the synthesized dyes exhibited good water solubility upon introduction of a quaternary ammonium into the chromophore. The structural design of synthetic azo dyes allows enhanced the water solubility due to the introduction of a cationic group. The dyeing properties of the synthesized dyes to cotton fabric were explored at various temperatures and salt and alkaline concentrations. The results showed that the synthesized dyes possessed good dyeing properties with nearly 80% fixation and good color fastness on cotton (3–5) in the absence of salt. The success of the salt-free dyeing of cotton fabric with these dyes is an excellent example of environmentally friendly cotton dyeing. This study provides an important platform for the design of novel reactive dyes for cotton dyeing to reduce effluent pollution.

The reactions of 2-pyridinesulfenyl halides with cyclopentene, 1,4-cyclohexadiene, 1,5-cyclooctadiene, 1,3-cyclooctadiene, and norbornene, depending on the structure of the alkene, the nature of the halogen, and the duration of the process, lead to the formation of two types of adducts, electrophilic addition products or condensed compounds, [1,3]thiazolo[3,2-a]pyridinium derivatives, in high yields.

International audience; Crystals of (H2AMP)2[FeIIIBr4]Br3, where AMP refers to the 2-(Ammoniomethyl)pyridinium ligand, have been successfully synthesized through redox chemistry and analyzed using X-ray crystallography. The new complex crystallizes as red needles in the monoclinic space group, P21/c, with eight formula weights in a unit cell of dimensions: a = 12.358 (13), b = 28.572 (3), c = 13.544 (14) Å and β=92.009(5) °. Analysis of absorption and reflectance data through the visible and near-infrared provide insight into the optical properties of the material. The structural data and the BVS (Bond Valence Sum) calculations are in agreement with the iron (III) oxidation. In this work, the experimental and theoretical study on molecular structure and vibrational spectral analysis of the new product has been reported. Theoretical calculations were performed by using density functional theory (DFT) at the B3LYP/LAN2DZ basis set levels. The electronic parameters such as frontier molecular orbital, electrostatic potential and HOMO-LUMO energy were calculated. Also, NLO were studied with the same level of DFT. The theoretical values show good agreement with experimental values. In addition, (H2AMP)2[FeIIIBr4]Br3 reveals broad absorption across the visible spectrum and an optical bandgap of 1.06 eV. Then the obtained material can be a promising eco-friendly light absorber in solar cell application. Finally, the thermal behavior of this material has been performed by TGA/DTA. In addition, two phase transitions at T1 = 108 °C and T2 = 170 °C were evidenced by DSC measurements.

Here we report that N-phosphonium pyridinium intermediates are unusually reactive for pyridine SNAr reactions. Specifically, forming phosphonium salts from halopyridines typically requires elevated temperatures and Lewis acid additives. The alternative activation mode described in this paper permits C–P bond formation to occur at ambient temperatures in many cases, and functions across a broad range of substrates.

The title complex is a triple-stranded metallohelicate organized by the self-assembly of 5,17-difunctionalized calix[4]arenes and metal cations with octahedral coordination geometry. Due to hydrophilic triethylene glycol chains on the lower rim of the calix[4]arene, the metallohelicate can encapsulate cationic guests in water. NMR and UV-vis titration experiments reveal that the metallohelicate captures a pyridinium guest with an alanine derivative to form a host-guest complex with a host-guest ratio of 1 : 1. CD spectroscopy confirms the bias of the P- and M-helical sense of the metallohelicate by the captured guest. The metallohelicate captures two molecules of dicationic N,N'-dimethyl-DABCO and monocationic N-methyl quinuclidine, exhibiting a positive allosteric effect. 1 H NMR titration experiments indicate that the bound guests are in close proximately to the aromatic rings of the ligands. Molecular mechanics calculations based on the UV-vis and NMR observations suggest that the first guest preorganizes the conformation of the metallohelicate to facilitate access of the second guest to the cavity.