Use Of Pyridine Research Articles

UNIVERSAL ELECTROCATALYTIC SYSTEM FOR CONVERSION OF ALCOHOLS INTO CARBONYL COMPOUNDS AND CARBOXY ACID FUNCTIONAL DERIVATIVES

A universal catalytic system 4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxyl/KI/pyridine base for the conversion of alcohols into carbonyl compounds and derivatives of carboxylic acids has been developed. The use of pyridine, 2,6-lutidine or collidine made it possible to obtain carbonyl compounds (yield up to 100%) after 2-2.2 F/mol. In the presence of pyridine, aliphatic alcohols are converted to esters (yield up to 35%) after 3-4 F/mol. Acid anhydrides (yield up to 80%) are formed using 2,6-lutidine or collidine after 5-6 F/mol. Nitriles were obtained in the presence of 2,6-lutidine and a source of nitrogen (yield up to 99%) after 3-4 F/mol.

Robust hole transport material with interface anchors enhances the efficiency and stability of inverted formamidinium–cesium perovskite solar cells with a certified efficiency of 22.3%

Herein, we report the use of pyridine anchoring group functionalized poly(triarylamine) (p-PY) as a hole transport layer at buried interfaces between the ITO and formamidinium–cesium perovskite layer to enhance the efficiency and stability of inverted PSCs.

Synthesis process optimization and field trials of insecticide candidate NKY-312

NKY-312 is a highly active insecticide candidate with a simple structure. In order to carry out field trials and toxicity tests, its scale preparation is urgently needed, but the final step of the original synthetic route is a low-yielding sulfonylation reaction that generates a high proportion of a bissulfonylated by-product, its foliar contact activities against bean aphid (80% at 100 mg/kg) is significantly lower than that of NKY-312 (100% at 5 mg/kg), and uses pyridine as the solvent. In this work, we developed a highly selective (4-dimethylaminopyridine)-catalyzed monosulfonylation reaction that avoids the use of pyridine as a solvent and shows a much higher yield (98% yield with 98% HPLC purity) than the original reaction (68%). Then, we carried out the field trials and toxicity tests. In field experiments, the activities of NKY-312 against rice planthopper and wheat aphid were equal to pymetrozine and imidacloprid respectively.

Synergistic Use of Pyridine and Selenophene in a Diketopyrrolopyrrole‐Based Conjugated Polymer Enhances the Electron Mobility in Organic Transistors

AbstractTo achieve semiconducting materials with high electron mobility in organic field‐effect transistors (OFETs), low‐lying energy levels (the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO)) and favorable molecular packing and ordering are two crucial factors. Here, it is reported that the incorporation of pyridine and selenophene into the backbone of a diketopyrrolopyrrole (DPP)‐based copolymer produces a high‐electron‐mobility semiconductor, PDPPy‐Se. Compared with analogous polymers based on other DPP derivatives and selenophene, PDPPy‐Se features a lower LUMO that can decrease the electron transfer barrier for more effective electron injection, and simultaneously a lower HOMO that, however, can increase the hole transfer barrier to suppress the hole injection. Combined with thermal annealing at 240 °C for thin film morphology optimization to achieve large‐scale crystallite domains with tight molecular packing for effective charge transport along the conducting channel, OFET devices fabricated with PDPPy‐Se exhibit an n‐type‐dominant performance with an electron mobility (μe) as high as 2.22 cm2 V−1 s−1 and a hole/electron mobility ratio (μh/μe) of 0.26. Overall, this study demonstrates a simple yet effective approach to boost the electron mobility in organic transistors by synergistic use of pyridine and selenophene in the backbone of a DPP‐based copolymer.

Pyridine assisted desilication of mordenite

Pyridine assisted alkaline desilication has been elaborated as new post-synthetic modification strategy of mordenite. The addition of pyridine during the desilication treatment revealed to impact materials properties through a dual action on textural and chemical properties; substantially different in comparison to the classical alkaline treatment or CTAB assisted desilication. As far as texture is concerned the use of pyridine permits to greatly modify the desilication scheme, hence yielding aggregates of smaller zeolite particles with substantially higher amount of external silanols. The presence of pyridine in the as-synthesized mordenites allows to in situ generate extra-framework aluminium (EFAL) species during final calcination step. Both of these features, smaller particle size and the presence of EFAL species improve catalytic properties considerably. Whilst the achievement of smaller particles reduces diffusion path length, the presence of EFAL species allow for exalting acidity and hence catalytic activity in n-hexane cracking and propene transformation.

Controlling aggregation using self-assembled axially coordinated pyridine-based ligands on porphyrin analogues for dye-sensitized solar cells

Porphyrin dyes are susceptible to aggregation which may cause lower short-circuit current density affecting its photoelectric conversion efficiency (PCE) in dye-sensitized solar cells. In this paper, we harness the inherent property of metallated porphyrins that it can axially coordinate with compounds containing lone-pair of electrons, such as pyridines, through the back π-bonding. The use of pyridine or bipyridine spacers to suppress aggregation in β-functionalized Zn-tetraphenylporphyrin-based dyes showed improvement of PCEs by 28% and 44% for 4-methylpyridine and 4,4′-bipyridine ligands, respectively. This clearly demonstrates the benefits of the simple but effective method in suppressing dye aggregation thereby increasing its efficiency.

Synthesis, 45Sc NMR characterization, and interconversion of structurally diverse scandium chloride hydrates

The dissolution of scandium metal (Sc°) in concentrated hydrochloric acid was found to generate a wide variety of products based on the reaction/processing conditions. The compounds [Sc(H2O)6]3[Cl] (1) and [ScCl2(H2O)4][Cl]·H2O (2) were isolated from the above reaction when an ice bath is used. If the reaction was allowed to warm uncontrolled during synthesis, [Sc(μ-OH)(H2O)5]24[Cl]·2H2O (termedOH) was produced. If 1 or 2 were heated (130 °C) in toluene or H2O, [ScCl2(H2O)4][ScCl4(H2O)2] (3) crystallized. Interconversion of the various hydrates and OH structure were studied via 45Sc NMR spectroscopy studies. Efforts to easily dehydrate 2 through the addition of a Lewis base led to the characterization of monohydrate solvates: [ScCl3(THF)2(H2O)]·THF (4·THF) or [ScCl3(κ2-DME)(H2O)] (5) where THF = tetrahydrofuran and DME = dimethoxyethane. In contrast, the use of pyridine formed [Sc(μ-OH)(Cl)2(py)2]2·py (6) where py = pyridine. The formation of the OH moiety is attributed to the higher reaction temperatures achieved using py as the solvent. These compounds were also characterized using 45Sc NMR spectroscopy and compared to commercial ScCl3 dissolved in the parent solvent.

Determination of Hydrogen Cyanide in Cigarette Smoke by Continuous Flow Analysis Method Using Safer Chemistry

Summary A new safe and sensitive method to determine hydrogen cyanide (HCN) in cigarette smoke using continuous flow analyser (CFA) has been developed and validated. The use of highly toxic potassium cyanide (KCN) as a standard necessitates the development of a safer method for the determination of HCN in cigarette smoke. In this described method KCN is replaced by less toxic potassium tetracyanozincate (Lethal Dose LD50 oral is 7.49 mg/kg for KCN and 2000 mg/kg for potassium tetracyanozincate). Furthermore, the new method uses isonicotinic acid-barbituric acid (coupling reagent) instead of pyridine-pyrazolone as a reagent for the determination of HCN, and hence eliminates the use of pyridine. In this method HCN is trapped on both the Cambridge Filter Pad, then extracted with aqueous sodium hydroxide solution, and in an impinger containing the same solution. The solution thus extracted is oxidised to cyanogen chloride by Chloramine-T and treated with coupling reagent, the resulting stable chromophore was measured colorimetrically at 600 nm. The regression equation was linear in the range of 1 to 25 μg/mL for cyanide with a correlation coefficient (R2) > 0.9998. The limit of detection (LOD) was 0.76 μg/cig and the overall relative standard deviation (RSD) of the method was less than 10%. Excellent recoveries of cyanide were obtained in the range from 92% to 112% and the HCN yields from the Kentucky Reference Cigarette 3R4F obtained from the newly developed method are in good agreement with those from the conventional KCN method. The proposed method is robust, reliable, selective and safer than any of the existing methods for determination of hydrogen cyanide in mainstream as well as in sidestream cigarette smoke.

Ligand‐Enabled γ‐C(sp3)–H Acetoxylation of Triflyl‐Protected Amines

A palladium‐catalyzed γ‐C(sp3)–H acetoxylation of triflyl‐protected amines has been achieved. The use of pyridine or 2‐alkoxyquinoline‐type ligands is key to the success of this transformation. The reaction is highly diastereoselective and easily scalable, and constitutes a direct approach for the synthesis of γ‐hydroxy‐α‐amino acids and β,γ‐dihydroxy amines, which are not readily accessible by other routes.

Nickel-Catalyzed Reductive Cross-Coupling of Vinyl Bromides with Unactivated­ Alkyl Halides

The use of pyridine as the sole ligand for the reductive vinylation of unactivated secondary alkyl halides under Ni-catalyzed conditions has been developed. Both alkyl- and aryl-substituted vinyl bromides are suitable, in which alkyl-decorated α-alkenyl bromides resulted in the α-products in good results.

Essential role of Bordetella NadC in a quinolinate salvage pathway for NAD biosynthesis.

Nicotinamide adenine dinucleotide (NAD) is produced via de novo biosynthesis pathways and by salvage or recycling routes. The classical Bordetella bacterial species are known to be auxotrophic for nicotinamide or nicotinic acid. This study confirmed that Bordetella bronchiseptica, Bordetella pertussis and Bordetella parapertussis have the recycling/salvage pathway genes pncA and pncB, for use of nicotinamide or nicotinic acid, respectively, for NAD synthesis. Although these Bordetellae lack the nadA and nadB genes needed for de novo NAD biosynthesis, remarkably, they have one de novo pathway gene, nadC, encoding quinolinate phosphoribosyltransferase. Genomic analyses of taxonomically related Bordetella and Achromobacter species also indicated the presence of an 'orphan' nadC and the absence of nadA and nadB. When supplied as the sole NAD precursor, quinolinate promoted B. bronchiseptica growth, and the ability to use it required nadC. Co-expression of Bordetella nadC with the nadB and nadA genes of Paraburkholderia phytofirmans allowed B. bronchiseptica to grow in the absence of supplied pyridines, indicative of de novo NAD synthesis and functional confirmation of Bordetella NadC activity. Expression of nadC in B. bronchiseptica was influenced by nicotinic acid and by a NadQ family transcriptional repressor, indicating that these organisms prioritize their use of pyridines for NAD biosynthesis.

ChemInform Abstract: Nickel‐Catalyzed Enantioselective Arylation of Pyridine.

We report an enantioselective Ni-catalyzed cross coupling of arylzinc reagents with pyridinium ions formed in situ from pyridine and a chloroformate. This reaction provides enantioenriched 2-aryl-1,2-dihydropyridine products that can be elaborated to numerous piperidine derivatives with little or no loss in ee. This method is notable for its use of pyridine, a feedstock chemical, to build a versatile, chiral heterocycle in a single synthetic step.

Design, selective alkylation and X-ray crystal structure determination of dihydro-indolyl-1,2,4-triazole-3-thione and its 3-benzylsulfanyl analogue as potent anticancer agents

Three sets of substituted indolyl-triazoles were synthesized by the alkylation of 1,2-dihydro-5-(1H-indol-2-yl)-1,2,4-triazole-3-thione with different alkyl halides. The use of pyridine restricted the alkylation to sulfur. Whereas, upon using K2CO3, the alkylation exceeded sulfur to one of the remaining triazole nitrogens. The assignment of which nitrogen is alkylated besides sulfur is made for the first time using X-ray analysis of single crystals and 2D NMR which indicated that S-, 2-N-isomers will be preferably formed over the S-, 1-N-isomers. The antiproliferative activity on HEPG-2 and MCF-7 cancer cell lines was tested. The results showed that compound 2a is the most active with an IC50 3.58 μg/mL and 4.53 μg/mL for HEPG-2 and MCF-7 respectively and compound 7 is the least active with an IC50 > 100 μg/mL compared to the standard drug doxorubicin (IC50 4.0 μg/mL). The interaction of the synthesized compounds with tyrosine kinases, namely, Akt, PI3, and EGFR was also studied using molecular docking simulation to predict their mode of action which will drive future work directions.

2D hyperbranched conjugated polymer for detecting TNT with excellent exciton migration

Efficient migration of excitons in conjugated polymers is important for sensor devices. In this study, we make use of pyridine and styrene as the sensing units to design the two-dimensional hyperbranched conjugated polymer P2 (poly(2,3,5,6-styrylpyrazine)s) and the one-dimensional linear conjugated polymer P1 (poly(2,5-styrylpyrazine)s) along with their two corresponding model compounds (M1, M2) to study the orbital energies of LUMO (the lowest unoccupied molecular orbital) and HOMO (the highest occupied molecular orbital). Interestingly, comparing with the Stern-Volmer constants (Ksv) of P1 (Ksv=2.49×104M−1), P2 shows excellent sensibility (Ksv=6.84×104M−1) in the presence of TNT (2,4,6-trinitrotoluene), indicating that super quenching effect may get involved in P2. The superior fluorescent quenching performance of P2 could be explained by the following theories: (i) hyperbranched conjugated polymers afford multi-dimensional transport pathways for excitons to migrate; (ii) The LUMO of P2 is closer to that of TNT molecules; (iii) Quenching speed is positively correlated with the rate of electron transfer. In addition, the fluorescence lifetimes of the polymers are almost constant as the TNT concentration increased, indicating that the sensing mechanism could be static quenching.

Studies on influence of polymer modifiers for fluorescent nanocrystals’ cytotoxicity

The presented studies aimed at investigation of the effect of CdSeS/ZnS quantum dots (QDs) stabilized with hyperbranched polyglycidol and its carboxylated derivative on adenocarcinomic human alveolar basal epithelial cells (A549). The first stage of studies concerned the modification of quantum dots with both types of the tested polymers with the use of pyridine as an intermediate agent. Subsequently, cytotoxic effect of the prepared nanoparticles was examined after various incubation time using MTT test (cell metabolic activity assay). Our studies revealed that CdSeS/ZnS with a diameter of 6nm, which were stabilized with hyperbranched polymers do not penetrate into cells, even after prolonged incubation time. Moreover, the cytotoxic effect of the tested QDs was observed over a range of tested concentrations (5–90μM of Cd2+). It was confirmed that tested nanoparticles had significant influence on cell culture viability. The examined cytotoxic effect of the tested quantum dots was dependent on the type of polymer applied and the experiments indicated, that the one bearing carboxylic moieties is more toxic to A549 cells.

Nickel-catalyzed enantioselective arylation of pyridine.

We report an enantioselective Ni-catalyzed cross coupling of arylzinc reagents with pyridiniumions formed in situ from pyridine and a chloroformate. This reaction provides enantioenriched 2-aryl-1,2-dihydropyridine products that can be elaborated to numerous piperidine derivatives with little or no loss in ee. This method is notable for its use of pyridine, a feedstock chemical, to build a versatile, chiral heterocycle in a single synthetic step.

ChemInform Abstract: Cross‐Coupling of [2‐Aryl‐1,1,2,2‐Tetrafluoroethyl](trimethyl)silanes with Aryl Halides.

The synthesis of arylCF2CF2SiMe3 and their reactivity in cross-coupling reactions with aryl iodides and aryl bromides to afford a range of 1,1,2,2-tetrafluoro-1,2-arylethanes is reported. The use of pyridine as an alternative to phenanthroline, and the ability to carry out the reaction at 60 °C or room temperature are the key features of this Cu–Ag mediated cross-coupling methodology. The chemistry is compatible with (hetero)aryl halides, offering a platform to develop products of interest in material and medicinal chemistry.

Reactions of Thioacetamide Derivatives with Sulfonyl Azides: An Approach to Active‐Methylene N‐Sulfonylacetamidines

AbstractReactions of functionalized [CN, CO2Et, C(O)NHR, C(S)NR1R2] derivatives of thiomalonic acid and 2‐arylthioacetamides with sulfonyl azides were shown to give active‐methylene N‐sulfonylamidines in 62–98 % yields. Various procedures for the reactions, including the use of pyridine, boiling ethanol, and water, or running the reactions in the absence of a base and solvent at 80 °C, were carried out and compared. The solvent‐free variant was the best in terms of yield, and also because it does not require the use of an excess of the toxic and hazardous azides. The reaction was shown to tolerate electron‐withdrawing substituents such as carbonyl, cyano, and aryl groups at the C‐2 position. The presence of alkyl and phenyl groups on the nitrogen atom of the thioacetamide fragment, and the presence of substituents on the sulfonyl group were also tolerated. Thus, an efficient solvent‐free, catalyst‐free, and base‐free synthetic approach for the synthesis of N‐sulfonylmalonacetamidines and 2‐arylacetamidines was found.

Cross-Coupling of [2-Aryl-1,1,2,2-tetrafluoroethyl](trimethyl)silanes with Aryl Halides.

The synthesis of arylCF2CF2SiMe3 and their reactivity in cross-coupling reactions with aryl iodides and aryl bromides to afford a range of 1,1,2,2-tetrafluoro-1,2-arylethanes is reported. The use of pyridine as an alternative to phenanthroline, and the ability to carry out the reaction at 60 °C or room temperature are the key features of this Cu-Ag mediated cross-coupling methodology. The chemistry is compatible with (hetero)aryl halides, offering a platform to develop products of interest in material and medicinal chemistry.

A new approach for molecular characterisation of sediments with Fourier transform ion cyclotron resonance mass spectrometry: Extraction optimisation

Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) can begin to tease apart the molecular character of sedimentary organic matter (SOM). We therefore tested five different solvents (aqueous base, CHCl3, MeOH, pyridine and water) for their ability to extract a representative fraction from two organic rich lacustrine sediments, Mangrove Lake, Bermuda (MLB) and Mud Lake, Florida (MLF). Following comparison using liquid state nuclear magnetic resonance spectroscopy (NMR) and negative ion mode electrospray ionization mass spectrometry (FTICRMS) we found that pyridine was the optimal solvent, extracting a more diverse (10–100× greater integration for carbonyl, amide and amine groups) and a larger number of peaks on average (1375–1450 vs. 380–1450). Comparison of the pyridine extracts between MLB, MLF and two organic poor sediments from the Mississippi River Delta and Bayou Grande (Pensacola, FL) showed that only 4.9% of the molecular formulae were common to all four and that unique formulae made up the highest proportion of the assignments. The use of pyridine for extracting immature (Holocene) SOM for FTICRMS analysis can therefore be widely applied to immature sediments and produce representative spectra.