Pivalate Research Articles

REACTION OPTIMIZATION AND QUANTUM-MECHANICAL CHARACTERIZATION OF SOME SEMISYNTHETIC PENICILLINS

In this paper, we report on the synthesis of new semisynthetic penicillins by acylating 6-aminopenicillanic acid with the sulphur derivatives transformed into pivalic acid anhydrides, containing nucleus composed of 3-[(5- nitroindazol-1̓-yl-methyl)]-4-aryl-5-mercapto-1,2,4-triazole. The antibacterial properties determined by the presence of β-lactam ring and 5-mercapto-1,2,4- triazoles nucleus in penicillin molecules has been previously evidenced. Factorial experiments were organized in order to establish the conditions in which the reaction yield becomes maximum. The obtained structures were analyzed from quantum-mechanical point of view and their physical-chemical properties were established by computation. The structure of the synthesized compounds was confirmed by the results of elemental and spectral analyses (FT-IR, 1H- and 13C-NMR). The semisynthetic penicillins were previously verified for toxicological action and antibacterial activity and the obtained results were close to those for amoxicillin, used as reference drug.

Chemical Transformations of [Pd(OOCMe)4Mn] in the Reactions with 1,10-Phenanthroline and Pivalic Acid

Chemical Transformations of [Pd(OOCMe)4Mn] in the Reactions with 1,10-Phenanthroline and Pivalic Acid

Integrating reaction pathways and downstream separation network for optimal sustainable process route selection

Reducing the environmental impact of chemical production has become a critical objective due to carbon emission regulations and the challenges the carbon market poses. Downstream separation network optimization, which can improve process sustainability by using complex heat exchanger networks, applying advanced separation techniques, optimizing the design/operating parameters, etc., has been researched for many years. However, most optimization work focuses solely on downstream separation sections without considering the selection of raw materials and different reaction pathways. This work aims to develop a mixed integer nonlinear programming (MINLP) optimization model, which integrates reaction pathway selection and downstream separation optimization, to select the optimal sustainable process route for utilizing raw materials or producing products. The objective is to maximize/minimize the process profit/cost. Decision variables such as binary variables, which represent the selection of separation task, key component, heating utility, and continuous variables, which influence the separation mass/energy balance, are considered. By giving parameters like reaction conversion rate, selectivity, and raw material/product price, this optimization model can identify the optimal process route for producing a target product or utilizing a raw material. The optimization model was applied to two case studies: one-step isobutylene and methanol utilization and two-step 1,4-butanediol (BDO) production. The process routes, using isobutylene for pivalic acid production and methanol for gasoline production, have the highest process profit per carbon emission. And the process route, which uses acetylene for BDO production, leads to minimum process cost.

Structural evolution and zero-field SMM behaviour in ferromagnetically-coupled disk-type Co7 clusters bearing exclusively end-on azido bridges

Concise chemistry leads to a family of heptanuclear CoII-clusters, [Co7(N3)12(CH3CN)12] [Y2(NO3)4(piv)4]·2CH3CN (DC1) (pivH = pivalic acid), [Co7(N3)12(CH3CN)10(NO3)0.4 (Cl)1.6]·4CH3CN (DC2) and [Co7(N3)12(CH3CN)10(NO3)2]·4CH3CN (DC3), in which the metal ions are exclusively bridged by end-on azido ligands to stabilize a beautiful disk-like topology. The resulting clusters exhibit interesting structural transformations and thermodynamically-distinct steady states verified by theoretical calculations. Magnetic studies reveal the first observation of zero-field SMM behaviour in disk-like heptanuclear CoII complexes.

Photocatalytic Reaction in Aqueous Suspension: FTIR Spectroscopy with Attenuated Total Reflection in Diamonds.

The photocatalytic conversion of an organic compound on rutile nanoparticles dispersed in aqueous solutions was characterized by infrared absorption spectroscopy. A diamond prism for total reflection of infrared light provided convenient and reliable access to the absorption spectrum of adsorbed chemical species photocatalytically converted under ultraviolet light irradiation. Pivalic acid, a reactant to be decarboxylated by hole capture, was dissolved in water at concentrations of 100-3 mmol L-1 and exhibited vibrational bands of 0.01-0.001 absorbance in the 1500-1100 cm-1 wave number region. When rutile particles were suspended in the solutions, dissociative adsorption leading to the formation of pivalate anions on the particles was detected in vibrational spectra. The adsorbed pivalate anions decomposed by ultraviolet light irradiation through the prism, releasing CO2. In an anaerobic atmosphere, the excited electrons were accommodated in the particles as small polarons, resulting in an optical absorption centered at 7000 cm-1. Conversely, in an aerobic atmosphere, the electrons were transferred to the surrounding atmosphere, eliminating the polaron-induced absorption. This study demonstrates the feasibility of infrared absorption spectroscopy for operando monitoring of vibrational and electronic transitions, enabling the tracking of photochemical reactions at liquid-solid interfaces.

A Zn-based Zig-Zag 1D chain type coordination polymer for removal of methylene blue dye from an aqueous solution

A 1D zig-zag zinc coordination chain, [Zn(piv)2]n (1) (where piv = pivalic acid) has been synthesized by a reaction of ZnCl2 with O-donor pivalic acid in the mixed solvent system (MeCN/MeOH) and structurally characterized via ultraviolet–visible spectroscopy (UV), Fourier transform infrared (FT-IR) spectroscopy, elemental analysis, and X-ray crystallography. The crystal structure is a bridging chain of zinc metal connected via pivalic acids. The synthesized coordination polymer was explored for photochemistry to study photoluminescence and photocatalytic properties. The photocatalytic properties were investigated against methylene blue (MB) dye under UV light illumination. Under optimal reaction conditions (catalyst dosage = 10 mg, initial concentration of dye = 20 mg/L, pH = 9) the maximum photodegradation of methylene blue was found to be 72.56% in 120 min illumination time. The photocatalytic reaction showed pseudo-second-order kinetics with a rate constant of 0.012 L.mg−1.min−1. Furthermore, the recyclability test showed that compound 1 retained its photocatalytic potential even after five successive uses. The compound 1 could be a proficient and economical choice for the photocatalytic elimination of pollutants from wastewater.

Exploring electrochemical and magnetic properties of Fe(III) coordination cluster: An efficient electrocatalyst for water oxidation

In the present study, we investigated the electrochemical, water oxidation and magnetic properties of iron complex, [Fe6III(µ3-O)2(piv)6(edteH)2(N3)2] (1), (where = piv: pivalic acid and edteH4; N,N,N′,N′-Tetrakis(2-hydroxyethyl)ethylenediamine). To investigate the electrocatalytic activity of 1 for water splitting, linear sweep voltammetry (LSV) was executed to acquire the polarization curve at a scan rate of 5 mVs−1. Electrochemical Impedance Spectroscopy (EIS) was measured to obtain resistance values. The electrochemical investigation indicates about the high efficiency of the complex for the oxidation of water and overpotential 210 mV with 10 mA.cm−2 inclusive of Tafel slope of 88 m.V.dec−1. The high value of current density confirms about the proof of oxygen evolution behavior for the complex. In EIS study, the low value of charge transfer resistance indicates the fast kinetics in water-splitting process (OER) which complies with the LSV results and tafel slopes. In chronopotentiometry test, there was no significant catalytic degradation and no observable change in potential over 24 h that is confirmation about excellent stability of the compound. Magnetic study reveals the existence of strong antiferromagnetic interactions in this complex. Moreover, magnetization indicates a value of 10.02 at 70 kOe which is a good Brillouin fitting with S = 5.0 and g = 2.0.

Influence of organic acids on locomotor activity of Stratiolaelaps scimitus (Mesostigmata, Laelapidae)

Increasing the activity of zoophage Acari in agrocenoses, for example luring them to concentrations of harmful insects, could be effectively performed using attractants, for example organic acids that people use in households and industry. In our experiment, we studied the influence of organic acids on the locomotor activity of Stratiolaelaps scimitus (Womersley, 1956) (Mesostigmata, Laelapidae). Different organic acids caused certain reactions in those zoophages. Acetic acid encouraged this mite to activity and attracted it, while thioacetic acid inhibited and repelled it. Fatty acids such as tridecylic and oleic acids had an activating effect on the locomotor activity of S. scimitus. Three isomers of valeric acid inhibited locomotor activity, and the mites exerted negative chemostasis to them. Maximum locomotor activity of the mites was observed when using asparagine, ornithine, propionic acid, tridecanoic acid, boric acid, and arginine. Locomotor activity of the mites was inhibited by 3,3-dimethylbutanoic acid, thioacetic acid, pivalic acid, maleic acid, formic acid, succinic acid, 2-methylbutanoic acid, isovaleric acid, 6-aminohexanoic acid, and 2-oxoglutaric acid. We propose using attractiveness coefficient and coefficient of migratory activity, which reflect the effects of aroma compounds on mites. Those coefficients are helpful in identification of a behaviour model for mites exposed to aroma compound: attack, motionless state or escape. High attractiveness and migratory-activity coefficients mean attack on victim; low coefficients indicate motionless mites; high migratory activity and low attractiveness coefficient mean escape reaction. Our results indicate complexity of behaviour reactions of mites, which were sensitive to volatile chemical compounds in the environment. We found a high potential of using those compounds in attracting zoophages during their introduction in agrocenoses of greenhouses and open plots.

Ultra-Endurance triathlon competition shifts fecal metabolome independent of changes to microbiome composition.

Understanding changes to gut microbiota composition and metabolic output in response to acute exercise may be necessary for understanding the mechanisms mediating the long-term health and performance benefits of exercise. Our primary objective was to characterize acute changes in the fecal microbiome and metabolome following participation in an ultra-endurance (3.9 km swim, 180.2 km bike, 42.2 km run) triathlon. An exploratory aim was to determine associations between athlete-specific factors [race performance (i.e., completion time) and lifetime years of endurance training] with pre-race gut microbiota and metabolite profiles. Stool samples from 12 triathletes (9 males/3 females; 43 ± 14 yr, 23 ± 2 kg/m2) were collected ≤48 h before and the first bowel movement following race completion. Intra- and inter-individual diversity of bacterial species and individual bacterial taxa were unaltered following race completion (P > 0.05). However, significant reductions (P < 0.05) in free and secondary bile acids [deoxycholic acid (DCA), 12-keto-lithocholic acid (12-ketoLCA)] and short-chain fatty acids (butyric and pivalic acids), and significant increases (P < 0.05) in long-chain fatty acids (oleic and palmitoleic acids) were observed. Exploratory analyses revealed several associations between pre-race bacterial taxa and fecal metabolites with race performance and lifetime history of endurance training (P < 0.05). These findings suggest that 1) acute ultra-endurance exercise shifts microbial metabolism independent of changes to community composition and 2) athlete performance level and training history relate to resting-state gut microbial ecology.NEW & NOTEWORTHY This is the first study to characterize acute changes in gut microbial ecology and metabolism following an ultra-endurance triathlon. We demonstrate changes in gut microbial community function, but not structure, as well as several associations between gut microbiome and fecal metabolome characteristics with race completion time and lifetime history of endurance training. These data add to a small but growing body of literature seeking to characterize the acute and chronic effects of exercise on the gut microbial ecosystem.

Zinc-based solvents free coordination complexes: Synthesis, structures, photoluminous properties, DFT calculations and Hirshfeld surface analysis

Two novel Zn(II) complexes, [Zn(2-MeImi)2(benz)2] (1) and [Zn(2-MeImi)2(piv)2] (2) were prepared by the reaction of Zn(NO3)2·6H2O with 2-methylimidazole (2-MeImi) and benzoic acid (benz) / pivalic acid (piv) in CH3OH/H2O solvents in triethylamine. Both these coordination compounds were characterized by different methods like UV, IR, elemental analysis, thermogravimetric study and single X-ray crystallography. In (1) and (2), 2-methylimidazole and two carboxylates in each complex are coordinated and overall these complexes exhibit distorted tetrahedral geometry. Carboxylates (benz and piv) act as a monodentate ligands in 1 and 2, respectively. The photoluminescence (PL) properties of 1 and 2 were recorded at 230 nm and broad peaks in 1 and 2 might be due to presence of the instruct defect states of zinc. The weak peaks in both of the complexes can be imputed because the relaxation of electrons comes out of the higher energy level to lower. In complexes 1 and 2, the intermolecular interactions were investigated by 3D Hirshfeld surface analysis (dnorm, fragment patch, curvedness and shape index) and 2D fingerprint plots. DFT calculation was used to further investigate the structural parameters of these complexes and their electronic transitions which results of DFT calculation were compatible with experimental findings.

Azole derivatives inhibit wildtype butyrylcholinesterase and its common mutants.

Azoles, which have been used for antifungal chemotherapy for decades, have recently been of interest for their efficacy against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). There is little known about the potential of azoles against BChE, however there is none regarding their inhibitory effects against mutants of BChE. In the current study, an azole library of 1-aryl-2-(1H-imidazol-1-yl)ethanol/ethanone oxime esters were tested against AChE and BChE, which yielded derivates more potent than the positive control, galantamine, against both isoforms. Kinetic analyses were performed for wildtype and mutant (A328F and A328Y) inhibition for the two most potent BChE inhibitors, pivalic and 3-bezoylpropanoic acid esters of 2-(1H-imidazol-1-yl)-1-(2-naphthyl)ethanol, which were found to have great affinity to the wildtype and mutant BChE types with Ki values as low as 0.173 ± 0.012 µM. The compounds were identified to show linear competitive or mixed type inhibition. Molecular modeling confirmed these kinetic data and provided further insights regarding molecular basis of BChE inhibition by the active derivatives. Thus, current study suggests new azole derivatives with promising cholinesterase inhibitory effects and reveals the first set of information to promote our understanding for the inhibitory behavior of this class against the mutant BChE forms.

High-Throughput Area-Selective Spatial Atomic Layer Deposition of SiO2 with Interleaved Small Molecule Inhibitors and Integrated Back-Etch Correction for Low Defectivity.

A first-of-its-kind area-selective deposition process for SiO2 is developed consisting of film deposition with interleaved exposures to small molecule inhibitors (SMIs) and back-etch correction steps, within the same spatial atomic layer deposition (ALD) tool. The synergy of theseaspects results in selective SiO2 deposition up to~23nm with high selectivity and throughput, with SiO2 growth area and ZnO nongrowth area. The selectivity is corroborated by both X-ray photoelectron spectroscopy (XPS) and low-energy ion scattering spectroscopy (LEIS). The selectivity conferred by two different SMIs, ethylbutyric acid, and pivalic acid has been compared experimentally and theoretically. Density Functional Theory (DFT) calculations reveal that selective surface functionalization using both SMIs is predominantly controlled thermodynamically, while the better selectivity achieved when using trimethylacetic acid can be explained by its higher packing densitycompared to ethylbutyric acid. By employing the trimethylacetic acid as SMI on other starting surfaces (Ta2 O5 , ZrO2 ,etc.) and probing the selectivity, a broader use of carboxylic acid inhibitors for different substrates is demonstrated. It is believed that the current results highlight the subtleties in SMI properties such as size, geometry, and packing, as well as interleaved back-etch steps, which are key in developing ever more effective strategies for highly selective deposition processes.

Laccase encapsulation immobilized in mesoporous ZIF-8 for enhancement bisphenol A degradation.

Endocrine disruptors (EDCs) such as bisphenol A (BPA) have many adverse effects on environment and human health. Laccase encapsulation immobilized in mesoporous ZIF-8 was prepared for efficient degradation of BPA. The ZIF-8 (PA) with highly ordered mesopores was synthesized using trimethylacetic acid (PA) as a template agent. On account of the improvement of skeletal stability by cross-linking agent glutaraldehyde, ZIF-8 (PA) realized laccase (FL) immobilization within the mesopores through encapsulation strategy. By replacing the template agent, the effect of pore size on the composite activity and immobilization efficiency by SEM characterization and kinetic analysis were investigated. Based on the physical protection of ZIF-8(PA) on laccase, as well as electrostatic interactions between substances and changes in surface functional groups (e.g. -OH, etc.), multifaceted enhancement including activity, stability, storability were engendered. FL@ZIF-8(PA) could maintain high activity in complex systems at pH 3-11, 10-70°C or in organic solvent containing system, which exhibited an obvious improvement compared to free laccase and other reported immobilized laccase. Combined with TGA, FT-IR and Zeta potential analysis, the intrinsic mechanism was elaborated in detail. On this basis, FL@ZIF-8(PA) achieved efficient removal of BPA even under adverse conditions (removal rates all above 55% and up to 90.28%), and was suitable for a wide range of initial BPA concentrations. Combined with the DFT calculations on the adsorption energy and differential charge, the mesoporous could not only improve the enrichment performance of BPA on ZIFs, but also enhance the interaction stability. Finally, FL@ZIF-8(PA) was successfully applied to the degradation of BPA in coal industry wastewater. This work provides a new and ultra-high performances material for the organic pollution treatment in wastewater.

β‐ and γ‐C(sp3)−H Heteroarylation of Free Carboxylic Acids: A Modular Synthetic Platform for Diverse Quaternary Carbon Centers

AbstractPdII‐catalyzed C(sp3)−H activation of free carboxylic acids represents a significant advance from conventional cyclopalladation initiated reactions. However, developing a modular synthetic platform for diverse quaternary and tertiary carbon centers based on this reactivity, two challenges remain to be addressed: mono‐selectivity in each consecutive C−H functionalization step; compatibility with heteroatoms. While the exclusive mono‐selectivity was achieved by β‐lactonization/nucleophilic attack, the latter limitation remains to be overcome. Herein, we report the PdII‐catalyzed β‐ and γ‐C(sp3)−H heteroarylation of free carboxylic acids using pyridine‐pyridone ligands capable of overcoming these limitations. A sequence of three consecutive C(sp3)−H activation reactions of pivalic acid provides an unique platform for constructing diverse quaternary carbon centers containing heteroaryls which could serve as an enabling tool for escaping the flat land in medicinal chemistry.

β- and γ-C(sp3 )-H Heteroarylation of Free Carboxylic Acids: A Modular Synthetic Platform for Diverse Quaternary Carbon Centers.

PdII -catalyzed C(sp3 )-H activation of free carboxylic acids represents a significant advance from conventional cyclopalladation initiated reactions. However, developing a modular synthetic platform for diverse quaternary and tertiary carbon centers based on this reactivity, two challenges remain to be addressed: mono-selectivity in each consecutive C-H functionalization step; compatibility with heteroatoms. While the exclusive mono-selectivity was achieved by β-lactonization/nucleophilic attack, the latter limitation remains to be overcome. Herein, we report the PdII -catalyzed β- and γ-C(sp3 )-H heteroarylation of free carboxylic acids using pyridine-pyridone ligands capable of overcoming these limitations. A sequence of three consecutive C(sp3 )-H activation reactions of pivalic acid provides an unique platform for constructing diverse quaternary carbon centers containing heteroaryls which could serve as an enabling tool for escaping the flat land in medicinal chemistry.

Ligand-dependent structural diversity and optimizable CO2 chemical fixation activities of Cu-doped polyoxo-titanium clusters.

Heterometallic oxo clusters have been attracting intensive interest due to their unique properties originating from the synergistic interactions between different components. Herein, we report the construction and catalytic applications of a family of copper-doped polyoxo-titanium clusters (Cu-PTCs) coordinated with different acetate derivative ligands. The solvothermal reactions of metal salts and trimethylacetic acid or 1,2-phenylenediacetic acid in ethanol produced Ti6Cu3(μ3-O)4(μ2-O)(OEt)16(L1)4 (L1 = trimethyl acetate, PTC-367) and H2Ti8Cu2Br2(μ4-O)2(μ2-O)4(OEt)20(L2)2 (L2 = 1,2-phenylenediacetate, PTC-368), respectively. When smaller acetic acid was introduced as a stabilizing ligand, higher nuclei H2Ti16Cu3(μ4-O)5(μ3-O)15(μ2-O)3(OiPr)18(Ac)8 (Ac = acetate, PTC-369) and H3Ti29Cu3(μ4-O)6(μ3-O)30(μ2-O)8(OiPr)17(Ac)20 (PTC-370) were prepared. The number of metal ions exposed on the surface of the four clusters changes due to variations in the steric hindrance of functionalizing ligands, and theoretically, so does their catalytic activity as Lewis acids. In light of this, we conducted a carbon dioxide cycloaddition reaction in an atmospheric environment and the four obtained compounds displayed increasing catalytic activities from PTC-367 to PTC-370. These results provide a feasible synthetic method for modulating the structures of Cu-doped titanium oxide materials and improving their catalytic activities.

Solid-state red-emissive (cyano)vinylene heteroaromatics via Pd-catalysed C-H homocoupling.

Thiophene-based π-conjugated systems are important materials for organic electronics; thus, their synthesis is of topical interest. We report fluorescent thiophene/furan-based vinylene and cyanovinylene systems via Pd-catalysed homocoupling [Pd(OAc)2, pivalic acid, KOAc, DMAc, 140 °C]. The methodology is versatile and allows the development of a variety of π-conjugated systems without the need for pre-functionalized building units. The reaction tolerates electron-rich, electron-deficient and large π-conjugated substrates. The developed compounds absorb in the visible region (400-515 nm) and emit green to orange fluorescence in the solution state (510-600 nm). Most importantly, the compounds exhibit strong aggregation-induced emission (AIE) in the NIR region (λem = 650 nm), with quantum yields reaching up to 10%. Steric hindrance imparted by vinylene/cyanovinylene units is responsible for the strong solid-state luminescence. DFT-optimized structures reveal an apparent twist of 20-40° in the molecular backbone of the compounds, supporting the AIE behaviour of the compounds.

Tetrapyridineplatinum(II) Carboxylates: Synthesis and Crystal Structure

A series of mono- and bimetallic cation-anionic complexes based on the [PtPy4]2+ cation with different single-charge anions of carboxylic acids (RCOO–) is synthesized and structurally characterized. A synthetic approach to the preparation of tetrapyridineplatinum complexes [PtPy4]2+ soluble in polar solvents from available reagents is developed. The reaction of tetrapyridineplatinum dichloride [PtPy4](Cl)2 with silver acetate or trifluoroacetate affords compounds [PtPy4](OOCMe)2·6H2O (I) and [PtPy4](OOCCF3)2· 2H2O (II) in the form of crystalline hydrates (CIF files CCDC nos. 2161100 and 2161101, respectively) in high yields. Other carboxylates can be prepared by the treatment of compound I with an excess of a stronger acid, for example, trifluoroacetic acid, with the formation of the corresponding complex trifluoroacetate [PtPy4](OOCCF3)2·4CF3COOH (IIa) (CIF file CCDC no. 2161102). Another method consists of the displacement of acetic acid with an excess of a lowly volatile acid, for example, pivalic acid, when [PtPy4](Piv)2· 5HPiv (III) is formed from the acid melt, and solvatomorph [PtPy4](Piv)2·4HPiv·3C6H12 (IIIa) (CIF files CCDC nos. 2161103 and 2161104, respectively) is formed in a cyclohexane medium. Heteroanionic heterometallic complex [PtPy4](OOCFc)(OOCMe) (IV) (CIF file CCDC no. 2161105) is shown to be formed by the reaction of complex I with ferrocenecarboxylic acid under mild conditions.

A one-step base-free synthesis of N-arylamides via modified pivaloyl mixed anhydride mediated amide coupling.

Pivalic anhydride is shown to be an effective reagent for direct amidation of carboxylic acids with N-alkyl anilines. The only by-product of this reaction is nontoxic pivalic acid, which can be easily removed by aqueous workup. The reactions are conducted under mild conditions and found to be compatible with a range of carboxylic acids, including aromatic, heterocyclic, acrylic, and aliphatic carboxylic acids and amino acids generating the desired amides in short reaction times.

A new cobalt(ii)–lithium(i) carboxylate complex with an N,O-donor mono-iminoacenaphthenone ligand: synthesis, structure and magnetic behavior

A new carboxylate complex [Co2Li2(Piv)6(L)2]·CH3CN (1) (Piv is the anion of pivalic acid) has been synthesized and structurally characterized. It exhibits a field induced slow magnetic relaxation.