Acetonitrile Yields Research Articles

Macrocyclic bis-diphosphenes demonstrating bimetallic exo- and endo-cyclic binding modes.

Macrocyclic bis-diphosphenes, formally heavier derivatives of macrocyclic azobenzenes, are accessed for the first time. These are synthesised in a reproducible fashion, through the nickel-mediated homocoupling of xanthene-derived NHC-stabilised bis-phosphinidene units. This gives direct access to target macrocyclic bis-diphosphenes 2, featuring exo-cyclic coordinated Ni0 fragments. The endo-cyclic binding mode in 3 is realised by NHC-abstraction using CuCl, so demonstrating two homometallic binding modes for this system. Additionally, reaction with CuCl in acetonitrile yields small amounts of a tetra-metallic NiII/CuI complex, which establishes simultaneous exo- and endo-cyclic metal binding. Fluctional solution state behavior in these systems is explored through variable temperature NMR spectroscopy, in addition to computational bonding analyses, giving the first insights into this novel class of compounds.

Ethane Ammoxidation over Sn/H-Zeolite Catalysts: Toward the Factors Contributing to the Yield of Acetonitrile.

Different Sn/H-zeolite (β, MOR, SSZ-13, FER, and Y zeolite) catalysts are prepared with the improved impregnation method. The effects of reaction temperature and the composition of the reaction gas (ammonia, oxygen, and ethane) on the catalytic reaction are investigated. Adjusting the fraction of ammonia and/or ethane in the reaction gas can effectively strengthen the ethane dehydrogenation (ED) route and ethylamine dehydrogenation (EA) route and inhibit the ethylene peroxidation (EO) route, whereas the adjustment of oxygen cannot effectively promote acetonitrile formation because it cannot avoid enhancing the EO route. By comparing the acetonitrile yields on different Sn/H-zeolite catalysts at 600 °C, it is revealed that the ammonia pool effect, the residual Brönsted acid in the zeolite, and the Sn-Lewis acid synergistically catalyze ethane ammoxidation. Moreover, a higher L/B ratio of the Sn/H zeolite is beneficial to the improvement of acetonitrile yield. With a certain application potential, the Sn/H-FER-zeolite catalyst shows an ethane conversion of 35.2% and an acetonitrile yield of 22.9% at 600 °C; although a similar catalytic performance was observed on the best Co-zeolite catalyst in literature, the Sn/H-FER-zeolite catalyst is more selective to ethene and CO than the Co catalyst. In addition, the selectivity to CO2 is less than 2% of that on the Sn-zeolite catalyst. This may be attributed to the special 2D topology and pore/channel system of the FER zeolite, which guarantee an ideal synergistic effect of the ammonia pool, the residual Brönsted acid in the zeolite, and the Sn-Lewis acid for the Sn/H-FER-catalyzed ethane ammoxidation reaction.

One-step selective dehydrogenation of cyclic hemiacetal sugars toward to their chiral lactones

Chiral glycosyl lactone is an important class of bioactive compound and pharmaceutical intermediate in nature, especially for chiral lactones with 4 carbon atoms, which are very useful building blocks for synthesis of biologically interesting compounds. Herein, a selective dehydrogenation and solvent matched catalytic system under oxygen-free conditions was developed to try to achieve the one-step direct conversion of cyclic hemiacetal sugars toward their chiral glycosyl lactones. During the process, the inherent structural characteristics of sugar was efficiently utilized, and the transfer of its chiral centers was realized. Under the optimum condition, the corresponding lactones were successfully prepared from C4-C6 sugars with cyclic hemiacetal structure in acetonitrile. The reaction mechanism in acetonitrile was explored by the first principle density functional theory calculations and tracking reaction process. It was found that the high lactone yield in acetonitrile was due to the high proportion of α-conformation form among multiple tautomers in it. This selective dehydrogenation process may further extend the possibility of the preparation of chiral synthons from carbohydrates directly.

Watching Hydrogens Migrate: Step by Step from [ReI(η6-C6H6)2]+ to [ReIII(η3-C6H9)(η6-C6H6)(NCCH3)2]2.

Arene substitution reactions in [M(η6-arene)2]0/2+ are well documented for Groups 6 and 8 but are essentially unknown for the manganese triad. Aiming to replace benzene in [ReI(η6-C6H6)2]+, we altered the hapticity of one coordinated benzene, which we found to be tunable stepwise from an η6 to an η3-allyl coordination mode. Reduction of [ReI(η6-C6H6)2]+ with hydrides gives [ReI(η5-C6H7)(η6-C6H6)]. Subsequent addition of acid yields [ReIIIH(η5-C6H7)(η6-C6H6)]+, which converts to [ReI(η4-C6H8)(η6-C6H6)NCCH3]+ in acetonitrile. Further protonation gives the title complex [ReIII(η3-C6H9)(η6-C6H6)(NCCH3)2]2+ by a rhenium-mediated, intramolecular hydride shift. Herein, we present a full mechanistic elucidation of these transformations based on NMR studies, isolation of reaction intermediates, and their full characterizations. The structural feature {ReIII(η6-C6H6)} is unprecedented. Direct arene exchange from [ReI(η6-C6H6)2]+ to [ReI(η6-arene)(η6-C6H6)]+ was found only under strongly acidic conditions in neat arene. The analogous chemistry of the lighter homologue technetium (99Tc) is distinctly different. Treatment of [TcI(η5-C6H7)(η6-C6H6)] with acid in acetonitrile yields only mixtures of [TcI(η6-C6H6)2]+ and [TcII(NCCH3)6]2+.

Catalytic and biological reactivities of mononuclear copper (II) and vanadyl (II) complexes of naphthalenylimino-phenolate sodium sulfonate

Two novel water-soluble mononuclear Cu(II) and VO(II)-complexes (CuSL and VOSL, respectively) were synthesized from easily accessible 2-((naphthalen-1-ylimino)methyl)phenolate sodium sulfonate as a Schiff base ligand (HSL). HSL, CuSL and VOSL were characterized by various spectral tools. Their catalytic potential was investigated and compared in 1,2-cyclohexene epoxidation using H2O2 or tBuOOH as an oxidizing agent, and in C―C cross-coupling protocols, including Suzuki-Miyaura and Sonogashira reactions, under homogeneous reaction conditions. Both complexes exhibited good catalytic potential in the epoxidation reaction. VOSL complex with the high oxidation state metal ion (VIV) exhibited slightly better performance in the epoxidation reaction, provided 93, 77 and 89% yield in acetonitrile, water and under solvent free condition. In contrast CuSL complex provided 89, 71 and 79% yield under the same reaction condition. While in Suzuki-Miyaura and Sonogashira C―C reactions using phenylboronic acid or phenylacetylene with aryl halides, CuSL afforded better catalytic potential (89% for Suzuki-Miyaura and 77% yield for Sonogashira C―C products) than VOSL catalyst (73% and 51% yield respectively). DFT studies were also carried to understand the catalytic behavior of CuSL and VOSL catalysts in their catalytic processes. Additionally HSL, CuSL and VOSL were also explored for their biological potential against some pathogens strains, as antimicrobial, antioxidant and anticancer agents. Both complexes (CuSL and VOSL) showed better inhibiting potential than their free ligand. The complex ctDNA-interaction was examined by UV–vis. spectrophotometry, viscosity measurements and gel electrophoresis to determine the nature of binding. Additionally, molecular docking was also carried out for better understanding.

Fully Solvated, Monomeric ReII Complexes: Insights into the Chemistry of [Re(NCCH3)6]2.

The oxidation of [Re(η6-C10H8)2]+ with AgI in acetonitrile yields [Re(NCCH3)6]2+. This fully solvated ReII compound was characterized by spectroscopic methods and X-ray structure analyses. We show that [Re(NCCH3)6]2+ acts as a precursor complex for a variety of substitution reactions. Treatment with monodentate triphenylphosphine (PPh3) and bidentate 1,2-bis(diphenylphosphino)ethane (dppe) yields the complexes [trans-Re(PPh3)2(NCCH3)4]2+ and [trans-Re(dppe)2(NCCH3)2]+, respectively. [trans-Re(dppe)2(NCCH3)2]+ is oxidized under mild conditions by AgI to its ReII analogue [trans-Re(dppe)2(NCCH3)2]2+. Reactions of [Re(NCCH3)6]2+ with a halide mixture consisting of NaX and AgX (X = Cl, I) result in the formation of the corresponding ReIII complexes [trans-ReX2(NCCH3)4]+. [trans-ReBr2(NCCH3)4]+ can be obtained directly from [Re(η6-C10H8)2]+ by oxidation with FeBr3 in acetonitrile. The title compound is thus a convenient starting material for ReII and ReIII complexes by simple solvent exchange, which are otherwise difficult to access.

An effective process for the synthesis of dihydropyridines via SO4−2/SnO2‐catalyzed Hantzsch reaction

AbstractSulfated tin oxide (STO) was established as an admirable heterogeneous catalyst for the single‐step synthesis of dihydropyridine derivatives via Hantzsch reaction. The synthetic method was mainly used in the presence of STO as a heterogeneous solid catalyst. STO‐catalyzed Hantzsch reaction afforded good yields (90–94%) in acetonitrile at 80°C. The synthesized titled compounds were characterized and confirmed by High Resolution Mass Spectroscopy (HRMS), Fourier Tranform‐Infrared (FTIR), 1H and 13C‐NMR, and spectral data.

A thiocoumarin-based turn-on fluorescent probe for hypochlorite detection and its application to live-cell imaging

A thiocoumarin-based turn-on fluorescence probe for the detection of hypochlorite anion (ClO−) was prepared and characterized. Coumarin dye (CZCN-O) exhibited intense fluorescence with good quantum yields (ΦPL = 0.98) in acetonitrile. Contrastingly, the fluorescence of thiocoumarin dye (CZCN-S) was almost completely quenched (ΦPL < 0.01) because of the efficient intersystem crossing from the emissive singlet excited state to the non-emissive triplet state. The addition of ClO− to the PBS buffer (pH = 7.4, containing 50% ACN) of thiocoumarin resulted in a remarkable fluorescence enhancement with an emission maximum at 486 nm, indicating the sensitive OFF–ON fluorescence sensing of ClO−. The calculated detection limit of ClO− in 50% aqueous ACN was 0.17 μM. An investigation of the sensing behavior to various analytes revealed that thiocoumarin dye had an excellent selectivity for ClO−. The recognition mechanism was attributed to the ClO−-induced conversion of thiocarbonyl coumarin into its oxo analogue through oxidative desulfurization. In particular, cell studies demonstrated that thiocoumarin dye could be used as an effective fluorescent probe for the detection of ClO− in living cells.

A Vanadium(III) Complex with Blue and NIR-II Spin-Flip Luminescence in Solution.

Luminescence from Earth-abundant metal ions in solution at room temperature is a very challenging objective due to the intrinsically weak ligand field splitting of first-row transition metal ions, which leads to efficient nonradiative deactivation via metal-centered states. Only a handful of 3dn metal complexes (n ≠ 10) show sizable luminescence at room temperature. Luminescence in the near-infrared spectral region is even more difficult to achieve as further nonradiative pathways come into play. No Earth-abundant first-row transition metal complexes have displayed emission >1000 nm at room temperature in solution up to now. Here, we report the vanadium(III) complex mer-[V(ddpd)2][PF6]3 yielding phosphorescence around 1100 nm in valeronitrile glass at 77 K as well as at room temperature in acetonitrile with 1.8 × 10-4% quantum yield (ddpd = N,N'-dimethyl-N,N'-dipyridine-2-ylpyridine-2,6-diamine). In addition, mer-[V(ddpd)2][PF6]3 shows very strong blue fluorescence with 2% quantum yield in acetonitrile at room temperature. Our comprehensive study demonstrates that vanadium(III) complexes with d2 electron configuration constitute a new class of blue and NIR-II luminophores, which complement the classical established complexes of expensive precious metals and rare-earth elements.

Realistic Ion Dynamics through Charge Renormalization in Nonaqueous Electrolytes.

While many practically important electrolytes contain lithium ions, interactions of these ions are particularly difficult to probe experimentally because of their small X-ray and neutron scattering cross sections and large neutron absorption cross sections. Molecular dynamics (MD) is a powerful tool for understanding the properties of nonaqueous electrolyte solutions from the atomic level, but the accuracy of this computational method crucially depends on the physics built into the classical force field. Here, we demonstrate that several force fields for lithium bistriflimide (LiTFSI) in acetonitrile yield a solution structure that is consistent with the neutron scattering experiments, yet these models produce dramatically different ion dynamics in solution. Such glaring discrepancies indicate that inadequate representation of long-range interactions leads to excessive ionic association and ion-pair clustering. We show that reasonable agreement with the experimental observations can be achieved by renormalization of the ion charges using a "titration" method suggested herewith. This simple modification produces realistic concentration dependencies for ionic diffusion and conductivity in <2 M solutions, without loss in quality for simulation of the structure.

Understanding Structural Changes through Excited-State Intramolecular Proton Transfer in 4'-N,N-Diethylamino-3-hydroxyflavone (DEAHF) in Solution Based on Quantum Chemical Calculations.

To design novel dyes with a controllable fluorescence on-off switching mechanism, understanding the dark state at the atomic level should be a key focus. In this study, we focused on the radiative and nonradiative mechanisms of 4'-N,N-diethylamino-3-hydroxyflavone (DEAHF) based on theoretical and experimental viewpoints. In the excited state, an excited-state intramolecular proton transfer (ESIPT) reaction of DEAHF occurs, and both the normal (N*) and tautomer (T*) forms exist in solution. To discuss the electronic structure changes through ESIPT, we mainly focused on two structural changes: the rotation of the diethylamino group and the bending motion of DEAHF in the excited state. The potential energy surfaces (PESs) passing through the rotation of the diethylamino group indicated that rotation may occur by thermal fluctuation during each phase. When the diethylamino group is rotated by 90° in the N* form, the oscillator strength becomes zero, which may be critical in nonradiative decay pathways. For the bending motion, we found a conical intersection, which could be a key pathway of nonradiative decay. By employing molecular orbital analysis, we concluded that the electronic structure changes induced by ESIPT play a key role in determining the decay pathways. Additionally, we compared the fluorescence quantum yield in acetonitrile with that in cyclohexane and showed that the solvent polarity also affects the radiative and nonradiative mechanisms of DEAHF.

Sustainable Production of Acetonitrile from Microalgae via Catalytic Fast Pyrolysis with Ammonia over Ga/HZSM-5 Catalysts

We report on catalytic fast pyrolysis microalgae under ammonia atmosphere into acetonitrile over Ga/HZSM-5, which provides a long-term sustainable option for acetonitrile production and microalgae valorization. The effect of various catalysts, reaction conditions and species of microalgae on acetonitrile production was explored systematically. Under the optimized conditions, the maximum carbon yield of acetonitrile from Chlorella vulgaris was 23.4%, and the selectivity of acetonitrile in bio-oil was up to 77.2%. The possible reaction pathways were proposed according to the comprehensive experimental investigation on the conversion of model compounds and intermediates (proteins, carbohydrates, lipids, amino acids, carboxylic acids, furans, and amines). High-resolution transmission electron microscopy (TEM) analysis showed that Ga was present mainly at the outer surface of zeolite crystals, and a small amount of Ga was doped into the zeolite crystals.

Catalytic fast pyrolysis of corn cob in ammonia with Ga/HZSM-5 catalyst for selective production of acetonitrile

In this work, corn cob was used as raw material to selectively produce acetonitrile via catalytic fast pyrolysis (CFP) in ammonia over Ga/HZSM-5 catalyst. A series of catalysts with different catalyst carriers (including HZSM-5, USY, MCM-41, HY, and γ-Al2O3) and active metals (including Fe, Co, Ni, Cu, Zn, Cr, Ca, Mg and Ga) were prepared and screened. The reaction conditions, such as temperature, ammonia flow rate and residence time were changed to investigate the effect on the product distribution and acetonitrile production. The results indicated that with the desired catalyst (2% Ga/HZSM-5) and optimal reaction conditions (Temperature 700 °C; ammonia flow rate 80 ml/min; residence time 2.4 s), the highest carbon yield of acetonitrile from corn cob with a value of 18.4% could be obtained, and the carbon selectivity in bio-oil was 83.5%. This study provides an economical and environmental-friendly method for the direct production of acetonitrile from abundant biomass.

Facile Preparation of Organometallic Nanorods from Various Ethynyl-Substituted Molecules.

A facile method to prepare one‐dimensional (1D) organometallic nanomaterials from various ethynyl‐substituted molecules is reported. The reactions of 3‐chloro‐1‐ethynylbenzene, p‐tBu‐phenylacetylene and 4‐ethynylbiphenyl with Cu+ ions in acetonitrile yield nanorod‐shaped copper acetylides (Cu−C≡C−R) crystals. In the case of linear alkynes, namely, propyne, 1‐pentyne and 1‐hexyne, it was found that using an aqueous ammonia/ethanol mixed solvent instead of acetonitrile is a better approach to obtain 1D nanostructures. This procedure also enables us to prepare functional 1D nanomaterials. We demonstrate the preparation of a paramagnetic nanorod from the organic radical p‐ethynylphenyl nitronyl nitroxide, and fluorescent nanorods from 9‐ethynylphenanthrene and 2‐ethynyl‐9,9′‐spirobifluorene.

Production of acetonitrile via catalytic fast pyrolysis of biomass derived polylactic acid under ammonia atmosphere

In this study, a series of catalysts including different metal oxides loading on HZSM-5(Si/Al = 25) and cobalt oxides loading on different supports were synthesized to catalyze fast pyrolysis (CFP) of biomass derived polylactic acid (PLA) to produce acetonitrile under ammonia atmosphere. Both the metal and the acid of the catalyst had a crucial influence on the yield of acetonitrile and Co/HZSM-5(25) produced most acetonitrile. Other factors that might affect the product distribution including cobalt loading, reaction temperature, resident time and NH3 flow rate have been investigated systematically. Under the optimized CFP condition (650 ℃; resident time 2.4 s; NH3 flow rate 80 ml/min), the carbon yield and selectivity of acetonitrile in liquid product reached 50.2% and 83.6%, respectively. The possible reaction pathway from PLA to acetonitrile was also studied and proposed. PLA firstly cracked into lactic acid through thermal decomposition and formed lactide at the same time. Then lactic acid and lactide cracked into low-molecular aldehydes, ketones and acids. These aldehydes and ketones reacted with ammonia to form imines, acids to amides, and finally to acetonitrile and small amount of proponitrile under the catalysis of Co/HZSM-5 catalyst.

Cobalt(II), copper(II), and zinc(II) isostructural, pseudotetrahedral, racemic complexes of pyrrolo[2,3-b]quinoxaline with bis(2-thienylmethyl)propylenediamine chain: Synthesis, crystal structure, spectroscopy

Cobalt(II), copper(II), and zinc(II) cations all have similar effective ionic radii so they form with (E)-1-phenyl-3-{N-[N′,N′-bis(thiophen-2-ylmethyl)-3-aminopropyl]aminophenylmethylidene}-1,3-dihydro-2H-pyrrolo[2,3-b]quinoxalin-2-one (1) isostructural, pseudotetrahedral complexes 2a, 2b, and 2c, respectively. Single crystal X-ray analysis of the synthesized complexes reveals that they are chiral (Λ-M-pS, pS; Δ-M-pR, pR) and crystalize as racemates in P 21/c space group. There is axial chirality connected with tetrahedrally substituted metal center and crystallization induced planar chirality of two symmetry independent ligand molecules (different conformers). In solution only metal center chirality is maintained due to the conformational lability of the 3-[N,N-bis(thien-2-ylmethyl)amino]propyl group. Chirality of zinc complex 2c in solution was confirmed by the analysis of 1D and 2D NMR spectra. NMR data show diastereotopic protons of aliphatic chain and the restriction of phenyl ring rotation at C(30) carbon atom. Complex 2c is fluorescent in solid state as well as in solution (fluorescence quantum yield in acetonitrile, ϕ = 0.1). The NMR titration at room temperature shows that the major product of zinc coordination is not 2c but the complex with a tautomeric form of the ligand having proton located at N(4) nitrogen atom (enamine-imine tautomerism). UV–Vis data for 2a, 2b, and 2c both in solid and in solution are discussed.

Laccase‐Based Oxidative Catalytic Systems for the Aerobic Aromatization of Tetrahydroquinazolines and Related N‐Heterocyclic Compounds under Mild Conditions

In this work, for the first time, laccase (metalloenzyme)/3,5‐di‐tert‐butylcatechol (DTBC) as a new class of bioinspired quinone‐based cooperative catalytic oxidation system and laccase/2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) catalyst system were used for the aerobic oxidative synthesis of 2‐substituted quinazolines through cascade reaction of structurally divers aldehydes with 2‐aminobenzylamine. The products were obtained in good to high yields in phosphate buffer (0.1 m, 12.5 mL, pH = 4.5) and acetonitrile (4 vol.‐%) mixture as solvent at 45 °C. Other N‐heterocycles are also successfully oxidized to their aromatic counterparts.

Manipulating Triplet Yield through Control of Symmetry-Breaking Charge Transfer.

The efficiency of an organic solar cell depends on the efficacy of exciton diffusion and dissociation processes, and this can be enhanced by reducing the exciton binding energy and increasing the exciton lifetime. Zinc chlorodipyrrin (ZCl) complexes exhibit reduced exciton binding energy due to ultrafast generation of intramolecular charge transfer (ICT) states via symmetry-breaking charge transfer in polar media. This Letter explores the fate of the ICT states using nanosecond transient absorption. In cyclohexane, ZCl undergoes intersystem crossing to produce triplets with ∼8 ns time constant (∼30% yield), and no ICT states are generated. However, in more polar solvents, triplets are generated within 1 ns via ICT state recombination with ∼3 times higher yield than produced via ISC. This high triplet yield in toluene (89%) and acetonitrile (76%) via ICT state recombination is a beneficial pathway to spin-protect the excited-state decay for additional charge generation from triplet excited states.

Solvent mediated catalysis and proton-shuttling in the formation of 3-methylphthalide from a ketene intermediate

Photoexcitation of o-acetylbenzaldehyde (oABA) in acetonitrile yields, via photoinduced intramolecular hydrogen transfer, the lactone 3-methylphthalide (3MP) with a quantum yield of ca. 0.3. Femtosecond stimulated Raman spectroscopy (FSRS) measurements revealed the formation of a Z-ketene-enol ground state intermediate during this process ca. 2–3 ps after excitation [Phys. Chem. Chem. Phys. 2015, 7, 376]. UV traces furthermore indicate the occurrence of a cyclic enol form shortly before the reaction proceeds towards the lactone. To obtain insight into the reaction mechanism and to clarify the potential role of a cyclic enol, we have identified stationary points along the oABA – 3MP ground-state reaction path with DFT methods applying implicit/explicit solvation models. The computations show that the reaction can efficiently proceed with or without involvement of the cyclic enol by a) catalysis through traces of water in the solvent or b) directly via acetonitrile proton shuttling.

Cadmium(II) Chloride‐Catalyzed Dehydrative C−P Coupling of Propargyl Alcohols with Diarylphosphine Oxides to Afford Allenylphosphine Oxides

AbstractThe cadmium(II) chloride‐catalyzed dehydrative C−P cross‐coupling reaction of propargyl alcohols with diarylphosphine oxides is reported. Several propargyl alcohols including those bearing the sterically demanding tert‐butyl group at the triple bond terminus can be used as good substrates in the reaction to produce the corresponding allenylphosphine oxides in good to high yields in acetonitrile at 100 °C. The reaction can also be easily scaled up to a gram‐scale synthesis. A mechanism study indicates that the reaction may proceed through a process of propargylic substitution to generate phosphonite intermediates followed by [2,3] sigmatropic rearrangement to produce the allenyl products, rather than through a common allenylative substitution resulting from P‐nucleophilicity.magnified image