Structural, Electrical, and Optical Properties of Single-Walled Carbon Nanotubes Synthesized through Floating Catalyst Chemical Vapor Deposition

Single-walled carbon nanotube (SWCNT) thin films were synthesized by using a floating catalyst chemical vapor deposition (FCCVD) method with a low flow rate (200 sccm) of mixed gases (Ar and H2). SWCNT thin films with different thicknesses can be prepared by controlling the collection time of the SWCNTs on membrane filters. Transmission electron microscopy (TEM) showed that the SWCNTs formed bundles and that they had an average diameter of 1.46 nm. The Raman spectra of the SWCNT films suggested that the synthesized SWCNTs were very well crystallized. Although the electrical properties of SWCNTs have been widely studied so far, the Hall effect of SWCNTs has not been fully studied to explore the electrical characteristics of SWCNT thin films. In this research, Hall effect measurements have been performed to investigate the important electrical characteristics of SWCNTs, such as their carrier mobility, carrier density, Hall coefficient, conductivity, and sheet resistance. The samples with transmittance between 95 and 43% showed a high carrier density of 1021-1023 cm-3. The SWCNTs were also treated using Brønsted acids (HCl, HNO3, H2SO4) to enhance their electrical properties. After the acid treatments, the samples maintained their p-type nature. The carrier mobility and conductivity increased, and the sheet resistance decreased for all treated samples. The highest mobility of 1.5 cm2/Vs was obtained with the sulfuric acid treatment at 80 °C, while the highest conductivity (30,720 S/m) and lowest sheet resistance (43 ohm/square) were achieved with the nitric acid treatment at room temperature. Different functional groups were identified in our synthesized SWCNTs before and after the acid treatments using Fourier-Transform Infrared Spectroscopy (FTIR).

Alcohols as Substrates in Transition-Metal-Catalyzed Arylation, Alkylation, and Related Reactions

Alcohols are abundant and attractive feedstock molecules for organic synthesis. Many methods for their functionalization require them to first be converted into a more activated derivative, while recent years have seen a vast increase in the number of complexity-building transformations that directly harness unprotected alcohols. This Review discusses how transition metal catalysis can be used toward this goal. These transformations are broadly classified into three categories. Deoxygenative functionalizations, representing derivatization of the C-O bond, enable the alcohol to act as a leaving group toward the formation of new C-C bonds. Etherifications, characterized by derivatization of the O-H bond, represent classical reactivity that has been modernized to include mild reaction conditions, diverse reaction partners, and high selectivities. Lastly, chain functionalization reactions are described, wherein the alcohol group acts as a mediator in formal C-H functionalization reactions of the alkyl backbone. Each of these three classes of transformation will be discussed in context of intermolecular arylation, alkylation, and related reactions, illustrating how catalysis can enable alcohols to be directly harnessed for organic synthesis.

Iridium-Catalyzed 1,3-Rearrangement of Allylic Ethers

The 1,3-rearrangement of allylic derivatives has rarely been reported, except for allylic alcohols. Herein, we describe an iridium-catalyzed 1,3-rearrangement of readily available allylic ethers to access the difficultly prepared allylic ethers with a large steric hindrance. The developed method shows a broad substrate scope and could be used in the late-stage modification of several natural products. In addition, a possible reaction pathway is also provided on the basis of the control experiments.

Solvent-free cross aldol condensation of aldehydes and ketones over SrMo1-xNixO3-δ perovskite nanocrystals as heterogeneous catalysts

Aldol condensation is arguably one of the most fascinating reactions that leads to the formation of C-C bonds. Its use in the pharmaceutical industry to synthesis complex drugs from simple aldehydes and ketones has become of paramount importance. Although this is one reaction that has lured a lot of attention, not enough has been explored in heterogeneous catalysis. In this work we have successfully synthesized multicationic perovskites via the soft-template method and characterized them thoroughly. The synthesized perovskite nanocrystals were found to have small SBET however their catalytic application in the conversion of benzaldehyde (BAL) in the aldol condensation with diethyl ketone (DEK) was found to be astonishing. The synthesis was confirmed using many techniques, from determining the oxidation states of the materials using XPS. This gave access to determine the coordination of the metals in the perovskite lattice and also qualitatively assess the oxygen environments that exist. The oxygen vacancies and SBET were used to assess the activity of the perovskite catalysts in the cross-aldol condensation reaction. The optimal conditions for this aldol condensation were found to be 120 °C after 25 h with no solvent using SrMo0.5Ni0.5O3-δ inorganic perovskite which had the highest amount of oxygen vacant sites which gave a conversion of 88 % and an 82 % selectivity towards the desired cross-aldol condensation product. The use of dimethylformamide (DMF) for this reaction is discouraged as it reacts with BAL to produce a higher amide.

The Bis(indolylmethyl) ethers: Design, Prototypical Synthesis, and Scope Studies

The design, prototypical synthesis, isolation, and characterization of bis(indolylmethyl) ethers from corresponding indolylcarbinols is described. This approach involves very mild conditions and exhibits good scope for indolylcarbinols (both N-electron withdrawing group and N-electron donating group). Cross etherification between two electronically different indolylcarbinols is also demonstrated for the generation of unsymmetrical ethers. For the first time, the intermediacy of the bis(indolylmethyl) ethers for the formation of bis(indolyl)methanes from indolylcarbinols is proved experimentally and by 1H NMR analysis.

DMSO-Assisted K3 PO4 -Catalyzed Cooperative Metal-Free, Base-Free Etherification of Chloroheteroarenes at Low Temperature

Etherification of chloroheteroarenes was performed at low temperatures under metal-free, ligand-free and base-free conditions, that is, the reaction is promoted by the cooperative effect of DMSO (solvent) as a promoter and K3 PO4 providing the catalytic surface (rather than a base). The protocol exhibits good substrate scope under mild reaction conditions and has also been explored mechanistically.

Novel Short PEG Chain-Substituted Porphyrins: Synthesis, Photochemistry, and In Vitro Photodynamic Activity against Cancer Cells

This work presents the synthesis and characterization of metal-free, zinc (II), and cobalt (II) porphyrins substituted with short PEG chains. The synthesized compounds were characterized by UV-Vis, ¹H and ¹³C NMR spectroscopy, and MALDI-TOF mass spectrometry. The origin of the absorption bands for tested compounds in the UV-Vis range was determined using a computational model based on the electron density functional theory (DFT) and its time-dependent variant (TD-DFT). The photosensitizing activity was evaluated by measuring the ability to generate singlet oxygen (ΦΔ), which reached values up to 0.54. The photodynamic activity was tested using bladder (5637), prostate (LNCaP), and melanoma (A375) cancer cell lines. In vitro experiments clearly showed the structure-activity relationship regarding types of substituents, their positions in the phenyl ring, and the variety of central metal ions on the porphyrin core. Notably, the metal-free derivative 3 and its zinc derivative 6 exerted strong cytotoxic activity toward 5637 cells, with IC₅₀ values of 8 and 15 nM, respectively. None of the tested compounds induced a cytotoxic effect without irradiation. In conclusion, these results highlight the potential value of the tested compounds for PDT application.

Branching out: redox strategies towards the synthesis of acyclic α-tertiary ethers

Acyclic α-tertiary ethers represent a highly prevalent functionality, common to high-value bioactive molecules, such as pharmaceuticals and natural products, and feature as crucial synthetic handles in their construction. As such their synthesis has become an ever-more important goal in synthetic chemistry as the drawbacks of traditional strong base- and acid-mediated etherifications have become more limiting. In recent years, the generation of highly reactive intermediates via redox approaches has facilitated the synthesis of highly sterically-encumbered ethers and accordingly these strategies have been widely applied in α-tertiary ether synthesis. This review summarises and appraises the state-of-the-art in the application of redox strategies enabling acyclic α-tertiary ether synthesis.

Organosulphur and organoselenium compounds as emerging building blocks for catalytic systems for O-arylation of phenols, a C-O coupling reaction

Diaryl ethers form an important class of organic compounds. The classic copper-mediated Ullmann diaryl ether synthesis has been known for many years and involves the coupling of phenols with aryl halides. However, the use of high reaction temperature, high catalyst loading and expensive ligands has created a need for the development of alternative catalytic systems. In the recent past, organosulphur and organoselenium compounds have been used as building blocks for developing homogeneous, heterogeneous and nanocatalysts for this C-O coupling reaction. Homogeneous catalytic systems include preformed complexes of metals with organosulphur and organoselenium ligands. The performance of such complexes is influenced dramatically by the nature of the chalcogen (S or Se) donor site of the ligand. Nanocatalytic systems (including Pd₁₇Se₁₅, Pd₁₆S₇ and Cu_1.8S) have been designed using a single-source precursor route. Heterogeneous catalytic systems contain either metal (Cu or Pd) or metal chalcogenides (Pd₁₇Se₁₅ or Cu_1.8S) as catalytically active species. This article aims to cover the simple and straightforward methodologies and approaches that are adopted for developing catalytically relevant organosulfur and organoselenium ligands, their homogeneous metal complexes, heterogeneous and nanocatalysts. The effects of chalcogen (S or Se) donor, halogen (Cl/Br/I) of aryl halide, nature (electron withdrawing or electron donating) of substituents present on the aromatic ring of aryl halides or substituted phenols and position (ortho or para) of substitution on the results of catalytic reactions have been critically analyzed and summarized. The effect of composition (Pd₁₇Se₁₅ or Pd₁₆S₇) on the performance of nanocatalytic systems is also highlighted. Substrate scope has also been discussed in all three types of catalysis. The superiority of heterogeneous catalytic systems (e.g., Pd₁₇Se₁₅ immobilised on graphene oxide) indicates the bright future possibilities for the development of efficient catalytic systems using similar or tailored ligands for this reaction.

Synthesis of Secondary Amines with Long Chains Containing Ether Bonds

A novel class of secondary amines with long chains containing ether bonds were synthesized by a three-step protection–etherification–deprotection process from diethanolamine. The optimum reaction conditions were examined. This method has the advantages of simplicity, low cost, and high yield. Furthermore, some new downstream products (diglycolamides) were prepared from the ether-containing long-chain secondary amines as reactants, and their loading capacities in extractions of several metal ions were evaluated.

Ligand-Free Copper-Catalyzed Ullmann-Type C-O Bond Formation in Non-Innocent Deep Eutectic Solvents under Aerobic Conditions

An efficient and novel protocol was developed for a Cu-catalyzed Ullmann-type aryl alkyl ether synthesis by reacting various (hetero)aryl halides (Cl, Br, I) with alcohols as active components of environmentally benign choline chloride-based eutectic mixtures. Under optimized conditions, the reaction proceeded under mild conditions (80 °C) in air, in the absence of additional ligands, with a catalyst [Cu^I or Cu^II species] loading up to 5 mol% and K₂ CO₃ as the base, providing the desired aryloxy derivatives in up to 98 % yield. The potential application of the methodology was demonstrated in the valorization of cheap, easily available, and naturally occurring polyols (e. g., glycerol) for the synthesis of some pharmacologically active aryloxypropanediols (Guaiphenesin, Mephenesin, and Chlorphenesin) on a 2 g scale in 70-96 % yield. Catalyst, base, and deep eutectic solvent could easily and successfully be recycled up to seven times with an E-factor as low as 5.76.

Seeking the Optimal Descriptor for SN2 Reactions through Statistical Analysis of Density Functional Theory Results

Bimolecular nucleophilic substitution is one of the fundamental reactions in organic chemistry, yet there is still knowledge to be gained on the role of the nucleophile and the substrate. A statistical treatment of over 600 density functional theory (DFT)-computed barriers for bimolecular nucleophilic substitution at methyl derivatives (S_N2@C) leads to the identification of numerical descriptors that best represent the entering and leaving ability of 26 different nucleophiles. The treatment is based on singular value decomposition (SVD) of a matrix of computed energy barriers. The current work represents the extension to a problem of reactivity of the hidden descriptor methodology that we had previously developed for the thermodynamic problem of bond dissociation energies in transition-metal complexes. The analysis of the results shows that a single descriptor is sufficient. This hidden descriptor has different values for nucleophilic and leaving abilities and, contrary to expectation, does not correlate especially well with either frontier molecular orbital descriptors or solvation descriptors. In contrast, it correlates with other thermodynamic and geometric parameters. This statistical procedure can be in principle extended to additional chemical fragments and other reactions.

Challenges & Opportunities on Catalytic Conversion of Glycerol to Value Added Chemicals

With the rapid expansion of biodiesel industry, its main by-product, crude glycerol, is anticipated to reach a global production of 6 million tons in 2025. It is actually a worrying phenomenon as glycerol could potentially emerge as an excessive product with little value. Glycerol, an alcohol and oxygenated chemical from biodiesel production, has essentially enormous potential to be converted into higher value-added chemicals. Using glycerol as a starting material for value-added chemical production will create a new demand on the glycerol market such as lactic acid, propylene glycol, alkyl lactatehydrogen, olefins and others. This paper briefly reviews the recent development on value-added chemicals derived from glycerol through catalytic conversion of refined and crude glycerol that have been proven to be promising in research stage with commercialization potential, or have been put in a corporate marketable production. Despite of the huge potential of products that can be transformed from glycerol, there are still numerous challenges to be addressed and discussed that include catalyst design and robustness; focus on crude or refined glycerol; reactor technology, reaction mechanism and thermodynamic analysis; and overall process commercial viability. The discussion will hopefully provide new insights on justified direction to focus on for glycerol transformation technology. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

A practicable synthesis of 2,3-disubstituted 1,4-dioxanes bearing a carbonyl functionality from α,β-unsaturated ketones using the Williamson strategy

We have observed that a reagent combination of NaIO₄ and NH₂OH·HCl reacts with α,β-unsaturated ketones followed by the nucleophile ethylene glycol allowing the synthesis of 2,3-disubstituted 1,4-dioxanes using cesium carbonate as a base under Williamson ether synthesis. This reaction is useful for the synthesis of functionalized 1,4-dioxane having a carbonyl functionality. A variety of 2,3-disubstituted 1,4-dioxanes have been synthesized using these reaction conditions. A probable reaction mechanism has also been proposed.

A fluoropolymer with a low dielectric constant at a high frequency derived from bio-based anethole

The copolymerization between a fluoro-containing monomer derived from bio-based anethole and a benzocyclobutene (BCB)-containing monomer gave a polymer with good dielectric properties and low water uptake.

Boosting the performance by the water solvation shell with hydrogen bonds on protonic ionic liquids: insights into the acid catalysis of the glycosidic bond

Hydrogen-bonding (HB) of protonic ionic liquids induced by the water solvation shell is proposed to dominate in the acid catalysis of the glycosidic bond in hydrolysis.

Coupling without Coupling Reactions: En Route to Developing Phenols as Sustainable Coupling Partners via Dearomatization-Rearomatization Processes

Transition-metal-catalyzed cross-coupling reactions represent one of the most straightforward and efficient protocols to assemble two different molecular motifs for the construction of carbon-carbon or carbon-heteroatom bonds. Because of their importance and wide applications in pharmaceuticals, agrochemicals, materials, etc., cross-coupling reactions have been well recognized in the 2010 Nobel Prize in chemistry. However, in the classical transition-metal-catalyzed cross-coupling reactions (e.g., the Suzuki-Miyaura, the Buchwald-Hartwig, and the Ullmann cross-coupling reactions), organohalides, which mainly stem from the nonrenewable fossil resources, are often utilized as coupling partners with halide wastes being generated after the reactions. To make cross-coupling reactions more sustainable, we initiated a general research program by employing phenols and cyclohexa(e)nones (the reduced forms of phenols) as pivotal feedstocks (coupling partners), instead of the commonly used fossil-derived organohalides, for cross-coupling reactions to build C-O, C-N, and C-C bonds. Phenols (cyclohexa(e)nones) are widely available and can be obtained from lignin biomass, highlighting their renewable and sustainable features. Moreover, water is expected to be the only stoichiometric byproduct, thus avoiding halide wastes.Notably, the cross-coupling reactions utilizing phenols/cyclohexa(e)nones are not based on the traditional transition-metal-catalyzed "oxidative-addition and reductive-elimination" mechanism, but via a novel "phenol-cyclohexanone" redox couple. This new working mechanism opens up new horizons of designing cross-coupling reactions via simple nucleophilic addition of cyclohexanones along with aromatization processes, thereby simplifying the design and avoiding laborious optimization of transition-metal precursors (e.g., Pd, Ni, Cu, etc.), as well as ligands in classical transition-metal-catalyzed cross-coupling reactions. Specifically, in this Account, we will summarize and discuss our related research work in the following three categories: "formal oxidative couplings of cyclohexa(e)nones", "formal reductive couplings of phenols", and "formal redox-neutral couplings of phenols". The successes of these research projects clearly demonstrated our initial inspirations and rational designs to develop cross-coupling reactions without the "conventional cross-coupling conditions" by pushing the reaction frontiers from initial cyclohexanones, ultimately, to the sustainable phenol targets.

Light-driven post-translational installation of reactive protein side chains

Post-translational modifications (PTMs) greatly expand the structures and functions of proteins in nature1,2. Although synthetic protein functionalization strategies allow mimicry of PTMs3,4, as well as formation of unnatural protein variants with diverse potential functions, including drug carrying5, tracking, imaging6 and partner crosslinking7, the range of functional groups that can be introduced remains limited. Here we describe the visible-light-driven installation of side chains at dehydroalanine residues in proteins through the formation of carbon-centred radicals that allow C-C bond formation in water. Control of the reaction redox allows site-selective modification with good conversions and reduced protein damage. In situ generation of boronic acid catechol ester derivatives generates RH2C• radicals that form the native (β-CH2-γ-CH2) linkage of natural residues and PTMs, whereas in situ potentiation of pyridylsulfonyl derivatives by Fe(II) generates RF2C• radicals that form equivalent β-CH2-γ-CF2 linkages bearing difluoromethylene labels. These reactions are chemically tolerant and incorporate a wide range of functionalities (more than 50 unique residues/side chains) into diverse protein scaffolds and sites. Initiation can be applied chemoselectively in the presence of sensitive groups in the radical precursors, enabling installation of previously incompatible side chains. The resulting protein function and reactivity are used to install radical precursors for homolytic on-protein radical generation; to study enzyme function with natural, unnatural and CF2-labelled post-translationally modified protein substrates via simultaneous sensing of both chemo- and stereoselectivity; and to create generalized 'alkylator proteins' with a spectrum of heterolytic covalent-bond-forming activity (that is, reacting diversely with small molecules at one extreme or selectively with protein targets through good mimicry at the other). Post-translational access to such reactions and chemical groups on proteins could be useful in both revealing and creating protein function.

Palladium nanoparticles anchored on amphiphilic Janus-type cellulose nanocrystals for Pickering interfacial catalysis

Developing green and sustainable Pickering interfacial catalysts for organic reactions in water is of great importance to both the environment and human health. In this study, Janus-type amphiphilic cellulose nanocrystals (CNCs) were synthesized by the surface modification of hydrophilic CNCs with hydrophobic alkyl chains for efficient Pickering emulsion stabilization. Further deposition of palladium nanoparticles on amphiphilic CNCs provides catalytic activity for organic reactions in water, which occur at the interface of water and the organic reactant phase. Different reactions, hydrogenation and C-C coupling, were performed using the obtained Pickering interfacial catalyst. Excellent results were achieved in both reactions. The catalyst developed in our study is expected to advance the field of environment-friendly catalyst systems for green chemistry.

Chemical synthesis and biological activity of peptides incorporating an ether bridge as a surrogate for a disulfide bond

Disulfide bridges contribute to the definition and rigidity of polypeptides, but they are inherently unstable in reducing environments and in the presence of isomerases and nucleophiles. Strategies to address these deficiencies, ideally without significantly perturbing the structure of the polypeptide, would be of great interest. One possible surrogate for the disulfide bridge is a simple thioether, but these are susceptible to oxidation. We report the introduction of an ether linkage into the biologically active, disulfide-rich peptides oxytocin, tachyplesin I, and conotoxin α-ImI, using an ether-containing diaminodiacid as the key building block, obtained by the stereoselective ring-opening addition reaction of an aziridine skeleton with a hydroxy group. NMR studies indicated that the derivatives with an ether surrogate bridge exhibited very small change of their three-dimensional structures. The analogs obtained using this novel substitution strategy were found to be more stable than the original peptide in oxidative and reductive conditions; without a loss of bioactivity. This strategy is therefore proposed as a practical and versatile solution to the stability problems associated with cysteine-rich peptides.

We report the first introduction of an ether linkage as surrogate into the disulfide-rich peptides using ether-containing diaminodiacid.

Improved Process for the Palladium-Catalyzed C-O Cross-Coupling of Secondary Alcohols

An improved protocol for the Pd-catalyzed C-O cross-coupling of secondary alcohols is described. The use of biaryl phosphine L2 as the ligand was key to achieving efficient cross-coupling of (hetero)aryl chlorides with only a 20% molar excess of the alcohol. Additionally, we observed an unusual reactivity difference between an electron-rich aryl bromide and the analogous aryl chloride, and deuterium-labeling suggested that currently unidentified pathways for reduction play an important role in explaining this disparity.

Green Methodology Development for the Surfactant Assisted Williamson Synthesis of 4-Benzyloxy Benzoic Acid (Ether) in Aqueous Media

Modern science and technology promote synthesis routes which are eco-friendly, chemicals which are promoted as “green” and solvents which are less toxic. A convenient method for the synthesis of ether by the reaction of 4-hydroxy benzoic acid and benzyl chloride using a surfactant as catalyst has been developed. The targeted ether is completely immiscible in water but in association with the interface active surfactants, the production of such a hydrophobic organic compound in water has been made possible. Micelles produce a pseudo-cellular organic environment to isolate species from the bulk solvent and favour the compartmentalization of reagents as well. Thus, the enhancement of the local concentration takes place and consequently the reactivity increases. The interaction of such unique chemo-, regio- and stereo-selectivity of surfactants made this reaction feasible. Organic species added to a micellar media are distributed between bulk water and micelles depending on their polarity, charge and dimension. This novel chemistry describes a set of green methods for carrying out this new generation Williamson reaction which can also be used for selective O-alkylation.

A highly selective fluorescent probe for Al3+ based on bis(2-hydroxy-1-naphthaldehyde) oxaloyldihydrazone with aggregation-induced emission enhancement and gel properties

An efficient fluorescent probe, bis(2-hydroxy-1-naphthaldehyde) oxaloyldihydrazone (1), has been prepared for the selective sensing of Al³⁺ over other common metal ions in water-containing media. The 1:1 stoichiometry of 1 and Al³⁺ was determined from Job's plot and Benesti-Hildebrand plot. The binding constant was observed as 1.6×10⁵M^-1, and the limit of detection was found to be 0.36μM, which was far below the drinking water restriction of Al³⁺ by EPA (the maximum allowable value is 7.4μM). In addition, the inherent AIEE features of 1 were observed upon addition of water to DMSO solution due to the restriction of the intramolecular motion, which makes the molecular conformations rigid and planar. Moreover, 1 could act as a novel gelator to form thermo-reversible supramolecular organogel with significant green emission in DMSO-H₂O (v/v, 9:1) solution.

Solvent-induced selectivity of Williamson etherification in the pursuit of amides resistant against oxidative degradation

This article reports two discoveries. (1) 2-Methoxyethanol induces unprecedented selectivity for etherification of 5-hydroxy-2-nitrobenzic acids without forming undesired esters. (2) Such compounds are precursors for amides showing unusual robustness against oxidative degradation, essential for molecular electrets that transfer strongly oxidizing holes at about −6.4 eV vs. vacuum.

Selective etherification produces precursors for amides resistant to oxidative degradation, i.e., showing reversible oxidation at 1.5 to 1.7 V vs. SCE.

Site-selective, catalytic, and diastereoselective sp3 C–H hydroxylation and alkoxylation of vicinally functionalized lactams

The C–H bond functionalization of sp³ carbon centres presents a significant challenge due to the inert nature of hydrocarbons as well as the need to selectively functionalize one of the numerous aliphatic C–H bonds embodied in organic molecules. Here, we describe catalytic, diastereoselective, and site-selective sp³ C–H hydroxylation/alkoxylation protocols featuring dihydroisoquinolones, γ-, and δ-lactams, which bear vicinal stereocenters. The hydroxylation strategy utilizes oxygen, a waste-free oxidant and affords attractive fragments for potential drug discovery. Fe-catalyzed dehydrative coupling of the resulting tertiary alcohols with simple primary alcohols has led to the construction of highly versatile unsymmetrical dialkyl ethers.

Catalytic, diastereoselective, and site-selective sp³ C–H hydroxylation and alkoxylation protocols featuring lactams that bear vicinal stereocenters, is described.

Measuring multiple 17O–13C J-couplings in naphthalaldehydic acid: a combined solid state NMR and density functional theory approach

A combined multinuclear solid-state NMR and a density functional theory computational approach, with SIMPSON simulations, is evaluated to determine the four heteronuclear ¹J(¹³C,¹⁷O) couplings in naphthalaldehydic acid.

α-Diimine-Niobium Complex-Catalyzed Deoxychlorination of Benzyl Ethers with Silicon Tetrachloride

α-Diimine niobium complexes serve as catalysts for deoxygenation of benzyl ethers by silicon tetrachloride (SiCl₄) to cleanly give two equivalents of the corresponding benzyl chlorides, where SiCl₄ has the dual function of oxygen scavenger and chloride source with the formation of a silyl ether or silica as the only byproduct. The reaction mechanism has two successive trans-etherification steps that are mediated by the niobium catalyst, first forming one equivalent of benzyl chloride along with the corresponding silyl ether intermediate that undergoes the same reaction pathway to give the second equivalent of benzyl chloride and silyl ether.

Synthesis of 2-(Prop-2-ynyloxy) Benzaldehyde using Salicyl Aldehyde and Propargyl Bromide in Aqueous Micellar Media

Advances in science and technology are promoting eco-friendly synthesis routes, green chemicals, and non-hazardous solvents. A suitable method for the synthesis of 2-(prop-2-ynyloxy) benzaldehyde was developed using three different aqueous micellar media. The targeted product ether is completely immiscible in water, but in combination with interface active surfactants it has been possible to produce the hydrophobic organic compound in water. Micelles function as a pseudocellular organic environment to isolate species from the main solvent and favor compartmentalization of reagents. There is an increase in the local concentration and consequently the reactivity increases. The use of such unique chemo-, regio-, and stereoselectivity renders this reaction new. Organic species added to a micellar media are distributed between water and micelles depending on polarity, charge, and size. In the experiments it was observed that salicylaldehyde and propargyl bromide interacted best in CTAB media and the yield of the formed product was 96 %.

Practical and Scalable Organic Reactions with Flow Microwave Apparatus

Microwave irradiation has been used for accelerating organic reactions as a heating method and has been proven to be useful in laboratory scale organic synthesis. The major drawback of microwave chemistry is the difficulty in scaling up, mainly because of the low penetration depth of microwaves. The combination of microwave chemistry and flow chemistry is considered to overcome the problem in scaling up of microwave-assisted organic reactions, and some flow microwave systems have been developed in both academic and industrial communities. In this context, we have demonstrated the scale-up of fundamental organic reactions using a novel flow microwave system developed by the academic-industrial alliance between the University of Shizuoka, Advanced Industrial Science and Technology, and SAIDA FDS. In this Personal Account, we summarize the recent progress of our scalable microwave-assisted continuous synthesis using the SAIDA flow microwave apparatus.

Cp*CoIII -Catalyzed Efficient Dehydrogenation of Secondary Alcohols

A novel, well-defined molecular Cp*Co^III complex was isolated and structurally characterized for the first time. The efficiency of this cobalt catalyst was demonstrated in the alcohol dehydrogenation and dehydrative coupling of secondary alcohols under mild conditions into ketones and ethers, respectively.

Efficient Approach for the Tritylation of Alcohols Using Recyclable Lewis Acid-Based Ionic Liquid (EMIM·AlCl4)

A new efficient approach has been reported for the tritylation of primary alcohols over secondary alcohols using triphenyl methyl alcohol and 4-monomethoxyl trityl alcohols in the presence of imidazolium-based ionic liquid 1-ethyl-3-methylimidazolium tetrachloroaluminate as catalyst. At room temperature, 5 mol % of catalyst in dichloromethane and acetonitrile solvent has been shown to be excellent for the tritylation of benzyl alcohol and various other alcohols The method was compatible with Fmoc/acetyl protecting group of amino and tert-butyldiphenylsilyl ether protecting group of alcohol. Moreover, the catalyst was reused for three to four catalytic cycles with little loss of catalytic activity. Excellent yields, reusability, chemoselectivity, and easy workup are advantages of this protocol.