Showing papers in "Australian Journal of Chemistry in 2013"
TL;DR: A review of recent literature describing these technologies is summarized and an outlook on the promising future of this emerging field is provided in this paper, where the combined use of hydrogels and nanoparticles in a single entity has gained enormous attention in areas such as catalysts, surface enhanced Raman scattering, biosensors, and drug delivery.
Abstract: Hydrogels have had extensive applications in scientific and industrial applications since their invention over 50 years ago. Responsive hydrogels based on temperature, light, and pH stimuli have been developed by changing the chemical components of the matrix structure. On the other hand, metallic nanoparticles of different shapes and sizes have been prepared by physical as well as chemical methods. These inorganic assemblies are currently widely used in the biomedical sciences and engineering fields. Recently, the combined use of hydrogels and nanoparticles in a single entity has gained enormous attention in areas such as catalysts, surface-enhanced Raman scattering, biosensors, and drug delivery. In this review, recent literature describing these technologies is summarized and an outlook on the promising future of this emerging field is provided.
138 citations
TL;DR: The most relevant results showing how carbonyl amides can be chemoselectively functionalised in the presence of electrophilic functionalities such as Weinreb amides are presented.
Abstract: Important advancements have been made in recent years in the development of chemoselective additions of nucleophiles to well known inert amide carbonyls in the presence of multi-electrophilic substrates. Herein, we present the most relevant results showing how carbonyl amides can be chemoselectively functionalised in the presence of electrophilic functionalities such as Weinreb amides.
73 citations
TL;DR: It is with great caution and diligence that compounds possessing a known PAINS core should be progressed through to medicinal chemistry optimisation, if at all, as the chances are very high that the hits will be found to be non-progressable, often after a significant waste of resources.
Abstract: Pan assay interference compounds (PAINS) are readily discovered in any bioassay and can appear to give selective and optimisable hits. The most common PAINS can be readily recognised by their structure. However, there are compounds that closely resemble PAINS that are not specifically recognised by the PAINS filters. In addition, highly reactive compounds are not encoded for in the PAINS filters because they were excluded from the high-throughput screening (HTS) library used to develop the filters and so were never present to provide indicting data. A compounding complication in the area is that very occasionally a PAINS compound may serve as a viable starting point for progression. Despite such an occasional example, the literature is littered with an overwhelming number of examples of compounds that fail to progress and were probably not optimisable in the first place, nor useful tool compounds. Thus it is with great caution and diligence that compounds possessing a known PAINS core should be progressed through to medicinal chemistry optimisation, if at all, as the chances are very high that the hits will be found to be non-progressable, often after a significant waste of resources.
70 citations
TL;DR: In this paper, a review examines how information on the three basic levels of the complex multi-scale structure of starch -individual chains, the branching structure of isolated molecules, and the way these molecules form various crystalline and amorphous arrangements -can be obtained from experiment.
Abstract: Improving starch-containing materials, whether food, animal feed, high-tech biomaterials, or engineering plastics, is best done by understanding how biosynthetic processes and any subsequent processing control starch structure, and how this structure controls functional properties. Starch structural characterization is central to this. This review examines how information on the three basic levels of the complex multi-scale structure of starch – individual chains, the branching structure of isolated molecules, and the way these molecules form various crystalline and amorphous arrangements – can be obtained from experiment. The techniques include fluorophore-assisted carbohydrate electrophoresis, multiple-detector size-exclusion chromatography, and various scattering techniques (light, X-ray, and neutron). Some examples are also given to show how these data provide mechanistic insight into how biosynthetic processes control the structure and how the various structural levels control functional properties.
52 citations
TL;DR: In this paper, the zwitterionic N-heterocyclic silylene (NHSi) with HCl at low temperatures was shown to have a kinetically stable 1,4-addition product.
Abstract: Reaction of the zwitterionic N-heterocyclic silylene (NHSi) 1 L′Si: (L′ = [HC(CMeNAr)(C(CH2)NAr)], Ar = 2,6-iPr2C6H3) with HCl at low temperatures affords the kinetically stable 1,4-addition product of 1, LSiCl (L = [HC(CMeNAr)2], Ar = 2,6-iPr2C6H3) (9a), which upon reaction with [Rh(Cl)cod]2 and [Ir(Cl)cod]2 (cod = 1,5-cyclooctadiene) selectively affords the NHSi complexes [L(Cl)Si:→Rh(Cl)cod] (10a) and [L(Cl)Si:→Ir(Cl)cod] (10b), respectively. The latter were employed as pre-catalysts in the catalytic reduction of amides in the presence of silanes. Remarkably, they show strikingly different activities and selectivities. While complex 10a yields selectively the C–O cleavage product, 10b affords both cleavage products (C–O and C–N). Moreover, the total conversion of the catalytic amide reduction with 10b is significantly higher than the conversion with a benchmark system [Ir(Cl)cod]2 highlighting the enhanced catalytic activity afforded by the coordination of the NHSi ligand. Introducing the hydride source Li[HBEt3] into the catalytic reactions retards the catalyst performance due to a competitive decomposition pathway. This appears to occur via a H-shift onto the cod ligand with concomitant liberation of cyclooctene, which is also presented. The different reactivity of 10a and 10b towards nucleophiles such as MeLi is also discussed. The reaction of 10a with MeLi affords an intractable array of products, while the reaction of 10b with one equivalent of MeLi selectively affords [L(Cl)Si:→Ir(CH3)cod] (14) with selective methylation at the Ir centre. The analogous reaction with two equivalents of 10b affords the double methylated product [L(CH3)Si:→Ir(CH3)cod] (15).
46 citations
TL;DR: In this paper, the state of the art for glycerol oxidation is evaluated and recommendations for further research and future directions are included, as well as the current state-of-the-art.
Abstract: Endeavours leading to the study of glycerol oxidation result from the imperative necessity for wise utilization of surplus glycerine generated as by-product from biodiesel manufacture. The oxidation of glycerol is one of the most promising reactions as it leads to the generation of valuable glycerol derivatives that find broad application in pharmaceutical, polymer, and food industries. This review highlights the processing alternatives for glycerol by means of biocatalyst-mediated, heterogeneous, homogeneous, and electrochemical oxidation. The current state of the art is evaluated and recommendations for further research and future directions are included.
45 citations
TL;DR: The unique chemistry of boron allows for the utilisation of novel building-blocks which are not traditionally found in medicinal chemistry as mentioned in this paper, and the pharmaceutical industry has begun to exploit boronic acid derivatives as new drugs and several research groups are also exploring 1,2-azaborines and icosahedral boranes known as carboranes with great promise for innovative drug design.
Abstract: The unique chemistry of boron allows for the utilisation of novel building-blocks which are not traditionally found in medicinal chemistry. The pharmaceutical industry has begun to exploit boronic acid derivatives as new drugs and several research groups are also exploring 1,2-azaborines and icosahedral boranes known as carboranes as boron-based structural motifs, with great promise for innovative drug design. Recent advances in the medicinal chemistry of these three important boron moieties are highlighted and illustrated with selected examples.
44 citations
TL;DR: In this paper, a multi-stage continuous flow polymerization process for the synthesis of block copolymers using the RAFT polymerization method was described, which resulted in polymers with molecular weights between 13500 and 34100 g mol-1, and dispersities typically between 1.21 and 1.58.
Abstract: This work describes a multi-stage continuous flow polymerisation process for the synthesis of block copolymers using the RAFT polymerization method. The process retains all the benefits and versatility of the RAFT method and has been adapted for a series of monomer combinations, including acrylates, acrylamides, and vinyl monomers. It resulted in polymers with molecular weights between 13500 and 34100 g mol–1, and dispersities typically between 1.21 and 1.58. Different architectures were prepared (including combinations of hydrophilic and hydrophobic blocks) which are soluble in a range of different solvents including aqueous and organic media.
43 citations
TL;DR: In this article, a bespoke microwave reactor with a glass containment cell has been developed for performing continuous flow reactions under microwave heating, and the prototype unit has been evaluated using a series of standard organic chemical transformations enabling scale-up of these chemical processes.
Abstract: A bespoke microwave reactor with a glass containment cell has been developed for performing continuous flow reactions under microwave heating. The prototype unit has been evaluated using a series of standard organic chemical transformations enabling scale-up of these chemical processes. As part of the development, a carbon-doped PTFE reactor insert was utilized to allow the heating of poorly absorbing reaction media, increasing the range of solvents and scope of reactions that can be performed in the device.
42 citations
TL;DR: In this paper, a study on the bonding in bis-pyridine halonium cations has been carried out using both theoretical and synthetic techniques and the results suggest that the iodine dipyridine complex ([pyr-I-Pyr]+) can be considered as a coordination complex of [I]+.
Abstract: A study on the bonding in bis-pyridine halonium cations has been carried out using both theoretical and synthetic techniques. The primary thrust for the study is to highlight the opportunities potentially afforded by considering iodine as a Lewis acid in a classic coordination sense. Our results suggest that the iodine dipyridine complex ([pyr-I-pyr]+) can be considered as a coordination complex of [I]+. The lighter bromine and chlorine analogues are more towards the covalent rather than the dative side of bonding, while [pyr-F-pyr]+ is best described as an ion-molecule complex with one strong covalent F-pyr bond and one weak F-pyr dispersion interaction. Finally, theoretical and synthetic studies suggest that the commercially available [pyr-F]+ cation cannot be considered as a coordination complex of ‘F+’, despite its use as a source of electrophilic fluorine.
42 citations
TL;DR: An extremely bulky secondary amine, HN(Ar†)(SiPr3i) HL† (Ar† = C6H2{C(H)Ph2}2Pri−2,6,4) has been synthesised and deprotonated with KH in toluene, to afford the potassium amide [KL†(η6-toluene)], which was structurally authenticated as mentioned in this paper.
Abstract: An extremely bulky secondary amine, HN(Ar†)(SiPr3i) HL† (Ar† = C6H2{C(H)Ph2}2Pri−2,6,4) has been synthesised and deprotonated with KH in toluene, to afford the potassium amide [KL†(η6-toluene)], which was structurally authenticated. Reaction of this with BBr3 and AlBr3, reproducibly gave the crystallographically characterised amido bromo-borane, [L†B(H)Br], and aluminacycle, [AlBr2{κ2-C,N-N(H)(SiPr3i){C6H2[CPh2][C(H)Ph2]Pri-2,6,4}}], respectively, via ligand C–H activation processes. The known secondary amines, HN(Dip)(Mes) (HLMes) and HN(Dip)(Trip) (HLTrip) (Dip =2,6-diisopropylphenyl, Mes = mesityl, Trip = 2,4,6-triisopropylphenyl), have been structurally characterised, and deprotonated to give the in situ generated lithium amides, [Li(LMes)] and [Li(LTrip)]. Reaction of these with BBr3 and AlBr3 has given the amido group 13 element halide complexes, [LMesBBr2] and [LAlBr2(THF)] (L = LMes or LTrip), the crystal structures of all of which have been determined. Synthetic routes to two new bulky amidine pro-ligands, ArN = C(But)-N(H)Ar, Ar = C6H2{C(H)Ph2}2Me-2,6,4 (Piso*H) or C6H2Pr2i(CPh3)-2,6,4 (Piso″H), have been developed, and the compounds crystallographically characterised. Deprotonation of Piso″H gave the potassium amidinate, [K(Piso″)], which was reacted with BBr3 to give [(Piso″)BBr2]. Reaction of Piso″H with AlMe3 afforded [(Piso″)AlMe2], which, when treated with I2 yielded [(Piso″)AlI2], the crystal structure of which was determined. Reductions of all of the prepared amido and amidinato group 13 element(iii) halide complexes were attempted using a variety of reducing reagents, with a view to prepare boron(i) or aluminium(i) complexes. While these were not successful, this study does offer synthetic inorganic chemists a variety of new very bulky anionic N-donor ligands, and boron/aluminium halide complexes thereof, for use in their own research.
TL;DR: In this article, the authors investigated the molecular interactions between methanol and [EMIM][LAC] using an ATR-FTIR and density functional theory (DFT) analysis.
Abstract: 1-Ethyl-3-Methylimidazolium lactate ([EMIM][LAC]) is an environmental friendly ionic liquid with potential industrial applications. Attenuated total reflectance infrared spectroscopy (ATR-IR) and density functional theory (DFT) calculations were employed to investigate the molecular interactions between methanol and [EMIM][LAC]. The infrared spectra were analyzed by two methods: excess spectroscopy and two-dimensional (2D) correlation spectroscopy. In the ATR-FTIR spectra, v(C4,5-H), v(C2-H), v(alkyl), v(-OD), and v(-COO) all show blue shifts upon addition of methanol. 2D correlation analysis indicated that the v(imidazolium ring C-H) band varies before that of v(alkyl C-H) with increasing CD3OD content. The following sequential order of interaction strength is established by DFT calculations: EMIM-methanol -LAC > EMIM-LAC > LAC-methanol > EMIM-methanol.
TL;DR: In this paper, the authors presented the synthesis, chemical characterisation (by NMR and FTIR spectroscopy, atomic absorption spectrophotometry, elemental analysis, and single crystal X-ray diffraction), electrochemistry, and DNA binding studies (with cyclic voltammetry, viscometry, and UV-vis spectroscopic) of six new ferrocene incorporated selenoureas.
Abstract: In this article we have presented the synthesis, chemical characterisation (by NMR and FTIR spectroscopy, atomic absorption spectrophotometry, elemental analysis, and single crystal X-ray diffraction), electrochemistry, and DNA binding studies (with cyclic voltammetry, viscometry, and UV-vis spectroscopy) of six new ferrocene incorporated selenoureas. All the six compounds interact electrostatically with DNA which was evident by a negative shift in the cyclic voltammetry peak potential of the drug–DNA adduct relative to the free drug. The drug–DNA binding constant was calculated by a decrease in peak current after the addition of DNA to the free drug. We have also reported binding site sizes and diffusion coefficients of the synthesised compounds.
TL;DR: In this paper, a mini-review discusses some of the recent work on novel process windows by the Micro Flow Chemistry and Process Technology group at the Eindhoven University of Technology, and their associates.
Abstract: This mini-review discusses some of the recent work on novel process windows by the Micro Flow Chemistry and Process Technology group at the Eindhoven University of Technology, and their associates. Novel process windows consist of unconventional approaches to boost chemical production, often requiring harsh reaction conditions at short to very short time-scales. These approaches are divided into six routes: the use of high temperatures, high pressures, and high concentrations (or solvent-free), new chemical transformations, explosive conditions, and process simplification and integration. Microstructured reactors, due to their inherent safety, short time-scales, and the high degree of process control, are the means that make such extreme chemistry possible.
TL;DR: In this paper, a review highlights recent progress in the self-assembly of complex organic molecular architectures that are enabled by dynamic imine chemistry, including molecular containers with defined geometry and size, mechanically interlocked molecules, and extended frameworks and polymers.
Abstract: The chemistry of imine bond formation from simple aldehyde and amine precursors is among the most powerful dynamic covalent chemistries employed for the construction of discrete molecular objects and extended molecular frameworks. The reversible nature of the C=N bond confers error-checking and proof-reading capabilities in the self-assembly process within a multi-component reaction system. This review highlights recent progress in the self-assembly of complex organic molecular architectures that are enabled by dynamic imine chemistry, including molecular containers with defined geometry and size, mechanically interlocked molecules, and extended frameworks and polymers, from building blocks with preprogrammed steric and electronic information. The functional aspects associated with the nanometer-scale features not only place these dynamically constructed nanostructures at the frontier of materials sciences, but also bring unprecedented opportunities for the discovery of new functional materials.
TL;DR: Current proteomic approaches for protein identification and characterisation, including post-translational modification (PTM) analysis and quantitative proteomics as well as investigation of protein–protein interactions (PPIs) are discussed.
Abstract: Characterisation of proteins and whole proteomes can provide a foundation to our understanding of physiological and pathological states and biological diseases or disorders. Constant development of more reliable and accurate mass spectrometry (MS) instruments and techniques has allowed for better identification and quantification of the thousands of proteins involved in basic physiological processes. Therefore, MS-based proteomics has been widely applied to the analysis of biological samples and has greatly contributed to our understanding of protein functions, interactions, and dynamics, advancing our knowledge of cellular processes as well as the physiology and pathology of the human body. This review will discuss current proteomic approaches for protein identification and characterisation, including post-translational modification (PTM) analysis and quantitative proteomics as well as investigation of protein–protein interactions (PPIs).
TL;DR: In this article, the authors report their efforts towards the design of a fragment library for nuclear magnetic resonance spectroscopy-based screening, demonstrate the performance of the library through analysis of 14 screens, and present a comparison to previously reported fragment libraries.
Abstract: The design of a suitable library is an essential prerequisite to establish a fragment-based screening capability. Several pharmaceutical companies have described their approaches to establishing fragment libraries; however there are few detailed reports of both design and analysis of performance for a fragment library maintained in an academic setting. Here we report our efforts towards the design of a fragment library for nuclear magnetic resonance spectroscopy-based screening, demonstrate the performance of the library through analysis of 14 screens, and present a comparison to previously reported fragment libraries.
TL;DR: Multi-bond forming processes as discussed by the authors, which form two or more new covalent bonds in a single synthetic operation, are preeminent in contemporary synthetic organic chemistry and have the ability to rapidly increase structural complexity.
Abstract: An increasing number of synthetic organic chemists are embracing the philosophy of efficiency. Herein we highlight multi-bond forming processes, which form two or more new covalent bonds in a single synthetic operation. Such processes, which have the ability to rapidly increase structural complexity, are preeminent in contemporary synthetic organic chemistry. In this short review we classify, analyse, and contrast contemporary multi-bond forming processes, frame these cutting edge contributions within a historical context, and speculate on likely future developments in the area.
TL;DR: Several aromatic and hetero-aromatic nitrenes and carbenes undergo photochemical and sometimes also thermal ring opening, and they are clearly distinguished by their characteristic electron spin resonance spectra as discussed by the authors.
Abstract: Several aromatic and heteroaromatic nitrenes and carbenes undergo photochemical and sometimes also thermal ring opening. Depending on benz-annelation, the ring-opened species may have the character of either nitrenes (for α-annelation) or 1,5-(1,7-)-biradicals (for β-annelation). Both types have been observed, and they are clearly distinguished by their characteristic electron spin resonance spectra. In addition, ring opening of hetarylnitrenes to nitrile ylides can be observed whenever there is a meta-relationship between a ring nitrogen atom and the nitrene (or carbene) centre. The factors governing the two types of ring opening have been investigated. The nitrenes and carbenes are generated by either low temperature Ar matrix photolysis or flash vacuum thermolysis of azides, tetrazoles, triazoles, or diazo compounds with matrix isolation of the products.
TL;DR: The biochemistry of PTMs is highlighted with an emphasis on mass spectrometry to help elucidate the mechanisms of many pathological conditions and provide opportunities for prevention, diagnostics, and treatment of these disorders.
Abstract: Proteins are the effector molecules of many cellular and biological processes and are thus very dynamic and flexible. Regulation of protein activity, structure, stability, and turnover is in part controlled by their post-translational modifications (PTMs). Common PTMs of proteins include phosphorylation, glycosylation, methylation, ubiquitination, acetylation, and oxidation. Understanding the biology of protein PTMs can help elucidate the mechanisms of many pathological conditions and provide opportunities for prevention, diagnostics, and treatment of these disorders. Prior to the era of proteomics, it was standard to use chemistry methods for the identification of protein modifications. With advancements in proteomic technologies, mass spectrometry has become the method of choice for the analysis of protein PTMs. In this brief review, we will highlight the biochemistry of PTMs with an emphasis on mass spectrometry.
TL;DR: A simple and sensitive colorimetric sensor employing single-stranded DNA ligand, cationic polymer, and gold nanoparticles (AuNPs) to detect silver ions, which exhibits high sensitivity and selectivity towards Ag+ versus other metal ions.
Abstract: This paper describes a simple and sensitive colorimetric sensor employing single-stranded DNA (ssDNA) ligand, cationic polymer, and gold nanoparticles (AuNPs) to detect silver ions. The positively charged polymer can electrostatically interact with ssDNA and destroy the charge balance leading to induction of AuNP aggregation. Silver ions (Ag+) can bind to cytosine (C)-rich nucleic acids to form the C-Ag+-C hair-pin structure, which can prevent its interaction with polymers. The resulting cationic polymer could aggregate AuNPs causing a remarkable change in colour. The concentration of Ag+ can be determined visually. This sensing platform exhibits high sensitivity and selectivity towards Ag+ versus other metal ions, with a detection limit of 48.6 nM. The assay did not require any labelling or modifying steps. This method is simple, effective, and convenient and can in principle be used to detect other metal ions or small molecules.
TL;DR: In this article, the effects of chemical activation on gas-phase isomerization of singlet nitrenes were investigated. But the effects were not observed in the formation of 3-cyanoindole and 1-cyanobenzimidazoles from 3-and 4-quinolylnitrenes and 4-quinazolinylnitrenes.
Abstract: Chemical activation (the formation of ‘hot’ molecules due to chemical reactions) is ubiquitous in flash vacuum thermolysis (FVT) reactions, and awareness of this phenomenon is indispensable when designing synthetically useful gas-phase reactions. Chemical activation is particularly prevalent in azide chemistry because the interesting singlet nitrenes are high-energy intermediates, and their reactions are highly exothermic. Consequently, chemical activation is observed in the isomerization of methylnitrene CH3N to methylenimine (methanimine) CH2=NH, facilitating the elimination of hydrogen to form HCN or HNC. Rearrangements of phenylnitrene, 1- and 2-naphthylnitrenes, and 2-, 3- and 4-pyridylnitrenes afford cyanocyclopentadiene, 3- and 2-cyanoindenes, and 2- and 3-cyanopyrroles, all showing the effects of chemical activation by undergoing facile interconversion of isomers. Chemical activation can often be reduced or removed entirely by increasing the pressure, thereby promoting collisional deactivation. Larger molecules having more degrees of freedom are better able to dissipate excess energy; therefore the effects of chemical activation are less pronounced or completely absent in the formation of 3-cyanoindole and 1-cyanobenzimidazoles from 3- and 4-quinolylnitrenes and 4-quinazolinylnitrenes, respectively. In compounds possessing nitro groups, chemical activation can cause the loss of the nitro group at nominal temperatures far below those normally needed to cleave the C-NO2 bond.
TL;DR: This review summarizes recent advances in the area of O-glycosylation of fibrillar collagens and their characterization using state-of-the-art liquid chromatography-mass spectrometry-based methodologies, and perspectives on future research are summarized.
Abstract: The most abundant proteins in vertebrates – the collagen family proteins – play structural and biological roles in the body. The predominant member, type I collagen, provides tissues and organs with structure and connectivity. This protein has several unique post-translational modifications that take place intra- and extra-cellularly. With growing evidence of the relevance of such post-translational modifications in health and disease, the biological significance of O-linked collagen glycosylation has recently drawn increased attention. However, several aspects of this unique modification – the requirement for prior lysyl hydroxylation as a substrate, involvement of at least two distinct glycosyl transferases, its involvement in intermolecular crosslinking – have made its molecular mapping and quantitative characterization challenging. Such characterization is obviously crucial for understanding its biological significance. Recent progress in mass spectrometry has provided an unprecedented opportunity for this type of analysis. This review summarizes recent advances in the area of O-glycosylation of fibrillar collagens and their characterization using state-of-the-art liquid chromatography–mass spectrometry-based methodologies, and perspectives on future research. The analytical characterization of collagen crosslinking and advanced glycation end-products are not addressed here.
TL;DR: The rate–pH profiles for the photolysis reactions indicate the highest rate of formylmethylflavin degradation is at ~pH 4 and above pH 10.0, and the increase in rate with pH is due to higher reactivity of the flavin triplet state.
Abstract: The kinetics of the photolysis of formylmethylflavin, a major intermediate product in the aerobic and anaerobic photolysis of riboflavin, was studied in the pH range 20–110 Formylmethylflavin and its photoproducts, lumichrome and lumiflavin, were determined in degraded solutions using a specific multicomponent spectrophotometric method The photolysis of formylmethylflavin in alkaline medium takes place by first-order kinetics and the rate constants (kobs) at pH 75–110 range from 027 × 10–4 to 388 × 10–4 and 036 × 10–4 to 563 × 10–4 s–1 under aerobic and anaerobic conditions respectively In acid medium, the photolysis involves a second-order mechanism and the rate constants at pH 20–70 range from 137 to 211 and 203 to 294 M–1 s–1 under aerobic and anaerobic conditions respectively The rate–pH profiles for the photolysis reactions indicate the highest rate of formylmethylflavin degradation is at ~pH 4 and above pH 10 In the alkaline region, the increase in rate with pH is due to higher reactivity of the flavin triplet state The photolysis of formylmethylflavin is catalyzed by phosphate ions and is affected by the solvent viscosity
TL;DR: In this article, two Hoveyda type ruthenium metathesis precatalysts, Umicore M51 and Umicores M71 SIMES, were immobilized on commercial silica in a simple and fast procedure through direct interaction with the support surface.
Abstract: Two Hoveyda type ruthenium metathesis precatalysts, Umicore M51 and Umicore M71 SIMES, were immobilized on commercial silica in a simple and fast procedure through direct interaction with the support surface. These precatalysts exhibited good activity in ring-closing, cross, and enyne metathesis reactions and were stable in terms of reusability to be used for consecutive runs under both batch and flow conditions. In non-polar media, the catalytic activity of the precatalysts is truly based on a heterogeneous species, and the contamination of the products with ruthenium was very low with respect to starting catalyst (0.003–0.01 %; 0.13–0.44 ppm). If necessary, such as in solvents like toluene, the ruthenium content can easily be reduced to levels below 0.5 ppm by treatment of the crude metathesis products with the commercial scavenger QuadraSil AP or by use of an additional QuadraSil AP scavenger cartridge under flow conditions.
TL;DR: Pace as discussed by the authors obtained a PhD in Chemistry under the guidance of Professor A. R. Alcantara at the Complutense University of Madrid (2010) and then undertook postdoctoral training at the University of Vienna (Austria) with Professor W. Holzer and at the United Kingdom's University of Manchester (UK), with Professor D. J. Procter.
Abstract: Vittorio Pace received a degree in Pharmacy from theUniversity of Perugia (Italy) in 2005 and anMSc inDrugDesign andDevelopment from theUniversity of Pavia (Italy) in 2008. He obtained a PhD in Chemistry under the guidance of Professor A. R. Alcantara at the Complutense University of Madrid (2010). He then undertook postdoctoral training at the University of Vienna (Austria) with Professor W. Holzer and at the University of Manchester (UK) with Professor D. J. Procter. In October 2013, he moved to the University of Stockholm (Sweden) for a third postdoctoral position with Professor B. Olofsson.
TL;DR: In this paper, a series of N-heterocyclic carbene (NHC) complexes involving zinc, cadmium, and the heavy Group 14 elements germanium, tin, and lead are reported.
Abstract: The synthesis of a series of N-heterocyclic carbene (NHC) complexes involving zinc, cadmium, and the heavy Group 14 elements germanium, tin, and lead is reported. The direct reaction between the bulky carbene IPr (IPr = (HCNDipp)2C:, Dipp = 2,6-iPr2C6H3) and the Group 14 halide reagents GeCl4 and SnCl4 afforded the 1 : 1 complexes IPr·ECl4 (E = Ge and Sn) in high yield; similarly, ZnI2 interacted with IPr in THF to give the THF-bound complex IPr·ZnI2·THF. CdCl2 underwent divergent chemistry with IPr and the major product isolated was the imidazolium salt [IPrH][IPr·CdCl3], which could be converted into IPr·CdCl2·THF upon treatment with Tl[OTf]. In addition, the stable PbII amide adduct, IPr·PbBr(NHDipp), was prepared. Each of the new carbene–element halide adducts was treated with the hydride sources Li[BH4] and Li[HBEt3] in order to potentially access new element hydride adducts and/or clusters. In most instances scission of the element–carbene bonds transpired, except in the case of IPr·ZnI2·THF, which reacted with two equivalents of Li[BH4] to yield the thermally stable bis(borohydride) zinc complex IPr·Zn(BH4)2.
TL;DR: Traditional applications of clay mineral mainly revolved around cosmetics and industrial products, but their scope of application is continuously expanding into pharmaceutics including drug delivery and tissue engineering.
Abstract: Traditional applications of clay mineral mainly revolved around cosmetics and industrial products, but their scope of application is continuously expanding into pharmaceutics including drug delivery and tissue engineering. The interest in clays amongst the scientific community has increased dramatically in recent years due to its composition and structure which can be easily modified to serve different purposes. Largely due to structural flexibility and its small particle size, clay nanostructure can be modified to tune rheological and mechanical properties, and can entrap moisture to suit a particular application. Additionally, interest in the synthesis of polymer-clay nanocomposites in tissue engineering is growing as it is cheap, easily available, and environmentally-friendly. The structure of clay allows the interclaysion of different biomolecules between the clay layers. These biomolecules can be released in a controlled manner which can be utilised in drug delivery and cosmetic applications.
TL;DR: An eco-friendly one-pot five-component synthesis of novel 1,2,3-triazole-linked pentasubstituted 1,4-dihydropyridines under ultrasonic and microwave irradiation in polyethylene glycol (PEG) 400 is described.
Abstract: An eco-friendly one-pot five-component synthesis of novel 1,2,3-triazole-linked pentasubstituted 1,4-dihydropyridines under ultrasonic and microwave irradiation in polyethylene glycol (PEG) 400 is described. All newly synthesised compounds were evaluated for antibacterial activity, antifungal activity, antioxidant activity, and photophysical properties. Antimicrobial activity was evaluated against six microbial strains. All compounds exhibited antifungal activity against Aspergillus niger and Aspergillus flavus and moderate antibacterial activity against Gram positive bacteria (Staphylococcus aureus and Bacillus subtilis). Antioxidant activity was evaluated using a 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay. All compounds showed good to moderate antioxidant activity. Furthermore all new compounds showed strong fluorescence in solution.
TL;DR: The tetradentate stibine and bismuthine ligands (o-(iPr2P)C6H4)3Sb (LSbP3) and (o(iPr 2P) C6H 4)3Bi (LBiP3)-phosphino groups were observed to react with CuCl and AgCl in THF at room temperature to enable the formation of tetrahedral PnM3 core as discussed by the authors.
Abstract: The tetradentate stibine and bismuthine ligands (o-(iPr2P)C6H4)3Sb (LSbP3) and (o-(iPr2P)C6H4)3Bi (LBiP3) react with CuCl and AgCl in THF at room temperature to afford (o-(iPr2P)C6H4)3SbCu3(μ2-Cl)3 (1), (o-(iPr2P)C6H4)3SbAg3(μ2-Cl)3 (2), (o-(iPr2P)C6H4)3BiCu3(μ2-Cl)3 (3), and (o-(iPr2P)C6H4)3BiAg3(μ2-Cl)3 (4), respectively. These complexes, which have been fully characterised, feature a central M3(μ2-Cl)3 cluster (M = Cu or Ag) supported by coordination of a LSbP3- or LBiP3-phosphino group to each group 11 metal ion. The heavy pnictogen atom (Pn) interacts simultaneously with the three group 11 metal ions of the M3(μ2-Cl)3 cluster leading to formation of a tetrahedral PnM3 core. Bonding analysis using the Natural Bond Orbital method indicates the presence of a four-centre two-electron Pn→M3 interaction whose strength is the highest in 1 and the lowest in 4. The triply bridging bonding mode of the stibine and bismuthine ligands observed in these complexes is, to our knowledge, unprecedented. We also note that the central M3(μ2-Cl)3 clusters found in these complexes are related to the cyclo-trimers observed in vapours of CuCl and AgCl.