Brandi et al detail progress made in the synthesis and transformations of alkylidenecyclopropanes and alkylidenecyclobutanes. The topics include the syntheses of methylene- and ...alkylidenecyclopropanes and the synthesis of alkylidencyclobutanes by ring formation.
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IJS, KILJ, NUK, PNG, UL, UM
The success of the rational bottom-up approach to nanostructured carbon materials and the discovery of the importance of their doping with heteroatoms puts under the spotlight all synthetic organic ...approaches to polycyclic aromatic hydrocarbons. The construction of atomically precise heteroatom doped nanographenes has evidenced the importance of controlling its geometry and the position of the doping heteroatoms, since these parameters influence their chemical-physical properties and their applications. The growing interest towards this research topic is testified by the large number of works published in this area, which have transformed a once "fundamental research" into applied research at the cutting edge of technology. This review analyzes the most recent synthetic approaches to this class of compounds.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The synthesis of polyhydroxylated indolizidines and pyrrolizidines belonging to the class of iminosugars, endowed with a vast and assorted biological activity, can be achieved in a straightforward ...manner by a general strategy consisting of a highly stereoselective 1,3‐dipolar cycloaddition of polyhydroxylated pyrroline‐N‐oxides followed by simple transformations of the isoxazolidine adducts. The strategy allows the complete control of the relative and absolute stereochemistry of the numerous stereogenic centers decorating these compounds.
Vast endowment: The synthesis of polyhydroxylated indolizidines and pyrrolizidines belonging to the class of iminosugars, endowed with a vast and assorted biological activity, can be achieved in a straightforward manner by a general strategy consisting of a highly stereoselective 1,3‐dipolar cycloaddition of polyhydroxylated pyrroline‐N‐oxides followed by simple transformations of the isoxazolidine adducts (see scheme).
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The interest for transition metal dichalcogenides (TMDs) as two-dimensional (2D) analogues of graphene is steadily growing along with the need of efficient and easy tunable protocols for their ...surface functionalization. This latter aspect holds a key role in the widespread application of TMDs in various technological fields and it represents the missing step to bridge the gap between the more popular C sp2-based networks and their inorganic counterparts. Although significant steps forward have already been made in the field of TMDs functionalization (particularly for MoS2), a rational approach to their surface engineering for the generation of 2D organic–inorganic hybrids capable to accommodate various molecules featured by orthogonal groups has not been reported yet. The paper paves the way toward a new frontier for “click” chemistry in material science. It describes the post-synthetic modification (PSM) of covalently decorated MoS2 nanosheets with phenylazido pendant arms and the successful application of CuAAC chemistry (copper-mediated azide–alkyne cycloaddition) towards the generation of highly homo- and hetero-decorated MoS2 platforms. This contribution goes beyond the proof of evidence of the chemical grafting of organic groups to the surface of exfoliated MoS2 flakes through covalent C–S bonds. It also demonstrates the versatility of the hybrid samples to undergo post-synthetic modifications thus imparting multimodality to these 2D materials. Several physico-chemical SEM microscopy, fluorescence lifetime imaging (FLIM), spectroscopic (IR, Raman, XPS, UV–vis), and analytical tools have been combined together for the hybrids’ characterization as well as for the estimation of their functionalization loading.
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Neutral ZrIV and HfIV alkyl/amido complexes stabilized by a tridentate N ligand that contains a “rolling” heterodentate benzoimidazole fragment have been prepared and characterized. The ultimate ...nature of the ligand denticity, the electronic properties of the ligand binding pocket and the metal coordination environment are controlled by the protection/deprotection of the benzoimidazole NH group. The metal precursor used MIV(Bn)4 or MIV(NMe2)4 also has an influence on the final coordination sphere of the complex; indeed, a permanent central pyridine dearomatization occurs in the presence of dimethylamido ancillary groups. DFT calculations on the real system have been used to elucidate the mechanism. Selected alkyl species from this series have been scrutinized for the tandem hydrosilylation of CO2 to CH4 in combination with the strong Lewis acid B(C6F5)3 using a variety of hydrosilanes. A positive effect of the hardness modification of the ligand donor atom set is observed in the catalytic outcomes. Indeed, κ3{N−,N,N−}ZrIV(Bn)2 catalyzes the process to methane selectively with a turnover frequency as high as 272 h−1 (at 96 % substrate conversion) almost twice as much as that claimed for the benchmark κ3{O−,O,O−}ZrIV(Bn)2 complex under similar experimental conditions.
Working in tandem: ZrIV/HfIV alkyl coordination compounds stabilized by a N ligand that contains a “rolling” heterodentate benzoimidazole fragment are prepared and employed with B(C6F5)3 for mild CO2 hydrosilylation to methane. The modification of the hardness of the ligand donor atom set translates into a better catalytic performance with respect to that of the benchmark catalytic system.
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FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
A new synthetic approach for the production of carbon nanomaterials (CNM) decorated with organophosphorus moieties is presented. Three different triphenylphosphine oxide (TPPO) derivatives were used ...to decorate oxidized multiwalled carbon nanotubes (ox-MWCNTs) and graphene platelets (GPs). The TPPOs chosen bear functional groups able to react with the CNMs by Tour reaction (an amino group), nitrene cycloaddition (an azido group) or CuAAC reaction (one terminal C-C triple bond). All the adducts were characterized by FTIR, Raman spectroscopy, TEM, XPS, elemental analysis and ICP-AES. The cycloaddition of nitrene provided the higher loading on ox-MWCNTs and GPs as well, while the Tour approach gave best results with nanotubes (CNTs). Finally, we investigated the possibility to reduce the TPPO functionalized CNMs to the corresponding phosphine derivatives and applied one of the materials produced as heterogeneous organocatalyst in a Staudinger ligation reaction.
Mechanochemistry is an emerging and reliable alternative to conventional solution (batch) synthesis of complex molecules under green and solvent-free conditions. In this regard, we report here on the ...conjugation of a dextran polysaccharide with a fluorescent probe, a phenylboronic acid (PBA)-functionalized boron dipyrromethene (BODIPY) applying the ball milling approach. The ball milling formation of boron esters between PBA BODIPY and dextran proved to be more efficient in terms of reaction time, amount of reactants, and labelling degree compared to the corresponding solution-based synthetic route. PBA-BODIPY dextran assembles into nanoparticles of around 200 nm by hydrophobic interactions. The resulting PBA-BODIPY dextran nanoparticles retain an apolar interior as proved by pyrene fluorescence, suitable for the encapsulation of hydrophobic drugs with high biocompatibility while remaining fluorescent.
The increasing resistance of bacteria to conventional antibiotics represents a severe global emergency for human health. The broad-spectrum antibacterial activity of silver has been known for a long ...time, and silver at the nanoscale shows enhanced antibacterial activity. This has prompted research into the development of silver-based nanomaterials for applications in clinical settings. In this work, the synthesis of three different silver nanoparticles (AgNPs) hybrids using both organic and inorganic supports with intrinsic antibacterial properties is described. The tuning of the AgNPs' shape and size according to the type of bioactive support was also investigated. Specifically, the commercially available sulfated cellulose nanocrystal (CNC), the salicylic acid functionalized reduced graphene oxide (rGO-SA), and the commercially available titanium dioxide (TiO
) were chosen as organic (CNC, rGO-SA) and inorganic (TiO
) supports. Then, the antimicrobial activity of the AgNP composites was assessed on clinically relevant multi-drug-resistant bacteria and the fungus
. The results show how the formation of Ag nanoparticles on the selected supports provides the resulting composite materials with an effective antibacterial activity.
Oxidized multiwalled carbon nanotubes were modified anchoring phosphine oxides and used as heterogeneous catalysts. A proper substitution of the phosphine oxides allowed the use of the Tour reaction ...and the nitrene cycloaddition to obtain functionalized carbon nanotubes (CNT) with a loading up to 0.73 mmol/g of material. The catalysts proved efficient in Wittig reactions, Mitsunobu reactions, and Staudinger ligations. Furthermore, the phosphorus decorated CNT were used to produce nanocomposite with Pd nanoparticles able to catalyze Heck reactions.
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