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A novel 6H-type hexagonal perovskite Ba3(Cr0.97(1)Te0.03(1))2TeO9 was prepared at high pressure (6 GPa) and temperature (1773 K). Both transmission electron microscopy and synchrotron powder X-ray diffraction data demonstrate that Ba3(Cr0.97(1)Te0.03(1))2TeO9 crystallizes in P63/mmc with face-shared (Cr0.97(1)Te0.03(1))O6 octahedral pairs interconnected with TeO6 octahedra via corner-sharing. Structure analysis shows a mixed Cr2+/Cr3+ valence state with ∼10% Cr2+. The existence of Cr2+ in Ba3(Cr2+0.10(1)Cr3+0.87(1)Te6+0.03)2TeO9 is further evidenced by X-ray absorption near-edge spectroscopy. Magnetic properties measurements show a paramagnetic response down to 4 K and a small glassy-state curvature at low temperature. In this work, the octahedral Cr2+O6 component is stabilized in an oxide material for the first time; the expected Jahn–Teller distortion of high-spin (d4) Cr2+ is not found, which is attributed to the small proportion of Cr2+ (∼10%) and the face-sharing arrangement of CrO6 octahedral pairs,...

This article deals with enantioselective gas chromatography (Es-GC) utilizing cyclodextrin derivatives as chiral stationary phases (CSPs) for chiral recognition in the flavour and fragrance field. It consists of two main parts. The first one concerns cyclodextrins and their use in Es-GC, and it deals with their introduction and evolution as CSPs in GC, together with some theoretical aspects involved with enantiomeric separation and their consequent influence on routine chiral recognition. The second part reports on the strategy of chiral recognition in routine analysis with cyclodextrin derivatives as CSP, illustrated with examples from the authors’ everyday experiences. This part describes how to identify enantiomers or to measure their excess or ratio determination in complex mixtures; in particular, it discusses the opportunities offered by multidimensional and fast GC techniques, the role of mass spectrometry, and the application of total analysis systems to chiral recognition.

Aryl ethers are prepared by cross-coupling of phenols with aryl iodides in isopropyl acetate as solvent.

ConspectusDensity functional theory (DFT) emerged in the last two decades as the most reliable tool for the description and prediction of properties of molecular systems and extended materials, coupling in an unprecedented way high accuracy and reasonable computational cost. This success rests also on the development of more and more performing density functional approximations (DFAs). Indeed, the Achilles’ heel of DFT is represented by the exchange-correlation contribution to the total energy, which, being unknown, must be approximated. Since the beginning of the 1990s, global hybrids (GH) functionals, where an explicit dependence of the exchange-correlation energy on occupied Kohn–Sham orbitals is introduced thanks to a fraction of Hartree–Fock-like exchange, imposed themselves as the most reliable DFAs for chemical applications. However, if these functionals normally provide results of sufficient accuracy for most of the cases analyzed, some properties, such as thermochemistry or dispersive interaction...

A critical overview of the very recent literature on heterogeneous electrochemical catalysis of CO2 reduction with organic metal modified electrodes is summarized. Five methods for electrode funtionalization are discussed and compared in terms of efficiency and selectivity: adsorption, by using membranes, adopting a “hybrid” covalent organic framework approach, performing electropolymerization directly on the electrode surface, and exploiting the formation of strong covalent chemical bonds between the surface and the desired catalyst.

A one-pot synthesis of secondary and tertiary amides from carboxylic acids and amines by using SOCl2 has been developed. Also when sterically hindered amines were used as the starting materials, excellent yields of the corresponding amides were obtained. The amidation of N-protected α-amino acids with secondary amines proceeds effectively with good yields. The process works well also in the presence of acid sensitive groups and occurs with almost complete retention of stereochemical integrity of chiral substrates. This protocol could be extended to industrial large-scale production processes.

We begin with a brief historical review of the development of our understanding of the normal ordering of nd orbitals of a transition metal interacting with ligands, the most common cases being three below two in an octahedral environment, two below three in tetrahedral coordination, and four below one in a square-planar environment. From the molecular orbital construction of these ligand field splittings evolves a strategy for inverting the normal order: the obvious way to achieve this is to raise the ligand levels above the metal d’s; that is, make the ligands better Lewis bases. However, things are not so simple, for such metal/ligand level placement may lead to redox processes. For 18-electron octahedral complexes one can create the inverted situation, but it manifests itself in the makeup of valence orbitals (are they mainly on metal or ligands?) rather than energy. One can also see the effect, in small ways, in tetrahedral Zn(II) complexes. We construct several examples of inverted ligand field syst...

In the last forty years Eni laboratories have contributed to the advancement of zeolite science and technology in both the synthesis and characterization of materials and their application in catalysis. This work has led to several industrial applications of zeolites, such as selective oxidation, acid–base catalysis, gas separation and water remediation. A brief review of the main results is reported with some comments on the future perspectives of this technology.

Reaction of pyrrole-2-carboxamides with Selectfluor in MeCN/water (4:1) affords 2-hydroxy-5-oxopyrrole-2-carboxamides in yields of up to 80 %. A variety of sensitive functional groups is tolerated, among them aldehydes and alkynes. The new method also works in the presence of allyl groups and appears to be superior to the use of singlet oxygen. Reaction of the monobrominated dihydropyrrolo[1,2-a]pyrazinone mukanadin C and its nonbrominated analogue afforded bicyclic hydroxypyrrolones. These compounds are interesting as they constitute a partial structure of the marine natural product oxocyclostylidol.

The CAN-catalyzed reaction of quinonoidal spirolactones with various aromatic hydrazines afford the title amino acids in moderate to excellent yields.

Simple and abundant carboxylic acids have been used as acyl radical precursor by means of visible-light photoredox catalysis. By the transient generation of a reactive anhydride intermediate, this redox-neutral approach offers a mild and rapid entry to high-value heterocyclic compounds without the need of UV irradiation, high temperature, high CO pressure, tin reagents, or peroxides.

Over the past few decades, there has been an increasing interest in the development of covalent enzyme inhibitors. As it was recently re-emphasized, the selective, covalent binding of a drug to the desired target can increase efficiency and lower the inhibitor concentration required to achieve a therapeutic effect. In this context, the naturally occurring antibiotic acivicin, and in particular its 3-chloro-4,5-dihydroisoxazole scaffold, has provided a wealth of inspiration to medicinal chemists and chemical biologists alike. In this Concept, to underline the great potentiality that the 3-halo-4,5-dihydroisoxazole warhead has in drug discovery, we present a number of examples, grouped by their potential biological activity and targets, in which this scaffold has been fruitfully used to develop novel biologically active compounds. Through these examples, we show that the 3-halo-4,5-dihydroisoxazole moiety represents an outstanding warhead with high potential for the design of novel covalent enzyme inhibitors.

The reaction of nitrobutadienes (I) with indole leads to 1,3,4- and 1,2,4-nitrocarbazoles (III) and (IV).

A highly effective synthesis of haloalkylidene-substituted heterocycles by copper(II)-catalyzed cyclization of alkynyl ureas and secondary amides has been developed. The reaction, which involves a catalytic amount of CuCl2 and a stoichiometric amount of N-halosuccinimide, occurs selectively through an alkoxyhalogenation process. Alternatively, alkoxychlorination and alkoxybromination reactions can be performed working solely with stoichiometric CuCl2 and CuBr2, respectively.

The synthesis, crystal structure and solid state properties of three different groups of magnetic organic–inorganic hybrid compounds are described and discussed. The reported examples are crystalline solids built from metal ions or metal clusters bonded to the organic moieties to form a single phase. The three families are: (a) perovskite metal halides, (b) electrical conductive radical-cation salts and (c) transition metal phosphonates and they differ by the type of chemical bonding between the organic and inorganic subnetworks. Organic–inorganic hybrid materials gained interest due to their potential applications in several fields and for their unusual collective electronic properties, such as magnetism, optical and electrical conductivity properties. Today they are experiencing a revival due to the discovery in some hybrids of coexistence of two physical properties such as ferroelectricity and magnetic order or ferromagnetism and metal-like electrical conductivity (dual-functional materials). The aim of this review is a survey of the crystal structure and properties of magnetic organic–inorganic hybrid compounds selected on the basis of their interesting electrical properties and for the potential applications.

A new chemical system is presented combining asymmetric amplification of autocatalyst HTP alongside a catalytic addition of Zn(iPr)2 to azaaryl aldehydes.

The asymmetric photo-organocatalytic α- or γ-alkylation of aliphatic aldehydes or α-branched enals with bromomalonates, respectively, is described.

The Pd-benzothiazolylidene complex (NHC) is shown to be a highly chemoselective catalyst for the Tsuji—Trost allylation of active methylene compounds using carbonates as allylating agents.

Review: overview of vegetable pigments in dye-sensitized solar cells, starting from main limitations of cell performance to cost analysis and scaling-up prospects; 669 refs.

Quaternary β-amino-ethers and -alcohols are synthesized by optimized one-pot, three-component reaction of aryl amines, ketones, and ethers or alcohols mediated by a TiCl4/Zn/tBuOOH system.

The decarboxylative reduction of α-amino acids and α-hydroxy acids is achieved in the presence of the (mesityl)methylacridinium photoredox catalyst in combination with bis(4-chlorophenyl) disulfide.

Review: design of photoelectrochemical cells that combine water oxidation and CO2 reduction; 50 refs.

Heteroatoms in zeolites provide them their catalytic activity. The silicon atom is always tetrahedrally coordinated and its valence IV, those of the heteroatoms much more varied. This is further complicated by the easy removal of heteroatoms out of the zeolite framework forming extra-framework phases. The change in coordination and removal of the framework atoms is often paralleled with enhanced catalytic performance and thus the precise characterization of heteroatoms in zeolites, as a function of synthesis and post-synthesis treatments, is topic of much research. In this review we summarize structural characterization of various heteroatoms using X-ray absorption spectroscopy. This method is in particular suitable, because it is element-specific, can be used to determine structure of amorphous samples, and can be applied under pretreatment and catalytic conditions. Aluminum shows a rich variation in coordination and, depending on the conditions, such as temperature and, notably, water content, zeolitic aluminum can be three, four, five and six-coordinate. The Bronsted acid site is associated with a strongly distorted tetrahedral coordination of the framework aluminum. During activation and along catalytic reactions, there is a large variation in the distortion of the local environment of aluminum, and the flexibility of the zeolite framework to accommodate such structural differences is essential to guarantee a long life time of the material as working catalyst. Iron in the zeolite framework is easily removed. The extra-framework iron species are extensively characterized, however, no consensus about their structure has been reached. Framework iron is Fe 3+ , extra-framework iron mostly Fe 2+ . The coordination of other tri- and tetravalent heteroatoms, such as gallium, boron, titanium, germanium, and tin are less investigated. It is however obvious that their structure is a function of the conditions the zeolite is exposed to. Like aluminum, the titanium atom easily switches coordination in a reversible way. All hetero-atoms often form extra-framework species. This review identifies the importance of changes in local structure of heteroatoms and the easy removal of these hetero-atoms from the framework. Often it is the extra-framework species that is responsible for catalytic activity.

Aqua iridium(III) complexes with 8-amino-5,6,7,8-tetrahydroquinolines CAMPY L1 and its derivatives as chiral ligands proved to be very efficient catalysts for the reduction of a wide range of prochiral aryl ketones, revealing a variety of behaviours in terms of reaction rate and stereoselectivity. As standard substrates, differently substituted acetophenones were studied and good enantioselectivity (86% ee) was achieved in the reduction of 1-(o-tolyl)ethan-1-one 6. Particularly interesting was the ATH reaction in the case of β-amino keto esters, precursors of β-lactams and azetidinones. The best results were obtained with [Cp∗Ir(H2O)(L1)]SO4 affording the corresponding diastereomeric alcohols in an (R,S)-configuration with an excellent 99% ee in the reduction of 2-(benzamido methyl)-3-oxo-3-(4-(trifluoromethyl)phenyl)propanoate 12.

[Zr(η8-C8H8)(OAr)(Cl)](Ar = 2,6-But2-C6H3)2 was transformed into the corresponding methyl, [Zr(η8-C8H8)(Me)(OAr)]3 and dimeric hydrido, [{Zr(η8-C8H8)(OAr)}2(µ-H)2]4 derivatives; the latter complex reduced CO to formaldehyde to produce the dimeric [{Zr(η8-C8H8)(OAr)}2(µ-CH2O)]5, isostructural to 4.

The synthesis and pharmacological evaluation of a series of pyrrolidine analogues of thymoxamine allowed access to the basic SAR for the aromatic substitution pattern. The results confirm the relevance of the simultaneous presence of the hydroxy and methyl groups on the benzene ring and prompted us to prepare the corresponding indole congener. The principle of the phenol—indol bioisosterism was confirmed by the results obtained. The introduction of the N -(2-methoxyphenyl)piperazine moiety instead of pyrrolidine changed the receptor affinity profile and introduced a good uroselectivity.

The vacuolar proton pump (V-ATPase) located on the plasma membrane of the osteoclast is a potential molecular target for the discovery of novel bone antiresorptive agents useful for the treatment of osteoporosis. In order to design novel compounds able to selectively inhibit the osteoclast V-ATPase we firstly identified the minimal structural requirements of bafilomycin A1, a macrolide antibiotic which potently inhibits all V-ATPases. This information allowed the design of 2-(indole)pentadienamide derivatives whose optimization led to a novel class of potent inhibitors that demonstrated a high degree of selectivity for the osteoclast V-ATPase. The most interesting derivative, SB-242784, was able to inhibit bone resorption by human osteoclasts in vitro and to completely prevent ovariectomy-induced bone loss in rats when administered orally at 10 mg kg(-1) day(-1). Structure activity relationships of this class of compounds were investigated further by replacing the 2,4-pentadienoyl chain with suitable spacers able to maintain the correct orientation and distance between the indole ring and the amide moiety.

In the last decade a number of selective and potent non-peptidic agents became available to explore the usefulness of the δ-opioid receptor in modulation of pain of different origins. As a continuing effort in this field, potent and selective δ-opioid agonists based on the pyrrolomorphinan framework have been designed, synthesised and characterised biologically in our laboratories. In animal models, a selected compound of interest, SB 235863, has proved the concept that selective δ-opioid agonists may have great potential as pain relief agents in inflammatory and neuropathic pain conditions. Importantly, such a compound was free of the unwanted side effects usually associated with narcotic analgesics such as morphine.

Three novel cembrane diterpenoids, decaryiols B–D (5–7), characterized by a bicyclic skeleton of the decaryiol-type, have been isolated from the Indonesian soft coral Lobophytum sp., along with three known cembranoids. The stereostructures of these metabolites have been established through extensive NMR spectroscopic analysis, application of the modified Mosher method, and chemical conversion. Cembranoids obtained from Lobophytum sp. (2–7) and six semisynthetic derivatives (9–14) prepared from decaryiol were tested for cell growth inhibitory activity against three different cell lines. O-Methyl decaryiol (10) exhibited a significant and selective activity against glioma cell lines.

A total synthesis of d-erythro-sphinganine [(2S,3R)-2-aminooctadecane-1,3-diol] starting from commercial N-tert-butyloxycarbonyl-l-serine methyl ester is described. The approach is based on the completely stereoselective preparation of an α-amino epoxide obtained by treating a protected l-serinal derivative with dimethylsulfoxonium methylide. The oxirane synthon is obtained with an anti configuration fitting the (2S,3R) stereochemistry of the 2-amino-1,3-diol polar head of d-erythro-sphinganine. The synthetic procedure afforded the target compound in a 68% overall yield based on the initial amount of the starting l-serine material.

Coating is the most widely used technique for the preparation of structured catalysts. This paper reviews the main methods reported in the open literature for depositing catalytic layers onto metallic substrates, specifically focusing on the coating of metallic honeycomb monoliths and open-cell foams. All the relevant steps, including substrate pre-treatments, means for catalytic activation and thermal treatments, are discussed.

In this highlight we present a snapshot of recent work using magnetic forces and particles to perform lab on a chip operations. Magnetic micro- & nanoparticles have been widely used for separations in cell biology & clinical diagnostics and as solid phase supports for reactions and chemical assays. Microscale approaches to control and manipulate magnetic particles can enable new functionality; allowing parallel and complex automation of assays, manipulation of fluids themselves, and precise separations based on small differences in magnetic properties. Here we discuss recent work demonstrating advances in these three areas.

Review: use of vibrational and electronic spectroscopies in the characterization of meallorganic materials, such as metal organic frameworks (MOFs); 194 refs.

The method can be used for the N-acylated sugars and oligosaccharides bearing small labels, spacers or peptides in the acyl part.

An oxidative route to N-substituted sulfonamidic azobenzene derivatives is reported. A mechanism, based on a rationalization of previous findings, is proposed. This simple one-pot method could be adapted to the synthesis of a range of substituted sulfonylazobenzenes with potential applications in the pharmaceutical and industrial fields.

The use of the ionic liquid allows for the rapid and clean removal of the nosyl protecting group and for subsequent reprotection of the free α-amino function with the acetyl- or Boc-group.

Since the beginning of the century, N-hydroxyphthalimide and related compounds have been revealed to be efficient organocatalysts for free-radical processes and have found ample application in promoting the aerobic oxidation of a wide range of organic substrates. When combined with different co-catalysts, they are activated to the corresponding N-oxyl radical species and become able to promote radical chains, involving molecular oxygen, directly or indirectly. Most of the examples reported in the literature describe the use of these N-hydroxy derivatives in the presence of transition-metal complexes. However, eco-friendly standards, including the demand for highly selective transformations, impose the development of metal-free processes, especially for large-scale productions, as in the case of the oxygenation of hydrocarbons. For this reason, many efforts have been devoted in the past decade to the design of new protocols for the activation of N-hydroxy imides in the presence of nonmetal initiators. Herein we provide a concise overview of the most significant and successful examples in this field, with the final aim to furnish a useful instrument for all scientists actively involved in the O2-mediated selective oxidation of organic compounds and looking for environmentally safe alternatives to metal catalysis.

The ring opening of 3-nitro-4-(phenylsulfonyl)thiophene with amines and proper modification of the resulting 1,3-diene enables a simple and versatile approach to N-fused pyrroles of both synthetic and biological interest through 1,6-H shift followed by 6π 1,5-electrocyclization. This protocol is effectively driven to the isolated pyrroles by an easy aromatization.

Dynamic combinatorial libraries (DCLs) are collections of structurally related compounds that can interconvert through reversible chemical reaction(s). Such reversibility endows DCLs with adaptability to external stimuli, as rapid interconversion allows quick expression of those DCL components which best respond to the disturbing stimulus. This Tutorial Review focuses on the kinetically controlled phenomena that occur within DCLs. Specifically, it will describe dynamic chiral resolution of DCLs, their self-sorting under the influence of irreversible chemical and physical stimuli, and the autocatalytic behaviours within DCLs which can result in self-replicating systems. A brief discussion of precipitation-induced phenomena will follow and the review will conclude with the presentation of covalent organic frameworks (COFs)—porous materials whose synthesis critically depends on the fine tuning of the crystal growth and error correction rates within large DCLs.

A synthetic method is presented for the preparation of title compounds (II) and (III) which may serve as starting material for new N-substituted derivatives such as (VI) or (VII).

Purified lipase fractions from crude commercial extract of Aspergillus niger lipase (ANL) were selectively immobilized on hydrophobic supports. A significant percentage of esterase activity remains in the supernatant, derived from esterase(s) unable to become adsorbed onto the employed matrices. These residual proteins were covalently immobilized on epoxy-acrylic resin. Immobilized hydrolases were tested in the hydrolysis of acetylated disaccharides in water-cosolvent systems. ANL-Esterase was able to catalyze regioselective deprotection of acetylated β-O-methyl lactoside in C-2 position and β-O-methyl lactosaminide in C-3′ position. The hydrolyzed products, never reported before, can be considered new building blocks for the synthesis of oligosaccharides of biological relevance. Furthermore, preparative hydrolyses were also performed in tert-butanol. This solvent is compatible with ANL-esterase stability and it appears to be a novel and promising approach because of its green status.