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Non-heme iron complexes are emerging as powerful and versatile catalysts in several oxidative transformations. The most investigated iron complex structures are based on aminopyridine ligands, but a number of imine-based ligands have been also tested. In this review a collection of recent results obtained in oxidation catalysis with non-heme imine-based iron complexes is presented. Their catalytic performances in CH, CC and S oxidation are spread over a wide range of efficiency, going from very low to quite high. Such performances are discussed, whenever possible, in light of the operating reaction mechanisms and of catalyst stability. In order to facilitate the discussion, an initial survey of the most useful mechanistic tools widely applied to distinguish a metal-based oxidation from a radical-chain process is also reported. Imine-based catalysts are divided into two classes: (i) salen-Fe complexes, and (ii) imine-Fe complexes. In some cases clues for free-radical oxidation mechanisms have been reported while in other cases evidence for metal-based mechanisms has been collected. The preferred mechanistic pathway is shown to be a function of catalyst structure and features. Interestingly, some imine-based iron complexes are able to perform stereospecific oxidation reactions, demonstrating that the imine functionality can be incorporated in ligands designed for oxidation catalysis.

The state of the art in the mechanisms operating in imine chemistry in organic solvents is critically discussed in the present review. In particular, the reaction pathways involved in imine formation, transimination and imine metathesis in organic media are taken into account, with the aim of organizing the poor, and sometimes scattered, information available in the literature. It is shown that 4-membered cyclic transition states, either polar or apolar, can be considered a leitmotif for the chemistry of imines in organic solvents. However, it is pointed out that further investigations will be necessary to reach an adequate degree of knowledge of the mechanisms involved in such important reversible processes.

Reactivity data relating to bimolecular reactions of compounds featuring complementary recognition sites are critically surveyed and discussed in terms of effective molarity (EM) as an absolute measure of the efficiency of the intracomplex reactions. Comparison of experimentally determined EM values with idealized values estimated for strain-free cyclizations on the basis of the number of internal rotors in the linker allowed quantification of the penalties of imperfect design in terms of entropy and strain.

Examples of reactivity of carbonyl and phosphoryl compounds controlled by calixarenes are illustrated in this review article. The molecular framework of calixarenes has been widely used as a versatile molecular platform for the dynamic arrangement of one or more structural units working as recognition and/or catalytic sites, in many cases with considerable levels of cooperation. The calixarene cavity itself has also been involved as a recognition unit for inclusion of the substrate or of part-structures of the substrate. Unique reactivity patterns of carbonyl or phosphoryl functional groups organised at the upper or lower rim of calixarenes will also be illustrated.

The present review offers an overview of the current approaches for the photochemical and photocatalytic generation of reactive intermediates and their application in the formation of carbon–carbon bonds. Valuable synthetic targets are accessible, including arylation processes, formation of both carbo- and heterocycles, alpha- and beta-functionalization of carbonyls, and addition reactions onto double and triple bonds. According to the recent advancements in the field of visible/solar light catalysis, a significant part of the literature reported herein involves radical ions and radicals as key intermediates, with particular attention to the most recent examples. Synthetic application of carbenes, biradicals/radical pairs and carbocations have been also reported.

Oxygen-bridged tetranuclear copper complexes having a Cu4O4 cubane-like core represent a really fascinating class of compounds, due to their similarity to copper oxidase active sites or to their molecular magnetism. Among these, hydroxo-bridged copper(II) cubanes are a restricted category when compared to alkoxo-bridged ones, {Cu4(μ3-OH)4}-based compounds structurally described via X-ray being only 18 (to the end of 2014), to the best of our knowledge. In this review, the key features of these compounds will be highlighted, with attention to their structural characterization and classification, their syntheses and their magnetic behavior.

A critical overview of the latest developments in the aluminum battery technologies is reported. The substitution of lithium with alternative metal anodes characterized by lower cost and higher abundance is nowadays one of the most widely explored paths to reduce the cost of electrochemical storage systems and enable long-term sustainability. Aluminum based secondary batteries could be a viable alternative to the present Li-ion technology because of their high volumetric capacity (8040 mAh cm(-3) for Al vs 2046 mAh cm(-3) for Li). Additionally, the low cost aluminum makes these batteries appealing for large-scale electrical energy storage. Here, we describe the evolution of the various aluminum systems, starting from those based on aqueous electrolytes to, in more details, those based on non-aqueous electrolytes. Particular attention has been dedicated to the latest development of electrolytic media characterized by low reactivity towards other cell components. The attention is then focused on electrode materials enabling the reversible aluminum intercalation-deintercalation process. Finally, we touch on the topic of high-capacity aluminum-sulfur batteries, attempting to forecast their chances to reach the status of practical energy storage systems.

Given the wide utility of click-chemistry reactions for the preparation of simple moieties within large architecturally complex materials, this minireview article aims at surveying papers exploring their scope in the area of π-conjugated polymers for application in organic electronics to enable advanced functional properties.

Different 2-sulfonylaminoaryl diselenides substituted with electron-withdrawing or -donating groups are transformed in one pot into benzo[b][1,4]selenazines. The reaction uses a substoichiometric amount of Cu(OTf)2, and the mechanism involves a base-mediated 1,4-elimination at selenium with the generation of an o-iminoselenoquinone and a 2-sulfonylaminoselenolate anion. The former is a dienic species that can react with electron-rich dienophiles to give the target cycloadducts. The latter is oxidised by air back to the starting diselenide, allowing its complete consumption. A preliminary investigation of the GPx-like activity of a selected selenazine is also described.

A heterogeneous fluoride catalyst was found to enable the straightforward formation of alkenyl nitriles from the reaction of aldehydes and simple or substituted acetonitriles, in the presence of commercially available silazanes and in solvent-free conditions. The protocol afforded the products in good to excellent yields with selectivity values dependent on the nature of the substrates. It represents an alternative to classic approaches using stoichiometric strong bases, and the catalyst can be easily recovered and reused for consecutive cycles.

The construction of aromatic rings has become a key objective for organic chemists. While several strategies have been developed for the functionalization of pre-formed aromatic rings, the direct construction of an aromatic core starting from polyunsaturated systems is yet a less explored field. The potential of such reactions in the formation of aromatics increased at a regular pace in the last few years. Nowadays, there are reliable and well-established procedures to prepare polyenic derivatives, such as dienynes, enediynes, enyne–allenes and hetero-analogues. This has stimulated their use in the development of innovative cycloaromatizations. Different examples have recently emerged, suggesting large potential of this strategy in the preparation of (hetero)aromatics. Accordingly, this review highlights the recent advancements in this field and describes the different conditions exploited to trigger the process, including thermal and photochemical activation, as well as the use of transition metal catalysis and the addition of electrophiles/nucleophiles or radical species.

The octa-1,7-diene-4,5-diamine skeleton is usually prepared by the addition of allylic organometallic reagents to glyoxal diimines. The relative and absolute configurations of the C4 and C5 stereocenters are dependent on the nature of the (chiral) nitrogen substituents. These compounds are useful intermediates for the construction of NHC carbene complexes and nitrogen heterocycles, such as 2,2′-bipyrrolidines, 2,5-diazabicyclo[2.2.1]heptanes, amino- and hydroxy-substituted 7-azanorbornane, and diamino-substituted cyclohexanols and cyclohexanediols.

PS-BEMP was used as a heterogeneous catalyst for the phospha-Michael addition of phosphorus nucleophiles to a variety of electron-poor alkenes. The addition reactions were generally performed with equimolar amounts of reagents under solvent free conditions. The protocol proved to be very efficient for the addition to aromatic, non-aromatic and cyclic ketones, giving good yields (78-85%) in all cases. The protocol was also extended with good results to α,β-unsaturated esters and nitriles. This demonstrates that PS-BEMP is a good catalyst for the phospha-Michael addition to electron-poor alkenes.

Despite the undisputed advances and progress in metal-catalyzed C–H functionalizations, this atom-economical approach had thus far largely been developed with the aid of various metal catalysts that were operative in a homogeneous fashion. While thereby major progress was accomplished, these catalytic systems featured notable disadvantages, such as low catalyst recyclability. This review summarizes the development of user-friendly, recyclable and easily separable heterogeneous catalysts for C–H activation. This strategy was characterized by a remarkably broad substrate scope, considerable levels of chemo- and site-selectivities and proved applicable to C–C as well as C–heteroatom formation processes. Thus, recyclable catalysts were established for arylations, hydroarylations, alkenylations, acylations, nitrogenations, oxygenations, or halogenations, among others. The rapid recent progress in selective heterogeneous C–H functionalizations during the last decade until December 2015 is reviewed.

A study of secondary, benzylic, and primary alcohols oxidation on a reference Au/TiO2 catalyst is reported. Reactions gave rise to ketones, aldehydes, or esters in good yields. The FT-IR results and catalytic tests data provide to elucidate the reaction mechanism and the specific role of the active sites on titania.

ConspectusQuantum chemical techniques today are indispensable for the detailed mechanistic understanding of catalytic reactions. The development of modern density functional theory approaches combined with the enormous growth in computer power have made it possible to treat quite large systems at a reasonable level of accuracy. Accordingly, quantum chemistry has been applied extensively to a wide variety of catalytic systems. A huge number of problems have been solved successfully, and vast amounts of chemical insights have been gained.In this Account, we summarize some of our recent work in this field. A number of examples concerned with transition metal-catalyzed reactions are selected, with emphasis on reactions with various kinds of selectivities. The discussed cases are (1) copper-catalyzed C–H bond amidation of indoles, (2) iridium-catalyzed C(sp3)–H borylation of chlorosilanes, (3) vanadium-catalyzed Meyer–Schuster rearrangement and its combination with aldol- and Mannich-type additions, (4) pallad...

Arene and heteroarenediazonium o-benzenedisulfonimides can be used as efficient reagents in Sandmeyer cyanation. This work reports such reactions carried out by us under very mild conditions using tetrabutyl ammonium cyanide as a safe cyanide source and, interestingly, without the need for a Cu catalyst. The reactions have given rise to aryl nitriles in good yields (25 examples, average yield 75%). A good amount of o-benzenedisulfonimide was recovered from each reaction and then reused to prepare other salts. Mechanistic insights have allowed us to highlight the fundamental role of the o-benzenedisulfonimide anion as an electron transfer agent.

Carotenoids are important isoprenoid compounds whose oxidative degradation produces a plethora of smaller derivatives, called apocarotenoids, which possess a range of different chemical structures and biological activities. Among these natural products, compounds having less than 15 carbon atoms in their frameworks are often relevant flavours or fragrances and their manufacturing represents an important economic resource for chemical companies. The strict correlation between stereochemical structure and odour has made the stereospecific synthesis of the latter biological active compounds increasingly important. In this review, the recent advances on the synthesis of the most relevant carotenoid-derived flavours and fragrances are discussed. In particular, the new synthetic methods that have given new and innovative perspectives from a scientific standpoint and the preparative approaches that might possess industrial importance are described thoroughly.

A domino Friedel-Crafts/nitro-Michael reaction between 4-substituted indoles and nitroethene is presented. The reaction is catalyzed by BINOL-derived phosphoric acid catalysts, and delivers the corresponding 3,4-ring-fused indoles with very good results in terms of yields and diastereo- and enantioselectivities. The tricyclic benzo[cd]indole products bear a nitro group at the right position to serve as precursors of ergot alkaloids, as demonstrated by the formal synthesis of 6,7-secoagroclavine from one of the adducts. DFT calculations suggest that the outcome of the reaction stems from the preferential evolution of a key nitronic acid intermediate through a nucleophilic addition pathway, rather than to the expected "quenching" through protonation.

These photocatalyzed radical conjugate addition reactions are carried out in a meso-scale flow photoreactor consisting in coils of UV-transparent FEP tubing wrapped around a water-cooled medium pressure mercury vapor lamp.

The advent of solid-state polymer electrolytes for application in lithium batteries took place more than four decades ago when the ability of polyethylene oxide (PEO) to dissolve suitable lithium salts was demonstrated. Since then, many modifications of this basic system have been proposed and tested, involving the addition of conventional, carbonate-based electrolytes, low molecular weight polymers, ceramic fillers, and others. This Review focuses on ternary polymer electrolytes, that is, ion-conducting systems consisting of a polymer incorporating two salts, one bearing the lithium cation and the other introducing additional anions capable of plasticizing the polymer chains. Assessing the state of the research field of solid-state, ternary polymer electrolytes, while giving background on the whole field of polymer electrolytes, this Review is expected to stimulate new thoughts and ideas on the challenges and opportunities of lithium-metal batteries.

The reactivity of metalated alkoxy-1,3-dienes and α-aryl-N-phenylnitrones in the presence of LIC-KOR base, equimolar mixture of alkyllithium (LIC) and potassium alcoxides (KOR), (Schlosser, 1994) [1] has been studied. A cascade reaction involving a E1cb process stereoselectively affords ethoxy-N-phenyl-1-arylpenta-2,4-dien-1-imines. Their acidic hydrolysis allows the synthesis of peptidomimetic 5-aryl-5-phenylaminocyclopentenones in good yields.

Carbocycles are essential building blocks for the synthesis of natural and synthetic bioactive compounds. Herein, we report the first example of palladium-catalyzed intramolecular carboalkynylation of non-activated olefins. Using activated carbonyl compounds as nucleophiles and an alkynyl bromide as an electrophile, the reaction gives access to cyclopentanes in 44-93% yield and one example of cyclohexane in 31% yield with simultaneous formation of a SP3-SP C-C bond. The reaction therefore combines ring formation with the introduction of a versatile triple bond for further functionalization. (C) 2015 Elsevier Ltd. All rights reserved.

The structural modification of the resveratrol scaffold is currently an active issue in the quest for more potent and versatile antioxidant derivatives for biomedical applications. Disclosed herein is an expedient and efficient entry to a novel class of resveratrol derivatives featuring an unprecedented 2-phenylbenzoselenophene skeleton. The new compounds were obtained in good yields by direct selenenylation of resveratrol with Se(0) and SO2Cl2 in dry THF. Varying the [Se : SO2Cl2 : resveratrol] ratio resulted in the formation of the parent benzoselenophene (1) and/or mono (2) and/or dichloro (3) benzoselenophene derivatives. All the benzoselenophene derivatives proved to be more efficient than resveratrol in the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing/antioxidant power (FRAP) assays, with 1 showing an activity nearly comparable to that of Trolox. 1–3 also proved to be more efficient inhibitors than the parent resveratrol in kinetic experiments of styrene autoxidation. DFT calculations of the O–H bond dissociation enthalpy (BDE) revealed that the introduction of the Se-atom causes a significant decrease of the BDE of 3-OH and 5-OH, with just a small increase of the 4′-OH BDE. Compounds 1–3 showed no cytotoxicity at 5 μM concentrations on human keratinocyte (HaCaT) and intestinal (CaCo-2) cell lines.

Di-2-pyridyl carbonate (I) reacts with various alcohols to form mixtures of 2-pyridyl carbonates (III) or (VIII) and 2-oxopyridine-1-carboxylates (IV) and (IX).

This gives exclusively the E isomers of the arylidene-hetarylium tetrafluoroborates, which can be easily reduced to the corresponding aryl-hetaryl-methanes.

Lithium-ion batteries are becoming increasingly important for electrifying the modern transportation system and, thus, hold the promise to enable sustainable mobility in the future. However, their large-scale application is hindered by severe safety concerns when the cells are exposed to mechanical, thermal, or electrical abuse conditions. These safety issues are intrinsically related to their superior energy density, combined with the (present) utilization of highly volatile and flammable organic-solvent-based electrolytes. Herein, state-of-the-art electrolyte systems and potential alternatives are briefly surveyed, with a particular focus on their (inherent) safety characteristics. The challenges, which so far prevent the widespread replacement of organic carbonate-based electrolytes with LiPF6 as the conducting salt, are also reviewed herein. Starting from rather "facile" electrolyte modifications by (partially) replacing the organic solvent or lithium salt and/or the addition of functional electrolyte additives, conceptually new electrolyte systems, including ionic liquids, solvent-free, and/or gelled polymer-based electrolytes, as well as solid-state electrolytes, are also considered. Indeed, the opportunities for designing new electrolytes appear to be almost infinite, which certainly complicates strict classification of such systems and a fundamental understanding of their properties. Nevertheless, these innumerable opportunities also provide a great chance of developing highly functionalized, new electrolyte systems, which may overcome the afore-mentioned safety concerns, while also offering enhanced mechanical, thermal, physicochemical, and electrochemical performance.

Picenes 2a–c were readily obtained via photocyclization of dinaphthylethenes 1a–c by a straightforward solar light-induced Mallory reaction. The product was easily recovered by simple filtration after exposure of the reaction mixture to sunlight. The polyene obtained was then characterized by means of Raman spectroscopy and X-ray diffraction.

The use of low temperature, sustainable processes based on cheap and safe chemicals as well as nontoxic, easy to handle chemicals and solvents is a challenging issue in modern inorganic chemistry; moreover the obtainment of crystalline functional nanostructures at low or even room temperature is the goal of many synthetic efforts. Within this framework, in these last years, we have developed in our group different room or low temperature (T

A general synthesis of C6-pyridylpurine nucleosides is described. The reported synthetic procedure exploits the regioselective addition of pyridinyl Grignard reagents, obtained by bromine/magnesium exchange between mono- or dihalopyridines and iPrMgCl, to the C6–N1–O– moiety of nebularine N1-oxide. The regioselective transmetallation of unsymmetrical dihalopyridines with iPrMgCl allowed C6-halopyridylpurine nucleosides to be obtained through the addition of halopyridinyl Grignard reagents. The presence of a halogenated pyridine ring in these nucleosides allows for further useful synthetic transformations.

Some N-Boc ynamides bearing a terminal ester or aryl group are treated with azides to produce the desired triazoles with complete regiocontrol.

The synergistic action of light, oxygen and a photosensitizer (PS) has found applications for decades in medicine under the name of photodynamic therapy (PDT) for the treatment of skin diseases and, more recently, for the treatment of cancer. However, of the thirteen PSs currently approved for the treatment of cancer over more than 10 countries, only two contain a metal ion. This fact is rather surprising considering that nowadays around 50% of conventional chemotherapies involve the use of cisplatin and other platinum-containing drugs. In this perspective article, we review the opportunities brought by the use of Ru(ii) complexes as PSs in PDT. In addition, we also present the recent achievements in the application of Ru(ii) complexes in photoactivated chemotherapy (PACT). In this strategy, the presence of oxygen is not required to achieve cell toxicity. This is of significance since tumors are generally hypoxic. Importantly, this perspective article focuses particularly on the Ru(ii) complexes for which an in vitro biological evaluation has been performed and the mechanism of action (partially) unveiled.

2,2,2-Trifluoroethoxy aryl sulfates, formed in situ from imidazolium salts (I), represent a new class of photoactive substrates capable of generating aryl cations which can be trapped by various nucleophiles.

The synthesis of the title compound (VI) is based on the highly diastereoselective addition of allylzinc bromide to bisimine (I) and ring-closing metathesis as the key steps.

Lithium/air is a fascinating energy storage system. The effective exploitation of air as a battery electrode has been the long-time dream of the battery community. Air is, in principle, a no-cost material characterized by a very high specific capacity value. In the particular case of the lithium/air system, energy levels approaching that of gasoline have been postulated. It is then not surprising that, in the course of the last decade, great attention has been devoted to this battery by various top academic and industrial laboratories worldwide. This intense investigation, however, has soon highlighted a series of issues that prevent a rapid development of the Li/air electrochemical system. Although several breakthroughs have been achieved recently, the question on whether this battery will have an effective economic and societal impact remains. In this review, a critical evaluation of the progress achieved so far is made, together with an attempt to propose future R&D trends. A forecast on whether Li/air may have a role in the next years' battery technology is also postulated.

The advantages of the title synthesis are high yield, complete stereoselectivity, low catalyst loading (0.2-0.5 mol%), and no need for CuI as co-catalyst.

o-Thioquinones, generated via a copper-mediated 1,4-elimination at sulfur of o,o′-dihydroxy disulfides (I), are trapped in an inverse electron-demand hetero Diels—Alder reaction with electron-rich alkenes to give dihydrobenzooxathiines (II).

Title diazonium salts are used for the first time as electrophilic partners in Negishi cross coupling reactions to produce biaryls.

The preparation of new chiral amino alcohols that possess a flexible biphenylazepine moiety and can work as tropos catalysts, is presented. In these compounds, the sign of the induced axial chirality depends on the nature of stereogenic centers near the flexible fragment and can determine the stereochemical outcome in asymmetric reactions mediated by them. The efficiency of these new ligands has been explored in the asymmetric addition of arylzinc species prepared in situ to aromatic aldehydes. Among them, amino alcohol (1R,2S)-4 gave the best results and afforded optically active diarymethanols, which are precursors of well-known chiral drugs, in high yields and with enantioselectivity up to 96 %.

α-Acryloylamidoalkyl sulfones are converted with in situ generated allylzinc bromides to give a range of dienic products.

Adipic acid, which is a very important commodity chemical, is traditionally manufactured industrially by an aged and unsustainable multistep process that involves homogeneous catalysts, aggressive oxidants (concentrated nitric acid) and the production of large quantities of the greenhouse gas nitrous oxide. Much research and development into alternative and cleaner process routes to adipic acid have been carried out over the past 70 years. Improved reaction schemes have invoked variations in fossil raw materials (from benzene and phenol to cyclohexane, cyclohexanol, cyclohexanone, cyclohexene, butadiene, and adiponitrile, etc.), oxidants (O2, air, H2O2, t-BuOOH, ozone), catalysts (homogeneous, heterogeneous, phase transfer, biomimetic) and reaction conditions (low temperature, atmospheric pressure, and solvent-, metal-, halide-, and corrosion-free). No single proposed alternative pathway—some of which are purely academic—simultaneously addresses the problems of petrochemical origin, toxic starting materia...

The highly diastereoselective anti-dioxylation of (1R,2R)-1,2-bis[(1S)-phenylethylamino]cyclohexene was accomplished through epoxidation of the double bond with m-chloroperbenzoic acid (mCPBA) in the presence of a sulfonic or trihaloacetic acid and ring opening of the epoxide in situ in the presence of sulfonate or carboxylate anions. The two procedures, after basic quenching and reductive removal of the N-substituents, provide stereoselective access to 2-exo-5-endo-5-amino-7-azabicyclo[2.2.1]heptan-2-ol and 4,5-diaminocyclohexane-1,2-diol, respectively. The different outcomes are explained by differing chair conformations of the protonated diamine-epoxide intermediates, which undergo ring opening through a preferred anti-diaxial mechanism.

Perfluoroalkyl radicals, generated by thermal decomposition of perfluorodiacyl peroxides, react selectively with quinone rings of 1,4-naphthoquinones. In the presence of a non-conjugated alkene such as 1-hexene, perfluoroalkyl radicals add to the double bonds of the olefin forming a radical adduct, which selectively adds to the naphthoquinone ring. Several perfluorodiacyl peroxides have been synthesized and used for the direct and alkene-mediated functionalization of naphthoquinones. Geometrical parameters and electron density topology of all perfluorodiacyl peroxides have been calculated by the density functional formalism and quantum theory of atoms in molecules to attempt a rationalization of the experimental reactivity.