Green synthetic approaches for biologically relevant organic compounds

The present review aims to present some framework of the effective and diverse green methodologies in conventional and unconventional media including water, solar energy, ionic liquids, ultrasonication and bio-based catalysts which constitute an important goal in organic synthesis and can be used to strengthen conventional laboratory techniques.     

Organoboron chemistry comes to light: Recent advances in photoinduced synthetic approaches to organoboron compounds

Photoinduced synthetic approaches to organoboron compounds have attracted significant attention in the recent years. Photochemical activation of organic molecules enables generation of reactive intermediates from a variety of precursors, resulting in borylation methods with improved and broader substrate scopes. The review summarizes recent developments in the area of photoinduced reactions of organoboron compounds with an emphasis on borylation of haloarenes, amine derivatives, and redox-active esters of carboxylic acids, as well as photoinduced rearrangements of organoboron compounds and photoinduced synthesis of organoboron compounds from alkenes and alkynes.     

An overview on novel synthetic approaches and medicinal applications of benzimidazole compounds

Benzimidazole, a benzene-fused heterocyclic compound, has acquired significant attention in the field of contemporary medicinal chemistry because of its wide array of pharmacological activities. Nitrogen containing heterocyclic compounds are part of several therapeutically important agents with several recent patents shedding light on their worth. For these reasons, this review is concerned with different methods for synthesis of benzimidazole derivatives and their biological importance.     

Recent developments in synthetic approaches to transition metal phosphide nanoparticles for magnetic and catalytic applications

Recent advances in synthetic methods have led to the preparation of a wide array of transition metal phosphide nanoparticles, and characterization of these materials has provided insight into nanoscale magnetic and catalytic properties. This review highlights advances in the field that have been made since the time of the last review [S.L. Brock, S.C. Perera, K.L. Stamm, Chem. Eur. J. 10(2004)3364–3371]. Synthetic methods include solvothermal, solution-phase arrested precipitation, metal nanoparticle conversion, and phosphate reduction. Magnetic properties of FeP, Fe₂P and MnP nanoparticles and nanorods (among others), and recent data on thiophene hydrodesulfurization catalyzed by discrete, unsupported Ni₂P particles, is presented. Finally, the future prospects for the field are discussed.     

Stannoxanes and phosphonates: New approaches in organometallic and transition metal assemblies

Phosphonate ligands, [RPO₃]^2-, are extremely versatile in the assembly of multi-tin and multi-copper architectures. We have used organostannoxane cores for supporting multi-ferrocene and multi-porphyrin peripheries. The copper-metalated multi-porphyrin compound is an excellent reagent for facile cleavage of DNA, even in the absence of a co-oxidant. Reaction oft-BuPO₃H₂ with Cu(C10₄)₂. 6H₂O in the presence of 2-pyridylpyrazole (2-Pypz) leads to the synthesis of a decanuclear copper (II) assembly.     

Solvation of transition metal complexes: thermochemical approaches

Conclusion and extensions We hope that this Review has made readers more aware of solvation of inorganic complexes, and of the importance of such knowledge in understanding their chemistryperhaps particularly their reactivity. The approach just set out for inorganic complexes should be of considerable value in the field or organometallic chemistry. In particular, informed use of solvation characteristics should help in optimising conditions for organometallic reactions and in homogeneous catalysis. Unfortunately, solvation data on reactants are too sparse (the subject index ofComprehensive Organometallic Chemistry contains justthree entries under solubility!) for serious examination of reactivity trends in terms of initial state and transition state contributions to be possible in almost all areas. Moreover, there are some fundamental problems over transfer parameters. Thus, a favourite electrochemical assumption is that the ferrocene/ferrocinium redox potential is independent of solvent. Yet, the dependence of rate constants on medium for outer-sphere electron transfer in the ferrocene/ferrocinium system can only be understood⁽⁶⁶⁾ in terms of specific solvation effects which are incompatible with the parallel solvation changes of these two substrates implicit in the redox potential assumption. The solvation of organometallic species should prove a most rewarding area for continued study, but it will be some time before the overall picture becomes as clear as in the more limited area of classical transition metal complexes considered in the present Review.     

A facile synthetic route to (η-benzoyleyclopentadienyl) metal compounds

A reaction between cyclopentadienylsodium and ethyl benzoate in refluxing THF produces (benzoylcyclopentadienyl)sodium (4) in 70–80% yield. Subsequent treatment of 4 in ethanol solution with thallium ethoxide affords (benzoyleyclopentadienyl)thallium (3) in nearly quantitative yield. Reactions of 3 with Mn(CO)₅Br, Re(CO)₅Br, [Rh(CO)₂Cl]₂ or FeCl₂ lead to the respective η⁵-benzoylcyclopentadienyl derivatives of these metals, and demonstrate the utility of 3 in organometallic syntheses. Reactions of several of these organometallic ketones with cymantrenyllithium [(η⁵-C₅H₄Li)Mn(CO)₃] provide a useful new route to bimetallic compounds.     

Alkali metal diphenylmethanides: synthetic, computational and structural studies

In search of new synthetic precursors for the preparation of alkaline earth organometallic compounds, we investigated the application of a powerful desilylation reaction to cleanly afford a variety of contact and charge-separated alkali metal derivatives without the difficulties commonly encountered in other methods. The resulting diphenylmethanides display both contact molecules and separated ion pairs. Analysis of the structural data demonstrates that simple electrostatic models are insufficient for predicting and explaining the solid-state structures of these complexes. Detailed computational investigations were performed to probe the nature of the metal-anion and metal-donor interactions and determine the contributions of each to the observed solid-state structures.     

Macromolecular metal complexes with transition-metal ions: Structure of a polymer and efficiency of complexation

A quantitative method of estimating the efficiency of formation of macromolecular metal complexes of carboxyl-containing (co)polymers with transition-metal ions in dilute solutions was developed. This method is based on the luminescence quenching of luminescently labeled macromolecules by transition-metal ions. With the use of this method, the effect of the chemical (including isomeric) structure of carboxyl-containing (co)polymers and external conditions on the stability of macromolecular metal complexes based on copper, nickel, and silver ions was assessed. With consideration for the data obtained, a targeted variation in the functional characteristics of macromolecular metal complexes may be accomplished.     

Antitumour metal compounds: more than theme and variations

Triggered by the resounding success of cisplatin, the past decades have seen tremendous efforts to produce clinically beneficial analogues. The recent achievement of oxaliplatin for the treatment of colon cancer should, however, not belie the imbalance between a plethora of investigated complexes and a very small number of clinically approved platinum drugs. Strategies opening up new avenues are increasingly being sought using complexes of metals other than platinum such as ruthenium or gallium. Based on the chemical differences between these metals, the spectrum of molecular mechanisms of action and potential indications can be broadened substantially. Other approaches focus on complexes with tumour-targeting properties, thereby maximizing the impact on cancer cells and minimizing the problem of adverse side effects, and complexes with biologically active ligands.     

DTA of natural and synthetic uranium compounds

A brief outline of structural considerations is given, concerning compounds one can meet as secondary uranium minerals. The authors report the thermal analysis of minerals deposited at the National Museum Collection in Prague. Three different types of instruments were used: a MOM derivatograph, a Netzsch DTA equipment, and an instrument constructed according to Rosický for microspecimens. The thermal analysis results were correlated with X-ray structure analysis and infrared spectra analysis data. The examples applied were: synthetic rutherfordine and related compounds, synthetic andersonite and the minerals liebigite and schoeckingerite, and synthetic schoepite.

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Zusammenfassung Ein kurzer Bericht über strukturelle Erwägungen bezüglich sekundärer Uraniumerz-Verbindungen wird gegeben. Es werden an die durch thermoanalytische Überprüfung der in der Sammlung des Nationalmuseums zu Prag befindlichen Erze gewonnenen Erfahrungen mitgeteilt. Drei verschiedene Typen von Geräten wurden eingesetzt: der Derivatograph MOM, die DTA-Vorrichtung Netzsch und ein nach Rosický gebautes Gerät für Mikroproben. Die Ergebnisse der Thermoanalyse wurden mit den Daten der Röntgen-Strukturanalyse und denen der Analyse des Infrarotspektrums in Zusammenhang gebracht. Als Beispiele wurden synthetisches Rutherfordin und verwandte Verbindungen, synthetisches Andersonit, sowie die Erze Liebigit und Schoekingerit und synthetisches Schopit verwendet.

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Résumé Un bref rappel sur les considérations structurales concernant les composés que l'on peut rencontrer comme minéraux secondaires d'uranium est donné. Les auteurs ont eu l'intention de faire partager leur expérience acquise lors de la révision des minéraux déposés dans la Collection du Musée National de Prague, à l'aide de l'analyse thermique. Trois types d'instruments ont été utilisés le Derivatograph MOM, l'appareil ATD Netsch et un instrument construit d'après Rosický, pour l'étude de microéchantillons. On a établi une corrélation entre les résultats de l'analyse thermique et ceux obtenus lors des analyses de structures par rayons X et par spectroscopie infrarouge. Les exemples cités concernent la rutherfordine synthétique et les composés analogues, l'andersonite synthétique, ainsi que les minéraux liebigite et schoeckingérite et la schopite synthétique.

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Shape-persistent macrocycles: structures and synthetic approaches from arylene and ethynylene building blocks

Shape-persistent arylene ethynylene macrocycles have attracted much attention in supramolecular chemistry and materials science because of their unique structures and novel properties. In this Review we describe recent examples of macrocycle synthesis by cross-coupling (Sonogashira: aryl acetylene macrocycle or Glaser: aryl diacetylene macrocycle) and dynamic covalent chemistry. The primary disadvantage of the coupling methods is the kinetically determined product distribution, since a significant portion of oligomers grow beyond the length of the cyclic targets ("overshooting"). Better results have been obtained recently by a dynamic covalent approach involving reversible metathesis reactions that afford macrocycles in one step. Mechanistic studies demonstrate that macrocycle formation is thermodynamically controlled by this route. Remaining synthetic challenges include the efficient preparation of site-specifically functionalized structures and larger, more complex two- and three-dimensional molecules.     

Toward uniform nanotubular compounds: synthetic approach and ab initio calculations

We propose to synthesize a new class of single-walled nanotubular compounds (SWNCs) and investigate the interplay between their structural and electronic properties using ab initio density functional calculations. SWNCs are composed of cyclacenes of variable diameter interconnected by various linker compounds. Cyclacenes map directly onto and can be viewed as the shortest segments of (n,0) zigzag carbon nanotubes. We focus on cyclacenes with n=6-12 fused benzene rings interconnected by biphenyl, tetrazine, or acetylene linkers. Depending upon the nature and the orientation of the linkers, we find it possible to change the systems from narrow-gap to wide-gap semiconductors, and to modulate the band dispersion, suggesting the possibility of band gap engineering.