Triazenes: a versatile tool in organic synthesis

Triazenes (RN=N-NR'R") are a class of compounds that hold much promise in preparative chemistry as they are reactive groups which are both stable and adaptable to numerous synthetic transformations. Useful to scientists in pharmacology, total synthesis, polymer technology, and the construction of novel ring systems, to name a few areas, triazenes also have a tendency to surprise chemists with new reactions and increasing applicability. This review highlights some of the recent advances and diversity possible with these types of systems.     

Microemulsion: A versatile synthesis tool for photocatalysis

Photocatalytic materials have complex nature, frequently with participation of multiple or complex multiatom components. These materials need to be synthesized with stringent control of their structural, morphological, and electronic properties in the quest to optimize functional properties. This is a challenge tackled with the help of the microemulsion method, which appears as a versatile tool to easily generate single or multicomponent catalysts. The review provides a perspective on this issue, highlighting the link between the control of physicochemical properties offered by microemulsion and the optimization of the photocatalytic activity.     

Hydroformylation: a versatile tool for the synthesis of new β-formyl-metalloporphyrins

Formyl derivatives of protoporphyrin-IX dimethyl ester metal complexes were obtained via hydroformylation reactions, catalysed by rhodium-triphenylphosphine complexes. The regioselectivity of the reaction is remarkably dependent on the metal centre of the porphyrin, yielding 100% of the branched aldehyde with zinc(II) complexes and 75% with the nickel(II). The NMR characterisation of the new compounds was carried out after their derivatisation into acetals.     

The Vilsmeier reagent: a useful and versatile reagent for the synthesis of 2-azetidinones

(Chloromethylene)dimethylammonium chloride (Vilsmeier reagent), prepared easily from N,N-dimethylformamide and oxalyl chloride or thionyl chloride, works as a versatile acid activator reagent for the direct [2+2] ketene-imine cycloaddition of substituted acetic acid and imines in one-pot synthesis under mild conditions. Monocyclic, spirocyclic and 3-electron-withdrawing group β-lactams were synthesized by this method and optimization of conditions were performed.     

In situ generation of carbenes: a general and versatile platform for organocatalytic living polymerization

A metal-free, organocatalytic approach to living polymerization using N-heterocyclic carbenes as nucleophilic catalysts generated and used in situ in a single-pot process is detailed. The N-heterocyclic carbene catalyst platform is extremely versatile, as the nature of the substituents has a pronounced effect of catalyst stability and activity toward different substrates. The generation of imidazolium- and thiazaolium-based carbenes was accomplished from the reaction of the corresponding salts with the appropriate bases. This allowed the rapid screening of libraries of catalysts that provided a basic understanding of catalyst structure (sterics, electronics, etc.) with the polymerization rate, control, substrate, and range of molecular weights. The imidazole-based catalysts were significantly more active toward ROP than the thiazolium-based analogues. No appreciable differences between imidazol-2-ylidene and imidazolin-2-ylidene catalysts were observed. Less sterically demanding carbenes were found to be more active toward ring-opening polymerization (ROP) than their sterically encumbered analogues for lactone polymerization. These data prompted the investigation of ionic liquid as a precatalyst reservoir in a phase-transfer polymerization with an immiscible THF solution of monomer and initiator. In situ activation of the ionic liquid generates carbene that migrates to the organic phase effecting living ROP. Precatalyst (ionic liquid) regeneration terminates polymerization. This simple reaction/recycle protocol readily allows repetitive ROPs from the ionic liquid using commercially available materials.     

Mechanochemistry as a versatile and scalable tool for nanomaterials synthesis: Recent achievements in Košice,Slovakia

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Organometallic reactions of α-haloimines as a useful tool in organic synthesis

The reaction of organometallic reagents, e.g. alkyllithiums, cuprates and alkylcoppers, with α-haloimines gave selectively a variety of synthetically useful reactions, including coupling to 1,4-diimines, homologation, and production of heterocycles.     

SERS: a versatile tool in chemical and biochemical diagnostics

Raman spectroscopy is a valuable tool in various research fields. The technique yields structural information from all kind of samples often without the need for extensive sample preparation. Since the Raman signals are inherently weak and therefore do not allow one to investigate substances in low concentrations, one possible approach is surface-enhanced (resonance) Raman spectroscopy. Here, rough coin metal surfaces enhance the Raman signal by a factor of 10⁴–10¹⁵, depending on the applied method. In this review we discuss recent developments in SERS spectroscopy and their impact on different research fields.     

Digital microfluidics: a versatile tool for applications in chemistry, biology and medicine

Digital microfluidics (DMF) has recently emerged as a popular technology for a wide range of applications. In DMF, nanoliter to microliter droplets containing samples and reagents can be manipulated to carry out a range of discrete fluidic operations simply by applying a series of electrical potentials to an array of patterned electrodes coated with a hydrophobic insulator. DMF is distinct from microchannel-based fluidics as it allows for precise control over multiple reagent phases (liquids and solids) in heterogeneous systems with no need for complex networks of connections, microvalves, or pumps. In this review, we discuss the most recent developments in this technology with particular attention to the potential benefits and outstanding challenges for applications in chemistry, biology, and medicine.     

Anionic polymerization methods: An efficient tool for the synthesis of tailor-made macromolecules

The criteria of livingness, as applied to anionic polymerizations, are discussed. A number of restrictions have to be taken into consideration, if anionic polymerizations are to be applied to the synthesis of model polymers, Several examples of synthesis of tailor-made polymers via anionic polymerization are presented, namely end-functionalizations, chain extensions, end-to-end cyclizations, block copolymer synthesis, grafting processes, methods to make star polymers. In each case the reliability of the methods is discussed thoroughly.     

Rapid, in situ synthesis of bidentate ligands: chromatography-free generation of catalyst libraries

The parallel synthesis of chiral bidentate ligands and their subsequent use in situ for a catalytic process is described. The ligands thus prepared gave comparable results to those obtained when the ligands were synthesized and purified by conventional means. This includes oxazolines and other compounds of similar complexity, meaning that for the first time these valuable compounds have been brought into the field of combinatorial catalysis.     

Biomimetic cyclization of geraniol derivatives, a useful tool in the total synthesis of bioactive monocyclic terpenoids

This review is a detailed account of authors' work in the field of biomimetic cyclization of geraniol-like dienes. The very high regio- and enantioselectivity achieved made these elegant reactions a viable tool for the synthesis of monocyclic building blocks used in the synthesis of valued terpenoids, like the precious aroma and perfume constituents' ionones and irones.     

In situ generation of the Coates catalyst: a practical and versatile catalytic system for the carbonylation of meso-epoxides

A highly active catalytic system for the carbonylation of meso- and terminal epoxides to β-lactones is described. The active catalyst, analogous to Coates' catalyst, is generated in situ from commercially available (TPP)CrCl and Co(2)(CO)(8). This practical system circumvents the preparation of air sensitive cobaltate salts, operates at low catalyst loadings, and allows the carbonylation of functionalized, sterically demanding and heterocyclic meso-epoxides.     

Photo-pens: a simple and versatile tool for maskless photolithography

We demonstrate conical pores etched in tracked glass chips for fabricating patterns at the micrometer scale. Highly fluorescent patterns based on photopolymerization of diacetylene films were formed by irradiating UV light through conical pores called "photo-pens". The properties of photopens were investigated through experiments, finite-difference-time-domain (FDTD) simulations and numerical calculations based on Fresnel equations. We show that the pattern dimensions are easily controlled by adjusting the exposure time. Thus, patterns with a range of dimensions can be fabricated without any need of changes in the pore diameter. Parallel patterning was also demonstrated by simultaneously exposing the films to photons through multiple pores in the chip. Our method provides an inexpensive, versatile, and efficient way for patterning without the use of sophisticated masks.     

Microwave energy: a versatile tool for the biosciences

As the range of techniques for microwave heating has expanded, so have the areas in which it can have a profound impact. Two emerging areas are the application of microwave heating for the synthesis of peptides, peptoids, oligopeptides and carbohydrates and in the field of proteomics.     

Oxazoline as a useful tool in organic synthesis: preparation of 4-aryl-1,2,3,4-tetrahydroisoquinoline alkaloid skeleton

New direct strategy for the synthesis of 4-aryl-1,2,3,4-tetrahydroisoquinolines. The key steps are based on oxazoline chemistry: nucleophilic substitution in an ortho-methoxyphenyloxazoline with a Grignard reagent and a 1,6-conjugate addition of a lithium amide to o-styrylphenyloxazoline.     

D-奎尼酸: 一个多用途的手性合成子

综述了D-奎尼酸在各种环状和链状生物活性化合物合成中的应用。奎尼酸分子中特有的顺式γ-羟基羧酸的结构单元提供了区别分子中各种羟基,以及进行其它区域选择性和立体选择性控制的方便途径。奎尼酸的结构特征以及其价廉、易得的优点,使之成为一个有用的而且重要的手性合成子。     

Comprehensive two-dimensional gas chromatography: a powerful and versatile analytical tool

Comprehensive two-dimensional gas chromatography (GC×GC) is a novel technique which is rapidly gaining importance for the analysis of complex samples. In the present review, attention is devoted to the principle and advantages, and main characteristics such as modulation, column combinations, detector requirements and data processing, of the technique. Specifically, GC×GC of a variety of real-life samples is discussed to demonstrate the applicability of the technique, with emphasis on the usefulness of the ordered-structure principle and on the analyte-identification power provided by a combination with time-of-flight mass spectrometric detection.