Current Organic Chemistry - Volume 17, Issue 4, 2013

While iron oxide nanoparticles enjoy rich applications as catalysts, solid supports, and magnets, the use of their reduced and much less stable counterparts in the oxidation state zero is still at an infant stage. This minireview summarizes recent developments in the area of such metallic iron(0) nanoparticles. A major emphasis is laid on the controlled synthesis of small particles (mostly < 50 nm) and their application as catalysts to organic synthesis. Initial catalytic studies include hydrogenation and cross-coupling reactions which clearly indicate the great potential of iron nanoparticles to rival the efficiency of nickel and palladium catalysts.

With the rapid development of materials science, the noble metal nanoparticles (NPs) with tunable size and shape have attracted much attention because the tailored nanoparticles affected the catalytic performance tremendously. Besides the noble metal nanoparticles, the easily available transition metal nanoparticles such as Ni-NPs have also been utilized as catalysts recently for various kinds of reactions. In this review, we presented primarily work towards the preparation approach for Ni nanoparticles with predictable and controllable size, shape, composition, and morphology. Especially, the synthetic routes to the controllable Ni nanoparticles through chemical reduction, thermal decomposition, ultrasonic and microwave irradiation, coupling with using reasonably environment-friendly, low cost alternative solvent systems like ionic liquid or w/o microemulsion were illustrated. The particular attention has been given to the recent research progress in employing Ni nanoparticles as catalysts in catalytic hydrogenation of olefins, α, β-unsaturated aldehydes and derivatives of nitrobenzene, and decisive factors influencing the catalytic activity of Ni nanoparticles were then summarized.

This review will intend to cover the main examples on the use of soluble and supported iridium metal nanoparticles as effective catalysts for hydrogenation of different substrates in conventional reaction medium, such as water, organic solvents, and ionic liquids. Some aspects involving the synthesis of these nanocatalysts will be also discussed in details.

Even if rhodium is one of the rarest and the most costly metals, this noble metal has found many catalytic applications, particularly in hydrogenation and hydroformylation reactions owing to its specific catalytic properties. Tremendous research activities are thus carried out by the scientific community for the development of novel rhodium-based catalysts. This interest for rhodium catalysts concerns also the modern “nanocatalysis” area, situated at the frontier between heterogeneous and homogeneous ones, nanoparticles soluble in a liquid phase being considered as “pseudo homogeneous” systems. A high number of papers describe the preparation of diverse rhodium nanoparticles in suspension for their application as catalysts in hydrogenation of various substrates (mainly olefins and aromatic derivatives) in various catalytic conditions (mainly organic or biphasic phases). Concerning hydroformylation catalysis, it appears that only a few papers deal with rhodium metal nanoparticles for investigation in this reaction, although rhodium is well-known as highly active metal in hydroformylation reaction in homogeneous conditions. In this review, rhodium nanoparticle systems that have been prepared for investigation as nanocatalysts in liquid phase hydrogenation and hydroformylation reactions are described. This work is not comprehensive but provides an overview of the main methods used to synthesize rhodium nanoparticles for these selected catalytic applications. The objective of this review is to give to the readership an outlook of the recent advances in this field, as well as of the great potential of rhodium-based nanocatalysts for hydrogenation and hydroformylation reactions, two reactions of importance in organic synthesis.

This review describes some of the fascinating advances in the field of chemoselective hydrogenation of α,β-unsaturated aldehyde to unsaturated alcohol over nanomaterials that have emerged in recent years. The examples described are categorized into three main sections, according to the research approach applied, including the size/shape/composition control of the metal nanoparticle catalysts, the employment of novel nanosized inorganic materials, and the design/selection of stabilizer/solvent for the synthesis and dispersion of nanoparticle catalysts. The interplay between various parameters and the relevant catalytic properties of NP catalysts are discussed and possible future research trends are highlighted.

Ionic liquids (ILs) are excellent media for the generation and stabilisation of metallic nanoparticles (NPs). Their ionic character coupled with 3-D structural pre-organisation in the liquid state, serves to direct the growth of transition metal NPs generated in situ, and to subsequently protect and stabilise them. Until now, many different NPs have been successfully synthesised within these media, however much attention has been paid to Ru-NPs. These have been prepared with small sizes and narrow size distributions by reduction of organometallic compounds with molecular hydrogen as well as decomposition of transition-metal complexes in the zero-valent state. These stable Ru-NPs immobilised in the ILs have proven to be efficient green catalysts for several reactions in multiphase conditions, including important energy-related processes such as biomass refinement. Furthermore, they present potential novel materials for use in the production of smarter electronic devices. In this review, the synthesis, stabilisation and size-control of Ru-NPs via various methods in different ILs is discussed, followed by their varied application in catalysis and potential in new fields.

This review deals with synthetic potential and utility of benzoylacetonitrile in the synthesis of pyridine derivatives. The reactions are subdivided into groups that cover the synthetic methods of pyridine derivatives from benzoylacetonitrile e.g. self condensation, Friedlander reaction, Michael Addition reaction, addition to enaminones, reaction with enamino-nitriles or enamino-esters, and one-pot three component reactions. A brief account on the synthesis of benzoylacetonitrile was also displayed.