Current Organic Chemistry - Volume 17, Issue 3, 2013

The set up of sustainable procedures of synthesis requires, inter alia, a careful reconsideration of the role of the solvent and of the catalyst. In the last years, room temperature ionic liquids (RTILs) and N-heterocyclic carbenes (NHCs) have drawn considerable attention as new rising generation of green solvents and organocatalysts. A simple cathodic reduction of C2-H imidazolium based ionic liquids yields, in mild conditions, a RTIL-NHC medium, i.e. a green solvent-derived catalyst system, able to trigger different NHCcatalyzed organic reactions. To verify the versatility of this medium, its efficiency has been tested in different reactions, i.e.: benzoin condensation, Stetter reaction, synthesis of γ-butyrolactones, synthesis of esters, Henry reaction, Staudinger reaction. In any case, after the addition of the suitable substrates to the electrogenerated RTIL-NHC systems, the products have been isolated in good to elevated yields.

The application of ionic liquids revealed a new dimension in many fields of chemistry. In the particular field of hydrogen storage system ionic liquids find application in several different ways. After a short introduction about the matter of hydrogen storage and its advantages and challenges, the different approaches of ionic liquid application in this field are presented. The different approaches can be classified into the application of ionic liquids as (i) solvent, as (ii) co-catalyst, as (iii) catalyst, as (iv) hydrogen storage material and as (v) stabilizing agent for nano particles. The benefit of ionic liquids for the system is discussed in this review.

Biomass transformations would certainly play an important role in the partial or total substitution of petroleum-based products, either in production of materials and fuels. However, big challenges must still be addressed before sustainable processes from economic, energetic, environmental and social point of view would be available. In this manuscript are reviewed different attempts to develop new and efficient industrial processes using ionic liquids as reaction media. In particularly, are reviewed the main attempts to transform sacarides and acylglycerides into industrial products, with special attention to uses where ILs do not behaves only as “innocent” solvents but play also an important role favoring the reaction or completely changing the selectivity of the process.

In this review update we provide a critical analysis of recent results concerning the use of ionic liquids (ILs) as viable, effective, and environmental friendly media for the Heck reactions (HR). The examples selected illustrate the multifaceted action of ILs as nanoparticles stabilizers, promoters of ligand-assisted HR, promoters of phosphine-free HR, solvent for the Heck-Matsuda reactions employing arenediazonium salts, in the dehydrative Heck olefination, and as charged-tagged pre-catalysts. These selected reports aim at demonstrating the scope and the impact of Ils on new discoveries, as well as to illustrate the new opportunities and challenges they offer for those interested in catalysis and organic synthesis in general.

This review provides an overview of the use of mass spectrometry (MS) and its various ionization techniques and an evaluation of their suitability to investigate structures and physico-chemical properties of ionic liquids (IL) and the types of information that can be obtained from such experiments. We will focus on most representative and comprehensive work, and on the work that we are been performing in an collaboration involving our laboratories, one devoted to the synthesis and uses of IL and to the other to the development of new MS techniques and their applications.

The current manuscript describes state-of-the-art research for Nuclear Magnetic Resonance (NMR) as an analytical tool to explore catalyzed reactions carried out in ionic liquids (ILs) as the media. Due to its versatility and informative data, NMR has offered valuable information for studies on how ILs affect catalytic reactions performed in these media. The article covers representative developments and recent progress with reactions such as hydrogenation, hydroformylation, Suzuki and Sonogashira cross-coupling, and gives insights on the information obtained from this technique.

Organic semiconducting materials have been a subject of intensive studies recently, fueled by both academic interest and a series of potential technological applications. Their molecular structure characterized by extended π-electron systems can be easily tuned by chemical substitution. The most promising organic semiconducting materials combine a number of critical properties, including processiblity, stability, conjugation length, band gap energy, and charge mobility. Heterocycle rings-containing polymers comprise a huge class of organic materials that have received considerable interest due to their significant electrical, electrochemical and optical properties. In this review, the recent advances on the use of cross-coupling reactions for the synthesis of heterocyclic, conjugated monomers and polymers for the potential optoelectronic applications are summarized. Some correlations between semiconducting parameters and molecular structure of the organic compounds are discussed. This review focuses on synthesis, polymerization, structures, properties and application of branched symmetric arylenes, which are of interest because of their viewpoint as material for environmental diagnostic devices. Synthesis of the symmetric heteroarylenes were provided due to Suzuki and Stille coupling. Polymerization was mostly processed as two steps two-electron oxidation of molecules. In single-electron oxidation, stable radical cation is formed with spin located on main unit of structure. The electrochemical properties of polymer are dependent on film thickness deposited on electrode. Analysis of polymer behaviour and results of spectrochemical measurements of obtained derivatives point on mixed type of electroconductivity of material.

Aldehydes were respectively converted to the corresponding 2-imidazolines in good yields by the reaction with ethylenediamine using iron (III) phosphate on water under reflux condition. Furthermore nitriles were converted to the corresponding 2-imidazolines under solvent-free condition at 100 °C. Utilizing of heterogeneous and recyclable catalyst, water as a solvent and solvent-free condition is the best medium from a green chemistry standpoint.

Suzuki-Miyaura cross-coupling of free (NH) indazoles is described. The reactions are carried out under microwave irradiation using various 3-bromoindazoles and boronic acids. Different reaction conditions were investigated and the best results were obtained using Pd(PPh3)4 and Cs2CO3 in a mixture of 1,4-dioxane/EtOH/H2O at 140 °C under microwave irradiation.

This article prepared a variety of novel singlet oxygen photosensitizers containing different numbers of bromine atoms, which could be divided into two groups (G1, G2) according to parent chemical structural characteristics. Effects of numbers of substituted bromine atoms on one- and two-photon optical properties of singlet oxygen photosensitizers were surveyed experimentally and theoretically. One-photon fluorescence emission spectra of the photosensitizers were affected more remarkably by numbers of substituted bromine atoms than one-photon absorption spectra. Two-photon absorption (TPA) properties of these photosensitizers were determined under 700~880nm near-infrared laser frequencies at 20nm step tuning. The photosensittizers with two substituted bromine atoms showed the largest TPA cross sections in two groups respectively. The generation of singlet oxygen by these photosensitizers under one- and twophoton irradiation was confirmed by photochemical methods and ESR (electron spin resonance) experiments. Singlet oxygen quantum yields of these photosensitizers were improved with increasing substituted bromine atoms, but the enhancement extents were different between G1 and G2. Molecular geometry optimization was performed to analyze further the fundamental reasons of influence of number of substituted bromine atoms on the ground and excited states of various photosensitizers.