In this work the thermal stability of four ionic liquids (ILs) derived from N-ethyl-N-(2-hidroxyethyl)-N,N-dimethyl ammonium cation  and N,N-di-(2-hidroxyethyl)-N-ethyl-N-methylammonium cation incorporating [NTf2] and [OTf] anions, were studied and compared with imidazolium and pyridinium ILs containing the same anions.For this proposal, a thermogravimetric analizer, TGA 7- Perkin Elmer, was used in dynamic mode from 100ºC to 800ºC at 10ºC/min under dry air atmosphere. Air atmosphere was chosen because it is more realistic to predict the stabilities in real applications such as lubrication systems or thermal fluids, which are nowadays between the main applications of ILs. From the ILs TG curves, the onset temperatures (Tonset) were determined, as well as the loss of mass at these Tonset. In all cases significant decomposition was detected at lower temperatures than Tonset, meaning that the true IL stability is lower than that provided by the dynamic TG. Isothermal studies at lower temperatures than Tonset were then carried out to estimate the long-term thermal stabilities at different temperatures.Up to now, a clear criterion on the degradation level allowed for the different ILs applications does not exist. In order to know the time that each IL takes to degrade and to obtain the maximum operation temperature allowed for every degradation level, different degradation levels (from 1% to 10%) at different temperatures were analyzed in this work.

Pyridinium salts are very useful synthetic building blocks to obtain substituted pyridine, dihydropyridine or piperidine. This synthetic strategy has been described for different applications such as total synthesis of Geissoschizine, cannabisativine, Lepadin B, among others. Pyridinium salts have been also used to achieve asymmetric and regioselective synthesis by additions of Grignard reagents. Furthermore, pyridinium salts have been applied as acylating agents, phase transfer catalyst or ionic liquid and dyes as a result of its intrinsic fluorescence. Frequently, these N-alkylated pyridine systems have been synthesized involving pyrylium salts as precursors. Pyrylium salts are cationic organic molecules with trivalent oxygen in a six member aromatic rings. These compounds have been exploited to design sensors for anions, amines, amino acids and chameleon labels for quantifying proteins. Herein, we report the synthesis and characterization of new 2,4,6-tri-arylpyrylium salts from small aldehydes and ketones. The synthesis of pyridinium salts by subsequent reaction with a primary alkyl amine or amino groups on carbohydrate moieties have been also explored. In one case, formation of pyridinium cation, that involves quaternary nitrogen, may provide a good potential candidate for gene delivery by using siRNA. We thank the AECID (Projects A/023577/09 and A/030422/10) and the 'Junta de Andalucía' (FQM 142 and Project P09-AGR-4597) for financial support.

Optically active isoindolinones are synthesized by asymmetric intramolecular aza-Michael reactions using cinchoninium phase-transfer organocatalysts. The resulting compounds are useful intermediates for the synthesis and development of benzodiazepine-receptor agonists.

Carbon nanotubes (CNT) are amongst the most studied nano-materials for their application in numerous fields as a result of their exceptional mechanical, thermal, and electronic and optical properties. However, the lack of solubility of CNT in many common solvents limits the exploration of their potential applications. For this reason, it is important to investigate new procedures to functionalize these materials in order to improve their solubility and their processability. Furthermore, functionalization can modify the physical properties of CNT and thus expand their potential applications.We report herein the functionalization of single-wall carbon nanotubes (SWCNT) by cycloaddition reactions with arynes under microwave irradiation. The efficiency of the functionalization was monitored by XPS, FTIR and Raman spectroscopies, TGA and HR-TEM. All experimental results point to the formation of SWCNT with a high degree of functionalization, with mass increases ranging from 6.4% to 15.1% depending on the aryne substitution.

Supported metal nanoparticles have emerged as a new class of nanocatalyst. These catalysts showed not only high catalytic activity and simple separation of them using an external magnet but also a high degree of chemical stability in various organic solvents. Multicomponent reactions (MCRs) allow the assembly of complex molecules in one-pot and show a facile execution, high atom-economy and high selectivity, as afford good yields and are fundamentally different from two-component and stepwise reactions in several aspects. Quinazolines are reported to possess interesting pharmacological activities such as antihypertensive, antihistaminic, analgesic and anti-inflammatory, anticancer, and anti-HIV activities. Moreover, many naturally occurring and synthetic compounds containing the benzimidazole derivatives possess interesting pharmacological properties. In continuation of our interest in the application of new catalysts in MCRs, herein, an efficient one-pot synthesis of benzimidazolo-quinazolinone derivatives from readily available amine sources, aldehydes and dimedone under simple and convenient conditions. Nanoparticles supported on biopolymer as catalyst offers advantages including simplicity of operation, ecofriendly, easy workup, high yields of products and the recyclability of the catalyst.

According to the cholinergic hypothesis, the inhibition of cholinesterase increases the levels of acetylcholine in the brain, thus improving cholinergic functions in Alzheimer´s Disease (AD) patients. Butyrylcholinesterase (BChE), is one of the enzymes involved in the metabolic degradation of acetylcholine, together with acetylcholinesterase (AChE). BChE activity increases as AD progresses, which suggests that BChE may play an important role at the latter stages of AD. Therefore, selective BChE inhibitors attract interest nowadays.Lup-20(29)-ene-3β,16β-diol (calenduladiol, 1), is a pentacyclic lupane-type triterpene with the interesting feature of being hydroxylated at C-16. Continuing our previous work on semisynthesis of derivatives obtained from the natural triterpene calenduladiol and their evaluation as potential cholinesterase inhibitors, we report here the synthesis of six new lupanes (3-8). These compounds have been obtained by sequential oxidations and reaction with NH₂OH of the starting compounds, the natural calenduladiol (1) and its analog 30-oxocalenduladiol (2), previously obtained by allylic oxidation with Se₂O. Their structures were confirmed by analysis of their 1H and 13C NMR and ESI-MS spectra. The complete assignation of the signals was achieved with the aid of 2D NMR experiments (COSY, HSQC, HMBC, NOESY). All of the new derivatives were evaluated as potential in vitro BChE inhibitors by the Ellman´s colorimetric method. In order to determine the BChE/AChE selectivity of compounds 3-8, their antiAChE activity was evaluated. All of them failed to inhibit AChE, but we found that the best BChE inhibition was observed for 3,16,30-trioxolup-20(29)-ene (4) with an IC₅₀ value of 21.5 μM, which elicited a selective inhibitor profile

To create a durable bioactive coating we investigated the effectiveness of the photochemical surface modification of polyethylene terephthalate (PET) by bifunctional dyes of phenothiazine series and selected the optimal conditions of the process. For that purpose a series of the bifunctional photosensitizers containing aryl azide group forming covalent bonds with the polymer matrix under UV and generating singlet oxygen under visible light exposure was synthesized. We have synthesized a series of amides of toluidine blue O (TBO) with 2– , 3– and 4– positions of benzoic acid substituted by the azide groups. Surface modification was carried out by irradiation of solutions of the synthesized bifunctional dyes when the samples of PET were submerged into acetonitrile by the low pressure mercury-quartz lamp. Based on the comparison of the UV spectra of PET films before and after the photochemical modification we found that the most effective modifier was TBO–4– azidobenzoic acid with concentration of 3 × 10^-3M, but the least effective modifier was TBO–2–azidobenzoic acid. Obviously it is caused by the sterically hindered insertion of a nitrene formed in the course of the azidobenzoic acid photolysis into the C=O bond of the polymer matrix.

Nitrogen heterocycles are a part of a special group of organic substances due to its many applications in the pharmaceutical market, exist a large number of structures carrying nitrogenous substances. Among these heterocycles the isoxazoles and tetrahydroquinolines (THQs)1 have shown significant biological activity on different therapeutic targets. They show several applications in diverse areas such as pharmaceuticals, agrochemistry, and industry.2 They are also found in natural sources showing insecticidal, plant growth regulation, and pigment functions.3 Within the field of activity of the heterocycles is found the antibacterial activity, which has had a growing interest because the inappropriated use of antibiotic has increased the resistance of bacterial to the commercial antibiotics, even the appearance of bacterial strain with no treatment knows.4 Similarly, the emergence of antibiotic resistance in some bacterial populations is yet a relevant field of study in some areas of Science included the organic chemistry.Due to mentioned previously, the THQs e isoxazole compounds have been considered a good starting material for the search of novel antimicrobial agents, therefore we include them in this research.Isoxazoles derivatives were synthesized by 1,3 dipolar cycloaddition and a serie of tetrahydroquinolines derivatives were synthesized by Povarov reaction, these compounds were purified by conventional chromatographic techniques and characterized spectroscopically. Antibacterial activity was assessed by spectrophotometric measurements, determining the MIC for each compound against the four bacterial, Escherichia coli, Pseudomona aeruginosa, Staphylococcus aureus and Acinetobacter baumannii.

The synthesis of bicyclic compounds has detained large significance due to their use as synthetic intermediates in the preparation of a vast variety of compounds of chemical, biological, and pharmaceutical interest. The most efficient and widely used method for the preparation of bicyclic compounds is the Diels-Alder reaction. Generally, activation by an electron-withdrawing group and a Lewis acid is required in order to achieve good conversion rates. The acid catalyzed Diels-Alder reactions, namely between cyclopentadiene (CPD) and acrylates, is well documented, the most important used Lewis acids being Al(III), Fe(III) or boron complexes, as well as Ti(IV) and Sn(IV) halides. The use of such strong acids is needed because ester dienophiles (as acrylate ones) are not very reactive. In this work we studied the use of moderate strength and environmentally safe Lewis acids as catalysts for Diels-Alder reaction between CPD and methyl acrylate by complexation – resulting in solubilization – of otherwise insoluble metal ions with a suitable ligand. L-Serine is a cheap and readily available natural aminoacid and it has three functional groups that can be easily functionalized, thus allowing chemical and structural design. In this context, new L-serine derivative ligands were prepared and tested as co-catalyst in the Diels-Alder reactions. Bidentate serine ligands showed good ability to coordinate medium strength Lewis acids, thus boosting their catalytic activity and hence being an alternative for the usual employment of strong Lewis acids. The synthesis of the L-serine ligands proved to be highly efficient and straightforward. Additionally, the prepared bidentate L-serine derivative ligands were silylated in order to allow posterior grafting onto inorganic materials for posterior employment in heterogeneous catalysis.

DNA is damaged by various oxidative stresses. Oxidized DNA can increase mutations and the risk of cancer. Guanine is highly sensitive to several oxidative stresses due to its low oxidation potential. It is known that 2,2,4-triamino-5(2H)-oxazolone (Oz), iminoallantoin (Ia) and spiroiminodihydantoin (Sp) are oxidized guanine lesions. These oxidized bases can be paired with guanine and cause G:C-C:G transversions. Although our previous results showed more effective incorporation of guanine opposite Oz compared to that opposite Ia or Sp (K. Kino et al., ChemBioChem, 2009), Oz:G base pair was less stable than Ia:G or Sp:G base pair by ab initio calculation (M. Suzuki et al., Molecules, 2012). Oz:G forms two hydrogen bonds and is planar, while Ia:G and Sp:G have three hydrogen bonds and are nonplanar. This difference can be due to the fact that Ia:G and Sp:G contain a sp³ carbon but not Oz:G. Since stacking planar base pairs in DNA significantly enhances the stability of DNA duplex, we investigate whether the stability of DNA duplex containing the oxidized lesion can be accounted for by the stacking effect in this study. The structure of DNA duplex containing Oz:G was the most stable. This our data agreed with the previous results that translesion synthesis across Oz was more effective than Ia or Sp.