Imidazol-5-ones as a substrate for [1,5]-hydride shift triggered cyclization
2-Dialkylamino-arylidene-imidazolones undergo intermolecular tandem [1,5]-hydride shift and cyclization to form spirocyclic tetrahydroquinoline derivatives under TiCl4 promotion. Different substitutions on each of the aryl, amino and imidazole fragments are tolerated, which results in 20+ examples and 25–95% yields.
1,11-Dien-6-ynes undergo cycloisomerization in the presence of the cobalt catalytic system CoBr2/phosphine ligand/Zn/ZnI2 giving cyclohexene, diene or cyclopropane structures depending on the type of the phosphine ligand. This unpredictable behaviour suggests that, although the availability of the cobalt catalytic system is appealing, the development of well-defined catalysts is desirable for further progress.
4-Arylidene-1H-imidazol-5(4H)-ones react with N-benzylazomethine methylide under trifluoroacetic acid catalysis to form 9-aryl-1,3,7- triazaspiro[4.4]non-1-en-4-ones in 66–95% yields as one diastereomer in each case.
A series of conjugated 4-alkenyl-1,3-dithiol-2-ones have been prepared by microwave-assisted rearrangement of S-(4-acyloxy-2-alkynyl)-O-ethyl xanthates in moderate to good yields. The synthetic approach is based on a combination of [3,3] and [1,5] sigmatropic rearrangements as well as the intermediacy of a reactive betaine that induces the ionic elimination of the acyloxy group. The [1,5] sigmatropic rearrangement was confirmed by a deuterium-labeling experiment.
We have performed a comparative analysis of the bio-oil produced by thermal liquefaction of microalgae in different solvents using high-resolution Orbitrap mass spectrometry and GC-MS approach. Water, methanol, ethanol, butanol, isopropanol, acetonitrile, toluene, and hexane were used as solvents in which the liquefaction was performed. It was observed that all resulting oils demonstrate a considerable degree of similarity. For all samples, compounds containing 1 and 2 nitrogen atoms dominated in the positive ESI spectra, while a relative contribution of other compounds was small. In negative ESI mode, compounds having 2 to 7 oxygens were observed. Statistical analysis revealed that products can be combined in two groups depending on the solvent used for the liquefaction. To the first group, we can attribute the products obtained by using protic (alcohols) and to the second by using aprotic (acetonitrile, toluene) solvents. Nevertheless, based on our results, we concluded that solvent possesses a minor impact on molecular composition of bio-oil. We suggested that the driving force of the liquefaction reaction is the thermal dehydration of the carbohydrate in algae, resulting in water formation, which could be the trigger of the producing of bio-oil. To prove this hypothesis, we performed the reaction with the dry algae in the absence of the solvent and observed the formation of bio-oil.
The New Russian Encyclopedia is a fundamental reference publication in 18 volumes that characterizes nature, population, economy, history, science, art, technology and other important aspects. Contains about 60,000 articles, about 30,000 biographies, about 15,000 color illustrations, maps, charts, diagrams, tables. Leaves since 2003.
This volume, being the 55th of this Series, contains a wealth of information on bioactive natural products. In Chapter 1, Watson and colleagues have discussed the synthesis of monoterpene indole alkaloids, an important class of structurally diverse natural products, with respect to conventional and biomimetic synthetic approaches.
Titanocene(III) has been widely used in the synthesis of complex organic molecules and natural products including polyketides, phenylpropanoids, antibiotics, and alkaloids. Oltra and coworkers have provided a review on the stereoselective synthesis of natural products facilitated by titanocene(III) in Chapter 2.
About 70 biologically active macrocyclic bisbibenzyls (MBBs) have been isolated and structurally elucidated during the last 30 years. Song and Zhao, in Chapter 3, have provided a review on the synthesis of MBBs with diverse pharmacological properties.
Diabetes mellitus is the most common endocrine/metabolic disorder that poses a global health concern. Reyes and colleagues have discussed the hypoglycemic activity of some terrestrial and marine bioactive compounds with potential for treating type 2 diabetes in Chapter 4. In Chapter 5, Pietruszka and coworkers have highlighted the importance of some marine oxylipins that exhibit different bioactive properties.
Depression has become a psychiatric disorder, which leads to various disabilities. Natural compounds like polyphenols and terpenoids have antioxidant and neuroprotective properties and can be used for the treatment of depression. In Chapter 6, Rodrigues et al. review the clinical studies and trials on polyphenols and terpenoids for the treatment of various psychiatric disorders. The lipid A phosphate and their phosphorylated analogues found in Gram-negative bacteria are of major importance because they provide the host with defense against infections from various microorganisms. Paradies and Zimmermann have discussed physical characteristics, isolation, and bioactivity of lipopolysaccharides (lipid A) for developing new vaccines and therapeutics in Chapter 7.
Hydroxycinnamic acids (HCAs) are a group of phytonutrients with numerous beneficial effects on human health that are largely derived from plants. HCAs play important roles like defense against UV rays or pathogenic attack during growth and development of plants. In Chapter 8, El-Seedi and colleagues present a review focusing on the therapeutic effects of HCAs for the treatment of cancer, diabetes, pulmonary, hepatic, neuro-, and cardiovascular diseases. In Chapter 9, Pomilio and Mercader have presented the study of natural anthocyanins and other related flavonoids for the readers, highlighting their possible and preferable uses as health-protecting food dyes over synthetic ones. They have also discussed the anthocyanins isolated from Ipomoea cairica along with their QSAR studies.
Cardiovascular diseases are considered to be a major threat to health. Polyphenols and carotenoids are structurally diverse groups of bioactive compounds isolated from fruits and vegetables, carrying protective effects against endothelial dysfunction. These therapeutic effects have been explored by Yamagata in Chapter 10.
The roots of licorice and ivy leaves have been used in folk medicine and drugs since long. The biological activity of these complexes has been discussed by Yakovishin and Grishkovets in Chapter 11. In Chapter 12, the chemical and biological characteristics of amicoumacins and xenocoumacins are reviewed by Korshun et al. with reference to the preparation of antibiotics.
I hope that this volume will be received with the same enthusiasm as the earlier volumes of this long-standing series the first volume of which was published under my Editorship in 1988. I would like to express my gratitude to Ms. Taqdees Malik and Mr. Mahmood Alam for their assistance in the preparation of this volume.
The hydrogenation of diphenylacetylene (DPA) on palladium–silver catalysts with a single-atom structure was investigated. It has been shown experimentally that the reaction rate of alkene to alkane hydrogenation is substantially lower than the rate of DPA semi-hydrogenation. The kinetic barriers of all stages of hydrogenation were calculated by the DFT method.
The swelling of a poly (methyl methacrylate) in supercritical carbon dioxide was studied by means of full atomistic classical molecular dynamics simulation. In order to characterize the polymer swelling, we calculated various properties related to the density, structure, and dynamics of polymer chains as a function of the simulation time, temperature, and pressure. In addition, we compared the properties of the macromolecular chains in supercritical CO2 with the properties of the corresponding bulk system at the same temperature and atmospheric pressure. It was shown that diffusion of CO2 molecules into the polymer led to a significant increase in the chain mobility and distances between them. Analysis of diffusion coefficients of CO2 molecules inside and outside the poly(methyl methacrylate) sample has shown that carbon dioxide actively interacts with the functional groups of poly (methyl methacrylate). Joint analysis of the radial distribution functions obtained from classical molecular dynamics and of the averaging interatomic distances from Car-Parrinello molecular dynamics allows us to make a conclusion about the possibility of formation of weak hydrogen bonds between the carbon dioxide oxygen atom and the hydrogen atoms of the polymer methyl groups.