Synthesis of Tetraalkenylmethane: Building Blocks for Three-Dimensional Hydrocarbon Networks

In this paper, we show a common strategy to synthesize tetraalkenylmethanes, a cross-linker series for building three-dimensional hydrocarbon networks. To demonstrate the feasibility of this method, we have synthesized tetrapentenylmethane. Attempts to synthesize this cross-linker from pentaerythrityl tetrabromide using substitution reactions resulted in the formation of a spiro compound due to intramolecular cyclization. We also show that the difficulty in reactions at the neopentyl carbon site is due to the neopentyl carbanion stability, not the sterics.     

Supramolecular hydrogen‐bonding patterns in two cocrystals of the N(7)–H tautomeric form of N6‐benzoyladenine: N6‐benzoyladenine–3‐hydroxypyridinium‐2‐carboxylate (1/1) and N6‐benzoyladenine–DL‐tartaric acid (1/1)

Two novel cocrystals of the N(7)—H tautomeric form of N⁶‐benzoyladenine (BA), namely N⁶‐benzoyladenine–3‐hydroxypyridinium‐2‐carboxylate (3HPA) (1/1), C₁₂H₉N₅O·C₆H₅NO₃, (I), and N⁶‐benzoyladenine–DL‐tartaric acid (TA) (1/1), C₁₂H₉N₅O·C₄H₆O₆, (II), are reported. In both cocrystals, the N⁶‐benzoyladenine molecule exists as the N(7)—H tautomer, and this tautomeric form is stabilized by intramolecular N—H...O hydrogen bonding between the benzoyl C=O group and the N(7)—H hydrogen on the Hoogsteen site of the purine ring, forming an S(7) motif. The dihedral angle between the adenine and phenyl planes is 0.94 (8)° in (I) and 9.77 (8)° in (II). In (I), the Watson–Crick face of BA (N6—H and N1; purine numbering) interacts with the carboxylate and phenol groups of 3HPA through N—H...O and O—H...N hydrogen bonds, generating a ring‐motif heterosynthon [graph set R₂²(6)]. However, in (II), the Hoogsteen face of BA (benzoyl O atom and N7; purine numbering) interacts with TA (hydroxy and carbonyl O atoms) through N—H...O and O—H...O hydrogen bonds, generating a different heterosynthon [graph set R₂²(4)]. Both crystal structures are further stabilized by π–π stacking interactions.     

Copper‐Mediated Coupling of 1,1‐Dibromo‐1‐alkenes with Nitrogen Nucleophiles: A General Method for the Synthesis of Ynamides

Mild reaction conditions are the advantage of the title reaction, which allows straightforward entry to a variety of ynamides starting from readily available 1,1‐dibromo‐1‐alkenes, which act as attractive alkynylating agents (see scheme; EWG=electron‐withdrawing group, DMF=N,N‐dimethylformamide).

     

On the mechanism of the Skraup-Doebner-Von Miller quinoline synthesis

The mechanism of the formation of substituted quinolines from anilines and alpha,beta-unsaturated ketones has been studied by the use of 13C-labeled ketones in cross-over experiments. In the reaction of doubly labeled 13C(2,4) mesityl oxide, a 100% scrambling of the label in the quinoline product was observed, whereas only a small (5-10%) amount of the starting mesityl oxide showed scrambling of the label. Similarly, the reaction of triply labeled pulegone clearly shows that the label in the product is 100% scrambled, whereas the label in the starting pulegone is retained. On the basis of these studies, a mechanistic pathway for the Skraup quinoline synthesis is proposed that involves a fragmentation-recombination mechanism. The aniline component condenses with the alpha,beta-unsaturated ketone initially in a conjugate fashion, followed by a fragmentation to the corresponding imine and the ketone itself. These fragments recombine to form the quinoline product.     

Raman spectral analysis of phenoxyacetic acid and some chloro substituted phenoxyacetic acids

Raman spectra of phenoxyacetic acid and chlorine substituted phenoxyacetic acids viz., o-chlorophenoxyacetic acid, p-chlorophenoxyacetic acid and 2,6-dichlorophenoxyacetic acid have been analysed with the aid of abinitio theoretical calculations. The effect of chlorine substituents on the Raman spectra of phenoxyacetic acid have also been analysed by considering some important vibrational modes.     

Interlaboratory study to improve the quality of trace element determinations in rainwater

This is the first publication which describes the development of a reference material (RM) for the determination of 11 trace elements (Cu, Pb, Mn, Ni, Zn, Fe, Cd, Co, V, As and Al) in rainwater at microgram per liter concentrations. An interlaboratory comparison study for the determination of trace elements in rainwater was carried out for material performance studies to establish analyte concentrations with a stated uncertainty. Fifteen reputed laboratories from Asia, Europe and North America participated in the study. These laboratories used their regular in-house methods to analyze the rainwater samples. The aim of this study is to establish concentration levels of trace elements in rainwater based on interlaboratory study results. Details of the production, homogeneity and stability of the reference sample are given in this article. The organization of the study and the quality assurance measures undertaken at the organizer's laboratory are described. The analytical results obtained from individual laboratories and the analytical methods used for the determination of trace elements in rainwater are discussed. Based on the results obtained from the intercomparison study, certified values as well as informative values are assigned to the 11 trace elements in rainwater.     

Common Fibril Structures Imply Systemically Conserved Protein Misfolding Pathways In Vivo

Systemic amyloidosis is caused by the misfolding of a circulating amyloid precursor protein and the deposition of amyloid fibrils in multiple organs. Chemical and biophysical analysis of amyloid fibrils from human AL and murine AA amyloidosis reveal the same fibril morphologies in different tissues or organs of one patient or diseased animal. The observed structural similarities concerned the fibril morphology, the fibril protein primary and secondary structures, the presence of post-translational modifications and, in case of the AL fibrils, the partially folded characteristics of the polypeptide chain within the fibril. Our data imply for both analyzed forms of amyloidosis that the pathways of protein misfolding are systemically conserved; that is, they follow the same rules irrespective of where inside one body fibrils are formed or accumulated.     

Investigation of the possible incorporation of protons into oxide cathodes during chemical delithiation

Chemical delithiation of layered LiCoO₂, LiNi_0.5Mn_0.5O₂, and Li₂MnO₃ and spinel LiMn₂O₄ cathodes have been investigated with both an acetonitrile (non-aqueous) solution of the oxidizer NO₂BF₄ and an aqueous acid. The products have been characterized by X-ray diffraction, wet chemical analyses for lithium and oxygen contents, infrared spectroscopy, and thermogravimetric analysis to determine whether or not protons are incorporated into the lattice during the delithiation process. While the delithiation in aqueous acid medium leads to an incorporation of protons into the layered oxide lattice, the non-aqueous delithiation with NO₂BF₄ does not involve any proton insertion into the lattice. In contrast to the layered oxides, the chemical delithiation of spinel LiMn₂O₄ even in the aqueous acid medium does not involve any proton insertion into the lattice.