Sums of continuous and differentiable functions in dynamical systems

We investigate stability of Martin boundaries for positive solutions of elliptic partial differential equations. We define a perturbation which isG _L ^D -semismall at infinity, show that Martin boundaries are stable under this perturbation, and give sufficient conditions for it. This work was carried out partially while the author was visiting the Department of Mathematics, Technion — Israel Institute of Technology. He wishes to thank the Israel Association for the Promotion of International Scientific Relations, the Japan Society of Promotion of Science, and the Technion.     

Multielement analysis and antioxidant capacity of Merlot wine clones developed in Montenegro

The overall aim of this paper was to compare the multielement composition and antioxidant capacity of two Montenegrin Merlot wines obtained from specific vine clones (VCR1 and VCR 101) along with commercial Merlot wine throughout the consecutive vintages in 2010 and 2011. Elemental composition was analysed using inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS). Additionally, antioxidant capacity was assessed by cyclic voltammetry. VCR 1 wine from 2011 stood out for its elemental composition. On the other hand, antioxidant capacity of VCR 101 wines was the highest one for the both vintages. According to the experimental data obtained, all three wines are good source of essential elements and products with a significant antioxidant activity and specific geographical origin.     

1 General analytical chemistry

Abstracts

1 General analytical chemistry1.3 Organic analysis     

1 General analytical chemistry

Abstracts

1 General analytical chemistry1.2 Inorganic analysis     

Diversity synthesis via C-H bond functionalization: concept-guided development of new C-arylation methods for imidazoles

Herein, we have formulated the concept of systematic derivatization of a structural motif via C-H bond functionalization. This concept may not only serve as a blueprint for new strategies in diversity synthesis but also provide systematic guidance for the identification of unsolved and important synthetic challenges. To illustrate this point, 2-phenylimidazole was selected as the core motif for this study, a choice inspired by numerous azole-based synthetics, including pharmaceuticals (compound SB 202190), and also fluorescent and chemiluminescent probes. We were able to show that systematic and comprehensive arylation of the 2-phenylimidazole core was feasible, and in the context of this study new arylation methods were developed. The direct 4-arylation of free 2-phenylimidazole was achieved with iodoarenes as the aryl donors in the presence of palladium catalyst (Pd/Ph(3)P) and magnesium oxide as the base. A complete switch from C-4 to C-2' arylation was accomplished using a ruthenium catalyst [CpRu(Ph(3)P)(2)Cl] and Cs(2)CO(3). The corresponding transformations for (N,2)-diphenylimidazole (C-5 and C-2' arylation) were accomplished via the palladium-based method [Pd(OAc)(2)/Ph(3)P/Cs(2)CO(3)] and a rhodium-catalyzed procedure [Rh(acac)(CO)(2)/Cs(2)CO(3)], respectively. All of the arylation methods described herein demonstrated broad synthetic scope, high efficiency, and exclusive selectivity. Furthermore, these new methods proved to be orthogonal to one another and applicable to sequential arylation schemes. With these methods in hand, arrays of arylated imidazoles may now be accessed in a direct manner from 2-phenylimidazole. This strategy stands in sharp contrast to a traditional approach, wherein a distinct and multistep synthesis would be required for each analogue.     

Direct palladium-catalyzed C-2 and C-3 arylation of indoles: a mechanistic rationale for regioselectivity

We have recently developed palladium-catalyzed methods for direct arylation of indoles (and other azoles) wherein high C-2 selectivity was observed for both free (NH)-indole and (NR)-indole. To provide a rationale for the observed selectivity ("nonelectrophilic" regioselectivity), mechanistic studies were conducted, using the phenylation of 1-methylindole as a model system. The reaction order was determined for iodobenzene (zero order), indole (first order), and the catalyst (first order). These kinetic studies, together with the Hammett plot, provided a strong support for the electrophilic palladation pathway. In addition, the kinetic isotope effect (KIE(H/D)) was determined for both C-2 and C-3 positions. A surprisingly large value of 1.6 was found for the C-3 position where the substitution does not occur (secondary KIE), while a smaller value of 1.2 was found at C-2 (apparent primary KIE). On the basis of these findings, a mechanistic interpretation is presented that features an electrophilic palladation of indole, accompanied by a 1,2-migration of an intermediate palladium species. This paradigm was used to design new catalytic conditions for the C-3 arylation of indole. In case of free (NH)-indole, regioselectivity of the arylation reaction (C-2 versus C-3) was achieved by the choice of magnesium base.     

Analysis and calculation of the 31P and 19F NMR spectra of hexafluorocyclotriphosphazene

The higher order high-resolution (31)P and (19)F NMR spectra of hexafluorocyclotriphosphazene (F(2)PN)(3) were measured at 183 K and interpreted using subspectral analysis and iterative fitting computation. (F(2)PN)(3) forms a rigid nine-spin system [A[X](2)](3) with D(3h) symmetry. Two complete and very similar sets of six experimental spin-spin coupling constants, (1)J(P,F), (2)J(P,P), (2)J(F,F), (3)J(P,F), (4)J(F,F)(cis) and (4)J(F,F)(trans), were determined for the first time. Theoretical DFT calculations of chemical shifts and coupling constants were performed to assess their predictive value. The PP/aug-cc-pVDZ treatment rendered the best agreement with experimental data.     

A new fluorogenic transformation: development of an optical probe for coenzyme Q

[reaction: see text] A new fluorogenic transformation based on a quinone reduction/lactonization sequence has been developed and evaluated as a tool for probing redox phenomena in a biochemical context. The probe presented herein is an irreversible redox probe and is reduced selectively by biologically relevant quinols such as ubiquinol but is inert to reduced nicotinamides (e.g., NADH). The ensuing cyclization is fast and quantitative and provides a measurable optical response.     

Quantitative trace analysis of fullerenes in river sediment from Spain and soils from Saudi Arabia

A quantitative method based on ultrasound-assisted toluene extraction followed by liquid chromatography–electrospray ionization–tandem mass spectrometry for the analysis of C₆₀ and C₇₀ fullerenes, N-methylfulleropyrrolidine, [6, 6]-phenyl C₆₁ butyric acid methyl ester and [6, 6]-thienyl C₆₁ butyric acid methyl ester has been developed. The method was validated using fortified blank river sediments according to the criteria of Commission Decision 2002/657/EC. The method limits of detection ranged from 14 to 290 pg/g, making it suitable for its application in environmental analysis. The method has been applied to investigate fullerene content in 58 soil samples collected from different urban and industrial areas in Saudi Arabia and in river sediment from six different sites in the Llobregat River Basin. In addition, in the case of the Llobregat River, superficial water samples from the same sites of the sediments were collected and analysed using a previous method. In soils from Saudi Arabia, C₆₀-fullerene was the only compound that was detected and quantified in 19 % of samples. In the sediments of the Llobregat River, C₆₀-fullerene was also the only one detected (33 % of the samples), while in river water, C₇₀-fullerene was the most frequent compound, and it was quantified in 67 % of the samples. However, C₆₀-fullerene was present in two of the six samples, but at higher concentrations than C₇₀-fullerene, ranging from 0.9 to 7.8 ng/L.