Annulation of pyrrole ring in 4-acylpyridine-3,5-dicarbonitriles in the presence of ammonia

Chemistry of Heterocyclic Compounds - 4-Acyl-2-amino-6-chloropyridine-3,5-dicarbonitriles underwent heterocyclization in the presence of ammonia in aqueous dioxane medium, involving the...     

Ionic Pd/NHC Catalytic System Enables Recoverable Homogeneous Catalysis: Mechanistic Study and Application in the Mizoroki–Heck Reaction

N-Heterocyclic carbene (NHC) ligands are ubiquitously utilized in catalysis. A common catalyst design model assumes strong M–NHC binding in this metal–ligand framework. In contrast to this common assumption, we demonstrate here that lability and controlled cleavage of the M−NHC bond (rather than its stabilization) could be more important for high-performance catalysis at low catalyst concentrations. The present study reveals a dynamic stabilization mechanism with labile metal–NHC binding and [PdX₃]⁻[NHC-R]⁺ ion pair formation. Access to reactive anionic palladium intermediates formed by dissociation of the NHC ligands and plausible stabilization of the molecular catalyst in solution by interaction with the [NHC-R]⁺ azolium ion is of particular importance for an efficient and recyclable catalyst. These ionic Pd/NHC complexes allowed for the first time the recycling of the complex in a well-defined form with isolation at each cycle. Computational investigation of the reaction mechanism confirms a facile formation of NHC-free anionic Pd in polar media through either Ph–NHC coupling or reversible H–NHC coupling. The present study formulates novel ideas for M/NHC catalyst design.     

The use of hypercrosslinked polymer sorbents and composites based on them in the sorption of toxic and bad-smelling substances

Russian Chemical Bulletin - The sorption of cadaverine from the air on hypercrosslinked polystyrene sorbents was investigated. An available technique for the introduction of iron oxide into the...     

Photothermal image flow cytometry in vivo

The capability of photothermal (PT) microscopy to image moving, unlabeled cells in real time in vivo is demonstrated in a study of circulating red and white blood cells in blood and lymph microvessels of rat mesentery. Potential applications of this optical tool, called PT flow cytometry, are discussed.     

Synthesis of new [2]rotaxane including a macrocyclic receptor and a photochromic unit

The novel photochromic [2]rotaxane based on chromene molecule introduced into a crown-containing macrocyclic receptor was synthesized. The photochemical properties of rotaxane could be modified by the complexation of the crown ether moiety.     

Complexity of local search for the p-median problem

We study the complexity of finding local minima for the p-median problem. The relationship between Swap local optima, 0–1 local saddle points, and classical Karush–Kuhn–Tucker conditions is presented. It is shown that the local search problems with some neighborhoods are tight PLS-complete. Moreover, the standard local descent algorithm takes exponential number of iterations in the worst case regardless of the tie-breaking and pivoting rules used. To illustrate this property, we present a family of instances where some local minima may be hard to find. Computational results with different pivoting rules for random and Euclidean test instances are discussed. These empirical results show that the standard local descent algorithm is polynomial in average for some pivoting rules.     

On the application of a ZrO2‐based solid electrolyte in isotope ratio mass spectrometry

The application of a high‐temperature electrochemical reactor based on stabilized zirconium dioxide (0.9 ZrO₂0.1 Y₂O₃) for organic gas sampling in continuous‐flow isotope‐ratio mass spectrometry (CF‐IRMS) has been found to be efficient. This solid electrolyte reactor (SER) can also be used as a chromatographic detector for the quantitative measurements of organic gases. A three‐electrode SER system was studied. Complete stoichiometric oxidation of organic gases has been achieved at 900–950°C due to the large catalytic surface area of the porous platinum coating. At this temperature, the oxygen ions formed from the oxygen of ambient air on the outer surface of the reactor migrate through the solid electrolyte under the action of the applied electric field and allow combustion of gases being analyzed to be effected. It should be noted that oxygen gas was not introduced into the gas‐carrier flow. Similar results for the measurements of carbon isotope ratios were obtained at the oxidation of hydrocarbon gases in both the standard and the solid electrolyte reactors. Copyright © 2009 John Wiley & Sons, Ltd.