Enantioselective Synthesis of [b]-Annulated Azepane Scaffolds

Cyclopenta-, benzo-, and cyclohepta[b]-annulated azepane scaffolds were prepared in two steps from optically active cyclic α-allyl-β-oxoesters. The first step was ruthenium-catalyzed olefin cross metathesis with acrylonitrile. The second step was palladium-catalyzed dihydrogenation which consists of three consecutive processes: The hydrogenation of the C−C double and C−N triple bonds was followed by the reductive amination via the iminium ion formed in situ from the primary amino function and the endocyclic carbonyl group. This last step gave, stereoselectively, the annulated azepanes with relative trans-configuration. The amino function and the ester group define two points for further diversification of the scaffolds. The trifluoroacetyl derivatives allowed to establish the enantiopurity of the products to be 97–98 % ee by GLC on a chiral phase. The relative trans-configurations and in one case also the absolute (R,R)-configuration was established by X-ray crystallography.     

ChemInform Abstract: Explaining Stability of Transition Metal Carbides — and Why TcC Does Not Exist.

The formation of transition metal (M) carbides M_xC_y and trends of their stability are systematically investigated using the USPEX code within the DFT.     

On the Statistical Calibration of Physical Models

We introduce a novel statistical calibration framework for physical models, relying on probabilistic embedding of model discrepancy error within the model. For clarity of illustration, we take the measurement errors out of consideration, calibrating a chemical model of interest with respect to a more detailed model, considered as “truth” for the present purpose. We employ Bayesian statistical methods for such model‐to‐model calibration and demonstrate their capabilities on simple synthetic models, leading to a well‐defined parameter estimation problem that employs approximate Bayesian computation. The method is then demonstrated on two case studies for calibration of kinetic rate parameters for methane air chemistry, where ignition time information from a detailed elementary‐step kinetic model is used to estimate rate coefficients of a simple chemical mechanism. We show that the calibrated model predictions fit the data and that uncertainty in these predictions is consistent in a mean‐square sense with the discrepancy from the detailed model data.     

Temperature effect on the microstructure and viscoelastic properties of aqueous micellar systems of sodium <Emphasis Type="Italic">N</Emphasis>-methyl-<Emphasis Type="Italic">N</Emphasis>-oleyl taurate

The quantitative characteristics of the temperature effect on the rheological properties of aqueous solutions of the anionic surfactant sodium methyl oleyl taurate (SMOT) are presented. An increase in the intensity of thermal motion of surfactant molecules on heating from 25 to 45 °С was shown to decrease the average contour length of SMOT micelles from 2 μm to 700 nm. The decrease in the length of cylindrical micelles is probably one of the main reasons for a substantial decrease in the viscosity of micellar solutions of the surfactant with temperature.     

Ultrasound synthesis of diaryl ethers

Russian Chemical Bulletin - 2,2-Bis[4-(4-nitroaryl)phenyl]hexafluoropropanes appropriate for the synthesis of monomers were prepared by the reaction of 2,2-bis[4-hydroxyphenyl)hexafluoropropane...     

Kinetic features of ammonium persulfate decomposition in aqueous medium

Russian Chemical Bulletin - Decomposition of ammonium persulfate in an aqueous medium (353–368 K) is limited by decomposition of persulfate ions with a rate constant logk 2 =...