Palladium-catalyzed regioselective synthesis of benzosultams from functionalized ynamides and benzotriazoles/tetrazoles

Palladium-catalyzed highly regioselective synthesis of benzotriazole appended benzosultams by the tandem-cyclization of functionalized ynamides with benzotriazoles has been accomplished. This transformation involves the formation of both CN and CC bonds in a single step. Donor solvents appear to enhance the yields of the products. The methodology is also applicable for the generation of triazole/tetrazole appended benzosultams.     

Microtiterplate phosphate assay based on luminescence quenching of a terbium complex amenable to decay time detection

We describe a terbium-ligand complex (TbL) for a microtiterplate assay for phosphate (P) in the 0.3-100 μmol L⁻¹ range based on luminescence quenching. As the pH optimum is at neutral pH (7.4) the probe is quenched by both, primary (H₂PO₄⁻) and secondary phosphate (HPO₄²⁻). The LOD is 110 nmol L⁻¹. A Stern-Volmer study revealed that quenching is mostly static. Due to the ms-decay time of TbL, the first luminescence lifetime assay for phosphate could also be developed. The lifetime-based calibration plot is linear between 0.5 and 5 μmol L⁻¹ of P. The effect of various surfactants on assay performance and a study on interferents are presented. The probe was successfully applied to determination of P in commercial plant fertilizers and validated against the molybdenum blue test. The probe is the most sensitive lanthanide-based probe for phosphate.     

Copper(II) fluoride-catalyzed N-arylation of heterocycles with halothiophenes

A novel, cheap copper(II) fluoride-mediated N-arylation of heterocycles with halothiophenes is described. The yield of the pyrazolylthiophene strongly depends on the nature of the initial thiophene. The molecular structure of 3,5-dimethyl-1-(5′-methyl-[2,2′]bithienyl-5-yl)-1H-pyrazole was studied by X-ray diffraction.     

IR and NMR spectra,intramolecular hydrogen bonding and conformations of para-tert-butyl-aminothiacalix[4]arene in solid state and chloroform solution

It is demonstrated that dissolution of aminothiacalix[4]arene in chloroform results in transformation of 1,3-alternate conformation, adopted in single-crystal and bulk polycrystalline solids, to the pinched-cone form. This conformer is stabilised by the intramolecular hydrogen bonds of two distal amino-groups acting as H-donors with another two amino moieties that appear as H-acceptors. The H-bonds cause quite small (ca. 10–20 cm^?1) red shift of the IR bands of the NH₂ stretching vibrations, which suggests rather weak NH?N hydrogen bonding. This latter is sufficient to stabilize the pinched-cone conformation in the chloroform solution, but the energy gap between the pinched-cone and other conformations is small, and solid-state intermolecular forces easily overcome it, leading to realisation of the 1,3-alternate conformer. The comparison of the DFT computed and experimental vibrational and NMR spectra demonstrates good quality of present quantum-chemical computations, allows complete interpretation of the spectra and reveals simple IR and NMR spectroscopic markers of the conformers of aminothiacalix[4]arenes.     

Equilibrium and kinetic investigation of the interaction of model palladium(II) complex with biorelevant ligands

Pd(DME)Cl₂ complex was synthesized and characterized, where DME is 2‐{[2‐(dimethylamino)ethyl]‐methylamino}ethanol. Stoichiometry and stability constants of the complexes formed between various biologically relevant ligands (amino acids, peptides, DNA constituents, and dicarboxylic acids) and [Pd(DME)(H₂O)₂]²⁺ are investigated at 25°C and at constant 0.1 M ionic strength. The effect of dielectric constant of the medium on the stability constant of Pd(DME)‐CBDCA complex, where CBDCA is cyclobutanedicarboxylate, is also reported. The concentration distribution diagrams of the various species formed are evaluated. The kinetics of base hydrolysis of amino acid esters coordinated to Pd(DME)²⁺ complex is investigated. The effect of the temperature on the kinetics of base hydrolysis of glycine methyl ester complex is studied. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 608–618, 2010     

Crystallization and crystal structure of poly(ester amide)s derived from L‐tartaric acid

The crystal structure and crystallization behavior of a series of poly(ester amide)s derived from L ‐tartaric acid, 1,6‐hexanediamine, and 6‐amino‐1‐hexanol were examined. The study included aregic polymers containing 5, 10, and 20% of ester groups in addition to the syndioregic polymer containing equal amounts of amide and ester groups. X‐ray diffraction data revealed that all the aregic poly(ester amide)s adopt the same crystal structure as the parent polyamide made of L ‐tartaric acid, and 1,6‐hexanediamine. In this structure, chains are slightly compressed and arranged as in the α‐form of nylon 66. Solid‐state nuclear magnetic resonance (NMR) revealed that ester groups are excluded from the crystal phase except for the case of the syndioregic polymer. Isothermal crystallization kinetics was analyzed according to the Avrami theory. Crystallization rates were found to decrease regularly with increasing contents in ester groups and with increasing crystallization temperature. Avrami exponent values close to 2 were found whereas spherulitic morphologies were observed by optical microscopy. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 116–125, 2007     

Two low-cost digital camera-based platforms for quantitative creatinine analysis in urine

In clinical analysis creatinine is a routine biomarker for the assessment of renal and muscular dysfunctions. Although several techniques have been proposed for a fast and accurate quantification of creatinine in human serum or urine, most of them require expensive or complex apparatus, advanced sample preparation or skilled operators. To circumvent these issues, we propose two home-made platforms based on a CD Spectroscope (CDS) and Computer Screen Photo-assisted Technique (CSPT) for the rapid assessment of creatinine level in human urine. Both systems display a linear range (r² = 0.9967 and 0.9972, respectively) from 160 μmol L⁻¹ to 1.6 mmol L⁻¹ for standard creatinine solutions (n = 15) with respective detection limits of 89 μmol L⁻¹ and 111 μmol L⁻¹. Good repeatability was observed for intra-day (1.7–2.9%) and inter-day (3.6–6.5%) measurements evaluated on three consecutive days. The performance of CDS and CSPT was also validated in real human urine samples (n = 26) using capillary electrophoresis data as reference. Corresponding Partial Least-Squares (PLS) regression models provided for mean relative errors below 10% in creatinine quantification.     

Snapshot location for POD in control of a linear heat equation

In the present work, we study the approximation of a distributed optimal control problem for a linear heat equation with model order reduction based on Proper Orthogonal Decomposition (POD-MOR). We show that snapshot location for control problems is crucial in model reduction. For the determination of the time instances (snapshot locations) we utilize an a-posteriori error control concept which is based on a reformulation of the optimality system of the underlying optimal control problem as a second order in time and fourth order in space elliptic system. Finally, we present a numerical test to illustrate our approach. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)