Domino Nitro Reduction-Friedländer Heterocyclization for the Preparation of Quinolines

The Friedländer synthesis offers efficient access to substituted quinolines from 2-aminobenzaldehydes and activated ketones in the presence of a base. The disadvantage of this procedure lies in the fact that relatively few 2-aminobenzaldehyde derivatives are readily available. To overcome this problem, we report a modification of this process involving the in situ reduction of 2-nitrobenzaldehydes with Fe/AcOH in the presence of active methylene compounds (AMCs) to produce substituted quinolines in high yields. The conditions are mild enough to tolerate a wide range of functionality in both reacting partners and promote reactions not only with phenyl and benzyl ketones, but also with β-keto-esters, β-keto-nitriles, β-keto-sulfones and β-diketones. The reaction of 2-nitroaromatic ketones with unsymmetrical AMCs is less reliable, giving a competitive formation of substituted quinolin-2(1H)-ones from the cyclization of the Z Knoevenagel intermediate which appears to be favored when certain large groups are adjacent to the AMC ketone carbonyl.     

A study of trinuclear iron(III) O-phthalates

Mössbauer data as well as infrared and magnetic susceptibility results indicate that Fe(III)-phthalates are high spin ferric complexes with a combination of trinuclear oxo-bridged and monomer structures. Values obtained for the isomer shift and quadrupole splitting parameters suggest that different counter ions, such as OH, NO₃, and Na, leave the Fe(III) ions in two very distorted octahedral arrangements, although they scarcely affect the electron densities at the iron nuclei.     

Mössbauer and TEM studies of the perovskite system (1-y)La2/3 $$A$$ 1/3TiO3·yLaFeO3

The microscopic nature of the Mössbauer phase analysis has been found as being particularly valuable in testing assumptions suggested by TEM results regarding the microdomain structure and the population of different lattice sites by iron ions in the perovskite system (1-y)La_{2/3 1/3}TiO₃·yLaFeO₃ with 0.04<y < 0.25 ( is an A-site vacancy). This system was found to contain only Fe₃₊-phases which are stable under normal conditions, but moderate heating in vacuo causes a partial reduction of ferric ions to ferrous ions.     

Simple route to the doubly ortho-palladated azobenzenes: building blocks for organometallic polymers and metallomesogens

A new class of doubly cyclopalladated complexes, {PdCl(dmf)}2(mu-azb) (1) and {PdCl(dmf)}2(mu-aazb) (2), has been prepared in dimethylformamide (dmf) by reaction of azobenzene (azb) and 4-aminoazobenzene (aazb), respectively, with an excess of PdCl2(CH3CN)2 complex. Recrystallization of 1 and 2 in dimethyl sulfoxide (dmso) yields complexes {PdCl(dmso)}2(mu-azb) (3) and {PdCl(dmso)}2(mu-aazb) (4), respectively. The crystal structures of 1 and 4 have been determined by X-ray diffraction. All complexes are characterized by 1H and 13C NMR spectra and elemental analysis. In both crystal structures, solvent molecules are bound to palladium through oxygen atoms and oriented trans to carbon. In view of greater preference of palladium to nitrogen and sulfur atoms, the experimental structures were rationalized by quantum-chemical calculations and confirmed as the most stable isomers.     

Electrospray ionization mass spectrometric investigation of ammonium ion complexes with anomeric 2,3-O-isopropylidene-1alpha- and -1beta-D-ribofuranosyl azides: anomeric and kinetic isotope effects in ammonium affinities.

[Methanol + ammonium acetate] solutions of anomeric 2,3-O-isopropylidene-1alpha- and 1beta-ribofuranosyl azides were investigated by electrospray ionization mass spectrometry (ESI-MS). The compounds included d6-labeled and/or unlabeled isopropylidene groups that enable the identification of peaks characteristic of the ammonium-attached monomeric (MNH4(+)), ammonium-bound homodimeric ([M]2NH4(+)) and heterodimeric ([MNH4M1](+)) complex ions in ESI mass spectra of solutions of a pair of compounds. The intensities of the product ion peaks obtained by the collisionally activated ammonium-bound dimeric ions are related to the secondary isotope effect k(alpha)/k(alphad6) = 0.88 and k(beta)/k(betad6) = 1.25 or to isotope plus anomeric effects k(alpha)/k(betad6) = 1.43 and k(beta)/k(alphad6) = 0.59 in the ammonium affinities of these compounds. The calculations of solely anomeric effects in the ammonium affinities of alpha and beta anomeric compounds obtained from the data presented previously give two series of values: k(alpha)/k(beta) = (k(alpha)/k(alphad6))(k(alphad6)/k(beta)) = 1.49 and k(alphad6)/k(betad6) = (k(alphad6)/k(beta))(k(beta)/k(betad6)) = 2.12 or k(alpha)/k(beta) = (k(alpha)/k(betad6))(k(betad6)/k(beta)) = 1.14 and k(alphad6)/k(betad6) = (k(alphad6)/k(alpha))(k(alpha)/k(betad6)) = 1.63. The disparities of these results indicate the different structures of hydrogen bonding in ammonium-bound dimeric complexes which decompose to monomeric ions with different rate constants. Comparison of experimental results obtained by the qualitative approach of the kinetic method and ammonium affinities of these compounds calculated by the semi-empirical molecular orbital method (AM1) show that the [MNH4M1](+) dimeric complex ions dissociate to the most stable MNH4(+) and M1NH4(+) monomeric ions. The obtained relative order of ammonium affinities of these compounds is: alphad6 > alpha > beta > betad6.     

The collapse transition of poly(styrene-b-(N-isopropyl acrylamide)) diblock copolymers in aqueous solution and in thin films

The thermal behavior of a poly(styrene-b-N-isopropyl acrylamide) diblock copolymer was studied in aqueous solution as well as in thick and in thin films. The polymer was synthesized using reversible addition–fragmentation chain transfer. The critical micelle concentration in aqueous solution was determined using fluorescence correlation spectroscopy. The lower critical solution temperature (LCST) of micellar solutions was detected using microcalorimetry and turbidimetry at 31 °C. Using dynamic light scattering, the collapse of the micelles at the LCST as well as their clustering above was observed. These findings were corroborated with small-angle X-ray scattering. In thick films immersed in water, similar findings were made. In a thin film, however, the LCST is depressed and is found at 26–27 °C.     

Computer-assisted optimization and validation of LC analysis of trimetazidine dihydrochloride and its impurities

Trimetazidine dihydrochloride is an anti-anginal drug, which possesses protective properties against ischemia inducing heart damage. In this paper, a new procedure for liquid chromatographic analysis was successfully developed, optimized, and applied in assessment of trimetazidine dihydrochloride content and its impurities, Y-145, Y-235, and Y-234 at most 1.0%, 0.2%, and 0.2%, respectively, in commercially available pharmaceutical preparation containing 35 mg of trimetazidine dihydrochloride. The retention behavior of trimetazidine dihydrochloride and its impurities is investigated by using several stationary and mobile phases to settle a simple, sensitive, and precise RP-HPLC method. The separation conditions are optimized by DryLab 2000 Plus Chromatography Optimization Software version 3.5.00. Separations are performed on PurospherSTAR RP18 endcapped (150 x 4.6 mm, 5 microm particle size) column at 20 degrees C with UV detection at 210 nm. The mobile phase composition is acetonitrile-aqueous phase (10 mmol/L disodium hydrogenphosphate and 2 mmol/L sodium dihydrogen phosphate, pH 7.6) (30:70 v/v). Afterwards, the method is validated; the important statistical parameters for selectivity/specificity, linearity, precision, limit of detection, and quantitation are defined. The recovery value of the trimetazidine dihydrochloride is 98.06%, and the content of impurities is 0.23% for Y-145, less than 0.02% for Y-235, and less than 0.01% for Y-234. In addition, this method is used for analyzing trimetazidine dihydrochloride and its impurities in pharmaceuticals and bulk drug.     

A Stochastic Algorithm for Fault Inverse Problems in Elastic Half Space with Proof of Convergence

A general stochastic algorithm for solving mixed linear and nonlinear problems was introduced in [11]. We show in this paper how it can be used to solve the fault inverse problem, where a planar fault in elastic half-space and a slip on that fault have to be reconstructed from noisy surface displacement measurements. With the parameter giving the plane containing the fault denoted by $m$ and the regularization parameter for the linear part of the inverse problem denoted by $C$,both modeled as random variables, we derive a formula for the posterior marginal of $m.$ Modeling $C$ as a random variable allows to sweep through a wide range of possible values which was shown to be superior to selecting a fixed value [11]. We prove that this posterior marginal of $m$ is convergent as the number of measurement points and the dimension of the space for discretizing slips increase. Simply put, our proof only assumes that the regularized discrete error functional for processing measurements relates to an order 1 quadrature rule and that the union of the finite-dimensional spaces for discretizing slips is dense. Our proof relies on trace class operator theory to show that an adequate sequence of determinants is uniformly bounded. We also explain how our proof can be extended to a whole class of inverse problems, as long as some basic requirements are met. Finally, we show numerical simulations that illustrate the numerical convergence of our algorithm.