Heterogeneous liquid phase synthesis of 3,4-dihydropyrimidine-2(1H)-ones using aluminated mesoporous silica

Aluminated mesoporous silica (Al-SBA-15) with different amounts of Al contents were synthesized and used for the synthesis of 3,4-dihydropyrimidine-2(1H)-ones in the liquid phase, as well as under microwave conditions. The catalytic activity results showed very high conversion and yields of the products over many substituted aromatic aldehydes.     

Ferrocene-linked thymine/uracil conjugates: base pairing directed self-assembly and supramolecular packing

Ferrocene-linked bis(nucleobase) (1a-c) and chimeric nucleobase (1d) conjugates have been synthesized from mono- and bis(hydroxybutyl)ferrocene 6 via Mitsunobu reaction as the key step. X-ray crystallographic studies of ferrocene bis(nucleobase) conjugates reveal two-dimensional supramolecular organizations of backbones through self-assembled Watson-Crick and reverse Watson-Crick type pairs. Ferrocene-bis(thymine) conjugate self-assembles by reverse Watson-Crick pairing, while the corresponding bis(uracil) conjugate self-assembles by alternating WC and reverse WC type pairing. Such continuous assemblies are not seen in monosubstituted ferrocene nucleobase conjugates which form only planar sheets. The results are interesting from the point of understanding and engineering supramolecular assemblies through rational design of base pairing patterns.     

Vapor-phase processable novel nonplanar donor-acceptor quateraryls for blue OLEDs(#)

A novel series of thermally stable blue light emitting quateraryls with a piperidine donor and a nitrile acceptor was prepared from a ketene- S, S-acetal under mild conditions without using an organometal catalyst. The performance of a blue quateraryl 6e was investigated by fabricating a multilayer OLED with a configuration of ITO/PEDOT:PSS (40 nm)/quateraryl (60 nm)/BCP (6 nm)/Alq(3) (20 nm)/LiF (0.5 nm)/Al (200 nm), which exhibited blue emission with a low turn on voltage of 4 V at a brightness of 0.22 cd/m(2).     

Oxidation of p-chlorotoluene and cyclohexene catalysed by polymer-anchored oxovanadium(IV) and copper(II) complexes of amino acid derived tridentate ligands

3-Formylsalicylic acid (Hfsal), covalently bound to chloromethylated polystyrene (PS) and cross-linked with 5% divinylbenzene reacts with d,l-alanine and l-isoleucine to give the Schiff-base tridentate ligands PS-H(2)fsal-d,l-Ala and PS-H(2)fsal-l-Ile, respectively. These anchored ligands upon reaction with VOSO(4) and Cu(CH(3)COO)(2).H(2)O form the complexes PS-[VO(fsal-d,l-Ala)(H(2)O)], PS-[Cu(fsal-d,l-Ala)(H(2)O)], PS-[VO(fsal-l-Ile)(H(2)O)] and PS-[Cu(fsal-l-Ile)(H(2)O)]. The structures of these immobilized complexes have been established on the basis of scanning electron micrographs, spectroscopic (infrared, electronic and EPR), thermogravimetric and elemental analysis studies. The oxidation of p-chlorotoluene and cyclohexene has been investigated using these complexes as the catalysts in the presence of H(2)O(2) as the oxidant. Reaction conditions have been optimised by considering the concentration of the oxidant, the amount of catalyst used and the temperature of the reaction mixture. Under the optimised conditions, p-chlorotoluene gave a maximum of 14% conversion using PS-[VO(fsal-d,l-Ala)(H(2)O)] as the catalyst, with the main products having a selectivity order of: p-chlorobenzaldehyde > p-chlorobenzylalcohol > p-chlorobenzoic acid > 2-methyl-5-chlorophenol > 3-methyl-6-chlorophenol. The oxidation of cyclohexene with PS-[VO(fsal-d,l-Ala)(H(2)O)] proceeds with 79% conversion, which is followed by PS-[VO(fsal-l-Ile)(H(2)O)] with 77% conversion, and the oxidation of cyclohexene by Cu-based catalysts occurs with considerably lower conversions (29-32%). The selectivity of the products follows the order: 2-cyclohexene-1-ol > cyclohexene oxide > cyclohexane-1,2-diol > 2-cyclohexene-1-one. Recycling studies indicate that these catalysts can be reused at least three times without any significant loss in their catalytic potential. However, EPR studies indicate that while the polymer supported V(iv)O-complexes do not change after being used, the EPR spectra of the Cu-complexes show significant changes. The corresponding non-polymer bound complexes [VO(fsal-d,l-Ala)(H(2)O)], [Cu(fsal-d,l-Ala)(H(2)O)], [VO(fsal-l-Ile)(H(2)O)] and [Cu(fsal-l-Ile)(H(2)O)] have also been prepared in order to compare their spectral properties and catalytic activities. The non-polymer bound complexes exhibit lower conversion, along with lower turn-over frequency as compared to their polymer-bound analogues. Several EPR, (51)V NMR and UV-vis studies have been undertaken to detect the intermediate species, and outlines for the mechanisms of the catalytic reactions are proposed.     

Spontaneous separation of charged grains

In 1867, Lord Kelvin described an experiment in which two streams of water droplets were connected so that each stream amplified the charge on the second stream [W. Thomson, Proc. R. Soc. London 16, 67 (1867)]. We present here a complementary effect in flowing grains that spontaneously separates similar and well-mixed grains into two charged streams of demixed grains. This effect has important consequences for industrial and natural processes.     

Total synthesis of potential antitumor agent, (-)-dictyostatin

[structure: see text] The potential antitumor agent (-)-dictyostatin has been synthesized utilizing Brown crotylboration to achieve eight of the eleven chiral centers. The yield for the 26-step longest sequence is approximately 4%. The C9-C10 coupling is achieved via a stereoselective vinylzincate addition.     

Feature extraction using molecular planes for fuzzy relational clustering of a flexible dopamine reuptake inhibitor

Six rigid-body parameters (Shift, Slide, Rise, Tilt, Roll, Twist) are commonly used to describe the relative displacement and orientation of successive base pairs in a nucleic acid structure. The present work adapts this approach to describe the relative displacement and orientation of any two planes in an arbitrary molecule-specifically, planes which contain important pharmacophore elements. Relevant code from the 3DNA software package (Nucleic Acids Res. 2003, 31, 5108-5121) was generalized to treat molecular fragments other than DNA bases as input for the calculation of the corresponding rigid-body (or "planes") parameters. These parameters were used to construct feature vectors for a fuzzy relational clustering study of over 700 conformations of a flexible analogue of the dopamine reuptake inhibitor, GBR 12909. Several cluster validity measures were used to determine the optimal number of clusters. Translational (Shift, Slide, Rise) rather than rotational (Tilt, Roll, Twist) features dominate clustering based on planes that are relatively far apart, whereas both types of features are important to clustering when the pair of planes are close by. This approach was able to classify the data set of molecular conformations into groups and to identify representative conformers for use as template conformers in future Comparative Molecular Field Analysis studies of GBR 12909 analogues. The advantage of using the planes parameters, rather than the combination of atomic coordinates and angles between molecular planes used in our previous fuzzy relational clustering of the same data set (J. Chem. Inf. Model. 2005, 45, 610-623), is that the present clustering results are independent of molecular superposition and the technique is able to identify clusters in the molecule considered as a whole. This approach is easily generalizable to any two planes in any molecule.     

Letter: Lanthanum-calcium-manganate (La0.67Ca0.33MnO3) nanoparticle assisted affinity probes for MALDI MS analysis of proteins

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) has been used extensively for the analysis of -intact proteins and for proteomics. Proteins or proteomics analyses with low molecular mass range have some limitations because of background interference from the salt or surfactant ions. Lanthanum-calcium- manganate La(0.67)Ca(0.33)MnO(3) nanoparticles (LCMONPs) have been used as the matrix-assisting material after surface modification to reduce the salt or surfactant interference. The detectable mass range was tested in the range of 800-16,000 Da. The surface-modified LCMONPs have affinity with protein molecules through ionic or electrostatic interaction at pH 4.0. The nanoparticles mixed with proteins give a spectrum with a large signal-to-noise ratio for the analytes, and effectively eliminate the noise from interfering salt or surfactant ions. The results indicate that surface-modified La(0.67)Ca(0.33)MnO(3) nanoparticles can be used with MALDI matrix for proteins to eliminate the excessive noise of selective surfactants or salt ions from the MALDI spectrum.     

Guerbet alcohol esters: Practical synthesis and applications

Guerbet alcohols are primary alcohols with beta branching and have lower melting point than their linear counterpart. Due to presence of branching, the products are liquid at lower temperatures; they have low volatility and exhibit better color and oxidation stability. The main advantage of the Guerbet branching material is their biodegradability. Present research work was carried out on synthesis of branch chain alcohols with varying hydrocarbon chain lengths. The main purpose was to study the effects of branching and varying chain length with performance properties. Branch chain esters with mono and di-carboxylic acids were synthesized with varying hydrocarbon chain lengths. The major limitation of Guerbet products is their cost. Guerbet alcohols were esterified with various monobasic and dibasic acids and found to have lower pour points. Load carrying capacity of prepared ester increased with increase in carbon chain. Wear scar of the prepared ester decreased with the increase in carbon number of ester molecule. These properties indicated their potential use as lubricating oil base stock which are environment friendly as they are biodegradable and with excellent liquidity.     

A simplified model of oscillating electrolytes

Unstable electrophoretic transport leading to oscillations in concentration profiles occur in certain electrolyte systems known as oscillating electrolytes whose eigenmobilities are complex valued. The study of the nonlinear behavior of such systems is of great interest but is constrained due to a high degree of complexity in the governing equations. Here we present a simplified model of unstable electrophoretic transport in a binary system that reduces the governing equations to two partial differential equations only and does away with other equations that characterize acid–base dissociation reactions and electroneutrality. We present analytical expressions for electromigration fluxes and validate the model with full nonlinear simulations. The model exhibits similar nonlinear behavior as the actual unstable electrophoretic system under various initial disturbances. For comparison, we also show that similar modeling for a stable system predicts concentration profiles that quantitatively agree with its nonoscillating dynamics. Moreover, the unique feature of electromigration flux in oscillating electrolytes that unfolds from the modeling led us to find an elegant explanation of the instability mechanism. Our theory gives a qualitative understanding of the existence and growth of large oscillation patterns in oscillating electrolytes.