A new recyclable ditribromide reagent for efficient bromination under solvent free condition

1,2-Dipyridiniumditribromide-ethane (DPTBE) has been synthesized and explored as a new efficient brominating agent. The crystalline ditribromide reagent is stable for months and acts as a safe source of bromine requiring just 0.5 equiv for complete bromination. It has high active bromine content per molecule and shows a remarkable reactivity compared to other tribromide reagents toward various substrates by just grinding the reagent and substrates in a porcelain mortar at room temperature. No organic solvent has been used during any stage of the reaction for substrates giving product as solid. Product can easily be isolated by just washing the highly water soluble 1,2-dipyridiniumdibromide-ethane (DPDBE) from the brominated product. The spent reagent can be recovered, regenerated, and reused without any significant loss.     

Phosphotungstic Acid Nanoclusters Grafted onto High Surface Area Hydrous Zirconia as Efficient Heterogeneous Catalyst for Synthesis of Octahydroquinazolinones and β-Acetamido Ketones

Phostungstic acid (PWA) nanoclusters grafted onto high surface area polycrystalline hydrous zirconia powder (PWA/ZrO₂) was prepared by wet impregnation method. The zirconia particles were synthesized using a modified sol–gel route. The obtained material was characterized by X-ray diffraction (XRD), UV–Vis–diffuse reflectance spectroscopy (UV–Vis–NIR–DRS), infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and sorptometric techniques. XRD study revealed the presence of tetragonal phase of zirconia in the synthesized sample. TEM study indicates presence of small PWA clusters with size in the range of 5–15 nm well dispersed on the surface of the ZrO₂ particles. The characteristic UV and IR absorption feature of the PWA was retained in the PWA/ZrO₂ material. The PWA/ZrO₂ material was used as an efficient catalyst for the preparation of octahydroquinazolinones and β-acetamido ketones. The octahydroquinazolinones were synthesized by the multicomponent condensation of dimedones, urea and aryl aldehydes in ethanol. Similarly, β-acetamido ketones were synthesized with high yield and purity by four component condensation of aryl aldehydes, enolizable ketones, and acetyl chlorides in acetonitrile. The protocols developed in this investigation using the PWA/ZrO₂ catalyst is advantageous in terms of simple experimentation, high yield and purity of the products and recovery and reutilization of the heterogeneous catalyst.     

Chemical Synthesis,X-ray Crystallography,Hirshfeld Surface Analysis,and Molecular Docking Studies of (E)-2-(((3-Bromophenyl)imino)methyl)-5-(diethylamino)phenol Schiff Base

Crystallography Reports - The title Schiff base compound (I), C17H19BrN2O, has been synthesized by the reaction of 4-(diethylamino)-2-hydroxybenzaldehyde and 3-bromoaniline. The dihedral angle...     

Immobilization of histidine-tagged proteins on nickel by electrochemical dip pen nanolithography

Dip-pen nanolithography (DPN) is becoming a popular technique to "write" molecules on a surface by using the tip of an atomic force microscope (AFM) coated with the desired molecular "ink". In this work, we demonstrate that poly-histidine-tagged peptides and proteins, and free-base porphyrins coated on AFM probes, can be chelated to ionized regions on a metallic nickel surface by applying an electric potential to the AFM tip in the DPN process. DPN has been accomplished in the Tapping Mode of AFM, which creates many possible applications of positioning and subsequently imaging biomolecules, especially on soft surfaces.     

Pulse radiolysis studies on the reactions of 3-pyridinol with oxidizing radicals

Reaction rate constants for the reactions of 3-pyridinol with oxidizing radicals viz. OH, N₃, Br ₂ ^– , Cl ₂ ^– , SO ₄ ^– and O^– have been determined in aqueous solutions at different, pH's. Absorption spectra of the product transient species have been recorded in the 320–600 nm region. In the alkaline region (pH 13) the N₃ reaction product decays in two steps and O^– does not bring about one-electron oxidation. Similarly, at neutral pH, SO ₄ ^– does not cause selective one-electron oxidation of 3-pyridinol.     

On-line temporal characterization of an X-ray streak camera

A simple system for an on-line temporal characterization of an X-ray streak camera is described. Multiple UV-transmitting fiber optic channels with known relative time delays facilitate measurements of sweep speed in addition to providing a fiducial signal. Results of measurements on variation of sweep speed across the output screen of an in-house developed X-ray streak camera of an average sweep speed of 24.5 ps/mm and a temporal resolution of 7.5 ps are presented.     

Raman spectroscopic investigation of frozen and deparaffinized tissue sections of pediatric tumors: neuroblastoma and ganglioneuroma

Raman spectroscopy is a nondestructive technique that can provide information at the molecular level about the biochemicals in tissues. We have investigated the cellular regions in neuroblastoma and ganglioneuroma using Raman spectroscopy and compared their spectral characteristics with those of the corresponding normal adrenal gland. Thin sections from both the frozen and the corresponding formalin‐fixed paraffin‐processed (FFPP) tissues were studied in conjunction with the pathological examination of the tissues. Investigation of the spectral data shows that the normal adrenal gland tissues have higher levels of carotenoids, lipids, and cholesterol compared with the neuroblastoma and ganglioneuroma frozen tissues. However, in comparison with the frozen tissues, the FFPP tissues show a significant alteration of several biochemicals, including the complete removal of carotenoids, lipids, and cholesterol in the adrenal tissues. A quantitative analysis using chemometric methods of principal component analysis and discriminant function analysis of the Raman spectral data obtained from the frozen tissues show a clear‐cut classification among pathological groups with high sensitivity and specificity. We have validated the classification results of the FFPP tissues against a training set data obtained from the archived FFPP tissues of nine other patients. The validation process correctly identified and grouped the data with the training set of normal adrenal gland (>97% of the time) and neuroblastoma (100% of the time) tissues, whereas the validation was not so strong for ganglioneuroma. This study shows that Raman spectroscopy combined with chemometric methods can be successfully used to distinguish neuroblastoma and ganglioneuroma at cellular level in frozen tissue sections. This study also shows that formalin fixation and paraffinization/deparaffinization of tissues can alter their biochemical composition. Copyright © 2012 John Wiley & Sons, Ltd.