Chemoselective hydrogenation of substituted nitroaromatics using novel water-soluble iron complex catalysts

Chemoselective hydrogenation of substituted nitroaromatic compounds by water-soluble iron complex catalysts with molecular hydrogen has been reported for the first time. This biphasic catalyst presents an opportunity for a solvent-free hydrogenation. This catalyst system provides a low-cost, efficient alternative to the selective but environmentally unacceptable stoichiometric reductions as well as the supported noble metal catalysts used for hydrogenation. An efficient recycling strategy has resulted in a cumulative turnover number above 6000.     

Determination of fluoride by spectrophotometry of Arsenazo(III) complex of the back-extracted Th(IV)

A method based on the back-extraction of Th(IV) from its TTA complex in benzene by aqueous F^– followed by spectrophotometric measurement of Th(IV), for the determination of fluoride has been developed. The coefficients of variation obtained are 2.4% and 1.4% in 11 determinations at F^– concentration levels of 1.0 g ml^–1, respectively.     

Novel approaches to the purification of penicillin acylase

Penicillin acylase ofE. coli NCIM 2400 has been purified to homogeneity using a combination of hydrophobic interaction chromatography and DEAE-cellulose treatment. A variety of substituted matrices were synthesized using D- or DL-phenylglycine, norleucine, ampicillin, or amoxycillin as ligands, all of which retained penicillin acylase at high concentrations of ammonium sulfate or sodium sulfate. The enzyme could be eluted nonbiospecifically by buffer of lower ionic strength with over 95% recovery of the activity. Ammonium chloride, ammonium nitrate, sodium chloride, sodium nitrate, and potassium chloride were ineffective in either adsorption or elution of the enzyme on these columns. Further purification of this partially pure enzyme with DEAE-cellulose at pH 7.0–7.2 yielded an enzyme preparation of very high purity according to electrophoretic and ultracentrifugal analyses, its specific activity being as high as 37 U/mg protein. The purifiedf enzyme has a molecular weight of 67,000 a sedimentation coefficient of 4.0S, and resolves into two forms upon isoelectric focusing. Overall recoveries ranged between 75 and 85%. Ease of operation, high recoveries, high purity of the enzyme and prolonged reuse of the conjugates make the process economically feasible and possibly of great commercial importance.     

Protonated chiral prolinamide catalyzed enantioselective direct aldol reaction in water

Protonated chiral prolinamide organocatalysts have been shown to catalyze an enantioselective direct aldol process in water to provide the aldol product in high yield and good enantioselectivity. The two diastereomeric catalysts (S,R)-4b and (S,S)-4c show different reactivity.     

Determining and reporting purity of organic molecules: why qNMR

Although NMR has been routinely used to determine/estimate relative number of protons for structure elucidation, it has been rarely used to determine and report the purity of organic compounds. Through this paper, we want to emphasize on routine use of quantitative NMR (qNMR) for this purpose. The results of qNMR can be routinely considered as documentation of purity much like other established methods (HPLC, elemental analysis and differential scanning calorimetry). qNMR is a fast, easy, accurate and non‐destructive alternate to speed up the whole analytical process and serves the purpose of both identification and purity determination of compounds using single technique. Copyright © 2012 John Wiley & Sons, Ltd.     

Rhodium-catalysed chemo- and regio-selective [3 + 2+2] cycloadditions of bis(methylenecyclopropanes) and alkynes: Synthesis of spirocyclic 5–7 condensed cycloheptenes

Abstract

Rhodium-catalyzed intermolecular [3?+?2+2] cycloaddition reactions of bis(methylenecyclopropanes) with different alkynes are described. The rhodium-catalyzed [3?+?2+2] cycloadditions resulted in the formation of functionalized 5–7–3 spirocyclic carbocycles in moderate yields with excellent regio- and chemo-selectivity.     

Synthesis,Photophysical Properties and Application of New Porphyrin Derivatives for Use in Photodynamic Therapy and Cell Imaging

New derivatives of tetrakis(4-carboxyphenyl) porphyrin were designed, synthesized and characterized by IR, proton NMR and mass spectroscopy. The ground and excited state nature of new derivatives were examined using UV-Vis. absorption and fluorescence spectroscopy, fluorescence quantum yield and fluorescence lifetime studies. The singlet oxygen quantum yield of each synthesized derivative of porphyrin was estimated for their further efficacy as potential photosensitizer in biological studies. The significant photophysical data of all synthesized derivatives was supplementary accessed to examine the cell imaging and cytotoxicity against two cancer cell lines viz. MBA-MD-231 and A375. The fluorescence lifetime, fluorescence quantum yield and efficiency of singlet oxygen generation suggests alkyl amine and alkyl hydrazide linked new porphyrin photosensitizers can be useful for PDT agent in cancer treatment.     

Liquid Crystals Posessing 1,2,4-Trisubstituted Benzene Derivatives

Abstract

The present work deals with synthesis of two homologous series possessing ester and amide linkage and a large lateral aryl substituent. The large lateral group is attached to the main molecule through an amide linkage. Mesogenic amides are rare even when the amide linkage is present in the main molecular framework. However, in the present work the compounds containing amide linkage in lateral moiety also exhibit mesophases of high thermal stability.