SO4 2−/SnO2: Efficient,Chemoselective, and Reusable Catalyst for Acylation of Alcohols,Phenols, and Amines at Room Temperature

Abstract

SO₄ ^2?/SnO₂ was employed for the acylation of a variety of alcohols, phenols, and amines under solvent‐free conditions at room temperature. This method showed preferential selectivity for acetylation of the amino group in the presence of a hydroxyl group. The reported method is simple, mild, and environmentally viable, using several other acid anhydrides at room temperature.     

Synthesis,mesomorphic, photophysical and computational studies of new achiral four-ring unsymmetrical bent-core mesogens and their Copper(II) complexes

New achiral four-ring unsymmetrical bent-core mesogens derived from 2,5-dihydroxybenzaldehyde and their copper(II) complexes have been synthesised as a new design with an imine and ester linkage. These new bent-core molecules resemble hockey-stick shape, which possesses 4-n-alkyloxy chain (4-n-hexyloxy and 4-n-decyloxy) at one end and methyl or methoxy group at the other end of the molecule. The synthesis, spectroscopic characterisation, phase transition temperature and characterisation of phase behaviour are reported. The bent-core molecules exhibited monotropic nematic and smectic A phase depending on the terminal chain length. Interestingly, copper(II) complexes of bent-core molecules displayed monotropic nematic phase. This is the first report on copper(II) complexes of bent-core molecules that exhibited nematic phase. The four-ring bent-core molecule exhibited fluorescence with large stoke shift. The density functional theory calculations of bent-core molecules and their copper(II) complexes are carried out using Gaussian 09 program at B3LYP level to obtain the stable molecular conformation, dipole moment, highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO) energies and bending angle of the compounds. The natural atomic charges and electronic configurations of the atoms of free ligands as well as the complexes have been evaluated.     

O-Aryloxime ether analogues as novel and efficient ligands for palladium-catalyzed Suzuki–Miyaura coupling in water

O-Aryloxime ether analogues L1–L3 were studied as ligands in palladium-catalyzed Suzuki–Miyaura cross-coupling reaction of aryl bromides and aryl boronic acids in water at room temperature. Reaction conditions for the cross-coupling were optimized using PdCl₂ and Pd(OAc)₂ under aerobic condition. From the three electronically diverse O-aryloxime ether ligands studied herein, the use of 1-phenyl-ethanone O-(4-chloro-phenyl)-oximeL2 exhibits the best catalytic system in the presence of K₂CO₃ as the base and TBAB as the promoter.     

Micelles catalyzed one pot regio- and chemoselective synthesis of benzo[a]phenazines and naphtho[2,3-d]imidazoles ‘in H2O’

An efficient, novel, and concise one pot regio- and chemoselective synthesis of benzo[a]phenazines (4) and naphtho[2,3-d]imidazoles (8) has been accomplished in excellent yields by nucleophilic substitution reaction of 2,3-dichloro-1,4-naphthoquinone (1) with o-phenylenediamine (2) and benzamidines (7) respectively ‘in H₂O’ using base and micelles (SDS) as catalyst. Analog reaction of 2,3-dichloro-1,4-naphthoquinone (1) with 2-aminobenzenethiol (9) under identical conditions led to formation of a mixture of benzo[b]phenothiazine (10), benzo[a]phenothiazine (11), and benzo[a]-1,4-benzothiazino-3,2-phenothiazine (12) in 17%, 23%, and 57% yields, respectively.     

An electrochemical pathway to prepare circular planar 90Sr/90Y sources for the calibration of surface contamination monitors

In this communication, we describe a novel method to prepare circular planar ⁹⁰Sr/⁹⁰Y sources (? = 16 mm) exploiting the intrinsic properties of the anodized titanium to electro-deposit predicted quantity of ⁹⁰Sr activity from an aqueous solution. The influences of various experimental parameters such as pH of the electrolyte, applied current density, electrodeposition time and carrier strontium concentration were thoroughly investigated to arrive at a condition resulting optimal deposition of the ⁹⁰Sr/⁹⁰Y activity on the substrate. An optimized electrochemical procedure to prepare ~3.7 MBq (~0.1 mCi) of circular planar ⁹⁰Sr/⁹⁰Y sources commensurate with regulatory safety requirement has been the positive outcome.     

Efficiency analysis of thermosyphon solar flat plate collector with low mass concentrations of ND–Co3O4 hybrid nanofluids: an experimental study

Journal of Thermal Analysis and Calorimetry - In the present study, the thermal efficiency, convective heat transfer and friction factor analysis are investigated for a flat plate solar collector...     

In Vitro Propagation,Encapsulation, and Genetic Fidelity Analysis of Terminalia arjuna: a Cardioprotective Medicinal Tree

The present study described an improved and reproducible in vitro regeneration system for Terminalia arjuna using nodal segment explants obtained from a mature plant. Shoot tips excised from in vitro proliferated shoots were encapsulated in 3 % sodium alginate and 100 mM CaCl₂?2H₂O for the development of synthetic seeds which may be applicable in short-term storage and germplasm exchange of elite genotype. Shoot multiplication was significantly influenced by a number of factors, namely types and concentrations of plant growth regulators, medium composition, repeated transfer of mother explants, subculturing of in vitro regenerated shoot clumps, agar concentrations, and temperature. Maximum numbers of shoots (16.50?±?3.67) were observed on modified Murashige and Skoog (MMS) medium containing 0.5 mg l^?1 of benzylaminopurine (BAP) and 0.1 mg l^?1 of naphthalene acetic acid (NAA). To shortening the regeneration pathway, rooting of micropropagated shoots under in vitro condition was excluded and an experiment on ex vitro rooting was conducted and it was observed that the highest percentage of shoots rooted ex vitro when treated with indole-3-butyric acid (IBA, 250 mg l^?1)?+?2-naphthoxy acetic acid (NOA, 250 mg l^?1) for 5 min. The well-developed ex vitro rooted shoots were acclimatized successfully in soilrite under greenhouse conditions with 80 % survival of plants. Randomly amplified polymorphic DNA (RAPD) analysis confirmed that all the regenerated plants were genetically identical to the mother plant, suggesting the absence of detectable genetic variation in the regenerated plantlets. To the best of our knowledge, this is the first report on synthetic seed production as well as ex vitro rooting and genetic fidelity assessment of micropropagated shoots of T. arjuna.     

Effect of Acetonitrile on the Colloidal Behavior of Conventional Cationic Surfactants: A Combined Conductivity,Surface Tension,Fluorescence and FTIR Study

A comprehensive study the effect of acetonitrile (ACN) with four cationic surfactants, viz. tetradecyltrimethylammonium bromide (TTAB), cetyltrimethylammonium bromide (CTAB), cetylpyridinium chloride (CPC) and cetylpyridinium bromide (CPB) was made by using the conductivity, surface tension, fluorescence and FTIR techniques. Significant micellar, interfacial and thermodynamic properties were studied by the tensiometeric and conductivity methods. The critical micelle concentration (CMC), aggregation number (Nagg), and Stern–Volmer constants (Ksv) have also been studied by the steady state fluorescence method using pyrene as probe. The fluorescence study also supports the CMC results obtained from conductivity and surface tension. FTIR was used to ascertain that the strength of intermolecular interactions such as hydrogen bonding, ion–ion pair interactions and induced dipole interactions between the surfactants and ACN depend upon the head-group of the surfactants. The interaction of surfactants with ACN is energetically favorable and occurs via direct interactions between the surfactants and ACN. The results further revealed that the strength of interactions between the surfactants and ACN follows the order: TTAB > CTAB > CPC > CPB.     

A theoretical perspective on the accuracy of rotational resonance (R 2)-based distance measurements in solid-state NMR

The application of solid-state NMR methodology for bio-molecular structure determination requires the measurement of constraints in the form of ¹³C–¹³C and ¹³C–¹⁵N distances, torsion angles and, in some cases, correlation of the anisotropic interactions. Since the availability of structurally important constraints in the solid state is limited due to lack of sufficient spectral resolution, the accuracy of the measured constraints become vital in studies relating the three-dimensional structure of proteins to its biological functions. Consequently, the theoretical methods employed to quantify the experimental data become important. To accentuate this aspect, we re-examine analytical two-spin models currently employed in the estimation of ¹³C–¹³C distances based on the rotational resonance (R ²) phenomenon. Although the error bars for the estimated distances tend to be in the range 0.5–1.0 Å, R ² experiments are routinely employed in a variety of systems ranging from simple peptides to more complex amyloidogenic proteins. In this article we address this aspect by highlighting the systematic errors introduced by analytical models employing phenomenological damping terms to describe multi-spin effects. Specifically, the spin dynamics in R ² experiments is described using Floquet theory employing two different operator formalisms. The systematic errors introduced by the phenomenological damping terms and their limitations are elucidated in two analytical models and analysed by comparing the results with rigorous numerical simulations.