Indium(III) Triflate: A Highly Efficient Catalyst for Reactions of Sugars[1]

Indium(III) trifluoromethanesulfonate has been found to be extremely efficient in catalyzing acyl transfer reactions of various carbohydrates and their derivatives. Selective acetolyses of certain benzyl ethers/isopropylidene acetals of sugars have been possible using In(OTf)₃ in Ac₂O (neat). Reaction of the per-O-acetate of 2-deoxy-2-phthalimido-D-glucose with benzyl mercaptan in the presence of In(OTf)₃ led to the formation of the corresponding thioglycoside in high yield. Facile formation and hydrolysis of the isopropylidene and benzylidene acetals of various carbohydrates have also been achieved very efficiently in the presence of In(OTf)₃. The results show great promise for In(OTf)₃ in synthetic carbohydrate chemistry.     

Convenient Procedure for Dethioketalisation in Nitrogen Heterocycles

Regeneration of Carbonyl compounds from the corresponding thioketals in nitrogen heterocycles have been effected using Dowex 50W acidic catalyst in reasonable yields.     

Inspection scheduling for imperfect production processes under free repair warranty contract

The paper considers scheduling of inspections for imperfect production processes where the process shift time from an ‘in-control’ state to an ‘out-of-control’ state is assumed to follow an arbitrary probability distribution with an increasing failure (hazard) rate and the products are sold with a free repair warranty (FRW) contract. During each production run, the process is monitored through inspections to assess its state. If at any inspection the process is found in ‘out-of-control’ state, then restoration is performed. The model is formulated under two different inspection policies: (i) no action is taken during a production run unless the system is discovered in an ‘out-of-control’ state by inspection and (ii) preventive repair action is undertaken once the ‘in-control’ state of the process is detected by inspection. The expected sum of pre-sale and post-sale costs per unit item is taken as a criterion of optimality. We propose a computational algorithm to determine the optimal inspection policy numerically, as it is quite hard to derive analytically. To ease the computational difficulties, we further employ an approximate method which determines a suboptimal inspection policy. A comparison between the optimal and suboptimal inspection policies is made and the impact of FRW on the optimal inspection policy is investigated in a numerical example.     

Selective functionalization of ferrocenyl compounds using a novel solvent free synthetic method for the preparation of bioactive unsymmetrical ferrocenyl derivatives

A novel solvent free synthetic method has been designed by using rice husk ash (RHA) as solid support for the selective functionalization of ferrocenyl derivatives and described the synthesis of a 1,1′‐unsymmetrically bi‐functionalized ferrocenyl compounds for their biological evaluation. Single crystal X‐ray structural evaluation showed some interesting intra‐molecular hydrogen bonding interactions across the chains of the ferrocenyl molecule, while DFT calculation revealed the significance of the orientation between the two cyclopentadienyl rings for the hydrogen bonding interaction. Redox and antibacterial properties have been studied to understand the electronic and biological effect of different hydrazone system and their potential for future application.     

Surface adsorption and collapse transition of linear polymer chains

The critical behaviour of surface adsorption and collapse transition of a flexible self-attracting self-avoiding polymer chain is examined. Depending upon the underlying lattice and space dimensionality, phase diagrams that exhibit many different universality domains of critical behavior are found. We discuss these phase diagrams and the values of the critical exponents found from different theoretical methods.     

Synthesis of Indolo[2,3-a]quinolizidine-3-One

The title compound 1 has been synthesised through the intermediacy of the salt 5 obtained by acid hydrolysis of the obtically active β-carboline derivative 10,11-cyclohexylidene-12β-hydroxy-13β-(l-tetrahydro-β-carbolinyl)tetrahydrofuran (4).     

A compact microfluidic geometry for multiplexing enzyme-linked immunosorbent assays

We have previously reported a novel approach to implementing multiplex enzyme-linked immunosorbent assay (ELISA) in connected microchannels by exploiting the slow diffusion of the enzyme reaction product across the different assay segments. This work builds on that report by implementing the noted assay in segments arranged along the circumference of a circular channel layout to reduce the footprint size and sample volume requirement. Using the current design, a 5-plex cytokine ELISA was demonstrated in a 1.5 × 1.5-cm region, which corresponded to a reduction in the footprint area by about a factor of 3 compared to that reported in our previous study. Additionally, the selective coating of our assay segments with the target molecules was realized in this work using electroosmosis instead of hydrodynamic flow as was the case in the previous report. This aspect of our experimental design is particularly significant as it permits the use of cross-sectional channel dimensions significantly shorter than those employed in the current work. Moreover, the use of an electric field for coating purposes enables the integration of functionalities such as electrokinetic preconcentration of analyte molecules during the sample incubation period that can further enhance the capabilities of our assay method.     

Spectroscopic and spectrometric studies of anion recognition with calix[4]pyrroles in different reaction conditions

The binding studies of calix[4]pyrroles (1–6) with fluoro, chloro, bromo, iodo and sulphato anions generated from normal-tetrabutylammoniumfluoride, normal-tetrabutylammoniumchloride, normal-tetrabutylammoniumbromide, normal-tetrabutylammoniumiodide, and normal-tetrabutylammoniumsulphate respectively were investigated by electrospray ionization mass spectrometry (ESI-MS) in dichloromethane–acetonitrile in negative ion mode. The efficacy of a particular calix[4]pyrrole to bind with anions was found maximum at low cone voltage of the instrument, at high cone voltage the binding was suppressed due to removal of anion from the cavity of the macrocycles. The binding strength was found inversely proportional to the size of anion for a particular calix[4]pyrrole. The fragmentation pattern of calix[4]pyrrole was observed at higher cone voltage of ESI-MS and was interpreted. The association constants of calix[4]pyrroles and anions obtained from electronic transition studies were in good agreement with that observed from ¹H NMR titration studies.     

Influence of reagent rotation on (H-, D2) and (D-, H2) collisions: a quantum mechanical study

Time-independent quantum mechanical (TIQM) approach (helicity basis truncated at k = 2) has been used for computing differential and integral cross sections for the exchange reaction H- + D2 (v = 0, j = 0-4) --> HD + D- and D- + H2 (v = 0, j = 0-3) --> HD + H- in three dimensions on an accurate ab initio potential energy surface. It is shown that the j-weighted differential reaction cross section values are in good agreement with the experimental results reported by Zimmer and Linder at four different relative translational energies (Etrans = 0.55, 0.93, 1.16 and 1.48 eV) for (H-, D2) and at one relative translational energy (Etrans = 0.6 eV) by Haufler et al. for both (H-, D2) and (D-, H2) collisions. The j-weighted integral reaction cross section values are in good agreement with the crossed beam measurements by Zimmer and Linder in the Etrans range 0.5-1.5 eV and close to the guided ion beam results by Haufler et al. for (H-, D2) in the range 0.8-1.2 eV. Time-dependent quantum mechanical (TDQM) results obtained using centrifugal sudden approximation are reported in the form of integral reaction cross section values as a function of Etrans in the range 0.3-3.0 eV for both reactions in three dimensions on the same potential energy surface. The TDQM reaction cross section values decline more sharply than the TIQM results with increase in the initial rotational quantum number (j) for the D2 molecules in their ground vibrational state (v = 0) for (H-, D2) collisions. The computed j-weighted reaction cross section values are in good agreement with the experimental results reported by Zimmer and Linder for (H-, D2) collisions and guided ion beam results by Haufler et al. for both (H-, D2) and (D-, H2) collisions for energies below the threshold for electron detachment channel.