Design and Synthesis of Benzimidazole-Linked meta-Substituted Benzylidenes/Benzyls as Biologically Significant New Chemical Entities

meta-Linked thiazolidinedione (TZD)– and diethyl malonate (DEM)–based benzylidenes and methyl acetoacetate (MAA)–based benzyl moieties linked to the 2-position of N-methyl benzimidazole were synthesized. TZD- and DEM-based compounds were synthesized by condensation of 2,4-thiazolidinedone and DEM respectively with the corresponding 3-substituted benzaldehyde, whereas MAA-based compounds were obtained by halogen displacement with the corresponding 3-substituted phenol. These new chemical entities were designed to provide a balanced agonism at the peroxisome proliferator activated receptor alpha/gamma (PPARα/γ) in the management of type 2 diabetes: a move from glitazones to selective PPARγ modulators (SPPARγMs).

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A phosgene and peroxide-free one-pot tandem synthesis of isatoic anhydrides involving anthranilic acid,Boc anhydride,and 2-chloro-N-methyl pyridinium iodide

A phosgene and peroxide-free approach for the synthesis of isatoic anhydrides has been described. The synthesis involves the carbamate formation with Boc anhydride followed by in situ cyclization to afford the isatoic anhydride. The importance of this synthetic strategy is in the ease of operation, scalability, and preparation from readily available raw materials.     

Thiourea dioxide promoted efficient organocatalytic one-pot synthesis of a library of novel heterocyclic compounds

The utility of thiourea dioxide as an efficient organocatalyst for the library synthesis of novel heterocyclic compounds via one-pot multicomponent coupling reactions is disclosed. Thiourea dioxide is an inexpensive and readily accessible catalyst, resulting in better product yields as compared to the corresponding thiourea as catalyst. Thiourea dioxide is found to be insoluble in various organic solvents and therefore at the end of the reaction products can be separated by extraction with diethyl ether and the recovered catalyst can be used several times with consistent catalytic activity.     

Base-mediated regio- and stereoselective intermolecular addition of alkynes to N-heterocycles

The regio- and stereoselective addition of N-heterocycles to alkynes using KOH is reported. Formation of (Z)-isomers and their conversion to (E)-products were found to be dependent upon time as well as the choice of base. Selective attack of N-heterocycles on a more electrophilic alkynyl carbon was supported by DFT calculations, and the stereochemistry of the products was established by X-ray crystallographic studies and intramolecular cyclization of ortho-haloalkynes in indolo-[2,1-a]isoquinolines.     

Solid-phase extraction combined with headspace single-drop microextraction of chlorophenols as their methyl ethers and analysis by high-performance liquid chromatography-diode array detection

Solid-phase extraction (SPE) of phenol and chlorophenols, their derivatization to methyl ethers, headspace single-drop microextraction (HS-SDME) of methyl ethers using 1-butanol as extraction solvent, and direct transfer of the drop into the injector for high performance liquid chromatography with diode array detection (HPLC-DAD) have been reported. A flanged-end polytetrafluoroethylene sleeve, 3 mm × 0.5 mm, placed at the tip of the syringe needle, allowed the use of 10 μL solvent drop for extraction. The procedure has been optimized for variables involved in SPE and HS-SDME. A rectilinear relationship was obtained between the amount of chlorophenols and peak area ratio of their methyl ethers/internal standard (4-methoxyacetophenone) in the range 0.01-10 mg L⁻¹, correlation coefficient in the range 0.9956-0.9996, and limit of detection in the range 1.5-3.9 μg L⁻¹ when HS-SDME alone was used for sample preparation. When using coupled SPE and HS-SDME, the linear range obtained was 0.1-500 μg L⁻¹, correlation coefficient in the range 0.9974-0.9998, and the limit of detection in the range 0.04-0.08 μg L⁻¹. Spiked real samples have been analyzed with adequate accuracy, and application of the method has been demonstrated for the analysis of chlorophenols formed upon bamboo pulp bleaching.     

Bifurcations and chaos in large-Prandtl number Rayleigh–Bénard convection

Rayleigh–Bénard convection with large-Prandtl number (P) is studied using a low-dimensional model constructed with the energetic modes of pseudospectral direct numerical simulations. A detailed bifurcation analysis of the non-linear response has been carried out for water at room temperature (P=6.8) as the working fluid. This analysis reveals a rich instability and chaos picture: steady rolls, time-periodicity, quasiperiodicity, phase locking, chaos, and crisis. Our low-dimensional model captures the reappearance of ordered states after chaos, as previously observed in experiments and simulations. We also observe multiple coexisting attractors consistent with previous experimental observations for a range of parameter values. The route to chaos in the model occurs through quasiperiodicity and phase locking, and attractor-merging crisis. Flow patterns spatially moving along the periodic direction have also been observed in our model.     

Cold gas dual-bell tests in high-altitude simulation chamber

An experimental investigation has been carried out to study dual-bell transition behavior in different set ups inside a high-altitude test facility. Cold gas tests were carried out under two different operating conditions namely (i) test nozzle operating in self-evacuation mode and, (ii) test nozzle operating with an additional ejector nozzle (pre-evacuated condition). Although forward transition nozzle pressure ratio does not show any change in its value irrespective of the type of test facility and test set up, the re-transition nozzle pressure ratio shows a significant increase (7–8%) in its value when tested in the high-altitude facility. The latter is caused due to plume blowback effect which dominates during shut down transients in such facilities. Driven by the high atmospheric pressure, the jet exhaust is pushed backwards into the altitude chamber causing the re-transition to occur earlier than that observed in sea-level tests. Further the reduced mass flow rates for nozzle operation in different test set ups in a high-altitude test facility also reduces the magnitude of side-load peaks during the dual-bell transitions.     

Onset of hydrogen bonded collective network of water in 1,4-dioxane

We have studied the evolution of water hydrogen bonded collective network dynamics in mixtures of 1,4-dioxane (Dx) as the mole fraction of water (X(w)) increases from 0.005 to 0.54. The inter- and intramolecular vibrations of water have been observed using terahertz time domain spectroscopy (THz-TDS) in the frequency range 0.4-1.4 THz (13-47 cm(-1)) and Fourier transform infrared (FTIR) spectroscopy in the far-infrared (30-650 cm(-1)) and mid-infrared (3000-3700 cm(-1)) regions. These results have been correlated with the reactivity of water in these mixtures as determined by kinetic studies of the solvolysis reaction of benzoyl chloride (BzCl). Our studies show an onset of intermolecular hydrogen bonded water network dynamics beyond X(w) ≥ 0.1. At the same concentration, we observe a rapid increase of the rate constant of solvolysis of BzCl in water-Dx mixtures. Our results establish a correlation between the onset of collective hydrogen bonded network with the solvation dynamics and the activity of clustered water.