Efficient catalyst-free synthesis of diversified bis (spirooxindoles) via one-pot,three-component reaction

A catalyst-free, one-pot synthesis of bis-spirooxindoles has been carried out by a three-component reaction of bis-isatins, malononitrile, and various cyclic enolizable carbonyl compounds in ethylene glycol at 100?°C. The protocol provides an easy and simple route for the synthesis of such complex compounds, in short reaction times and high yields. No chromatographic techniques have been employed for the purification of the compounds.     

Organotellurium Ligands & Their Metal Complexes: Recent Developments

Abstract

The ligand chemistry of telluroethers, halotellurium ligands, and polytellurides has received good attention in the last decade. Tellurium-containing species have been used to design clusters. In the recent past the ligation of di and tri-telluroethers (including bis(4-methoxyphenyltelluro)methane) has been studied. Hybrid organotellurium ligands, N-[2-(4-methoxyphenyltelluro)propyl]phthalimid (L ¹ ), 2-(4-ethoxyphenyltelluromethyl)-tetrahydro-2H-pyran (L ² ), 2-(2-{4-ethoxyphenyl} telluroethyl)-1,3-dioxane (L ³ ), N-{2-(4-methoxyphenyltelluro)ethyl}morpholine (L ⁴ ), N-{2-(4-methoxyphenyltelluro)ethyl}-pyrrolidine (L ⁵ ), bis{2-(pyrrolidine-N-yl)ethyl}telluride (L ⁶ ), 1-(4-methoxyphenyltelluro)-2-[3-(6-methyl-2-pyridyl) propoxy]ethane (L ⁷ ), and 2-[2-(4-methoxyphenyltelluro)ethyl]thiophene (L ⁸ ) have been designed recently and studied for their complexation reactions. The (Te, N) and (N, Te, N) ligands, L ⁵ and L ⁶ , coordinate with Hg(II) through Te and N both, but the bonding with N is some what weak. The morpholine nitrogen of L ⁴ does not coordinate with Pd(II) or Pt(II) along with Te. The L ⁷ behaving as a (Te, N) ligand has formed 20-membered metallomacrocycle ring with Pt(II). Tellurated Schiff bases 4-MeOC₆H₄TeCH₂CH₂N═C(CH₃)C₆H₄-2-OH (L ⁹ ) and 2-HO-C₆H₄-(CH₃)C═NCH₂CH₂TeCH₂CH₂N═C(CH₃)C₆H₄-2-OH (L ¹⁰ ) and their reduction products 4-MeOC₆H₄TeCH₂CH₂NHCH(CH₃)C₆H₄-2-OH (L ¹¹ ) and 2-HO-C₆H₄-(CH₃)CHNHCH₂CH₂TeCH₂CH₂NHCH(CH₃)C₆H₄-2-OH (L ¹² ) respectively have been synthesized and studied for ligation behaviour. The L ⁹ on reaction with the [Ru(p-cymene)Cl₂]₂ results in [Ru(p-cymene)(4-MeOC₆H₄TeCH₂CH₂NH₂)Cl]Cl · H₂O whereas in the reaction of L ¹⁰ with [Ru(p-cymene) Cl₂]₂, p-cymene ligand is lost resulting in [RuCl(L ¹⁰ -H)]. The recent developments, particularly designing of L ¹ to L ¹² and their ligand chemistry, are reviewed in the present paper.     

A Natural Isolate Producing Shikimic Acid: Isolation, Identification, and Culture Condition Optimization

Shikimic acid has wide use in pharmaceuticals due to its application in the synthesis of drug Tamiflu used in the treatment of Swine flu. The high cost and limited availability of shikimic acid isolated from plants has impeded the use of this valuable building block of the drug. In this context, fermentation route to produce shikimic acid from renewable resources has become increasingly attractive. The present study was embarked upon isolation of wild-type microorganisms able to produce shikimic acid. Out of the 42 isolates obtained from the soil, isolate GR-21 was selected as the best with initial production of 0.54 g/L shikimic acid and later identified as Citrobacter sp. The process optimization resulted in 14-fold increase in the shikimic acid production, thereby claiming this process to be a sustainable alternative for the production of this important biomolecule. The process was further scaled up to 14 L bioreactor to validate the production of shikimic acid. Further, the product formed is shikimic acid was confirmed by FTIR analysis. The current studies suggest that the selected isolate could be used as a promising agent to fulfill the worldwide demand of shikimic acid.     

Electrochemical sensing for the detection of 2,4-dichlorophenoxy acetic acid using molecularly imprinted polymer membrane

Molecularly imprinted polymer (MIP) membranes were used to develop highly sensitive chemical sensors for the detection of herbicide 2,4-dichlorophenoxy acetic acid (2,4-d). The 2,4-d imprinted composite MIP membranes were prepared, and the characterization was done by UV-VIS spectrophotometer, Fourier transform infrared spectroscopy, and scanning electron microscopy, and the same were fitted in a new electrochemical sensor model. Membrane electroconductivity measurements were performed by applying a small-amplitude alternating voltage (20 mV) with a varying frequency from 20 Hz to 80 kHz generated by a low-frequency wave form generator. The measured changes in the membrane ionic/electric conductivity as a function of 2,4-d concentration was allowed to evaluate the recognition properties of the prepared membrane. This sensor is useful in detecting 2,4-d herbicide having concentration range 10^-3 M to 10^-6 M. The cross-selectivity of the sensor, reproducibility of results, and reusability of MIP membrane were examined and found remarkable and recommendable.     

Study of intermixing and Zr-silicide formation using swift heavy ion irradiation

Swift heavy ion (SHI) beam induced irradiation is an established technique for investigating structural modifications in thin films depending on the S _e sensitivity of material. Intermixing due to 120 MeV Au ion irradiation at different fluences from 10¹² to 10¹⁴ ions/cm² has been reported as a function of ion fluence in a-Si/Zr/a-Si thin films on Si substrate. The samples are characterized before (pristine) and after irradiation using Grazing Incident X-ray Diffraction (GIXRD) and Rutherford Backscattering Spectroscopy (RBS), which confirm the formation of ZrSi at thin film interface. It is suggested that mixing is mainly due to electronic energy loss since the energy transferred from high energy ions seems to create a transient molten zone along the ion track. It is found that the interface mixing increases linearly with the increase in ion fluence. The mixing effect explained in the framework of Thermal spike model. The irradiation effect on the surface roughness of the system is measured using Atomic Force Microscopy (AFM) technique. The current conduction mechanism and Schottky barrier height are also calculated by taking I–V curves across the Metal/Si junction.     

CuSO4-glucose for in situ generation of controlled Cu(I)-Cu(II) bicatalysts: multicomponent reaction of heterocyclic azine and aldehyde with alkyne, and cycloisomerization toward synthesis of N-fused imidazoles

The catalytic efficiency of mixed Cu(I)-Cu(II) system in situ generated by partial reduction of CuSO(4) with glucose in ethanol (nonanhydrous) under open air has been explored. With this catalysis, the multicomponent cascade reaction of A(3)-coupling of heterocyclic amidine with aldehyde and alkyne, 5-exo-dig cycloisomerization, and prototropic shift has afforded an efficient and eco-friendly synthesis of therapeutically important versatile N-fused imidazoles. Diverse heterocyclic amidines, several of which are known to be poorly reactive, and aldehydes are compatible in this catalytic process.     

The first diastereoselective nitroaziridination of N-tosylaldimines with 1-bromonitroalkanes

The first expeditious nitroaziridination of N-tosylaldimines is reported. The protocol involves operationally simple catalyst-free reaction of N-tosylaldimines, 1-bromonitroalkanes and NaOAc to afford 2-nitro-1-tosylaziridines in excellent yields with high Z-diastereoselectivity in a one-pot procedure under ambient conditions.     

Comprehensive study towards the desulfonylation/desulfinylation of cis-3-functionalized 3-phenylsulfonyl/sulfinyl-β-lactams to access novel cis-3-monosubstituted-β-lactams

An inclusive study towards the stereospecific synthesis of novel cis-3-monosubstituted-β-lactams from cis-3-functionalized 3-phenylsulfonyl/sulfinyl-β-lactams is described. 3-Sulfinyl-β-lactams 5/5? successfully furnished stereospecific cis-3-monosubstituted-β-lactams 6, however 3-sulfonyl-β-lactams 2 failed to give the desulfurized product 6?. The final stereochemical and structural conformations of novel β-lactams were established by single crystal X-ray crystallographic study (5c). The cis configuration of the β-lactams 5/5? and 6 was assigned in relevance to E and C4-H and C3-H and C4-H respectively.     

A synthesis technique of single square loop frequency selective surface at terahertz frequency

In this paper, we have explored and extended the use of frequency selective surface towards the terahertz regime of the electromagnetic spectrum where interesting applications such as imaging, sensing and communication exist. We have discussed a synthesis technique to design the single square loop frequency selective surface (SSLFSS) at 150 and 300 GHz which have found suitable application in the fast analysis and fabrication of the frequency selective surface. Moreover, the analytical results have been supported by the CST Microwave Studio and Ansoft HFSS commercial simulators. We have discussed the angular insensitivity of the SSLFSS at 150 GHz as well as 300 GHz. However, the specific problems arise at terahertz frequencies as compared to the radio and microwave frequencies are the ohmic losses. The proposed analysis has been extended from 100 GHz to 350 GHz to discuss the ohmic and dielectric losses. We have also discussed the other important issues which are very much significant in the terahertz regime of the spectrum such as skin depth and surface roughness.