Catalytic Method for Synthesis of Aspirin by a Green,Efficient and Recyclable Solid Acid Catalyst (Preyssler's Anion) at Room Temperature

Synthesis of aspirin at room temperature via O‐acetylation of salicylic acid in the presence of Preyssler type heteropolyacids has been investigated in order to contribute toward clean technology, which is the most important need of the society. All of the catalysts are recyclable and reusable.     

Acid induced reactions of a sydnone ketoxime

3-(2-Acetylphenyl)sydnone oxime 1a reacts with acids (methanesulfonic-, p-toluenesulfonic, trifluoroacetic-acid or Amberlite IR 118) to give products apparently derived from protonation of the oxime oxygen or nitrogen atom followed by cyclization to the sydnone ring or interception by water.     

A robust-adaptive fuzzy coverage control for robotic swarms

In this paper, a decentralized adaptive control scheme for multi-robot coverage is proposed. This control method is designed based on centroidal Voronoi configuration integrated with robust adaptive fuzzy control techniques. We consider simple single integrator mobile robots used for covering dynamical environments, where an adaptive fuzzy logic system is used to approximate the unknown parts of control law. A robust coverage criterion is used to attenuate the adaptive fuzzy approximation error and measurement noises to a prescribed level. Therefore, the robots motion is forced to obey solutions of a coverage optimization problem. The advantages of the proposed controller can be listed as robustness to external disturbances, computation uncertainties, and measurement noises, while applicability on dynamical environments. A Lyapunov-function based proof is given of robust stability, i.e. convergence to the optimal positions with bounded error. Finally, simulation results are demonstrated for a swarm coverage problem simultaneous with tracking mobile intruders.     

The Activation of Imines to Nucleophilic Attack by Grignard Reagents

The reaction of trimethylsilyl trifluoromethanesulfonate (trimethylsilyl triflate, TMSOTf) with imines leads to the formation of N-trimethylsilyliminium salts which react efficiently with soft nucleophiles to form secondary amines.     

Use of nanoporous Na+-montmorillonite sulfonic acid (SANM) as an eco-benign, efficient and reusable solid acid catalyst for the one-pot synthesis of 14-aryl-14-H-dibenzo[a,j]xanthenes and 1,8-dioxo-dodecahydroxanthene derivatives

Nanoporous Na⁺-montmorillonite sulfonic acid was found to be an efficient and green catalyst for the synthesis of various 14-aryl-14H-dibenzo[a,j]xanthenes and 1,8-dioxo-dodecahydroxanthene derivatives by the reaction of aldehydes with 2-naphthol and 1,3-cyclohexanedione, respectively. This novel synthetic method has the advantages of high yields, short reaction times and recyclability of the catalyst, simplicity and easy workup compared to the conventional methods reported in the literature.     

Preparation of N-Arylated Heterocycles by Nucleophilic Aromatic Substitution

Nucleophilic aromatic substitution of fluorobenzoates and fluorophenylnitriles with weakly basic heterocycles readily occur. This synthetic methodology is utillized to produce potent angiotensin-II antagonists.     

AN EASY CONVERSION OF THE BAYLIS-HILLMAN ADDUCTS INTO tert-BUTYLDIMETHYLSILYL ETHERS WITH tert-BUTYLDIMETHYLSILYL CHLORIDE AND Li2S

The hydroxy group of the Baylis-Hillman adducts is protected with the t-butyldimethylsilyl (TBDMS) group using the reaction of adducts 1a–h with tert-butyldimethylsilyl chloride (TBDMSCl) in the presence of lithium sulfide under nearly acidic reaction conditions.     

Facile and Efficient Method for the Synthesis of 14-Substituted-14-H-dibenzo[a,j]xanthenes Catalyzed by Ruthenium Chloride Hydrate as a Homogeneous Catalyst

Synthesis of dibenzoxanthenes through condensation of β-naphthol with various aromatic and aliphatic aldehydes in ethanol as an ecofriendly solvent using Ru^III as catalyst is reported.

High Na+ Mobility in rGO Wrapped High Aspect Ratio 1D SbSe Nano Structure Renders Better Electrochemical Na+ Battery Performance

We chose to understand the cyclic instability and rate instability issues in the promising class of Na⁺ conversion and alloying anodes with Sb₂Se₃ as a typical example. We employ a synthetic strategy that ensures efficient rGO (reduced graphene oxide) wrapping over Sb₂Se₃ material. By utilization of the minimum weight of additive (5 wt.% of rGO), we achieved a commendable performance with a reversible capacity of 550 mAh g⁻¹ at a specific current of 100 mA g⁻¹ and an impressive rate performance with 100 % capacity retention after high current cycling involving a 2 Ag⁻¹ intermediate current step. The electrochemical galvanostatic intermittent titration technique (GITT) has been employed for the first time to draw a rationale between the enhanced performance and the increased mobility in the rGO wrapped composite (Sb₂Se₃-rGO) compared to bare Sb₂Se₃. GITT analysis reveals higher Na⁺ diffusion coefficients (approx. 30 fold higher) in the case of Sb₂Se₃-rGO as compared to bare Sb₂Se₃ throughout the operating voltage window. For Sb₂Se₃-rGO the diffusion coefficients in the range of 8.0×10⁻¹⁵ cm² s⁻¹ to 2.2×10⁻¹² cm² s⁻¹ were observed, while in case of bare Sb₂Se₃ the diffusion coefficients in the range of 1.6×10⁻¹⁵ cm² s⁻¹ to 9.4×10⁻¹⁵ cm² s⁻¹ were observed.     

A bis-bithiophene from Tridax procumbens L. (Asteraceae)

The ethyl acetate soluble part of hexane extract of Tridax procumbens yielded a new bis-bithiophene named tridbisbithiophene along with four known terpenoids: taraxasteryl acetate, beta-amyrenone, lupeol and oleanolic acid, which have never been reported so far from Tridax procumbens. The structures of all the isolated constituents were elucidated with the aid of 1D-NMR spectroscopy whereas, the structure of new constituent tridbisbithiophene was confirmed via COSY and HMBC interactions.