A One Pot Synthesis of 5-Phenyl-1,3-Dioxane-4,6-Dione Derivatives

A general procedure for synthesis of 5-phenyl-1,3-dioxane-4,6-dione derivatives is described. The synthesis involves the cycloaddition of (α-chlorocarbonyl)phenyl ketene with carbonyl compounds to generate the corresponding substituted 2-oxetanone's which is readily transformed to the final products in one step. The 1,3-dioxane-4,6-dione is a rigid cyclic structure, and can undergo easy hydrolysis.     

Preparation of Aminovinyl Phosphonates by Four-Component Aminoalkylation of Aldehydes Mediated by Lithium Perchlorate

Several aminovinyl phosphonates were prepared in good yield by four-component aminoalkylation of aldehydes with diethyl(trimethylsilyl)amine, triethylphosphite and dimethyl acetylenedicarboxylate mediated by a 5 molar solution of lithium perchlorate in diethyl ether.     

Numerical investigation of cone angle effect on the flow field and separation efficiency of deoiling hydrocyclones

In this study, the effect of cone angle on the flow field and separation efficiency of deoiling hydrocyclones is investigated taking advantage of large eddy simulation. The dynamic Smagorinsky is employed to determine the residual stress tensor of the continuous phase. The method of Lagrangian particle tracking with an optimized search algorithm (closest cell) is applied to evaluate the separation efficiency of deoiling hydrocyclone. Simulations are performed on a 35-mm deoiling hydrocyclone with the three different cone angles of 6, 10 and 20 degree. The numerical results revealed that the changes in the cone angle would affect the velocity and pressure distribution inside hydrocyclone, and lead to changes in the separation efficiency. However, the large cone angle increases the tangential velocity and pressure gradient inside the hydrocyclone, but reduces the separation efficiency. The reasons behind the decrease in the separation efficiency are the flow structure and reduction of oil droplets residence time in hydrocyclones with large cone angles.     

Photothermal deflection spectroscopy PDS investigation of optical and thermal properties of BGaAs/GaAs alloys

Optical and thermal properties of metal organic chemical vapor deposition (MOCVD) grown BGaAs/GaAs alloys with boron composition of 3% and 8% are investigated by photothermal deflection spectroscopy (PDS). The band gap energy, absorption spectrum and thermal conductivities are evaluated by comparing the experimental and the theoretical PDS signals amplitude and phase. The boron effects in these parameters have been shown. In fact, it was found that gap energy and thermal conductivity of BGaAs/GaAs alloys with 3% of boron are respectivelly 1376 mev and 4.7 W/m K, these values decrease to 1360 mev and 3.5 W/m K for 8% of boron composition.     

Non-trivial extension of the (1+2)-Poincaré algebra and conformal invariance on the boundary of {\mathrm{AdS}}_3

Using recent results on strings on AdS$_3\times N^d$, where N is a d dimensional compact manifold, we re-examine the derivation of the non-trivial extension of the (1+2)-dimensional-Poincaré algebra obtained by Rausch de Traubenberg and Slupinsky. We show by explicit computation that this new extension is a special kind of fractional supersymmetric algebra which may be derived from the deformation of the conformal structure living on the boundary of AdS. The two so(1,2) Lorentz modules of spin used in building of the generalization of the (1+2) Poincaré algebra are re-interpreted in our analysis as highest weight representations of the left and right Virasoro symmetries on the boundary of AdS. We also complete known results on 2d-fractional supersymmetry by using spectral flow of affine Kac–Moody and superconformal symmetries. Finally we make preliminary comments on the trick of introducing Fth roots of g-modules to generalize the so(1,2) result to higher rank Lie algebras g. Received: 20 July 2000 / Published online: 19 September 2001     

Oxidative conversion of amines into benzoxazoles using hydrogen transfer catalysis

Benzoxazoles are synthesised directly by oxidative condensation of primary and secondary amines with o-aminophenols under hydrogen transfer catalysis. The optimal system utilises 1 mol % of the Shvo catalyst, with dimethoxybenzoquinone as the hydrogen-accepting terminal oxidant.     

Microwave Promoted Reductive Coupling of Carbonyl Compounds to Bis(Trimethylsilyl) Pinacols Under Solvent-Free Conditions

Reductive coupling of carbonyl compounds was performed with trimethylchlorosilane (TMS-Cl) on montmorillonite K10 clay in conventional microwave oven in short time wih quantitative yields of bis(trimethylsilyl) pinacols.     

Three‐Component One‐Pot Synthesis of 4‐Aryl‐2,3‐dihydropyrimido[1,2‐a]benzimidazol‐2‐ones Catalyzed by l‐Proline

An efficient chemoselective synthesis of 4‐aryl‐2,3‐dihydropyrimido[1,2‐a]benzimidazol‐2‐one derivatives from three‐component reactions of 2‐aminobenzimidazole, Meldrum's acid, and aldehydes via [3+3] atom combination is described. The reaction occurs in different conditions such as in DMF as solvent at reflux and in the presence of l ‐proline as base catalyst.     

Highly chemoselective reductive amination by one pot reaction of aldehydes, amines and Dihydropyridine Catalyzed by TMSCl

More efficient, cost effective and metal free DHP/TMSCl system for one pot reductive amination of aldehydes was developed. The method allows the efficient one pot synthesis of structurally diverse amines with Hantzsch ester as the hydrogen source in the presence of trimethylsilyl chloride as a catalyst in high to quantitative yields under mild conditions.     

Growth conditions effects on optical properties of InAs quantum dots grown by molecular beam epitaxy on GaAs (1 1 3)A substrate

We have investigated the optical properties of InAs/GaAs (1 1 3)A quantum dots grown by molecular beam epitaxy (MBE) with different growth rates by photoluminescence spectroscopy (PL) as a function of the excitation density and the sample temperature (10–300 K). Reflection high-energy electron diffraction (RHEED) is used to investigate the formation process of InAs quantum dots (QDs). A redshift of the InAs QDs PL band emission was observed when the growth rate was increased. This result was explained by the increase of the InAs quantum dot size with increasing growth rate. A significant redshift was observed when the arsenic flux was decreased. The evolution of the PL peak energy with increasing temperature has showed an S-shaped form due to the localization effects and is attributed to the efficient relaxation process of carriers in different InAs quantum dots and to the exciton transfer localized at the wetting layer.