Nucleophilic acylation of α-haloketones with aldehydes: an umpolung strategy for the synthesis of 1,3-diketones

The first example of N-heterocyclic carbene (NHC)-promoted intermolecular acylation of α-haloketones with aldehydes and α,β-unsaturated aldehydes (enals) is reported. The protocol involves carbonyl umpolung reactivity of aldehydes and enals in which the carbonyl carbon attacks nucleophilically on electrophilic terminal of α-haloketones to afford 1,3-diketones and α,β-unsaturated 1,3-diketones, respectively. Short reaction time, ambient temperature, operational simplicity, and high yields are the salient features of the present procedure.     

BF3·OEt2-catalyzed tandem Prins Friedel-Crafts reaction: a novel synthesis of sugar fused diarylhexahydro-2H-furo[3,2-b]pyrans

d-Glucose based homoallylic alcohol reacts smoothly with various aldehydes in the presence of arenes and a catalytic amount of BF₃·OEt₂ under mild conditions to afford a novel series of 5,7-diaryl-hexahydro-2H-furo[3,2-b]pyrans in good yields with high cis-selectivity.     

Reductive Cleavage of Phthalides with Iodotrimethylsilane

A convenient reductive cleavage of 3-arylphthalides 1 into corresponding 2-benzylbenzoic acids and 2-(2-thienylmethyl)benzoic acid 2 by using iodotrimethyisilane is described.     

Total Synthesis of Aculeatins A and B from L‐Malic Acid

An efficient total synthesis of the cytotoxic spiroketal natural products aculeatin A and B is described. The synthesis of the 1,3,5‐triol moiety with appropriate configuration was accomplished from the commercially available L ‐malic acid. The key steps in this synthesis are the Barbier allylation, LiAlH₄/LiI‐mediated syn‐stereoselective 1,3‐asymmetric reduction, and phenyliodine bis(trifluoroacetate) (=[bis(trifluoroacetoxy)iodo]benzene; PIFA) mediated oxidative spirocyclization.     

Fabrication of double-aperture hololens imaging system: application to mechanics

Duffy suggested the use of double-aperture imaging system for the measurement of in-plane displacement component. In this arrangement, twin apertures are placed symmetrically over the imaging lens. This imaging system is used in speckle metrology to measure component of displacement parallel to the line joining the two apertures. The imaging lens used in such configuration need not be diffraction limited over the entire lens aperture, but only over the two small areas encompassed by the two apertures. In present work, compact holographic lenses have been used to generate the two apertures of Duffy's double-aperture interferometer. This imaging system has been used in speckle metrology to measure crack mouth opening displacement (CMOD) in an aluminium beam specimen having central edge crack subjected to three point bending. Experimental results are in good agreement with theoretical predictions. Present experimental investigation reveals that compact holographic lenses can be used advantageously to generate apertures of double-aperture speckle interferometer for its use in the measurement of in-plane displacement component.     

微极热弹性无限板的轴对称自由振动

研究了在应力自由和刚性固定边界条件下,无能量耗散的均匀、各向同性微极热弹性无限板的轴对称自由振动波的传播,导出了相应的对称和斜对称模态波传播的闭合式特征方程和不同区域的特征方程.对短波的情况,应力自由热绝缘和等温板中对称和斜对称模态波传播的特征方程退化为Rayleigh表面波频率方程.根据导出的特征方程得到了热弹性、微极弹性和弹性板的结果.在对称和斜对称运动中计算了板的位移分量幅值、微转动幅值和温度分布,给出了对称和斜对称模式的频散曲线,并示出了位移分量和微转动幅值和温度分布的曲线.能够发现理论分析和数值结论是非常一致的.     

Investigation of the Thermal Properties of Alkali Metal Thorium Phosphates and Their Application for the Sorption of Uranyl Ion from Acidic Medium

Thermo physical properties of potassium, rubidium and cesium thorium phosphate compounds were investigated. All compounds were synthesized by conventional solid state method. Formation of orthorhombic AMThP₃O₁₀, tetragonal AM₂Th(PO₄)₂ and monoclinic AMTh₂(PO₄)₃; [AM=K, Rb and Cs] was confirmed using Powder X-ray diffraction (XRD) technique. Structural study of CsThP₃O₁₀ was carried out for the first time from Rietveld refinement of XRD data. Thermal stability of all compounds was established using Thermogravimetric analysis (TGA) technique. When heated at 1673 K for 30 h in air, all the compounds decompose to ThO₂. High temperature X-ray diffraction (HT-XRD) data of the compounds, synthesized during present study, were collected in an inert atmosphere from ambient to 973 K and their thermal expansion coefficients were calculated. These compounds show positive thermal expansion up to 973 K. Molar heat capacities for all phosphates were measured between 300–863 K using Differential Scanning Calorimeter. Alkali metal thorium phosphates, AMThP₃O₁₀ and AMTh₂(PO₄)₃, showed efficient uptake of uranyl ion from aqueous acidic medium predominantly following Langmuir isotherm and Webber Morris intra particle diffusion kinetics.