Reversed‐Polarity Synthesis of Diaryl Ketones through Palladium‐Catalyzed Direct Arylation of 2‐Aryl‐1,3‐dithianes

An umpolung approach to the synthesis of diaryl ketones has been developed based on in situ generation of acyl anion equivalents and their catalytic arylation. This method entails the base‐promoted, palladium‐catalyzed direct C‐H arylation of 2‐aryl‐1,3‐dithianes with aryl bromides. Use of MN(SiMe₃)₂ (M=Li, Na) base results in reversible deprotonation of the weakly acidic dithiane. In the presence of a Pd(NiXantphos)‐based catalyst and aryl bromide, cross‐coupling of the metallated 2‐aryl‐1,3‐dithiane takes place under mild conditions (2 h at rt) with yields as high as 96 %. The resulting 2,2‐diaryl‐1,3‐dithianes were converted into diaryl ketones by either molecular iodine, N‐bromo succinimide (NBS) or Selectfluor in the presence of water. The dithiane arylation/hydrolysis can be performed in a one‐pot procedure to yield a variety of diaryl ketones in good to excellent yields. This method is suitable for rapid and large‐scale synthesis of diaryl ketones. A one‐pot preparation of anti‐cholesterol drug fenofibrate (TriCor®) has been achieved on 10.0 mmol scale in 86 % yield.

     

粉末冶金法制备Al-SrB_6复合材料（英文）

采用粉末冶金法制备Al-SrB6复合材料。对Al-15Sr/Al-4B混合粉末进行球磨,在球磨过程中Al_4Sr颗粒充分破碎。球磨态铝合金晶粒截面表明Al_4Sr与AlB_2之间不发生反应。混合球磨粉末经高温退火后形成SrB_6。若在700℃进行退火,混合粉末需球磨1h可使SrB_6成为主要相,而若在600℃进行退火,混合粉末则需球磨2h才能使SrB_6成为主要相。提高退火温度和延长球磨时间都可以促进SrB_6相的形成,但后者对Al-SrB_6复合材料的微观组织影响更大。经600℃和700℃退火处理之前,SrB_6颗粒更细小,在铝基体中分布也更均匀。     

Ultrasonic characterization of lactose dissolution

The ultrasonic properties (at 2.25 MHz) of lactose solutions and suspension of lactose crystals (d ∼ 50 μm) were measured as a function of concentration (0–40 wt.%). Ultrasonic velocity increased linearly with concentration regardless of the state of dissolution of the lactose crystals while ultrasonic attenuation was low and concentration-independent when the lactose was dissolved and increased approximately linearly with the concentration of suspended crystals. Therefore the amount of lactose present and the state of dissolution can be determined simultaneously with single ultrasonic sensor. A sensor based on this principle was applied to a stirred tank and used to measure the time taken to mix powdered lactose into a solution and the time for the added lactose to dissolve.     

Numerical and experimental investigation of hydrogen-rich syngas production via biomass gasification

In this work, the relation between hydrogen-rich syngas production and the gasification parameters such as equivalence ratio (ER), gasification temperature and biomass moisture content were studied. Stoichiometric equilibrium model that developed during this study was used to investigate the optimum hydrogen output generated from woody biomass in a fixed bed downdraft gasifier by considering the thermodynamic equilibrium limit. The mathematical model, based on thermodynamic equilibrium is necessary to understand complicated gasification process that will contribute to obtain maximum attainable hydrogen production. The effects of different oxidizing agents on the hydrogen concentration in the product gas as well as the effect of various air-biomass, oxygen-biomass and steam-biomass ratios were investigated. For validation, the results obtained from the mathematical model were compared with the experimental data obtained from the gasifier that uses air as gasification medium. The validated mathematical model was used to represent the gasifier that uses both oxygen and air-steam mixture as the gasification medium and the theoretical results were obtained for both cases. The theoretical results clearly show that the gasification process specially ones that use the air-steam mixture as the gasification medium can be used for hydrogen production.     

A preliminary study on the manufacturing aluminum–potassium feldspar metal matrix composite materials

This study reports the results of a preliminary study of manufacturing aluminum–potassium feldspar metal matrix composites including its castability and mechanical properties. The material was composed considering 0.25 %, 0.5 %, and 0.75 % additive ratios to examine the impact of the amount of potassium feldspar on the material and mechanical properties of the manufactured aluminum metal matrix composite material. Aluminum alloy (A356) was utilized as the matrix of the composition. The composite material was manufactured by the stir casting technique. The modulus of elasticity, yield strength, tensile strength, elongation, density, and quality index of the material parameters was taken into account to determine the materials′ practicality. The preliminary results indicated that potassium feldspar is a promising mineral to be utilized as an additive for aluminum metal matrix composites since it has a positive impact on mechanical properties. By optimizing the casting parameters, the positive aspects of the potassium feldspar may make the material more practical to be utilized in vast engineering applications.