Efficient Route for the Synthesis of New Dinaphthosulfoxide Aza Crowns Using Ethyleneglycol Under Microwave (MW) Irradiation: Macrocyclization is Preferred to Oligomerization Under MW Irradiation

Abstract

New dinaphthosulfoxide aza crowns were prepared from the corresponding dinaphthosulfoxide diester and diamines under reflux conditions (conventional heating) and microwave (MW) irradiation. These reaction routes were used for the synthesis of a series of aza crowns, such as dinaphthosulfide, dinaphthosulfone, dibenzosulfide, and dibenzosulfoxide. The synthesis of aza crowns under MW irradiation in comparison with conventional heating has several advantages, such as shorter reaction times, simpler reaction conditions, and the use of ecofriendly solvents, higher yields, and regioselectivity. In the MW synthesis, macrocyclization is preferred to oligomerization, and thus, the yields of byproducts are low.

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GRAPHICAL ABSTRACT      

Reaction of Red Phosphorus with Allylbenzene in Superbasic System KOH-DMSO

Abstract

Red phosphorus reacts with allylbenzene in the superbase system KOH-DMSO (130°C, 3 h, Ar) to give a mixture of bis(1-methyl-2-phenylethyl)phosphane (1), bis(1-methyl-2-phenylethyl)phosphane oxide (2), and 1-methyl-2-phenylethylphosphinic acid (3). Secondary phosphane oxide 2 and phosphinic acid 3 have been isolated from this mixture in 35% and 32% yield, respectively. Microwave activation of the reaction (200 W, 30 min) affords secondary phosphane 1 as the main product in 48% yield.

GRAPHICAL ABSTRACT      

Synthesis Optimization of Quaternized Chitosan and its Action as Reducing and Stabilizing Agent for Gold Nanoparticles

The optimal conditions for synthesizing quaternized chitosan (QCS) via microwave irradiation were explored. The microwave temperature, time, power, mole ratio between chitosan and 2,3-epoxypropyltrimethyl ammonium chloride (ETA), volume ratio between isopropanol and water, and pH value of the reaction system were studied to evaluate the effect on the degree of substitution (DS). The structure of QCS was characterized by means of FT-IR, NMR, XPS and XRD. TGA and DTG were used to measure its thermal stability. At last, QCS acted as a reducing and stabilizing agent to greenly synthesize gold nanoparticles without adding any other chemical reagent.     

Demulsification of Solids‐Stabilized Emulsions Under Microwave Radiation

Experimental data are presented to show the influence of solid particles on demulsification. It was found that the solid particles could effectively resist demulsification. Compared with conventional heating, microwave radiation can enhance the demulsification rate by an order of magnitude and increase the demulsification effectiveness. The demulsification effectiveness of the emulsions stabilized by graphite powder can reach 82%–89% in a very short time under microwave radiation, whilst that of the emulsions stabilized by barium sulfate can attain 100% under similar conditions.     

Microwave‐assisted Chemical Reactions

Microwave (MW) radiation has been used in chemical analysis and chemical synthesis. MW heating under controlled conditions offers distinct advantages over conventional heating. The reactions are carried out in environmentally clean and safe solvents and in many cases, reactions can be carried out under solvent‐free conditions. This method of synthesis has grown rapidly and found its use in various sectors. This paper reviews some of the reactions that have been accelerated with higher yields under MW irradiation. The application of MW‐assisted synthesis in the medicinal and pharmaceutical industries will be emphasized.     

Preparation and Characterization of Quaternized Chitosan Under Microwave Irradiation

For the first time, N-(2-hydroxyl) propyl-3-trimethyl ammonium chitosan chloride (HTCC) was prepared through a fast, easy and efficient method with the assistance of microwave irradiation, and the quaternized chitosan was also degraded via the microwave irradiation. A comparative study was performed by using the conventional heating method to prepare HTCC. The structure and property of the quaternized chitosan obtained by these two methods were characterized by GPC, XRD, FTIR, NMR, TG and elemental analysis. It was shown that quaternized chitosan was successfully prepared within 50 min via microwave irradiation method, while a much longer time of 6–7 h was needed with the conventional heating method. The substitutions both occurred on the C2 position of chitosan with the two different methods, and their HTCC products had weight average similar molecular weight (Mw), structure and thermal stability. The HTCC prepared by the microwave irradiation method had a little lower degree of substitution (DS) than those prepared via conventional heating with the same mole ratio (6:1) of the intermediate to chitosan. The degradation study showed that the Mw of HTCC decreased rapidly from 4.6 × 10⁵ to 1.1 × 10⁵ in 1 h under microwave irradiation, while it only decreased from 4.6 × 10⁵ to 2.1 × 10⁵in 1 h through conventional heating degradation. These results revealed that microwave irradiation is a more efficient and environment-friendly way to obtain the water-soluble chitosan derivatives and their degraded products.     

Novel Copolymer of Diisopropyl Fumarate and Benzyl Acrylate Synthesized Under Microwave Energy and Quasielastic Light Scattering Measurements

Microwave assisted free radical copolymerization of diisopropyl fumarate (DIPF) and benzyl acrylate (BzA) with different copolymer compositions was performed using benzoyl peroxide as initiator. The effect of the reaction conditions on the macromolecular characteristics, monomer reactivity ratio and copolymer properties were studied. The monomer conversion and average molecular weights increase with the content of BzA units in the copolymer. The copolymers were characterized by IR, ¹H and ¹³C-NMR spectroscopies and the molecular weights were analyzed with size exclusion chromatography (SEC). The reactivity ratios obtained from an extended Kelen-Tüdös method under microwave irradiations are a factor which is double than those obtained by thermal copolymerization. The product r₁r₂ = 0.152 suggests a preference of both propagating macroradicals toward consecutive homopolymerization. The hydrodynamic and polydispersity size were measured in ethylacetate, tetrahydrofuran and methylethylketone with a quasi-elastic light scattering (QELS) technique showing that the quality of the solvents increases in the order: EA < THF < MEK.     

多孔软硬磁Ni0.5Zn0.5Fe2O4/SrFe12O19复合纤维制备及吸波性能

通过静电纺丝技术制备了多孔软硬磁Ni_0.5Zn_0.5Fe₂O₄/SrFe₁₂O₁₉复合纤维,利用综合热重分析仪（TG-DSC）、X射线衍射仪（XRD）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、X射线能谱仪（EDS）和矢量网络分析仪（VNA）等对复合纤维的晶体结构、微观形貌和电磁性能进行了表征,研究了不同软硬磁质量比对纤维结构和性能的影响。结果表明：900℃下制备的复合纤维具有立体多孔结构,软硬磁质量比为1∶3时,复合纤维的比表面积达到55 m²·g^-1。吸波性能测试结果显示,当吸波剂涂层厚度为3.5 mm时,复合纤维在10.6 GHz处反射损失（R_L）值达到-31.9 dB,在2~18 GHz频率范围内,R_L值小于-10 dB的吸收带宽达到10.5 GHz,覆盖了整个X波段（8.2~12.4 GHz）和Ku波段（12.4~18 GHz）,显示出优异的宽波段吸收性能。     

Multicomponent Domino [4+1+1] Carbocyclization Providing an Efficient and Regioselective Strategy to Fluoren-9-ones

Concise and efficient three‐component domino [4+1+1] carbocyclization to highly substituted fluoren‐9‐one derivatives promoted by K₂CO₃ has been developed under microwave irradiation conditions. The direct bis‐cyanation and aryl amination residing in fluoren‐9‐one framework were achieved in a one‐pot operation. The reaction proceeds at fast rates and can be finished within 30 min, which makes workup convenient to give good to excellent chemical yields.