Asymmetric Direct Aldol Reaction of Cyclohexanone Catalyzed by( N'-Benzyl-N'-D-prolyl)-trans-4-hydroxy-L-proline Hydrazide

A new proline catalyst, namely (N′‐benzyl‐N′‐D‐prolyl)‐trans‐4‐hydroxy‐L‐proline hydrazide, has been prepared and proved to be a superior catalyst for the asymmetric aldol reaction of cyclohexanone and aromatic aldehydes, affording up to 98:2 dr and 98% ee.     

The influence of lanthanum doping on the physical and electrical properties of BTV ferroelectric thin films

In this study, the ferroelectricity of as-deposited Bi_3.9La_0.1Ti_2.9V_0.1O₁₂ (BLTV), Bi_3.9Ti_2.9V_0.1O₁₂ (BTV), and Bi₄Ti₃O₁₂ (BIT) thin films was prepared and compared by rf magnetron sputtering technology. For the BLTV, BTV, and BIT thin films deposited on Pt/Ti/SiO₂/Si and SiO₂/Si substrate, the physical and electrical characteristics of lanthanum doped BTV (BLTV) were better than those of BIT and BTV thin films. Regarding the physical properties, the micro-structure of as-deposited BTV and BLTV thin films were obtained and compared by XRD patterns and SEM images. The BLTV and BTV thin films were also exhibited clear the ferroelectricity. The remanent polarization (P _r ) of as-deposited BLTV thin films was 11 μC/cm² as the measured frequency of 100 kHz. It was higher than those of BTV thin films. Finally, the polarization of BLTV thin film capacitor decreased by 9%, while that of the BTV decreased by 15% after the fatigue test with 10⁹ switching cycles.     

Thermal Decomposition Kinetics of Ginkgo biloba Leaves Polyprenol in Nitrogen Atmosphere

The nonisothermal decomposition kinetics of Ginkgo biloba leaves polyprenol (GBP) and cleaved situation of its chemical bond during thermal decomposition process were first investigated using thermogravimetric (TG) and TG‐FTIR technology. The results of thermal decomposition kinetics revealed that the nonisothermal decomposition mechanism of GBP corresponds to first‐order chemical reaction with n = 1, integral form g(a) = –ln(1 – a) and differential form f(a) = 1 – a. TG‐FTIR results demonstrated that absorbance of –CH₃, unsaturated C–H bond, =CH₂, accumulated C=C, –OH, and so on constantly increased with thermal decomposition reaction went on. In addition, storage life of GBP was also evaluated. These data could provide theoretical guidance for purification under high temperature and other thermal application of GBP.     

Hantzsch Ester as a Photosensitizer for the Visible‐Light‐Induced Debromination of Vicinal Dibromo Compounds

The debromination of vicinal dibromo compounds to generate alkenes usually requires harsh reaction conditions and the addition of catalysts. Just recently the visible‐light‐induced debromination of vicinal dibromo compounds emerged as a possible alternative to commonly used methods, but the substrate scope of this reaction is limited and a photocatalyst is necessary for the successful conversion of the starting compounds. A catalyst‐free visible‐light‐induced debromination of vicinal dibromo compounds with a base‐activated Hantzsch ester as photosensitizer is reported. The method has a wide substrate scope and a broad functional‐group compatibility.     

Differentiating parts of Cinnamomum cassia using LC‐qTOF‐MS in conjunction with principal component analysis

Cinnamon bark (Rou Gui in Chinese), cinnamon twig (Gui Zhi) and shaved cinnamon bark (Gui Sin) have been widely used as spices and in traditional Chinese medicine since ancient times. On‐going issues related to quality and authenticity necessitate the development of analytical methods capable of providing an objective evaluation of samples. In this study, chemical fingerprints of cinnamon bark, cinnamon twigs and shaved cinnamon bark were established using liquid chromatography quadruple time‐of‐flight mass spectrometry in conjunction with principal component analysis (PCA). From 125 samples of cinnamon, we identified the following eight compounds and their the detection ratios: coumarin, cinnamaldehyde, cinnamyl alcohol, cinnamic acid, 2‐hydroxycinnamaldehyde, 2‐hydroxycinnamic acid, 2‐methoxycinnamaldehyde and 4‐methoxycinnamaldehyde. Of these, 4‐methoxycinnamaldehyde presented the largest variations in detection ratio, making up 64.0, 97.4 and 50.0% in cinnamon bark, cinnamon twig, and shaved cinnamon bark, respectively. The quantities of cinnamyl alcohol, coumarin and cinnamaldehyde also varied between the three parts of the plant. Chemical fingerprints of the three cinnamon samples were established using principal component analysis, the results of which indicate that cinnamon bark and shaved cinnamon bark could be easily differentiated, despite a marked similarity in outward appearance. Cinnamon twig was also shown to depart from the other clusters. The proposed method provides a fast and efficient means of identifying cinnamon herbs for quality control purposes. Copyright © 2016 John Wiley & Sons, Ltd.     

Research on the defect structure and g factors for the tetragonal (CrO4)3− impurity center in ZrSiO4: Cr5+ crystal

ABSTRACT

The EPR g factors g// and g⊥ for the tetragonal (CrO₄)^3? impurity center in ZrSiO4: Cr⁵⁺ crystal are studied from the high-order perturbation formulas based on the two-mechanism (the crystal field and charge-transfer mechanisms) model. The studies indicate that differing from the tetragonally-elongated host (SiO4)^4- tetrahedron, the dominant defect structure of the substitutional (CrO₄)^3? tetrahedron is tetragonally- compressed with the ground state |d_z² due to the Jahn-Teller distortion. Furthermore, the agreement of g factors between calculation and experiment requires a small admixture of the first excited state |d_x²_?y² to the ground state |d_z² due to the vibrational motion of ligands, which leads a compressed (CrO₄)^3? tetrahedron to become a twinkling elongated one, These results are discussed.