2-硒代咪唑类化合物催化CO与胺的羰基化反应

首次研究了2-硒代咪唑类化合物催化的一氧化碳对胺的羰基化生成对称脲或噁唑啉-2-酮的反应,目标产物收率中等到良好.与传统的单质硒催化的羰基化反应相比,新催化体系有效避免了有恶臭气味的含硒化合物的产生.     

N-Heterocyclic Carbene-Palladium Complex Catalyzed Oxidative Carbonylation of Amines to Ureas

Palladium carbene shows high efficiency without any promoter on oxidative carbonylation of amines to ureas and a new type of palladium carbene complex containing both an aniline and an NHC ligands was found to be the active species for the reaction.     

手性2-噁唑烷酮的无溶剂合成法

手性2-噁唑烷酮的无溶剂合成法;手性氨基醇;脲;手性噁唑烷酮     

Effect of urea on the structure and functional activity of proteins. Chymotrypsinogen A and α-chymotrypsin

The effect of urea on the structural stability and functional activity of globular proteins,viz., chymotrypsinogen A (ChtG) and -chymotrypsin (Cht), was studied over a wide range of concentrations (0.5–6 rnol L-1), and the existence of two different mechanisms of the action of urea on these proteins was demonstrated. No changes in the spatial structure of ChtG were observed in the concentration range from 0,5 to 3 mol L^–1 (region 1). Differential UV spectroscopy shows tile redistribution of aromatic groups between the inner volume and the outer surface of a protein molecule (protein denaturation) at concentrations >3 mol L^–1 (regionII), In regionI, urea changes the kinetic parameters of enzymatic reactions involving Cht, which is explained on the basis of millimeter spectroscopy data by its action on the structure and nucleophilic reactivity of water.Deceased.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 998–1002, April, 1996.     

Rapid dissolution of cellulose in LiOH/urea and NaOH/urea aqueous solutions

Rapid dissolution of cellulose in LiOH/urea and NaOH/urea aqueous solutions was studied systematically. The dissolution behavior and solubility of cellulose were evaluated by using (13)C NMR, optical microscopy, wide-angle X-ray diffraction (WAXD), FT-IR spectroscopy, DSC, and viscometry. The experiment results revealed that cellulose having viscosity-average molecular weight ((overline) M eta) of 11.4 x 104 and 37.2 x 104 could be dissolved, respectively, in 7% NaOH/12% urea and 4.2% LiOH/12% urea aqueous solutions pre-cooled to -10 degrees C within 2 min, whereas all of them could not be dissolved in KOH/urea aqueous solution. The dissolution power of the solvent systems was in the order of LiOH/urea > NaOH/urea > KOH/urea aqueous solution. The results from DSC and (13)C NMR indicated that LiOH/urea and NaOH/urea aqueous solutions as non-derivatizing solvents broke the intra- and inter-molecular hydrogen bonding of cellulose and prevented the approach toward each other of the cellulose molecules, leading to the good dispersion of cellulose to form an actual solution.     

Copper-catalyzed one-pot process to construct triazole-linked urea derivatives

A new one-pot synthetic methodology has been developed to construct the triazole-linked urea derivatives. In the same step, triazole forms from azide and alkyne via click reaction and urea forms from addition reaction of amines and isocyanates. The notable features of this work include wide substrate scope, atom economy, environmental friendliness, and easily accessible starting materials. The preliminary biological screening of synthesized compounds show promising cytotoxic activity in basal cell carcinoma (BCC) cell lines.     

尿素溶液法合成纳米AlN粉体

以尿素为固体氮源,甲醇为溶剂,AlCl3·6H2O为铝源,采用尿素溶液法制备了纳米AlN粉体.采用FT-IR对前驱盐进行了结构分析,并通过XRD和SEM分别对最终煅烧产物进行了结构和形貌的表征.重点研究了尿素/金属摩尔比R值和煅烧温度对合成产物的晶体结构和形貌的影响.结果发现: AlN的纯度随R值的增加而增大,R值大于6可以获得单一AlN相,R值小于6获得AlN和Al2O3的混合相;此外,R值也直接影响到AlN纳米粉体和团聚颗粒的形貌,所制备AlN纳米粉体的粒径和团聚的球状颗粒的粒径随R值的增加出现细化的趋势.     

Raman microspectrometric investigationof urea in calcite and gypsum powder matrices

Raman microspectrometry was used for the nondestructive detection of urea in artificially prepared mineral matrices. Various concentrations of urea, a possible biomarker, mixed with calcite and gypsum powders were analyzed using the 514.5‐nm line of an argon laser. Two types of measurements were carried out: direct measurements of powders and analysis of the same mixtures through natural, transparent crystals of calcite and gypsum. The detection limit for urea in artificial powder mixtures was 1 wt% for both calcite and gypsum. In the case of measurements through the monocrystals, the detection limit was between 1 and 5 wt% for calcite and slightly above 5 wt% in the case of gypsum. Copyright © 2010 John Wiley & Sons, Ltd.     

Mass spectrometric study of oligourea macrocycles and their anion binding behavior

Two series, one of tris‐urea macrocycles and another of hexakis‐urea macrocycles, are examined by (tandem) Fourier‐transform ion cyclotron resonance (FTICR) mass spectrometry with respect to their fragmentation patterns and anion binding properties. All macrocycles are based on two different building blocks, one of which is a very rigid xanthene unit and the other one is a more flexible diphenyl ether. The composition and the sequence of these units thus determine their flexibility. During the fragmentation of deprotonated oligourea macrocycles in the gas phase, one urea N? CO bond is cleaved followed by a scrambling reaction within the macrocycle structure. Consequently, fragments are observed that deviate from those that would be expected from the sequence of the subunits. Interesting anion binding properties involve the simultaneous recognition of two chloride anions by one of the hexakis‐urea macrocycles, whose flexibility allows this host to form a double‐helical structure. Flexibility also determines which of the hexameric receptors bears a high sulfate affinity. The interaction energy between some of the macrocycles and sulfate is high enough to even stabilize the intrinsically unstable sulfate dianion. Copyright © 2009 John Wiley & Sons, Ltd.