Selective synthesis of carbon monoxide via formates in reverse water–gas shift reaction over alumina-supported gold catalyst

Thermal decomposition of formic acid on SiO_2, CeO_2 and γ-Al_2O_3 was studied as an elementary step of reverse water–gas shit reaction(RWGS) over supported Au catalysts. γ-Al_2O_3 showed the highest CO selectivity among the tested oxides in the decomposition of formic acid. Infrared spectroscopy showed the formation of four formate species on γ-Al_2O_3: three η~1-type and one μ~2-type species, and these formates decomposed to CO at 473 K or higher. Au-loaded γ-Al_2O_3 samples were prepared by a depositionprecipitation method and used as catalysts for RWGS. The supported Au catalyst gave CO with high selectivity over 99% from CO_2 and H_2, which is attributed to the formation of formates on Au and subsequent decomposition to CO on γ-Al_2O_3.     

Synthesis of Sulfur/Selenium-containing Polyester with Recyclability and Controllable Hydrophilicity and Glass Transition Temperature

We present a ring-opening polymerization of bridged cyclic lactone utilizing alcohol as the initiator and organic base as the catalyst.Bridged γ-butyrolactone monomers(PhSGBL and PhSeGBL) were synthesized efficiently from commercially available 3-cyclohexene-1-carboxylic acid. Due to the ring strain of the bridged structure, ring-opening polymerization of this type of γ-butyrolactone derivative was successfully carried out under mild conditions, e.g., using ethylene glycol as the initiator and a...     

Al2O3基Ni-Cu双金属催化剂上乙酰丙酸氢解（英）

Inexpensive γ-alumina-based nickel-copper bimetallic catalysts were studied for the hydrogenolysis of levulinic acid,a key platform molecule for biomass conversion to biofuels and other valued chemicals,into γ-valerolactone as a first step towards the production of 2-methyltetrahydrofurane.The activities of both monometallic and bimetallic catalysts were tested.Their textural and chemical characteristics were determined by nitrogen physisorption,elemental analysis,temperature-programmed ammonia desorption,and temperature-programmed reduction.The monometallic nickel catalyst showed high activity but the highest bγ-product production and significant amounts of carbon deposited on the catalyst surface.The copper monometallic catalyst showed the lowest activity but the lowest carbon deposition.The incorporation of the two metals generated a bimetallic catalyst that displayed a similar activity to that of the Ni monometallic catalyst and significantly low bγ-product and carbon contents,indicating the occurrence of important synergetic effects.The influence of the preparation method was also examined by studying impregnated- and sol-gel-derived bimetallic catalysts.A strong dependency on the preparation procedure and calcination temperature was observed.The highest activity per metal atom was achieved using the sol-gel-derived catalyst that was calcined at 450 ℃.High reaction rates were achieved;the total levulinic acid conversion was obtained in less than 2 h of reaction time,yielding up to 96%γ-valerolactone,at operating temperature and pressure of 250 ℃ and 6.5 MPa hydrogen,respectively.     

Al_2O_3基Ni-Cu双金属催化剂上乙酰丙酸氢解(英)

Inexpensive γ-alumina-based nickel-copper bimetallic catalysts were studied for the hydrogenolysis of levulinic acid,a key platform molecule for biomass conversion to biofuels and other valued chemicals,into γ-valerolactone as a first step towards the production of 2-methyltetrahydrofurane.The activities of both monometallic and bimetallic catalysts were tested.Their textural and chemical characteristics were determined by nitrogen physisorption,elemental analysis,temperature-programmed ammonia desorption,and temperature-programmed reduction.The monometallic nickel catalyst showed high activity but the highest bγ-product production and significant amounts of carbon deposited on the catalyst surface.The copper monometallic catalyst showed the lowest activity but the lowest carbon deposition.The incorporation of the two metals generated a bimetallic catalyst that displayed a similar activity to that of the Ni monometallic catalyst and significantly low bγ-product and carbon contents,indicating the occurrence of important synergetic effects.The influence of the preparation method was also examined by studying impregnated- and sol-gel-derived bimetallic catalysts.A strong dependency on the preparation procedure and calcination temperature was observed.The highest activity per metal atom was achieved using the sol-gel-derived catalyst that was calcined at 450 ℃.High reaction rates were achieved;the total levulinic acid conversion was obtained in less than 2 h of reaction time,yielding up to 96%γ-valerolactone,at operating temperature and pressure of 250 ℃ and 6.5 MPa hydrogen,respectively.     

Development of aspartic acid ligation for peptide cyclization derived from serine/threonine ligation

Based on a mechanism analogous to the serine/threonine ligation, the aspartic acid ligation, which is facilitated by the γ-amino alcohol based ligation and oxidation, is developed and applied to the synthesis of cyclic peptides. The γ-hydroxyl group triggers the ring-chain tautomerization via a 6-endo-trig process,while the δ-hydroxyl group facilitates the oxidative cleavage of the vicinal diol to give carboxylic acid.     

Synthesis, Mass Spectrometric Studies, and Biological Evaluation of 3,5-Dimethoxyhomophthalic Acid and Related Compounds

3,5-Dimethoxyhomophthalic acid was synthesized in four steps from 3,5-dimethoxycinnamic acid via a series of reactions including cyclization of 3-(3',5'-dimethoxyphenyl)propionic acid to 5,7-dimethoxy-1-indanone and oxidative decomposition of methyl-2-hydroxy-2-[5,7-dimethyoxy-1-oxo-1H-inden-2(3H)-ylidene]acetate to 3,5-dimethoxyhomophthalic acid.The synthesized compounds were characterized by elemental analysis,IR,1H NMR,and MS.The biological evaluation experiments of 3,5-dimthoxyhomophthalic acid and the related synthesized compounds were also carried out.Naturally occurring biologically active isocoumarins were prepared in a single step by the condensation of the homophthalic acid with appropriate acid chlorides.     

Effects of Zr/Ti molar ratio in SO42-/ZrO2-TiO2 calcined at different temperatures on its surface properties and glucose reactivity in near-critical methanol

Effects of Zr/Ti molar ratio in SO42-/ZrO2-TiO2 solid acid catalyst calcined at different temperatures on its surface properties and catalytic activity were thoroughly investigated in this paper. The physicochemical characteristics of prepared samples were determined by N2 adsorptiondesorption, XRD, NH3-TPD and XPS techniques, respectively. It was found that the crystallization temperature of the samples increased after the combination of ZrO2 and TiO2; and phase transformations from the anatase to the rutile of TiO2 species and the tetragonal to the monoclinic of ZrO2 species were effectively suppressed at higher temperature. The sample with a Zr/Ti molar ratio of 3/1 calcined at 450℃ showed the highest surface area and the most acid sites among all the tested samples. The acid site densities of samples were relatively closed to each other if they were calcined at the same temperature, however, decreased with the calcination temperature. The result indicates that the sulfur content in samples is a crucial factor to control the acid site density. Calcining the sample at 650℃ and higher temperatures resulted in a significant desorption of sulfate ion on the samples. The synthesized samples were evaluated as a potential catalyst for glucose conversion under the near-critical methanol conditions (200℃/4 MPa). The results suggested that the relatively weaker acid sites of the catalyst were more favorable for the accumulation of methyl glucosides, while the moderate acid sites were responsible for the formation of methyl levulinate. The catalytic activity for methyl levulinate production almost increases linearly with the catalyst acid site density. The catalyst deactivation is due to the loss of sulfate ion and the two catalysts with Zr/Ti molar ratios of 3/1 and 1/3 could effectively alleviate the deactivation caused by sulfate solution in the reaction medium and can be reused after calcination with the reuse rate of over 90% in terms of the methyl levulinate selectivity.     

ESR STUDY OF FREE RADICALS IN IRRADIATED POLYAMIDE-1010

Polyamide-1010 samples were irradiated in vacuum at room temperature by Cobalt-60 γ-rays. The free radicals formed in irradiation were studied by means of electron spin resonance (ESR)techniques.The ESRspectra consisted of a quartet and a superimposed singlet which were attributed to radical -CO-NH-CH-CH_2 and -CH_2-C=O, respectively. The effects of temperature and crystaUinity on the radicals were discussed and the mechanism for the production and decay of the radicals was also proposed.     

Studies on Silicon-Containing Fragrance Raw Materials (Ⅳ)——Synthesis of Spiro-Acetals of 5-Trimethylsilylcyclohex- 2- (or 3)enone

Some novel spiro-acetals of 5-trimethylsilylcyclohex-2(or 3)-enone were synthesized from the reaction of silylcyclohexenones with the corresponding a, ω-diols in the presence of oxalic acid or adipic acid.     

Inhibition of Homo-coupling of Arylboronic Acids in Ligand Free Pd（ll）-Catalyzed Suzuki Reaction

A series of solvents were examined for the ligand free Pd（II）-catalyzed Suzuki reaction of 4-bromotoluene with phenylboronic acid. It was found that the PdCl2/i-PrOH system could efficiently inhibit the homo-coupling of phenylboronic acid and give a cross-coupling product in high yields. The substrates with a wide variety of functional groups were tolerated in the system. A possible mechanism for this system was proposed.     

有机酸在γ-Al~2O~3表面自发单层分散及苯甲 酸-γ-Al~2O~3表面结构的研究

有机酸如苯甲酸,水杨酸,邻-或对-苯二甲酸,酒石酸均可在γ-Al~2O~3表面自发单层分散,分散的临界温度取决于有机酸分子中极性基团的数目和极性的强弱。XRD,Raman,FT-IR,UV-vis和TG对苯甲酸-γ-Al~2O~3体系的表征结果表明,苯甲酸在室温下即可在γ-Al~2O~3表面自发单层分散;分散后,苯甲酸分子间的氢键缔合结构垮塌;苯甲酸的羧基与γ-Al~2O~3表面羟基发生相互作用并缩水形成类似羧酸盐的结构;分子中的苯环与载体表面没有直接的相互作用。XRD相定量测得的分散阈值为1.1mmol苯甲酸/100m^2γ-Al~2O~3,与按苯环垂直表面计算所得的最大分散容量1.2mmol/100m^2相近。     

Synthesis of phthalimidines. Acid-catalyzed cyclodehydration versus cyclodeamination of γ-hydroxyamides obtained from dilithio-N-substituted benzamides and ketones

An earlier method of preparation of γ-hydroxyamides from N-substituted benzamides and ketones or aldehydes by means of n-butyllithium was improved and extended. The γ-hydroxyamides were found to undergo cyclodehydration to form γ-lactams with relatively strong acids, but cyclodeamination formed γ-lactones with relatively weak acids; the γ-lactams are substituted phthalimidines. The predominant course of cyclization was dependent also on the structure of the γ-hydroxyamide. Certain γ-hydroxyamides afforded phthalimidines with cold, concentrated sulfuric acid whereas certain others yielded γ-lactones with this acid. The latter γ-hydroxyamides, however, produced phthalimidines with the stronger acid, perchloric acid. The cyclodehydration reaction furnished a convenient and, apparently, quite general method for the synthesis of 2,3,3-trisubstituted or 2,3-disubstituted phthalimidines. Mechanisms are considered.     

γ-Fe2O3@SiO2@4-(sulfoamino)butanoic acid as a novel superparamagnetic nanocatalyst promoted green synthesis of 5-(aryl)-5H-spiro[diindeno[1,2-b:2′,1′-e]pyridine-11,3′-indoline]-2′,10,12-trione derivatives

Research on Chemical Intermediates - Grafting of 4-(sulfoamino)butanoic acid on superparamagnetic γ-Fe2O3@SiO2 nanoparticles afforded γ-Fe2O3@SiO2@4-(sulfoamino)butanoic acid as a novel...     

RuCl3催化氧化γ-甲基吡啶合成γ-吡啶羧酸的研究

吡啶类含氧化合物是一类很重要的有机化合物 ,在药物、食品和饲料添加剂、染料工业等诸多领域应用极为广泛。关于吡啶羧酸的制备 ,实验室和工业上都有较多的研究报道[1 ] 。但不外乎两大类 ,一类反应是化学计量氧化法 ,如高锰酸钾氧化法[1 ] 和硝酸氧化法[2 ,3] ,这类方法原料消耗量大 ,成本高 ,不适合于规模生产。另一类反应是催化氧化法 ,对这类反应研究的报道 ,工业上普遍采用的一种生产工艺是氨氧化法[1 ] ,此法是工业上生产烟酰胺和烟酸的重要方法之一 ,其条件苛刻。文献[4～ 6] 报道以醋酸作溶剂、以醋酸钴、醋酸锰和溴化物作催化剂 ,…     

γ—氧化铝膜的表面酸碱性

研究了氧化铝膜的表面酸碱性,发现采用溶胶－凝胶法制备的氧化铝膜的表面酸碱性受膜的择优取向性的影响;焙烧温度越高,形成的氧化铝膜的（110）面择优取向性越强,氧化铝膜表面呈碱性OH基团密度越大,碱量越大;而γ-氧化铝膜表面酸性OH基团密度越小,酸量越少。经700℃焙烧形成的氧化铝膜表面,双碱性OH基团为主,对酸性气体有良好的选择吸附性。含25％（体积分数）CO2／N2混合气体经700℃焙烧一 γ－氧化铝膜分离后,混合气中的CO2浓度降为0.7％。     

Convenient esterification of poly(γ-glutamic acid) produced by microorganism with alkyl halides and their thermal properties

The esterification of poly(γ-glutamic acid) (γ-PGA) produced by Bacillus subtilis F2-01 with alkyl halides was carried out at 60°C in N-methyl-2-pyrrolidinone (NMP) in the presence of sodium bicarbonate to obtain the corresponding esterified γ-PGA. The thermal properties of these γ-PGA esters were examined by differential scanning calorimetry and thermogravimetry. γ-PGA esters were more stable than free acid type γ-PGA, which decomposed at 210°C. Melting temperature (T_m) of γ-PGA esters could be observed at 230-250°C. T_m of γ-PGA n-alkyl esters reached a maximum at an alkyl chain length of n = 3. © 1995 John Wiley & Sons, Inc.     

Distal γ-C(sp3)−H Olefination of Ketone Derivatives and Free Carboxylic Acids

Reported herein is the distal γ-C(sp³)−H olefination of ketone derivatives and free carboxylic acids. Fine tuning of a previously reported imino-acid directing group and using the ligand combination of a mono-N-protected amino acid (MPAA) and an electron-deficient 2-pyridone were critical for the γ-C(sp³)−H olefination of ketone substrates. In addition, MPAAs enabled the γ-C(sp³)−H olefination of free carboxylic acids to form diverse six-membered lactones. Besides alkyl carboxylic acids, benzylic C(sp³)−H bonds also could be functionalized to form 3,4-dihydroisocoumarin structures in a single step from 2-methyl benzoic acid derivatives. The utility of these protocols was demonstrated in large scale reactions and diversification of the γ-C(sp³)−H olefinated products.     

High-Speed Separation of Oleanolic acid and Ursolic acid from the Fruit of Ligustrum Lucidum ait and Crataegus by Cyclodextrin-Modified Micellar Electrokinetic Chromatography

ABSTRACT

A cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) technique for determining oleanolic acid and ursolic acid in the fruit of Ligustrum lucidum Ait and Crataegus was developed. The two bio-active components were successfully separated within 4 minutes using a pH 8.5 sodium borate buffer containing 60mM SDS and 2mM γ-CD. The correlation coefficients of the linear calibration graphs for the analyses exceeded 0.9980. The effects of pH, SDS, γ-CD, sodium borate and temperature on separation were also investigated.     

γ-alkylation of α,β-unsaturated acids : A technique of stereospecific isoprenoid homologation

This paper describes the synthesis of various isomers of farnesol by means of two different isoprenoid homologations; the γ-alkylation of 2-butynoic acid and the γ-alkylation of 3-methyl crotonic acid.     

基于配合共保护策略合成γ-L-谷氨酰二肽的新方法

提出了一种采用谷氨酸席夫碱Ni(II)配合物共保护L-谷氨酸的α-氨基和α-羧基合成γ-L-谷氨酰二肽的新方法. 首先由手性助剂——2-[N-(N-苄基-脯氨酰)氨基]二苯甲酮(1)、六水合氯化镍和L-谷氨酸反应, 得到谷氨酸席夫碱Ni(II)配合物2, 产率为98.2%; 进而采用二异丙基碳二亚胺(DIC)/1-羟基-苯并三唑(HOBt)复合缩合剂法分别与L-氨基酸3a～3h反应, 得到相应的γ-L-谷氨酰二肽席夫碱Ni(II)配合物4a～4h, 产率为93.1%～99.0%; 最后稀酸水解配合物, 得到γ-L-谷氨酰二肽5a～5h, 产率为73.0%～86.4%, 高收率(92.2%～97.4%)回收手性助剂. 中间产物和终产物的结构经由旋光, 1H NMR, 13C NMR和HRMS表征.