An unusual gold-catalyzed rearrangement of α-hydroxy epoxides

A novel gold-catalyzed rearrangement of α-hydroxy epoxides has been investigated. The reaction proceeds efficiently under mild conditions to afford unsymmetrical 1,5 or 1,6-diketones and monoketones in moderate to high yields. The selective formation of the two products could be controlled by substituents and ring strain.

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Biodiesel Production Using a Carbon Solid Acid Catalyst Derived from β‐Cyclodextrin

A novel carbon solid acid catalyst was prepared by incomplete hydrothermal carbonization of β‐cyclodextrin into small polycyclic aromatic carbon sheets, followed by the introduction of –SO₃H groups via sulfonation with sulfuric acid. The physical and chemical properties of the catalyst were characterized in detail. The catalyst simultaneously catalyzed esterification and transesterification reactions to produce biodiesel from high free fatty acid (FFA) containing oils (55.2 %). For the as‐prepared catalyst, 90.82 % of the oleic acid was esterified after 8 h, while the total transesterification yield of high FFA containing oils reached 79.98 % after 12 h. By contrast, the obtained catalyst showed comparable activity to biomass (such as sugar, starch, etc.)‐based carbon solid acid catalyst while Amberlyst‐15 resulted in significantly lower levels of conversion, demonstrating its relatively high catalytic activity for simultaneous esterification and transesterification. Moreover, as the catalyst can be regenerated, it has the potential for use in biodiesel production from oils with a high FFA content.     

Electrosynthesis of β-methylpentadecanedioic acid dimethyl ester

β-Methylpentadecanedioic acid dimethyl ester ( I ) was synthesized electrochemically by Kolbe reaction using β-methylglutaric acid monomethyl ester ( II ) and α,ω-dodecanedioic acid monomethyl ester (III) as starting materials in MeOH solution. Electrolysis was carried out ofr about 4–5 h, when solution pH ≥ 7, followed by extraction with petroleum ether and distillation to obtain a colourless oily product ( I ) The minimum production cost occurred when the mole ration of II to III was 1:1·38 and unreacted III could be recovered. The product synthesized ( I ) completely met the requirement of artificially synthesized musk.     

Studies of the reactions of anhydrosulphites of α-hydroxy acids,part IX. thermal polymerisation of anhydrosulphites of α-hydroxy α-methyl carboxylic acids

The anhydrosulphites of a series of unsymmetrically substituted α-hydroxy acids have been prepared and their susceptibility to polymerisation by thermal decomposition studied. The first order rate determining ring scission process, leading to the formation of a reactive α-lactone intermediate which then undergoes spontaneous polymerisation, is the predominant mechanism even with substituents up to C₈. As the length of the n-alkyl substituent is increased the rate of decomposition and thus polymerisation increases until a plateau value is reached at around C₃. Further increase in substituent length decreases the rate of decomposition, an effect which is attributed to steric hindrance of the leaving group by long (C₆—C₈) substituents.     

Oxidation of potato starch with NO2: characterization of the carboxylic acid salts

Oxidation of primary hydroxyl groups of potato starch to the corresponding carboxylic acids was performed in a fluidized bed using N₂-diluted NO₂ as oxidant. FT-IR spectrum of the oxidized starch show the presence of two absorption bands at 1743 and 1379 cm⁻¹. The absorption at 1743 cm⁻¹ which normally attributed to carbonyl absorption vanishes after washing the oxidized starch by water. Then two new absorption bands appeared at 1650 and 1400 cm⁻¹ corresponding to the ionized carboxyl groups.

The presence of nitrate favor the un-ionized form of carboxyl groups and then the band at 1743 cm⁻¹ can be observed. Furthermore, the ionized carboxyl absorption (1600, 1400 cm⁻¹) are replaced by carbonyl absorption at 1743 cm⁻¹ by adding DCl. By means of ¹³C NMR analysis, oxidized starch, show a band around 200 ppm attributed to carboxylic acid, no formic acid was detected indicating that no cleavage took place under the applied reactions conditions.     

Effects of a carboxylic acid/sulfonic acid copolymer on the material properties of cementitious materials

The effects of a carboxylic acid/sulfonic acid copolymer (PMAMP) on the properties of mortars or concrete made with Type I Portland cement were investigated. PMAMP was prepared from methacrylic acid and 2-acrylamido-2-methylpropane sulfonic acid (AMP) in a basic condition through a free radical polymerization. The results indicate that PMAMP with the AMP content of 20-60%, and a weight-average molecular weight (MW) of about 5 × 10⁴, is effective in dispersing cement particles and the resulting mortars or concrete show good fluidity or workability. Besides, PMAMP with higher molecular weigh is more capable of maintaining the workability along with elapsed time. Compared with a commercial sulfonated naphthalene formaldehyde superplasticizer (SNF), PMAMP appears to be more effective in promoting concrete workability and preventing the slump loss. Finally, concrete incorporated with different PMAMPs at W/B = 0.28 shows similar compressive strength-developing behavior and meets the designed strength value.     

Grafting of cotton with β‐cyclodextrin via poly(carboxylic acid)

Cyclodextrins are cyclic oligosaccharides. Cyclodextrin molecules can form inclusion complexes with a large number of organic molecules. The properties of cyclodextrins enable them to be used in a variety of different textile applications. Cyclodextrins can act as auxiliaries in washing and dyeing processes, and they can also be fixed onto different fiber surfaces. Because of the complexing abilities of cyclodextrins, textiles with new functional properties can be prepared. Poly(carboxylic acid)s such as 1,2,3,4‐butane tetracarboxylic acid (BTCA) are well‐known non‐formaldehyde crosslinking reagents. BTCA has four carboxylic acid groups, which can react with hydroxyl groups of cellulose and form stable ester bonds. We crosslinked β‐cyclodextrin molecules on hydroxyl groups of cellulose via BTCA. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1323–1328, 2005     

Characterization of the activity of β-galactosidase immobilized on Teflon membranes preactivated with different monomers by γ-irradiation

The activity of β-galactosidase, immobilized by grafting technique on Teflon membranes preactivated with four different monomers, has been characterized from the biochemical and biophysical points of view. The monomers used were acrylic acid or acrylamide, or methacrylic acid and 2-hydroxyethyl methacrylate. When 2-hydroxyethyl methacrylate was used in the second grafting, the first three monomers have been used in the first modification step. The behavior of the free and immobilized enzyme has been analyzed as a function of temperature and pH. For each catalytic membrane, we have found general equations relating the absolute enzyme activity to pH and temperature. From these expressions, the experimental conditions giving the best yield of each catalytic membrane have been calculated. The kinetic parameters for the four membranes have also been determined. The advantages of using these membranes in nonisothermal bioreactors are also indicated. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 613–623, 1998     

Oleic acid esterification with ethanol under continuous water removal conditions

The production of ethyl ester was investigated using a new reaction system consisting of a reactor coupled to an adsorption column. The adsorption system was used to shift the equilibrium toward ethyl ester production by removing the water from commercial ethanol and the water produced during the esterification reaction. A condenser placed above the adsorption column was responsible to condensate the vapor, returning water free ethanol to the reactor. Ethyl ester was produced by esterification of oleic acid and ethanol using sulfuric acid as catalyst. The results showed a yield of 99.9%. The best operating condition was found operating the reactor at 110 °C, 1% of catalyst (w/w) and with an oleic acid to ethanol ratio of 1:3.     

Lipase-catalyzed esterification of glycerol and n-3 polyunsaturated fatty acid concentrate in organic solvent

Enzymatic synthesis of glycerides from glycerol and n-3 polyunsaturated fatty acid in organic solvent was studied. Optimal conditions for glyceride synthesis by lipases were established. Of the commercially available lipases that were investigated, lipase PS-30 fromPseudomonas sp. and lipase IM-60 fromMucor miehei resulted in the highest extent of esterification. Isooctane and hexane were particularly useful organic solvents in glyceride synthesis. The water content in the reaction mixture was of primary importance. For lipase PS-30 and lipase IM-60, optimal water contents were 5 and 1%, respectively. Lipases PS-30 and IM-60 manifested contrasting positional specificities in glyceride synthesis. Glycerides containing predominantly eicosapentaenoic acid and docosahexaenoic acid can be easily synthesized.     

Kinetics of the esterification of phthalic anhydride with 2-ethylhexanol. I. Sulfuric acid as a catalyst

The kinetics of the esterification of mono-2-ethylhexyl phthalate in the presence of sulfuric acid as a catalyst has been investigated in an isothermal semibatch reactor. The reaction appears to be first order with respect to mono-2-ethylhexyl phthalate alone and the reaction rate does not depend on the concentration of 2-ethylhexanol. The kinetic parameters have been determined.     

β-galactosidase immobilization on premodified Teflon membranes using γ-radiation grafting

γ-Radiations have been used to immobilize, by mutual grafting, the β-galactosidase enzyme and monomers of 2-hydroxyethyl methacrylate on Teflon (polytetrafluoroethylene) membrane previously grafted with acrylic acid monomers. This double grafting technique improved the catalytic activity of the membrane. Membrane activity has been studied as a function of some of the most relevant parameters affecting the grafting degree and of the amount of enzyme used for immobilization. Experimental conditions producing the best membrane activity have been characterized. The advantages in using Teflon catalytic membrane in nonisothermal bioreactors, more efficient than the analogous isothermal bioreactors, are also discussed. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 625–636, 1998     

Chemoenzymatic Preparation of Enantiopure Homoadamantyl β‐Amino Acid and β‐Lactam Derivatives

Racemic cis‐10‐azatetracyclo[7.2.0.1^2,6.1^4,8]tridecan‐11‐one was prepared from homoadamant‐4‐ene by chlorosulfonyl isocyanate addition. The transformation of the β‐lactam to the corresponding β‐amino ester followed by Candida antarctica lipase A‐catalyzed enantioselective (E>>200) N‐acylation with 2,2,2‐trifluoroethyl butanoate afforded methyl (1R,4R,5S,8S)‐5‐aminotricyclo[4.3.1.1^3,8]undecane‐4‐carboxylate and the (1S,4S,5R,8R)‐butanamide with>99% ee at 50% conversion. Alternatively, transformation of the β‐lactam to the corresponding N‐hydroxymethyl‐β‐lactam and the following Pseudomonas cepacia (currently Burkholderia cepacia) lipase‐catalyzed enantioseletive O‐acylation provided the (1S,4S,6R,9R)‐alcohol (ee=87%) and the corresponding (1R,4R,6S,9S)‐butanoate (ee>99%). In the latter method, competition for the enzyme between the (1R,4R,6S,9S)‐butanoate, 2,2,2‐trifluoroethyl butanoate and the hydrolysis product, butanoic acid, tended to stop the reaction at about 45% conversion and finally gave racemization in the (1S,4S,6R,9R)‐alcohol with time.     

Liquid phase esterification of acrylic acid with 1-butanol catalyzed by solid acid catalysts

Esterification of acrylic acid with 1-butanol has been studied in a heterogeneous solid–liquid reaction system using a variety of solid acids including an acidic salt of H₃PW₁₂O₄₀, Cs_2.5H_0.5PW₁₂O₄₀. The catalytic activity (per proton) of liquid acids such as heteropolyacids, H₂SO₄, and para-toluenesulfonic acid increased as the acid strength of the solution increased, but the difference in the activity among them was not significant. In the solid–liquid reaction system, Cs_2.5H_0.5PW₁₂O₄₀ exhibited the highest catalytic activity in the unit of catalyst weight among the solid oxide catalysts, while the activity of Cs_2.5H_0.5PW₁₂O₄₀ was less than those of organic resins such as Nafion and Amberlyst 15. Contrary to the liquid acids, the specific activity values (per proton) of solid acids were significantly different. It was demonstrated that the activity of Cs_2.5H_0.5PW₁₂O₄₀ was almost retained after the addition of water, while the activities of the organic resins greatly decreased. The water-tolerant property of Cs_2.5H_0.5PW₁₂O₄₀ is presumed to be due to the hydrophobic nature of the surface.     

连续法固体超强酸催化酯化反应的研究

以ＳＯ２－４／ＴｉＯ２型固体超强酸为催化剂,在固定床反应器上,通过连续法考察了乙酸与乙醇酯化反应的情况。确定了反应的最佳条件：加料速度１０ｍＬ／ｈ,反应温度１００℃。在该条件下,起始物９０％可转化为产物酯。同时考察了该催化剂对其他几种酯化反应的催化情况,并与硫酸催化作了对比,结果表明本方法优于硫酸法     

纳米固体超强酸SO2-4/SnO2-La2O3-SiO2制备及催化反应研究

制备纳米SO4^2-／SnO2-La2O3-SiO2固体超强酸催化剂,讨论了在纳米载体SiO2的存在下,Sn、Si摩尔比、焙烧温度对乙酸转化率的影响,并与SO4^2-／SnO2-SiO2催化剂进行了对比,讨论了金属La^3 对固体超强酸的影响。实验表明,SO4^2-／SnO2-La2O3-SiO2催化剂在焙烧温度为450℃,n(Sn)：n(Si)=0．5时,乙酸的转化率达到98．1％。     

Synthesis and Pharmacological Evaluation of α4β2 Nicotinic Ligands with a 3‐Fluoropyrrolidine Nucleus

Nicotinic acetylcholine receptors (nAChRs) play an important role in many central nervous system disorders such as Alzheimer’s and Parkinson’s diseases, schizophrenia, and mood disorders. The α₄β₂ subtype has emerged as an important target for the early diagnosis and amelioration of Alzheimer’s disease symptoms. Herein we report a new class of α₄β₂ receptor ligands characterized by a basic pyrrolidine nucleus, the basicity of which was properly decreased through the insertion of a fluorine atom at the 3‐position, and a pyridine ring carrying at the 3‐position substituents known to positively affect affinity and selectivity toward the α₄β₂ subtype. Derivatives 3‐(((2S,4R)‐4‐fluoropyrrolidin‐2‐yl)methoxy)‐5‐(phenylethynyl)pyridine ( 11 ) and 3‐((4‐fluorophenyl)ethynyl)‐5‐(((2S,4R)‐4‐fluoropyrrolidin‐2‐yl)methoxy)pyridine ( 12 ) were found to be the most promising ligands identified in this study, showing good affinity and selectivity for the α₄β₂ subtype and physicochemical properties predictive of a relevant central nervous system penetration.