Rearrangements of Neoclovene Epoxides in Acidic Media

Rearrangements of neoclovene epoxides in the presence of a solid superacid ZrO₂/SO₄ ^{2 -} and in formic acid were investigated. In the latter case a ketone was obtained with a previously unknown carbon skeleton. The most probable pathway of its formation was derived from calculations by molecular mechanics and quantum-chemical methods.     

Rearrangements of Epoxides of Some Acyclic Terpenoids in Acidic Media

2,3-Epoxygeraniol undergoes dissimilar rearrangements in contact with liquid superacids at low temperature or on solid superacids at room temperature due to different location of the arising cationic center depending on the superacid character. 2,3-Epoxynerol, 6,7-epoxycitronellol, and 6,7-geranyl acetate on ZrO₂SO₄ ^{2 -} afford the corresponding ketones via epoxy ring opening followed by 1,2-hydride shift. With 6,7-geranyl acetate 7-oxanobornane formed as a minor product. The mode of generation of the cationic center (either the olefin protonation or the epoxy ring opening) affects the rearrangement direction at similar conditions.     

Role of Epoxides in the Oxidation of Allyl Alcohol,Allyl Formate,and Allyl Acetate in Acetic Acid

The formation of epoxy derivatives as intermediate products in the oxidation of allyl alcohol, allylformate, allyl acetate in acetic acid was proved. Intermediate epoxy compounds undergo further trans-formations: They react with acetic acid to give glycerol esters or are converted into polyethers of glyceroland its esters. The rate constants for transformations of 2,3-epoxypropanol, 2,3-epoxypropyl formate, and 2,3-epoxypropyl acetate along these pathways were measured. Higher selectivity of glycerol ester formation from allyl formate was substantiated.     

3,3,3-三氟丙酸的合成

3,3,3-三氟丙酸是一种新型三氟甲基合成切块,在医药、农药、染料及功能材料等精细化工领域有着广泛的应用。以3,3,3-三氟-1-氯丙烷和Cl₂为原料,在紫外光照下经氯化反应合成了3,3,3-三氟-1,1,1-三氯丙烷,再与Oleum试剂经水解反应合成了3,3,3-三氟丙酸,收率47.7%,其结构经¹H NMR, ¹³C NMR和MS确证。并对反应条件进行了优化。     

Enantiomeric Distribution Studies of Linalool and Linalyl Acetate. A Powerful Tool for Authenticity Control of Essential Oils

The enantiomeric distributions of linalool and linalyl acetate in various natural products are measured by enantioselective gas chromatography on alkyl-substituted cyclodextrins. Different plant cultivars were investigated by four extraction processes: steam distillation, solvent extraction, supercritical fluid extraction, and headspace analysis. Careful attention must be paid to linalool which undergoes partial racemization under certain processing conditions. In most cases, enantiomeric distribution is a powerful tool for authenticity testing.     

有机相中α-氰基-3-苯氧基苄醇乙酯的酶促醇解反应

研究了有机相中脂肪酶催化α-氰基-3-苯氧基苄醇乙酯的醇解化反应。制备α -氰基-3-苯氧基苄醇。考察了酶、溶剂、醇、醇用量、溶剂水含量以及底物浓度等 因素对反应的影响，结果表明Novozym435脂肪酶催化活性最高，经实验确定的最佳 条件为：脱水甲苯为溶剂，正辛醇为酰基受体，正辛醇、酯的摩尔比为1.5:1，酶 量为8 mg/mL时的最佳底物浓度为108.13 mmol/L，在上述条件下反应30 h酯的转化 率 > 96%。     

氨基酸盐酸盐催化二氧化碳与环氧化物的环化反应

利用氨基酸盐酸盐作为催化剂,二氧化碳可以和环氧化物发生偶联反应,高产率和高选择性地生成环状碳酸酯,详细研究了反应条件如二氧化碳压力,反应温度,时间及催化剂用量对反应的影响。     

有机相中α-氰基-3-苯氧基苄醇乙酯的酶促不对称醇解反应

研究了有机相中脂肪酶催化α-氰基-3-苯氧基苄醇乙酯(CPBAc)的不对称醇解反应,制备了S-α-氰基-3-苯氧基苄醇(S-CPBA).以脂肪酶Lipase AS 为催化剂,四氢呋喃为反应介质,甲醇为酰基受体,对反应过程的各种影响因素进行了研究.得到该酶反应的较适反应条件为:温度为35～45℃,脱水溶剂加水量为0%～1%,摇床转速大于200 r/min,酯醇摩尔比大于1:0.5,CPBAc为337.08mmol/L时需要10me/mL的酶量.然后对底物和产物抑制、产物稳定性以及酶的重复利用进行了研究.对酶催化反应过程的详细考察表明,在200g/L的底物浓度下反应依然可以高效进行,反应约33 h,S-CPBA转化率可达49%左右,ee大于98%,剩余底物R-CPBAc的ee也大于95%.最后进行了反应放大实验,取得了较好的实验结果.     

Photodegradation of Cinnamic Acid in Different Media

The photodegradation of cinnamic acid under UVB irradiation was evaluated in different vehicles, such as water solutions at different pH values, Tween‐20 micelles, liposomes, and O/W emulsions prepared with Xalifin 15 or Montanov 68 as emulsifiers. The increase of pH decreases the photodegradation of cinnamic acid in all the vehicles studied. Micellar solutions showed a protective effect against cinnamic acid photodegradation; this property increases according to the surfactant percentage. Emulsions appeared to be the most efficient protective systems while liposomes had lower ability to protect cinnamic acid against UVB photodegradation.     

Electroactivity of Cacodylic Acid in Aqueous and Nonaqueous Media

Abstract

The electroreduction of dimethylarsenic acid (cacodylic acid), (CH₃)AsO₂H, and methylarsonic acid, (CH₃)ASO₃H₂, in both nonaqueous and aqueous buffer electrolytes, is described.     

Conductance of Dilute Sodium Acetate Solutions to 469 K and of Acetic Acid and Sodium Acetate/Acetic Acid Mixtures to 548 K and 20 MPa

In order to obtain accurate association constants for sodium acetate, a very precise flow method was used to measure the electrical conductivity of dilute aqueous solutions of sodium acetate at ambient conditions and 469 K and 20 MPa. Measurements at ambient conditions, 469 and 548 K and 20 MPa, were also made on sodium acetate/acetic acid mixtures and acetic acid. In order to determine the limiting the equivalent conductances and the association constant for sodium acetate, and dissociation constant for acetic acid, the results were fitted to two modern conductance equations (Fuoss–Hsia–Fernandez–Prini and Turq–Blum–Bernard–Kunz) with accompanying activity coefficient models (mean spherical approximation and the Debye–Hückel with the Bjerrum distance). The choice of conductance equation, activity coefficient model, assumed values for the limiting equivalent conductance for minor species, and assumed equilibrium constants for minor reactions, did not significantly change the resulting equilibrium constants. The insensitivity of the calculated equilibrium constants to these choices in conjunction with the inherent precision of the flow conductance technique leads us to believe that the present results are the most accurate sodium acetate ion-pairing constants published to date. Our results for acetic acid are in good agreement with previously published results from other laboratories.     

Highly Selective and Practical Iron-Catalyzed Formal Hydrogenation of Epoxides to Primary Alcohols Using Formic Acid

A highly selective, efficient and practical method for synthesizing primary alcohols was presented. By using cheap Fe(BF₄)₂ ⋅ 6H₂O and /tris[2-(diphenylphosphino)phenyl]phosphine ( L1 ) as catalysts with formic acid as hydrogen source, a variety of primary alcohols bearing versatile functional groups could be obtained from both alkyl- and aryl-substituted epoxides under mild conditions.     

Facile Conversion of Epoxides to Thiiranes with Ammonium Thiocyanate Catalyzed with Oxalic Acid

Epoxids are efficiently converted to the corresponding thiiranes by ammonium thiocyanate (NH 4 SCN) in the presence of catalytic amounts of oxalic acid with excellent isolated yields under mild and nonaqueous reaction conditions. This conversion performed under both conventional heating and microwave conditions. Distinct rate enhancement is observed under microwave irradiation.     

Fries Rearrangement of Phenyl Acetate over Solid Acid Catalyst

A silica-supported zirconium based solid acid (ZS) has been used as catalyst for the Fries rearrangement of phenyl acetate (PA). The catalyst showed a higher PA conversion activity and a much higher selectivity for o-hydroxyacetophenone (o-HAP) than for strongly acidic zeolite catalysts. The supported catalyst was characterized by XRD,IR,XPS,pyridine-TPD and the surface area measurements. The catalytic properties were influenced significantly by pretreatment temperature.     

无机固体酸催化合成乙酸乙酯

介绍了利用一水硫酸氢钠、六水三氯化铁、五水四氯化锡、十二水合硫酸铁铵和水合硫酸铁催化乙醇和乙酸制备乙酸乙酯的方法。     

铌酸催化液相合成乙酸乙酯

报道了铌酸催化乙醇与乙酸的液相酯化反应考察了反应温度、催化剂用量、酸醇比、反应时间对产品乙酸乙酯经的影响。在优化条件下,产品收率棕达８８．０％,选择性为１００％,同时我们采用自制间式反应,对催化剂的稳定性进行了考察,发现铌酸在该实验条件下,能保持较高的稳定性和较高的催化活性。     

An Improved Procedure for the Epoxidation of Methyl Cinnamate Derivatives and Production of Acid Sensitive Epoxides

By using a biphasic epoxidation system, unreactive methyl cinnamate derivatives were epoxidized at higher rates, and epoxides that decomposed in the presence of m-chlorobenzoic acid (mCBA) to diol ester opening products under standard conditions were obtained in fair to excellent yields.