Quantitative Analysis of Mixtures of Various Linear Anhydrides and Carboxylic Acids

Only a few quantitative methods have been described to analyze mixtures of symmetric anhydrides, mixed anhydrides and their corresponding carboxylic acids. Reversed-phase liquid chromatography using acetonitrile-water as solvent was optimized for the quantitative determination of such mixtures obtained by reacting acetic or propionic anhydrides with various fatty acids (from C3 to C18). Complex mixtures containing up to three mixed anhydrides, four symmetric anhydrides and four carboxylic acids have been quantitatively analyzed successfully in a single run.     

Hypervalent Iodine in Synthesis

A new and facile method for the preparation of arenetellurinic mixed anhydrides is described from diaryl ditellurides and phenyliodine (III) dicarboxylates. Hydrolysis of the arenetellurinic mixed anhydrides gives arenetellurinic anhydrides and a one - pot procedure involving the reaction of diaryl ditellurides with phenyliodine (III) dicarboxylates in a two - phase system of methylene chloride and aqueous solution of sodium hydroxide for the preparation of arenetellurinic anhydrides is provided.     

The synthesis of P-chiral amino acid-derived phosphonamidic anhydrides

The synthesis of an array of P-chiral amino acid-derived phosphonamidic anhydrides is described. These anhydrides are prepared by condensation of allylated amino acids 19-22 with methyl- or vinylphosphonic dichlorides 23 or 24 to produce three diastereomeric anhydrides 4-11a-c in good to excellent yields. The mechanistic issues concerning anhydride formation are discussed and supported by experimental results. Vinylphosphonamidic anhydrides 8-11 are further derivatized via the ring-closing metathesis (RCM) reaction to yield amino acid-derived bicyclic phosphonamidic anhydrides.     

Synthesis and hydrolysis behaviour of poly(ester anhydrides) from polylactone precursors containing alkenyl moieties

Hydroxyl-group functional polylactones were prepared and converted to acid- terminated polyesters in a reaction with a series of alkenylsuccinic anhydrides containing 8, 12, or 18 carbons in their alkenyl chains. These polyester precursors were then linked into higher molecular weight poly(ester anhydrides) containing alkenyl moieties in their polyester blocks. The hydrolysis behaviour of the poly(ester anhydrides) was found to depend on the thermal properties of the polyester precursors. For poly(ester anhydrides) prepared from low molecular weight prepolymers with thermal transitions below 37 degrees C, the presence of hydrophobic alkenyl chains in the polyester precursors slowed the rate of weight loss. Poly(ester anhydrides) prepared from higher molecular weight prepolymers showed the opposite weight-loss behaviour; i.e., the crystallinity and thermal transitions of the alkenyl chain-containing poly(ester anhydrides) were low, and the weight loss was faster than for poly(ester anhydrides) without the alkenyl chains. The differences in length of the alkenyl chain, as such, had little effect on the hydrolysis behaviour and thermal properties of the poly(ester anhydrides).     

Regioselectivity of Friedel-Crafts acylation of aromatic compounds with several cyclic anhydrides

The Friedel-Crafts acylations of various aromatic compounds with cyclic anhydrides such as 2-(p-substituted phenyl)butanedioic, 3-phenylpentanedioic and homophathlic anhydrides were carried out under various conditions in order to obtain informations about the regioselectivity of the ring opening of the cyclic anhydrides and about the possible reaction pathways in the acylations.     

Determination of aliphatic anhydrides and acids by reversed-phase liquid chromatography

Few chromatography methods have been reported for the determination of anhydrides in mixtures or as mixed anhydrides. The potential reactivity of anhydrides with water and other common eluent components complicates possible schemes for separation and analysis. By optimizing variables that affect hydrolysis, including the stationary phase, conditions can be found to successfully analyze anhydrides as reactive as acetic anhydride. The corresponding acids can be determined at the same time. The effect of the stationary phase on anhydride hydrolysis rates may prove to be a sensitive means of probing stationary phase chemistry.     

Analysis of some anhydrides as their corresponding acids by capillary electrophoresis

Summary The potential of capillary electrophoresis for the indirect determination of anhydrides was demonstrated by the analysis of five closely-related anhydrides as their corresponding acids. Direct analysis of such substances is generally difficult because of their susceptibility to hydrolysis. In this work anhydrides were first hydrolyzed in water, hydrolysis being monitored using micellar electrokinetic chromatography (MEKC) which separated neutral anhydrides and anions of corresponding acids. After hydrolysis, separation of the acids was quickly achieved within two minutes by reversed electroosmotic-flow, capillary electrophoresis (REF-CE), with UV detection at 210 nm.     

The preparation of 7-substituted norbornadiene-2,3-dicarboxylic anhydrides and an experimental and theoretical study of their reactivity

Four new substituted methano-bridged or heteroatom-bridged norbornadienomaleic anhydrides have been prepared and converted to sesquinorbornadiene anhydrides by reaction with cyclic 1,3-dienes. The versatility of parity reversal, in conjunction with N-substituent steric effects, has been used to produce all three possible stereoisomers of the N,O-sesquinorbornadiene anhydrides in separate, stereoselective cycloadditions. The anhydrides have been synthesized by cyclization of their diacids (in situ production) or by flash vacuum pyrolysis of their furan adducts (yielding crystalline products); further fragmentation occurs at these or higher temperatures to produce five-membered carbocyclic or heterocyclic anhydrides. Activation energies have been evaluated for the fragmentation and cycloaddition processes using DFT calculations (B3LYP/6-31G∗) and these calculations correctly predict, which reaction can be intercepted at the norbornadienomaleic anhydride stage and preferred stereochemistry of cycloadducts.     

Ligand differentiated complementary Rh-catalyst systems for the enantioselective desymmetrization of meso-cyclic anhydrides

Two distinct systems for the rhodium-catalyzed enantioselective desymmetrization of meso-cyclic anhydrides have been developed. Each system has been optimized and are compatible with the use of in situ prepared organozinc reagents. Rhodium/PHOX species efficiently catalyze the addition of alkyl nucleophiles to glutaric anhydrides, while a rhodium/phosphoramidite system is effective in the enantioselective arylation of succinic and glutaric anhydrides.     

Doubly-charged positive ions following loss of oxygen dianion under conditions of field desorption mass spectrometry

A number of cyclic aromatic anhydrides have been found to exhibit doubly-charged positive ions in their field desorption mass spectrum which correspond to the formal loss of oxygen dianion followed by clustering with a neutral molecule. Admixtures of two anhydrides, which both exhibit this phenomenon, produce heterogeneous doubly-charged cluster ions. Admixture with anhydrides which do not show the effect, produces only homogeneous clusters at reduced intensity.     

脂肪族聚酯酸酐的合成及其药物控制释放性能的研究

合成了一系列脂肪族聚酯酸酐并研究了其降解和药物控释性能．结果表明,脂肪族聚酯酸酐具有较低的熔融温度(约70℃);体外降解速率随单体中次甲基数增多而降低,在24～40h降解完全;含乙酰水杨酸的聚酯酸酐基质片的药物释放速率与聚酯酸酐的降解行为有关．     

Magnesium bistrifluoromethanesulfonimide as a new and efficient acylation catalyst

Magnesium bistrifluoromethanesulfonimide catalyzed the acetylation of phenols, alcohols, and thiols under solvent-free conditions at room temperature and in short times. Electron-deficient and sterically hindered phenols provided excellent yields. The catalyst was found to be general for acylation with other anhydrides, such as propionic, isobutyric, pivalic, chloroacetic, and benzoic anhydrides. The rate of acylation was influenced by the electronic and steric factors associated with the anhydride. The reaction with less electrophilic anhydrides (e.g., chloroacetic and benzoic anhydrides) required higher temperature (approximately 80 degrees C). Chemoselective acetylation, pivalation, and benzoylation took place with acid-sensitive alcohols without any competitive dehydration/rearrangement.     

The anilic acid number,an analytical index for testing dibasic acid anhydrides

For testing the purity of dibasic acid anhydrides and for analysing mixtures of these anhydrides with the corresponding free acids the determination of a new index number is recommended, indicated as the “anilic acid number”. The process is based on the fact that these acid anhydrides, when dissolved in acetone, under suitable experimental conditions can be added readily and quantitatively to aniline with resulting formation of the corresponding anilic acids.Immediately after addition, titration is effected with alcoholic potassium hydroxide on phenolphthalein. Pure dibasic acid anhydrides in this case yield the calculated anilic acid number. In the presence of free acids the values found are too high. The free acid content can be easily determined from the difference between the theoretical and the found anilic acid number.     

Novel transformation of arenediazonium salts to acid anhydrides under palladium catalysis

Palladium catalyzed reaction of arenediazonium salts, carbon monoxide and sodium carboxylates gave mixed anhydrides, which in turn could be converted to aromatic acid anhydrides in good yields.     

Nickel catalyzed decarboxylative alkylation of aryl triflates with anhydrides

Aliphatic acid anhydrides are the versatile building blocks and the new method for the conversion of anhydrides is thus of great significance. Herein, we report the decarboxylative alkylation of aryl triflates with aliphatic acid anhydrides via nickel catalysis. This novel method provides a facile access to construct Csp²-Csp³ bond. In addition, this method is compatible with a broad array of functional groups and exhibits good substrates scope.     

Investigation of the reaction of some unsaturated dicarboxylic acid anhydrides with cyclic carbonates

This work reports attempts to extend to unsaturated anhydrides the rapid reaction of dicarboxylic acid anhydrides with ethylene carbonate to form polymer directly. The reaction of unsaturated diacid anhydrides with two cyclic carbonates, ethylene and propylene carbonate, leads to gelled products whenever the anhydride is capable of Michael addition, while an anhydride without such unsaturation gave linear polymer in- stead. The GC/MS results, along with efforts to trap radical reactions, support Michael addition as an explanation of gelation in these systems.     

Scandium Trifluoromethanesulfonate as an Extremely Active Lewis Acid Catalyst in Acylation of Alcohols with Acid Anhydrides and Mixed Anhydrides

Scandium trifluoromethanesulfonate (triflate), which is commercially available, is a practical and useful Lewis acid catalyst for acylation of alcohols with acid anhydrides or the esterification of alcohols by carboxylic acids in the presence of p-nitrobenzoic anhydrides. The remarkably high catalytic activity of scandium triflate can be used for assisting the acylation by acid anhydrides of not only primary alcohols but also sterically-hindered secondary or tertiary alcohols. The method presented is especially effective for selective macrolactonization of omega-hydroxy carboxylic acids.     

Resonance in aromatic and heteroaromatico-dicarboxylic acids,their anhydrides and imides

It is found thato-dicarboxylic acids derived from pyrrole and 1,2,5-thiadiazole do not form cyclic anhydrides as readily as phthalic acid. This is discussed in terms of ionic resonance structures and derived stabilization of the anhydrides and acids.     

A facile synthesis of alkyl substituted maleic anhydrides: radical approach

Synthetic background for the preparation of alkyl substituted maleic anhydrides and maleimides based on radical alkylation of 2,3-dichloromaleic anhydride (maleimide) by hydrocarbons was developed. The best conditions for the selective synthesis of 2-alkyl-3-chloro- and unsymmetrically substituted dialkylmaleic anhydrides were elaborated.     

Dihydro-3-(triphenylphosphoranylidene)-2,5-thiophendione: A Convenient Synthon for the Preparation of Substituted 1,4-Thiazepin-5-ones and Piperidinones via the Intermediacy of Thioacids

Reaction of thiomaleic anhydride with triphenylphosphine gives the title compound, which undergoes reaction with a variety of aldehydes to give a range of alkylidene thiomaleic anhydrides (substituted monothioitaconic anhydrides). Subsequent treatment with tert-butoxycarbonylamino-substituted thiols, or under radical conditions with tert-butoxycarbonylamino-substituted alkyl halides results in a series of substituted monothiomaleic anhydrides, that on exposure to trifluoroacetic acid and then base lead to thiocarboxyl substituted 1,4-thiazepin-5-ones and piperidinones, respectively, that are ultimately trapped by reaction with 2,4-dinitrobenzenesulfonamides to give the corresponding amides.