The effective use of substituted benzoic anhydrides for the synthesis of carboxamides

Various carboxamides are synthesized from the corresponding carboxylic acids and amines with high product-selectivities using 2-methyl-6-nitrobenzoic or 2,4,6-trichlorobenzoic anhydride in the presence of 4-(dimethylamino)pyridine.     

Development of effective Lewis acids for the catalytic Diels-Alder reaction of α,β-unsaturated lactones with cyclopentadiene

We found that ‘Tf₂CH₂ + Me₃Al’ systems are effective catalytic systems for the DA reaction of less reactive α,β-unsaturated lactone derivatives, compared to α,β-unsaturated ester derivatives, with cyclopentadiene. Mononuclear aluminum methide complex, Tf₂CHAlMe₂, as an active species is formed in these catalytic systems. Effects of lactone ring-size on the reactivity and stereoselectivity were also examined. By expanding ring-size, reactivity of α,β-unsaturated lactones reduced but endo-selectivity notably increased.     

对三氟甲基苯甲酸和2，2′-联吡啶双核铽配合物的合成、晶体结构及发光性质

A new dinuclear complex [Tb₂(BA)₆(2,2′-bipy)₂] (BA=4-(trifluoromethyl)benzoic acid, 2,2′-bipy=2,2′-bipyridine) has been synthesized. The complex was characterized by X-ray single-crystal structure analysis. The complex is a dimer with an inversion center. In the complex, two Tb3+ ions are linked by four carboxylate groups of BA ligands in bridging-bidentate coordination mode. Each Tb³⁺ ion is eight-coordinated with two nitrogen atoms from one 2,2′-bipy molecule, four oxygen atoms from four bridging-bidentate BA ligands and two oxygen atoms from one chelating-bidentate BA ligand. Intermolecular hydrogen bonds are formed in the crystal. The complex exhibits strong green fluorescence under ultraviolet light and the fluorescence spectrum consists of four lines peaking at 489, 545, 584 and 620 nm, which are corresponding to the ⁵D₄→⁷F_j (j=6～3) transitions of Tb³⁺ ion, respectively. CCDC: 727763.     

Syntheses and characterizations of five coordination polymers constructed by 3,5-bis(pyridin-3-ylmethoxy)benzoic acid ligand

Five coordination polymers, namely [Cd(L3)₂]·H₂O (1), [Zn(L3)₂] (2), [Co(L3)₂] (3), [Ni(L3)₂] (4) and [Cu₂(L3)₂]·3H₂O (5), where L3 = 3,5-bis(pyridin-3-ylmethoxy)benzoic acid, have been synthesized under hydrothermal conditions. Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, and thermogravimetric (TG) analyses. Compound 1 is a binodal (3,4)-connected net with (6³)(6⁶) topology. Compounds 2–4 are isostructural and described by the uninodal (4,4)-connected net with (4⁴ · 6²) Schläfli symbol. The structure of 5 is a 2D binodal (6,3) net. In addition, the luminescent properties of compounds 1 and 2 have been studied in the solid state at room temperature.     

An effective use of benzoic anhydride and its derivatives for the synthesis of carboxylic esters and lactones: a powerful and convenient mixed anhydride method promoted by basic catalysts

Various carboxylic esters are obtained at room temperature in excellent yields with high chemoselectivities from nearly equimolar amounts of carboxylic acids and alcohols using 2-methyl-6-nitrobenzoic anhydride with triethylamine by the promotion of a basic catalyst such as 4-(dimethylamino)pyridine. A variety of lactones are also prepared in high yields at room temperature from the corresponding omega-hydroxycarboxylic acids with use of 2-methyl-6-nitrobenzoic anhydride in the presence of 4-(dimethylamino)pyridine. A similar reaction occurs with triethylamine when using a catalytic amount of 4-(dimethylamino)pyridine 1-oxide as an effective promoter for the intramolecular condensation reaction. These methods are successfully applied to the synthesis of erythro-aleuritic acid lactone and an eight-membered-ring lactone moiety of octalactins A and B. The efficiency of the cyclizations is compared to those of other reported lactonizations.     

2-Iodo benzoic acid: An unconventional precursor for the one pot multi-component synthesis of quinoxaline using organo Cu (II) catalyst

This is the first reported, unconventional, efficient strategy for the synthesis of quinoxaline from 2 to iodo benzoic acid and sodium azide in presence of organo Cu (II) catalyst. Herein, a very simple, versatile one pot multi-component protocol for the synthesis of biologically active compound, quinoxaline has been described via Schmidt reaction and the nucleophilic substitution reaction. The isolated compounds were characterized by 1H NMR, 13C NMR. Our reported organo catalyst was characterized by single crystal XRD, SEM.     

A new and efficient method for the facile synthesis of N-acyl sulfonamides under Lewis acid catalysis

The N-acylation of sulfonamides with carboxylic acid anhydrides in the presence of Lewis acids is described. Several Lewis acids such as BF₃·Et₂O, ZnCl₂, MoCl₅, TiCl₄, B(C₆F₅)₃, Sc(OTf)₃ and I₂ were found to catalyze the reaction efficiently to furnish the N-acylated products in good yields under solvent-free conditions. The reactions of various sulfonamides were studied with different carboxylic acid anhydrides including the less reactive benzoic and pivalic anhydrides, in the presence of 3 mol % ZnCl₂ as the catalyst. Carboxylic acids were also successfully used as acylating agents via the mixed anhydride method.     

An effective kinetic resolution of racemic α-arylpropanoic acids, α-arylbutanoic acids, and β-substituted-α-arylpropanoic acids with bis(9-phenanthryl)methanol as a new achiral nucleophile in the asymmetric esterification using carboxylic anhydrides and the acyl-transfer catalyst

A general method for the kinetic resolution of racemic α-arylalkanoic acids with achiral alcohols is described. It was determined that bis(9-phenanthryl)methanol is a suitable nucleophile which reacts with the intermediary mixed anhydrides generated from aromatic anhydrides with α-arylpropanoic acids or β-substituted-α-arylpropanoic acids in the presence of (+)-benzotetramisole to produce the corresponding optically active esters with high ee’s under very mild conditions.     

Synthesis of (9E)-isoambrettolide, a macrocyclic musk compound, using the effective lactonization promoted by symmetric benzoic anhydrides with basic catalysts

Two alternative methods for the synthesis of (9E)-isoambrettolide are established via the rapid lactonization of the free threo-aleuritic acid or its protected seco-acid using substituted benzoic anhydrides with basic catalysts. The most efficient lactonization of the threo-aleuritic acid is performed using 2-methyl-6-nitrobenzoic anhydride (MNBA) with a catalytic amount of 4-dimethylaminopyridine N-oxide (DMAPO).     

Ionothermal syntheses and characterization of 2-D coordination polymers with 4-(1H-imidazol-1-yl) benzoic acid

4-(1H-imidazol-1-yl) benzoic acid and its coordination polymers [M(IBA)Cl] _n (M?=?Zn (1) and Co (2)) have been synthesized. Compounds 1 and 2 were obtained under ionothermal conditions and possess a 2-D laminar [M(IBA)] _n layer based on M₂(CO₂)₂ building blocks with coordinated chloride completing tetrahedral coordination of the metal. Compound 1 exhibits two photoluminescence emission peaks at 410 and 510?nm. The low-energy emission can be attributed to ligand-centered transition and the high-energy band can be assigned to ligand-to-metal charge transfer between the aromatic systems of the organic ligands and the 4s orbitals of Zn(II). The role of the ionic liquid in ionothermal synthesis and crystallization of 1 and 2 are briefly discussed.     

Precolumn derivatization of reducing carbohydrates with 4-(3-Methyl-5-oxo-2-pyrazolin-1-yl) benzoic acid. Study of reaction, high-performance liquid chromatographic separation and quantitative performance of method

Summary A simple method for quantitative determination of carbohydrates by reversed-phase, high-performance liquid chromatography after pre-column derivatization and UV detection has been developed. Reducing sugars are condensed with 4-(3-methyl-5-oxo-2-pyrazolin-l-yl) benzoic acid (PMPA) to yield UV adducts absorbing at 271 nm, which are resolved under typical reversed-phase conditions. After derivatization, excess PMPA is easily removed from the reaction mixture by precipitation with mineral acids at pH<4. The influence of experimental conditions on reaction yield, as well as chromatographic separation of derivatives, were investigated. The quantitative performance was evaluated by means of a protocol comprising replicate measurements at several analyte levels. The calibration curves obtained for 8 sugars showed excellent linearity over 10–5000 pmol. Limits of detection and quantification for several monosaccharides were ca. 10 and 50 picomoles, respectively. Optimized conditions were successfully used for quantitative determination of monosaccharides released after hydrolysis from fetuin, mucin, α₁-acid glycoprotein, ovalbumin and transferrin.     

Preparation and spectroelectrochemical characterization of composite films of poly(3,4-ethylenedioxythiophene) with 4-(pyrrole-1-yl) benzoic acid

The possibility of incorporation of 4-(pyrrole-1-yl) benzoic acid, PyBA, during electrodeposition of poly(3,4-ethylenedioxythiophene), PEDOT, is demonstrated here. The resulting novel composite material has been fabricated as moderately thin (ca 200–300 nm thick) PEDOT/PyBA film on electrode surface. As evidenced from scanning tunneling microscopy (STM) and scanning electron microscopy (SEM), morphology of the composite film is dense and granular, and it is composed of larger granules in comparison to the PyBA-free PEDOT film. It is apparent from infrared reflectance absorption spectroscopy and spectroelectrochemical measurements that the PEDOT/PyBA composite film cannot be viewed as simple mixtures of PEDOT and PyBA components. Some specific (chemical) interactions between PEDOT and PyBA can be expected. The conducting polymer serves as a robust, positively charged conductive polmer matrix for anionic (carboxylate-group derivatized) partially polymerized PyBA structures. Upon incorporation of PyBA, the overall stability of PEDOT film (resistance to dissolution during prolonged voltammetric potential cycling) has been improved. The fact, that the composite PEDOT/PyBA film is capable of preconcentrating (under open circuit conditions) both cations (Cu²⁺) or anions implies the presence of both free (available for binding) carboxylate groups and positively charged PEDOT sites. The presence of PyBA in PEDOT seems to facilitate charge propagation in the composite film. “Contribution to the International Workshop on Electrochemistry of Electroactive Materials (WEEM-2006), Repino, Russia, 24–29 June 2006”.     

A simple, convenient method for the synthesis of maleic anhydrides from α-keto esters and alkanoic acid anhydrides using the TiCl4/n-Bu3N reagent system

Reaction of α-keto esters with alkanoic acid anhydrides using the TiCl₄/n-Bu₃N reagent system gives the corresponding maleic anhydrides in 62-95% yields.     

A new and efficient method for the synthesis of 3-(2-nitrophenyl)pyruvic acid derivatives and indoles based on the Reissert reaction

The formation of 3-(2-nitrophenyl)pyruvic acid and its amide and ester derivatives – key compounds for the Reissert indole synthesis – was achieved under various reaction conditions via the acid catalyzed hydrolysis of 5-(2-nitrobenzyliden)-2,2-dimethyl-1,3-oxazolidin-4-one, which is readily available from 3-(2-nitrophenyl)oxirane-2-carboxamide. A new and highly efficient method for the synthesis of indole-2-carboxylic acid derivatives via the intramolecular reductive cyclization of o-nitrophenylpyruvic acid and its amide and ester derivatives was developed using Na₂S₂O₄ in dioxane/water at reflux.     

Syntheses and Characterization of Two Coordination Polymers Constructed by the Ligand 3,5‐Bis(pyridin‐4‐ylmethoxy)benzoic Acid

Two coordination polymers, namely [Zn(L1)(OAc)]·H₂O ( 1 ) and [Cd(L1)₂] ( 2 ), where L1 = 3,5‐bis(pyridin‐4‐ylmethoxy)benzoic acid, have been synthesized under hydrothermal conditions and characterized by single‐crystal X‐ray diffraction analysis. Complex 1 has a 2D layer structure in which the hydrogen bonds between lattice water molecules and uncoordinated carboxylate oxygen atoms of the ligand L1 in the adjacent layers extend the 2D layer into a 3D supramolecular architecture. The structure of 2 is a 2D (3,5)‐connected net with (3·5²)(3²·5³·6⁴·7) topology. In addition, the luminescent properties of complexes 1 and 2 have been studied in the solid state at room temperature.     

One-step method for synthesis of 2,4-disubstituted quinazoline 3-oxides by reaction of a 2-aminoaryl ketone with a hydroxamic acid using Zn(OTf)2 as the catalyst

A simple and efficient method for the preparation of 2,4-disubstituted quinazoline 3-oxides by reaction of a hydroxamic acid with 2-aminoaryl ketones using zinc(II) triflate as the catalyst is described.     

Microwave‐assisted derivatization of cellulose in an ionic liquid: An efficient,expedient synthesis of simple and mixed carboxylic esters

Microwave (MW)‐assisted cellulose dissolution in ionic liquids (ILs) has routinely led either to incomplete biopolymer solubilization, or its degradation. We show that these problems can be avoided by use of low‐energy MW heating, coupled with efficient stirring. Dissolution of microcrystalline cellulose in the IL 1‐allyl‐3‐methylimidazolium chloride has been achieved without changing its degree of polymerization; regenerated cellulose showed pronounced changes in its index of crystallinity, surface area, and morphology. MW‐assisted functionalization of MCC by ethanoic, propanoic, butanoic, pentanoic, and hexanoic anhydrides has been studied. Compared with conventional heating, MW irradiation has resulted in considerable decrease in dissolution and reaction times. The value of the degree of substitution (DS) was found to be DS_ethanoate > DS_propanoate > DS_butanoate. The values of DS_pentanoate and DS_hexanoate were found to be slightly higher than DS_ethanoate. This surprising dependence on the chain length of the acylating agent has been reported before, but not rationalized. On the basis of the rate constants and activation parameters of the hydrolysis of ethanoic, butanoic, and hexanoic anhydrides in aqueous acetonitrile (a model acyl transfer reaction), we suggest that this result may be attributed to the balance between two opposing effects, namely, steric crowding and (cooperative) hydrophobic interactions between the anhydride and the cellulosic surface, whose lipophilicity has increased, due to its partial acylation. Four ethanoate‐based mixed esters were synthesized by the reaction with a mixture of the two anhydrides; the ethanoate moiety predominated in all products. The DS is reproducible and the IL is easily recycled. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 48: 134–143, 2010     

Lewis Acids as Mild and Effective Catalysts for the Synthesis of 3,5‐Bis[(hetero)arylidene]piperidin‐4‐ones

The aldol‐crotonic condensation reactions of N‐alkyl‐ and NH‐piperidin‐4‐one derivatives with (hetero)aromatic aldehydes promoted by Lewis acids or bases were examined. This comparative study has revealed three effective catalytic systems based on Lewis acids, i.e., LiClO₄ and MgBr₂ (in the presence of tertiary amine), and BF₃⋅Et₂O, for the synthesis of N‐alkyl‐substituted 3,5‐bis(heteroarylidene)piperidin‐4‐ones, including those bearing acid‐ or base‐labile groups both in the (hetero)aromatic groups and in the alkyl substituent at the N‐atom. The highest reaction rate was observed for LiClO₄‐mediated synthesis. Both MgBr₂‐ and LiClO₄‐mediated syntheses were inefficient in the case of NH‐piperidin‐4‐one, while BF₃⋅Et₂O provided the final compounds in high yields. This catalyst is especially advantageous as it allows simultaneous condensation and deprotection in the case of O‐protected piperidin‐4‐one.     

One-pot synthesis of dihydropyrimidones using silica-supported heteropoly acid as an efficient and reusable catalyst: Improved protocol conditions for the Biginelli reaction

An efficient synthesis of 3,4-dihydropyrimidinones or thiones (DHPMs) is described, using silica-supported heteropoly acid H₃PW₁₂O₄₀/SiO₂ (PW/SiO₂) for the first time as the catalyst from an aldehyde, β-keto ester and urea or thiourea in acetonitrile. Compared to the classical Biginelli reaction conditions, this method consistently has the advantage of excellent yields, mild reaction conditions, ease of workup, survival of different functional groups, and short reaction times.     

A sequential injection method for the fluorimetric determination of aluminum in drinking water using 8-hydroxy-7-(4-sulfo-1-naphthylazo)-5-quinoline sulfonic acid

A robust and simple sequential injection (SI) method for the assay of aluminum ions in drinking water is described. The method is based on the complex formation between aluminum and 8-hydroxy-7-(4-sulfo-1-naphthylazo)-5-quinoline sulfonic acid (HSNQ). The fluorescence of the complex is monitored at an emission wavelength of 492 nm with excitation at 357 nm. The HSNQ concentration, aspirated reagent and sample volumes were optimized simultaneously using 3(3) full factorial design. The optimum operating conditions are aspirated sample and reagent volumes of 90 and 70 microL, respectively, and HSNQ concentration of 20 microM. With these conditions linear calibration curves were obtained from 100 to 800 ppb. The detection limit was 4 ppb. The maximum relative standard deviation of the method was 1.43% (n=5). The method was successfully applied for the determination of aluminum in drinking water samples.