A convenient synthesis of coumarin-3-carboxylic acids via Knoevenagel condensation of Meldrum's acid with ortho-hydroxyaryl aldehydes or ketones

Coumarin-3-carboxylic acids were obtained in high yields with excellent purity from ortho-hydroxybenzaldehydes and Meldrum's acid after a 2 h reflux in ethanol. The less reactive ketones were first reacted with alcoholic ammonia to form ketimines, which were then condensed with Meldrum's acid to generate 4-alkylcoumarin-3-carboxylic acids in moderate yields.     

Aqueous Synthesis of N-Phenyl/alkyl-2-quinolinone-3-carboxylic Acids from Coumarin-3-carboxylic Acids

An efficient, ecofriendly aqueous synthesis of aromatic/aliphatic amines with coumarin-3-carboxylic acid in a one pot reaction in a sealed tube or InCl₃/ H₂O in open vessel to afford N-phenyl/alkyl-2-quinolinones is achieved. This method provides high yield of products in shorter time, making it a useful process for the synthesis of structurally diversified 2-quinolinones from corresponding coumarins.     

Decarboxylation of indole-3-carboxylic acids under metal-free conditions

Abstract

Two reaction systems have been developed for the decarboxylation of indole-3-carboxylic acids. The decarboxylation can be achieved smoothly under K₂CO₃-catalyzed or acetonitrile-promoted basic conditions. It provided an efficient and simple method for the transformation of indole-3-carboxylic acids and the corresponding indoles were isolated with good to excellent yields. From the experimental facts, we put forward the possible reaction mechanism.     

Quinoline- and 1,8-naphthyridine-3-carboxylic acids using a self-catalyzed Friedländer approach

One-step syntheses of 2-alkyl- and 2,4-dialkyl-substituted quinoline-3-carboxylic acids and 1,8-naphthyridine-3-carboxylic acids are reported using a catalyst-free Friedländer reaction. The reaction is carried out in one step by simple heating of 2-aminobenzaldehyde, 2-amino-5-chlorobenzaldehyde, 2-aminonicotinaldehyde, or 2-aminoacetophenone with a β-ketoester in toluene or xylene for 24 h. Under these conditions, the carboxylic acid product is isolated directly from the reaction mixture without need for further purification. The observation that the reaction starts slowly and accelerates as it proceeds suggests that the transformation is self-catalyzed. This hypothesis is also supported by the finding that attempts to extend the current reaction to diketones, which cannot hydrolyze to an acid, were generally unsuccessful.     

A new insight into the Pfitzinger reaction. A facile synthesis of 6-sulfamoylquinoline-4-carboxylic acids

The unusual formation of 6-sulfamoylquinoline-4-carboxylic acids from 5-sulfamoylisatins under the conditions of Pfitzinger reaction is described. Key step in the suggested mechanism is the reaction of in situ generated acetaldehyde with the hydrolytically cleaved isatin ring. The suggested mechanism has been confirmed by dynamic LCMS measurements and by reactions with isotopically labeled reactants.     

Synthesis of functionalized 3-arylpyridazines via Pd-catalyzed decarboxylative cross-coupling of pyridazine-3-carboxylic acids

An efficient and general protocol for the decarboxylative cross-coupling of pyridazine-3-carboxylic acids with aryl-bromides has been described. This method provides a new avenue for the synthesis of 3-arylpyridazines via decarboxylative cross-coupling strategy by employing the dual-catalyst system of Pd(PPh₃)₄/Cu₂O in the presence of Li₂CO₃ at 160 °C in DMA.     

Uncatalyzed solventless Diels-Alder reaction of 2-amino-3-nitroacrylate: synthesis of new epimeric 2-amino-3-nitro-norbornene- and norbornane-2-carboxylic acids

A highly diastereoselective Diels-Alder reaction between cyclopentadiene and ethyl (Z)-2-N-Boc-amino-3-nitroacrylate in neat conditions affords the ethyl 2-t-butoxycarbonylamino-3-endo-nitro-bicyclo[2.2.1]hept-5-ene-2-exo-carboxylate: a new constrained carbocyclic amino acid. Catalytic hydrogenation of this cycloadduct gave the corresponding reduced norbornane derivative. A preliminary investigation into the chemistry of these two amino acids was performed. In particular, the epimerization to their corresponding 3-exo-nitro compounds by treatment both with acid and base was studied. From this study, valuable information on the endo/exo process at the C-3 carbon atom, as well as on the stability of the different stereomers, was obtained. The stability is closely related to the presence or the absence of the double bond in the ring and to the substitution pattern. Finally, deprotection of the amino acid function has been performed.     

香豆素-3-羧酸分子印迹聚合物复合膜对底物的结合及渗透选择性质的研究

在光照和引发剂的作用下, 模板分子香豆素-3-羧酸、 功能单体丙烯酰胺和交联剂乙二醇二甲基丙烯酸酯(EDMA)或三甲氧基丙烷三甲基丙烯酸(TRIM)在聚偏氟乙烯(PVDF)微孔滤膜表面聚合形成分子印迹聚合物复合膜. 用高效液相色谱仪测定了分别以TRIM和EDMA为交联剂制备的分子印迹聚合物膜在不同溶剂中对混合底物的结合和渗透选择性. 结果表明, 以TRIM为交联剂的印迹膜对模板分子具有更高的结合和渗透选择性. 另外, 以乙腈或乙腈/水作为溶剂对分子印迹膜所作的实验和讨论有助于为从复杂样品中分离模板分子奠定理论和实验基础.     

Facile and efficient synthesis of quinoline-4-carboxylic acids under microwave irradiation

<正>A facile and efficient method for the preparation of 2-non-substituted quinoline-4-carboxylic acids is described via the Pfitzinger reaction of isatins with sodium pyruvate following consequent decarboxylation under microwave irradiation.     

Palladium-catalyzed domino protodecarboxylation/oxidative Heck reaction: regioselective arylation of coumarin-3-carboxylic acids

A protocol for straightforward and step-economical synthesis of neoflavones from coumarin-3-carboxylic acids is developed. This approach enables controlled protodecarboxylation/regioselective C–H arylation of coumain-3-carboxylic acids in one-pot using a monometallic catalytic system. A wide variety of electron-donating and -withdrawing substituents on both coumarins and arylboronic acid are tolerated under the reaction conditions and 4-aryl coumarins are constructed in high yields.     

Silica Sulfuric Acid: A Versatile and Reusable Catalyst for Synthesis of Coumarin-3-carboxylic Acids in a Solventless System

Synthesis of substituted coumarin-3-carboxylic acid via Knoevenagel condensation of meldrum's acid with ortho-hydroxyaryl aldehydes in solventless system is described.     

1H-吲唑-3-羧酸的合成

综述了1H-吲唑-3-羧酸的合成方法,并评述了其优缺点;同时介绍了作者在寻找其新合成方法中的一些探索。参考文献28篇。     

Practical synthesis of a functionalized 1-oxo-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid

The synthesis of a functionalized 1-oxo-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid has been performed in 10 steps from the readily available dimedone. Only three purifications by flash chromatography are required through the whole sequence. The key step is the reaction between a dimedone derivative and a chlorotetrolic ester, that gives a tetrasubstituted benzene ring (through a Diels-Alder/retro- Diels-Alder process) bearing the substituents in the suitable positions for further functionalization.     

Unnatural amino acids. 3. Aziridinyl ketones from esters and amides of aziridine-2-carboxylic acids

A series of N-substituted amides and esters of aziridine-2-carboxylic acids have been prepared and have been subjected to deprotonation with lithium diisopropylamide. The intermediate carbanions reacted more readily with the carbonyl groups of the substrates than with methyl iodide. So, in place of the expected amides or esters of methylaziridine-2-carboxylic acids, amides or esters of 2-aziridinylcarbonylaziridine-2-carboxylic acids were isolated. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, 220–225, February, 2007.     

Synthesis and transformations of polysubstituted diastereomeric 5-oxomorpholin-2-carboxylic acids

A series of trans- and cis-3,4-disubstituted 5-oxomorpholine-2-carboxylic acids 5 were prepared by a cyclocondensation between diglycolic anhydride 3 and arylideneamines 4. Transformations of the carboxylic group leading to a peptide bond in the side chain to the morpholinone ring were effected. The relative configurations and the preferred conformations of the substituents at the morpholinone ring in some of the newly prepared derivatives were determined by means of ¹H NMR and X-ray analysis.     

Determination of type A trichothecenes by high-performance liquid chromatography with coumarin-3-carbonyl chloride derivatisation and fluorescence detection

A method for the analysis of type A trichothecenes T-2 toxin, HT-2 toxin, neosolaniol and diacetoxyscirpenol by high-performance liquid chromatography with fluorescence detection using coumarin-3-carbonyl chloride has been developed. Different parameters concerning the analytical procedure such as stability of both the reagent and derivatised analytes, time and temperature of the derivatisation reaction, were studied and optimised. Three different clean-up procedures (solid-phase extraction with silica gel or C-18 cartridges, and liquid–liquid partition between toluene and dihydrogen phosphate buffer) were tested in order to remove the excess reagent peaks. The last procedure gave the best results when the buffer pH was 3–5.5, and is therefore recommended. Separations were performed on a stainless steel LiChrospher 100 C-18 reversed-phase column with pre-column of the same phase. The mobile phase was acetonitrile/water (65:35, v/v) containing 0.75% acetic acid at a flow-rate of 1.0 ml/min. The proposed method provides good separation between the four trichothecenes and good reproducibility (RSD of calibration standards <5%). The limits of detection of the studied trichothecenes at a signal-to-noise ratio of 3:1, with an injection volume of 20 μl were 10 ng/g sample for T-2 toxin and about 15 ng/g sample for the remaining mycotoxins. The calibration curve was linear between 10 and 2000 ng for the four trichothecenes assayed. The method was applied to the analysis of these mycotoxins in fungal cultures (corn and rice) of Fusarium sporotrichioides, and is also perfectly suitable for the quantification of type A trichothecenes in contaminated cereals.     

取代吲哚-3-甲酸类化合物的合成

吲哚-3-甲酸是一种重要的有机中间体,被广泛应用于医药与农药的合成.以取代邻硝基甲苯为原料,与N,N-二甲基甲酰胺二甲基缩醛(DMFDMA)反应制得取代2-硝基-β-二甲氨基苯乙烯,再经铁粉和冰乙酸还原环合生成取代吲哚,取代吲哚与三氟乙酸酐经酰化、碱性条件下水解制得5种取代吲哚-3-甲酸类化合物,该合成方法操作简单,条件温和,收率较高.     

Facile One-Pot Synthesis of 1,2,3,4-Tetrahydroquinoline-3-carboxylic Acids and Their Heterocyclic Analogs

A facile one-pot method for the synthesis of 1,2,3,4-tetrahydroquinoline-3-carboxylic acids and their heterocyclic analogs based on the tert-amino effect. A set of 1,2,3,4-tetrahydroquinoline-3-carboxylic acids was readily prepared starting from various ortho-dialkylaminoaldehydes and Meldrum's acid using Me₃SiCl in dimethylformamide (DMF) solution.     

The One-Pot Synthesis and Diels-Alder Reactivity of 2,5-Dihydrothiophene- 1,1-dioxide-3-carboxylic Acid

Abstract

A one-pot preparation of 2,5-dihydrothiophene-1,1-dioxide-3-carboxylic acid (3-sulfolene-3-carboxylic acid) is reported. The carboxylation of 3-sulfolene, exclusively at the 3-position, using CO₂ and DBU proceeds to >90% conversion. A rapid workup gives 3-sulfolene-3-carboxylic acid, a stable precursor to 1,3-butadiene-2-carboxylic acid. High conversions to Diels-Alder adducts were obtained upon treatment of 3-sulfolene-3-carboxylic acid with various dienophiles.