Facile synthesis of some novel triazolo[3,4-b]thiadiazines and triazolo[4,3-b]tetrazines

4-Amino-5-ethyl-4H-1,2,4-triazole-3-thiol was used as a key intermediate for the synthesis of triazolo[3,4-b][1,3,4]thiadiazines, triazolo[4,3-b][1,2,4,5]tetrazines and Schiff’s base via reactions with various hydrazonoyl halides and salicyaldehyde, respectively. Moreover triazolyl-N-N′-triazole derivatives were prepared from reaction of Schiff’s base with various hydrazonoyl halides. The structures of all the newly synthesized heterocyclic compounds were established by considering elemental analysis and spectral data.     

Efficient novel synthesis of pyrano[3,2-a]- and pyrazolo[4,3-a]-acridines

The synthesis of pyrano[3,2-a]acridines is presented, where 7-chloro-9-phenyl-2,3-dihydroacridin-4(1H)-one reacts with arylaldehydes and malononitrile in the presence of piperidine in ethanol, giving with high yield via a multicomponent method. Also a new synthesis of pyrazolo[4,3-a]acridines is reported, where 7-chloro-9-aryl-2,3-dihydroacridin-4(1H)-one on Claisen condensation with ethylformate followed by hydrazine hydrate treatment through the intermediate 7-chloro-4-hydroxy-9-aryl-1,2-dihydroacridin-3-carbaldehyde. The structures of newly synthesized compounds were deduced by spectroscopic techniques, elemental analysis, and single-crystal x-ray diffraction.     

Efficient One-Pot,Four-Component Synthesis of 1,2,3-Triazole-Linked Tetrahydrobenzo[b]pyrans

A one-pot procedure has been developed for the synthesis of (1,2,3-triazolyl) methoxyphenyl tetrahydro-5-oxo-4H-chromene derivatives by concurrent reaction of aryloxy propargylated aldehydes, various azides, active methylene compounds, and 1,3-cyclohexanediones using catalytic amounts of Cu(OAc)₂ / sodium ascorbate and diammonium hydrogen phosphate in aqueous ethanol media. Excellent conversion of starting materials was achieved to the desired (1,2,3-triazolyl) methoxyphenyl tetrahydro-5-oxo-4H-chromene products.     

SO3H‐functionalized nano‐MGO‐D‐NH2: Synthesis,characterization and application for one‐pot synthesis of pyrano[2,3‐d]pyrimidinone and tetrahydrobenzo[b]pyran derivatives in aqueous media

An SO₃H‐functionalized nano‐MGO‐D‐NH₂ catalyst has been prepared by multi‐functionalization of a magnetic graphene oxide (GO) nanohybrid and evaluated in the synthesis of tetrahydrobenzo[b]pyran and pyrano[2,3‐d]pyrimidinone derivatives. The GO/Fe₃O₄ (MGO) hybrid was prepared via an improved Hummers method followed by the covalent attachment of 1,4‐butanesultone with the amino group of the as‐prepared polyamidoamine‐functionalized MGO (MGO‐D‐NH₂) to give double‐functionalized magnetic nanoparticles as the catalyst. The prepared nanoparticles were characterized to confirm their synthesis and to precisely determine their physicochemical properties. In summary, the prepared catalyst showed marked recyclability and catalytic performance in terms of reaction time and yield of products. The results of this study are hoped to aid the development of a new class of heterogeneous catalysts to show high performance and as excellent candidates for industrial applications.     

Molecular Iodine: An Efficient Catalyst for the Synthesis of Tetrahydrobenzo[b]pyrans

An iodine/DMSO system is introduced as an excellent catalyst in three‐component coupling reactions of tetrahydrobenzo[b]pyran synthesis. The reaction proceeds quickly under very mild reaction conditions.     

A Mild and Environmentally Benign Synthesis of Tetrahydrobenzo[b]pyrans and Pyrano[c]chromenes Using Pectin as a Green and Biodegradable Catalyst

Pectin was applied as a green and biodegradable catalyst for the one‐pot three‐component synthesis of tetrahydrobenzo[b]pyrans and pyrano[c]chromenes, from the condensation between aromatic aldehydes, malononitrile, and dimedone or 4‐hydroxycumarine at ambient temperature. This protocol has many advantages such as mild conditions, high yields, environmental benignity, simple work‐up procedures, short reaction time, as well as the use of a natural, easily accessible, convenient handling, and inexpensive catalyst. Another advantage of this method is that the products do not require further purification such as column chromatography.     

A Recyclable and Highly Effective ZnO-beta Zeolite as a Catalyst for One-pot Three-Component Synthesis of Tetrahydrobenzo[b]pyrans

4H‐Benzo[b]pyrans was synthesized under reflux condition in ethanol via condensation of benzaldehyde, malononitrile and dimedone with ZnO‐beta zeolite as an inexpensive and effective catalyst. The key features of the reported protocols are good to excellent yields, short reaction time and recovery and reusability of catalytic material.     

Novel type of SO3H–functionalized nano‐titanium dioxide as a highly efficient and recyclable heterogeneous nanocatalyst for the synthesis of tetrahydrobenzo[b]pyrans

n ‐Butylsulfonated nano‐titania (n‐TiO₂‐NH‐(CH₂)₄‐SO₃H) as a highly efficient and reusable nanocatalyst was prepared by grafting 2,4‐toluene diisocyanate as a bi‐functional covalent linker onto a nano‐titania support, followed by reduction and then ring opening‐reaction of the synthesized amine with 1,4‐butanesultone. Fourier transform infrared spectroscopy, X‐ray diffraction, field‐emission scanning electron microscopy and thermogravimetric analysis were used to characterize the catalyst. The catalytic activity of n‐TiO₂‐NH‐(CH₂)₄‐SO₃H was evaluated in the synthesis of tetrahydrobenzo[b ]pyrans, which affords high yields. Statistical experimental design was applied as an efficient and powerful method to achieve the optimal conditions for this catalytic reaction leading to high yield. Moreover, the catalyst was recovered and reused at least six times without a significant decrease in catalytic activity.     

Facile Method for the Synthesis of Pyrazolo[3,4-b]-pyrido[4,3-d]-pyrimidine-4-ones via a Tandem Aza-Wittig Reaction

Fifteen novel pyrazolo[3,4-b]-pyrido[4,3-d]-pyrimidine-4-ones (7a–o) were designed and have been successfully synthesized via tandem aza-Wittig and annulation reactions of the corresponding iminophosphorances 5, phenylisocyanate, and substituted phenols in 60–77% isolated yields. Their structures were clearly verified by infrared (IR), ¹H NMR, electron impact–mass spectrometry (EI-MS), and elemental analysis. The results of a preliminary bioassay indicated that some compounds possess inhibition activities against the root of Brassica napus (rape) and Echinochloa crusgalli (barnyard grass) at a dosage of 100 mg/L and 10 mg/L.     

Theophylline as a new and green catalyst for the one-pot synthesis of spiro[benzo[a]pyrano[2,3-c]phenazine] and benzo[a]pyrano[2,3-c]phenazine derivatives under solvent-free conditions

A green, convenient, high yielding and one-pot procedure for the synthesis of novel spiro[benzo[a]pyrano[2,3-c]phenazine] derivatives by domino multi-component condensation reaction between 2-hydroxynaphthalene-1,4-dione, benzene-1,2-diamines, ninhydrine, and malononitrile in the presence of a catalytic amount of 1,3-dimethyl-7H-purine-2,6-dione (theophylline) as an expedient, eco-friendly and reusable solid base catalyst under thermal, microwave irradiation and solvent-free conditions. This procedure has also been applied successfully for the synthesis of benzo[a]pyrano[2,3-c]phenazines.     

微波辐射下硅磺酸催化的香豆素并[4,3-d]吡唑并[3,4-b]吡啶的高效合成

在硅磺酸催化下,通过微波辐射的3-酰基香豆素与5-氨基吡唑的反应,一步高产率地合成了一系列香豆素并[4,3-d]吡唑并[3,4-b]吡啶衍生物.该方法具有反应时间短(20~30 min)、选择性好、产率高、操作简单和环境友好等优点.产物的结构经红外光谱、核磁共振谱及高分辨质谱予以确定.     

Catalyst-free three-component approach to efficient synthesis of chromeno[4,3-b]pyrrol-4(1H)-one derivatives

A mild, efficient, and environmentally benign one-pot synthesis of functionalized chromeno[4,3-b]pyrrol-4(1H)-ones by a three-component domino reaction of 4-aminocoumarins, arylglyoxal monohydrates, and 1,3-dicarbonyl compounds in refluxing ethanol without the use of catalyst is reported. The present protocol features operational simplicity, short reaction time, good yields, and the absence of aqueous workup procedure and chromatographic separation.     

10-氯-5-二乙氧基甲基-1,3-二甲基色烯并[4,3-d]吡唑并[3,4-b]吡啶-6(3H)-酮的合成和晶体结构

利用L-脯氨酸催化的5-氯水杨醛(1)与6-甲基-4-羟基吡喃酮(2)的缩合反应及硫酸铜催化下与1,3-二甲基-5-氨基吡唑(3)的串联反应,合成得到了10-氯-1,3-二甲基-5-(2-氧代丙基)色烯并[4,3-d]吡唑并[3,4-b]吡啶-6(3H)-酮(4)和10-氯-5-二乙氧基甲基-1,3-二甲基色烯并[4,3-d]吡唑并[3,4-b]吡啶-6(3H)-酮(5).化合物5的结构通过单晶X射线衍射法确定:晶体属于三斜晶系,空间群P-1;相对分子质量Mr=803.68;晶胞参数a=1.03160(10)nm,b=1.42900(13)nm,c=1.44268(15)nm;V=1.9448(3)nm~3;Z=2;晶胞密度Dc=1.372g/cm~3;吸收系数μ=0.228mm-1;单胞中电子的数目F(000)=840.晶体结构用直接法解出,经全矩阵最小二乘法对原子参数进行修正,最终的偏离因子为R=0.0681,w R=0.2051.在晶体结构中色烯环与吡啶环及吡唑环近似于共平面.     

Ru(II) complexes bearing tertiary phosphine ligands: a novel and efficient homogeneous catalyst for one‐pot synthesis of dihydropyrano[3,2‐c]chromene and tetrahydrobenzo[b]pyran derivatives

A number of ruthenium complexes were prepared and their catalytic activities in three‐component one‐pot condensation of aldehydes, malononitrile and 4‐hydroxycoumarin or dimedone was considered to afford dihydropyrano[3,2‐c]chromenes and tetrahydrobenzo[b]pyran derivatives under optimum reaction conditions. We found that a catalytic amount of RuBr₂(PPh₃)₄ efficiently promotes the reaction in a short time (3–15 min) and with high yield (75–88%). Copyright © 2012 John Wiley & Sons, Ltd.     

Mn(III)–pentadentate Schiff base complex supported on multi‐walled carbon nanotubes as a green,mild and heterogeneous catalyst for the synthesis of tetrahydrobenzo[b]pyrans via tandem Knoevenagel–Michael cyclocondensation reaction

Mn(III)–pentadentate Schiff base complex supported on multi‐walled carbon nanotubes as a recyclable and reusable, green and nano‐heterogeneous catalyst was designed and fully characterized using infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy , inductively coupled plasma mass spectrometry, elemental analysis and thermogravimetric analysis. A facile, eco‐friendly, mild and green procedure was developed for the one‐pot three‐component synthesis of tetrahydrobenzo[b ]pyrans via tandem Knoevenagel–Michael cyclocondensation reactions between aromatic aldehydes, 1,3‐diones and malononitrile using a catalytic amount of Mn(III)–pentadentate Schiff base complex supported on MWCNTs as an efficient recyclable heterogeneous catalyst under solvent‐free conditions at room temperature. This process has the advantages of easy availability, stability, recyclability and eco‐friendliness of the catalyst, short reaction times, high to excellent yields and simple work‐up procedure.     

Sodium bromide catalysed one-pot synthesis of tetrahydrobenzo[b]pyrans via a three-component cyclocondensation under microwave irradiation and solvent free conditions

Sodium bromide catalysed three-component cyclocondensation of aryl aldehydes, alkyl nitriles and dimedone proceeds under microwave irradiation in solvent free conditions to give highly functionalised tetrahydrobenzo[b]pyrans in excellent yields.     

Three-Component,One-Pot Synthesis of Benzo[b][1,4]oxazines in Ionic Liquid 1-Butyl-3-methylimidazolium Bromide

Benzo[b][1,4]oxazines have been synthesized in good to excellent yields in the presence of the ionic liquid 1-butyl-3-methylimidazolium bromide [bmim]Br under relatively mild conditions without any added catalyst, The method offers the advantages of good yields and short reaction times, and the ionic liquid can be easily separated from the product and reused.     

Synthesis of some substituted triazolo[4,3-b][1,2,4]triazines as potential anticancer agents

The synthesis of some 3-substituted amino-6,7-diphenyl-1,2,4-triazolo[4,3-b][1,2,4]triazines (15) by cyclodesulfurisation of the corresponding N-(5,6-diphenyl-1,2,4-triazin-3-yl)-N-[substituted thio (carbamoyl)]hydrazines (3) using dicyclohexylcarbodiimid (DCC) and mercuric chloride is described. Moreover, trials to prepare 3-substituted amino-7-hydroxy-6-methyl-1,2,4-triazolo[4,3-b][1,2,4]triazines were not successful.

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Synthese einiger substituierter Triazolo[4,3-b][1,2,4]-triazine als potentielle Antikrebswirkstoffe

Zusammenfassung Es wird die Synthese einiger 3-substituierter Amino-6,7-diphenyl-1,2,4-triazolo[4,3-b][1,2,4]-triazine (15) mittels Cyclodesulfurisierung der entsprechenden N-(5,6-Diphenyl-1,2,4-triazin-3-yl)-N-[subst.thio(carbamoyl)]-hydrazine (3) unter Verwendung von Dicyclohexylcarbodiimid (DDQ) beschrieben. Versuche zur Herstellung von 3-substituierten Amino-7-hydroxy-6-methyl-triazolo[4,3-b][1,2,4]-triazinen schlugen fehl.