One-Pot Synthesis of N-Substituted 4-Aryl-1,4-dihydropyridines Under Solvent-Free Conditions and Microwave Irradiation

Summary.  The three-component condensation of benzaldehyde derivatives, alkyl propiolates, and primary amines catalyzed by silica gel, zeolite HY, montmorillonite K-10, and acidic alumina under microwave irradiation gave N-substituted 4-aryl-1,4-dihydropyridines in short reaction times and high yields. The best results were obtained with silica gel. Received March 26, 2001. Accepted (revised) June 18, 2001     

Trifluoroacetic Acid as an Efficient Catalyst for One-Pot,Four-Component Synthesis of 1,2,4,5-Tetrasubstituted Imidazoles Under Microwave-Assisted,Solvent-Free Conditions

An efficient method for synthesis of various tetrasubstituted imidazoles, using trifluoroacetic acid (TFA) as a catalytic support, by four-component condensation of benzil, aldehydes, amines, and ammonium acetate under microwave-irradiated, solvent-free conditions is described.     

One-Pot Synthesis of 2,4,5-Trisubstituted Imidazoles Using MoO3/SiO2, an Efficient and Recyclable Catalyst

A simple one-pot synthesis has been developed for the synthesis of 2,4,5-trisubstituted imidazoles using an efficient and recyclable MoO₃/SiO₂ solid acid catalyst by condensation of benzil or benzoin, benzaldehyde, and ammonium acetate in acetonitrile as a solvent. Using this solid catalyst, the reactions could be carried out under mild reaction conditions with very good yield of imidazoles, up to 95%. This catalyst could be recycled very easily, which makes this methodology environmentally benign.     

One-Pot Synthesis of Salicylanilides by Direct Amide Bond Formation from Salicyclic Acid Under Microwave Irradiation

A highly efficient protocol for the preparation of aromatic amides is described by the direct reactions between salicyclic acid and aromatic amines in the presence of phosphorous trichloride under microwave irradiation. The method has several advantages over the conventional methods, including operational simplicity, good yield, and reduced reaction time.

Green One-Pot Synthesis of 2H-Pyrans Under Solvent-Free Conditions Catalyzed by Ethylenediammonium Diacetate

Ethylenediammonium diacetate readily catalyzes the Knoevenagel-type condensation between 1,3-dicarbonyl substrates and α,β-unsaturated aldehydes at room temperature under solvent-free conditions. This rapid, efficient, and convenient one-pot approach to the synthesis of 2H-pyrans stands as a significant advance over previously reported protocols. This environmentally friendly methodology has been successfully applied to the synthesis of biologically active natural products of interest zanthosimuline, N-methylflindersine, and ferprenin.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications ^® to view the free supplemental file.     

Facile One-Pot,Multicomponent Synthesis of Pyridines Under Microwave Irradiation

A series of 2-amino-6-(2-oxo-2H-chromen-3-yl)-4-pyridine-3-carbo-nitriles were synthesized by the one-pot, multicomponent reaction of 3-acetyl-coumarin, aromatic aldehydes, malononitrile, and ammonium acetate in acetic acid under microwave irradiation. The reactions were completed in 10–13 min with 61–86% yields, were environmental benign, and had easy workup. Their structures were confirmed by ¹H NMR, IR, and MS spectra and elemental analysis.     

无溶剂条件下离子液体[Hnmp]HSO4催化一锅法合成2 -氨基苯并噻唑-芳甲基-2-萘酚

以离子液体[Hnmp]HSO₄为催化剂, 在无溶剂条件下催化芳香醛、2-氨基苯并噻唑和2-萘酚合成一系列的2 -氨基苯并噻唑-芳甲基-2-萘酚. 该方法条件温和, 反应时间短, 产率高和对环境友好. 此外催化剂可以方便地回收, 且循环使用四次其催化活性并没有显著降低. 目标产物经过了¹H NMR, IR, MS和元素分析确证.     

Acidic Ionic Liquid [(CH2)4SO3HMIM][HSO4]: A Green Media for the Simple and Straightforward Synthesis of 2,4,5-Trisubstituted Imidazoles

2,4,5-Trisubstituted imidazoles have been synthesized in excellent yields (85–95%) in the presence of 5 mol% of [(CH₂)₄SO₃HMIM][HSO₄] as a Brønsted acidic ionic liquid.     

Synthesis of 1,3-Dioxanes Catalyzed by TsOH-SiO2 Under Solvent-Free Conditions

Silica-supported p-toluene sulfonic acid is found to be an excellent catalyst for the Prins reaction to produce 1,3-dioxanes in good yields from olefins and aliphatic aldehydes in dichloromethane at room temperature and solventless microwave irradiation within a short reaction time.     

Highly Efficient Method for the Synthesis of 1,4-Phenylenedithioureas Under Solvent- and Catalyst-Free Conditions Promoted by Microwave Irridiation

A highly efficient method for the synthesis of 1,4-phenylenedithioureas promoted by microwave irridiation is reported. It is based on the nucleophilic addition reaction of 1,4-phenylenediisothiocyanate to aromatic amines under solvent- and catalyst-free conditions. The reaction has the advantages of short reaction time, good yields, and environmental acceptability.     

Molecular Iodine–Catalyzed,Mild, Effective,Ecofriendly, Microwave-Assisted,One-Pot Synthesis of 5-Arylmethylidene-2-phenyloxazol-4-ones (Azalactones) Under Solvent-Free Conditions

Fourteen azalactones have been synthesized in excellent yields under solvent-free conditions by heating an aldehyde, hippuric acid, and acetic anhydride in the presence of molecular iodine as a catalyst in a microwave oven. The short reaction time, cleaner reaction, and easy workup make this protocol practical and economically attractive.     

Microwave Promoted,Sodium Acetate Catalyzed One Pot Synthesis of Poly Functionalized 4H‐Pyrans

A clean and efficient one pot synthesis of 4H‐pyran derivatives through condensation of aromatic aldehydes, malononitrile and dicarbonyl compounds under microwave irradiation in presence of Sodium acetate as a catalyst is described.     

Convenient Synthesis of 2-Aminothiophene Derivatives by Acceleration of Gewald Reaction Under Ultrasonic Aqueous Conditions

Under ultrasound irradiation and in the presence of H₂O/Et₂NH, ethyl cyanoacetate or malononitrile can combine with α-methylene carbonyl compounds and elemental sulfur to efficiently yield 2-aminothiophene derivatives within a few minutes. Products are easily obtained by simple filtration because of their spontaneous precipitation in the reaction mixtures.     

无溶剂InCl_3·4H_2O催化下微波促进芳香醛与环酮的缩合反应

InCl_3·4H_2O作催化剂，在无溶剂微波照射下合成了一系列双亚苄基环酮衍 生物，为该类化合物的合成提供了一种新方法。产物的结构经~1H NMR，IR，MS及 元素分析确证。     

One-Pot Synthesis of 3,4-Dihydropyrimidin-2(1H)-ones Catalyzed by Acidic Ionic Liquids Under Solvent-Free Conditions

The acidic ionic liquids were new catalysts for the one-pot Biginelli reaction coupling of aldehyde, 1,3-dicarbonyl compound, and urea to afford the corresponding dihydropyrimidinones in good yields under solvent-free conditions. The catalysts could be recycled and reused five times without a noticeable decrease in catalytic activity.     

A Convenient One-Pot Synthesis of Some New 3-(2-Phenyl-6-(2-thienyl)-4-pyridyl)hydroquinolin-2-ones Under Microwave Irradiation and Their Antimicrobial Activities

A series of 3-(2-phenyl-6-(2-thienyl)-4-pyridyl)hydroquinolin-2-ones 4a–o were synthesized in high yields by a one–pot cyclocondensation reaction under Kröhnke's reaction conditions using 2-chloro-3-formyl quinoline 1a–c, 2-acetyl thiophene 2, and various N-phenacylpyridinium bromides 3a–e in a mixture of ammonium acetate and acetic acid by microwave irradiation. All the compounds have been characterized by elemental analysis, FT-IR, ¹H NMR, and ¹³C NMR spectral analysis. These compounds have been screened for their antimicrobial activities.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Microwave Assisted Synthesis of 3,3',3″,3'″-o-,p-Phenylenedi-methylidinetetrakis-(4-hydroxy-2H-1-benzopyran-2-one)

Under microwave irradiation,2,2'-alkoxy-bridging or 4,4'-alkoxy-bridging dibenzaldehydes reacted with 4-hydroxycoumarin in DMF to give a series of 3,3',3″,3'″-o-and 3,3',3″,3'″-p-phenylenedimethylidinetetrakis-(4-hydroxy-2H-1-benzopyran-2-ones) in moderate yields.The structures of the synthetic coumarin derivatives were characterized with IR,1H NMR and MS spectroscopy as well as X-ray single crystallography.     

微波辐射下Zr(SO4)2·4H2O/SiO2催化合成芳香磺酰亚胺

微波辐射无溶剂条件下,以Zr(sO4)2·4H2O/SiO2固体酸为催化剂,芳香醛与芳香磺酰胺反应合成了一系列芳香磺酰亚胺化合物.此方法具有操作简便,催化剂价廉易得、活性高、可回收重复使用、对环境友好等优点.     

微波促进活性炭负载四氯化锡催化合成乙酰乙酸乙酯缩酮

在微波辐射下,以活性炭负载四氯化锡(SnCl4·5H2O/C)为催化剂,不用溶剂,合成了乙酰乙酸乙酯乙二醇缩酮和乙酰乙酸乙酯1,2-丙二醇缩酮。以乙酰乙酸乙酯与乙二醇缩合为模型反应进行优化,其优化条件是:负载量为20%的SnCl4·5H2O/C催化剂0.1 g,乙酰乙酸乙酯5 mL,乙二醇6 mL,微波辐射功率600 W,辐射时间2.5 min,产率达81.6%。产物经过红外光谱表征。     

Novel Dual Use of Formamide-POCl3 Mixture for the Efficient,One-Pot Synthesis of Condensed 2H-Pyrimidin-4-amine Libraries Under Microwave Irradiation

The novel dual use of formamide-POCl₃ mixture for the incorporation of a C-N fragment to form the pyrimidine nucleus and its subsequent chlorination in an efficient, one-pot synthesis of potentially bioactive condensed 2H-pyrimidin-4-amine libraries under microwave irradiation (MWI) is reported. The one-pot microwave-assisted synthetic protocol is high-yielding, ecofriendly, rapid, and novel as well as eliminates intermittent workups. The protocol can be adapted for the library synthesis of series of a condensed pyrimidines.