A Neat and Rapid Synthesis of 2‐Aryloxymethylene‐6‐Arylimidazo[2,1‐b]‐1,3,4‐Thiadiazole Under Microwave Irradiation

A neat and rapid procedure is reported for the synthesis of a variety of 2‐aryloxymethylene‐6‐arylimidazo[2,1‐b]‐1,3,4‐thiadiazole (3a–3r) by condensation reaction of 2‐amino‐5‐aryloxymethylene‐1,3,4‐thiadiazole (1a–1f) with ω‐bromoacetophenone (2a–2c) in ethanol solvent under microwave irradiation, which yielded a series of novel compounds. The yields are good to excellent. The procedure is simple and does not need any added catalyst or dehydrating reagent. Moreover, the crystals do not require further purification to give the products.     

An Efficient Synthesis of 1,5-Thiadiazepines and 1,5-Benzodiazepines by Microwave-Assisted Heterocyclization

A novel and efficient method for the synthesis of substituted thiazepines and diazepines has been developed. A simple one-pot reaction of chalcones 1a–f with 1-amino-2-mercapto-5-phenyl-1,3,4-triazole and o-phenylenediamine in the presence of a catalytic amount of sodium acetate under microwave irradiation gave 2-(3,8-diphenyl-7,8-dihydro[1,2,4]triazolo[3,4-b][1,3,4]thiadiazepin-6-yl)phenoles 2a–f and 2-(2-phenyl-2,3-dihydro-1H-1,5-benzodiazepin-4-yl)phenoles 3a–f, respectively. The structure of all the synthesized compounds was elucidated on the basis of elemental analysis, IR, ¹H and ¹³C NMR, and mass spectral data.     

Efficient solvent-free synthesis of bis(indolyl)methanes on SiO<Subscript>2</Subscript> solid support under microwave irradiation

An efficient synthesis of bis(indolyl)methanes was developed. Bis(indolyl)methanes were synthesized starting from various aromatic aldehydes with indole under microwave irradiation and solvent-free conditions (85–98 %). Solid support SiO₂ was found to possess favorable catalytic and dispersancy parameters for the condensation reaction. Moreover, novel bis(indolyl)methanes containing an isoxazole ring were synthesized via this method in excellent yields (> 94 %) using 3-substituted isoxazole-5-carbaldehydes and indole.     

Microwave‐Assisted One‐Pot Synthesis of 1,2,3,4‐Tetrahydrocarbazoles

A series of 1,2,3,4‐tetrahydrocarbazoles 3a–m were synthesized by the reaction of substituted 2‐bromocyclohexanones 2a–c with appropriate anilines 1a–i under microwave irradiation without any other catalysts.     

NOVEL N,S-SUBSTITUTED DIENES BY THE REACTION OF 2-NITROTHIOSUBSTITUTED HALODIENES AND PRIMARY AMINES

Mono(thio)substituted 1a–c gave compounds 3a–c and 5a with o-toluidin (2) and m-toluidin (4) in ether. Compounds 9a–c and 11a, b were obtained from the reaction of compounds 1a–c with p-fluorophenylamine (8) and p-fluorobenzylamine (10). Compounds 7a and 15c were obtained from the reaction of 1a and 1c with p-phenylendiamine (6) and o-phenylendiamine (14). Compound 13c was synthesized from the reaction of compound 1c with benzidine (2).     

A FACILE METHOD FOR THE SYNTHESIS OF NOVEL PYRIDINONE DERIVATIVES VIA KETENE N,S-ACETALS

A simple and easy method is provided for the synthesis of the novel pyridinone derivatives (3a–e), (8a–c) and (10a–c) by the reaction of ketene acetals (2a–e), (7a–c) and (9a–c) with ethyl cyanoacetate respectively. Compounds (3b–d) reacted with triethyl orthoformate to afford the pyridinone derivatives (4-6) respectively. Compound 7a reacted with ethyl acetoacetate or diethyl malonate to give thiazolopyridinone derivative 11 or 12 respectively.     

On the 3-Aminophenothiazine Synthesis

Abstract

Investigation of the key step of 3-aminophenothiazine (5) synthesis, that is thiation of N-(4-phenylaminophenyl)-phthalimid (3) was carried out. The best results were achieved using microwave irradiation, when 55% of the pure thiation product 3-phalimidophenothiazine (4) were isolated in 10–20 min reaction time.     

The Microwave-Assisted Dehydrative Cyclization of Thiosemicarbazides Forming Substituted 1,2,4-Triazoles

Different types of 4,5-disubstituted 1,2,4-triazole-3-thiones were prepared by microwave irradiation as well as by a classical method. The beneficial effect of microwave irradiation on the dehydrative cyclization of thiosemicarbazides in different reaction media is described. Our results show that the effect of microwave irradiation on the reaction studied was the shortening of reaction times (from 2–9 h to 2–4 min) and a minor decrease (1–4%) in yields. The structure of the new compounds was established by FTIR, MS, and ¹H NMR spectral data.     

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.     

Potassium–Tertiary Butoxide–Assisted Addition of Thioglicolic Acid to Chalcone Derivatives Under Solvent-Free Conditions

A series of chalcone derivatives containing thioglicolic acid (4a–j) was prepared by addition of thioglicolic acid to the chalcones (3a–j) in the presence of KOt-Bu under solvent-free conditions. The mechanistic pathway of the reaction can be explained by the Michael-type addition of thioglicolic acid to chalcone derivatives (3a–j).     

Michael reaction of indoles with 3-(2′-nitrovinyl)indole under solvent-free conditions and in solution. An efficient synthesis of 2,2-bis(indolyl)nitroethanes and studies on their reduction

Michael reaction of 3-(2′-nitrovinyl)indole with eight 3-unsubstituted indoles on TLC-grade silica gel furnished unsymmetrical bis(indolyl)nitroethanes in 7-12 min under microwave irradiation and in 8-14 h at rt. In contrast, the p-TsOH-catalysed reaction of the nitrovinylindole with the 3-unsubstituted and two 3-substituted indoles in solution under reflux furnished both unsymmetrical and symmetrical bis(indolyl)nitroethanes, the latter resulting from novel tandem Michael addition-elimination-Michael addition reactions. The synthesis of a 2′,3″-bis(indolyl)nitroethane, the precursor core structure of two bioactive marine metabolites, and the reduction of 2,2-bis(3′-indolyl)nitroethane to the corresponding ethylamine, isolated as its N-acetyl derivative, have been achieved. Significantly, attempted hydrolysis of three nitronates, derived from the corresponding bis(indolyl)nitroethanes, with buffered aqueous TiCl₃ has led to the first isolation of oximes (syn/anti-mixture) as the only products.     

Microwave Promoted One‐Pot Synthesis of Some Novel N‐Aryl Isoquinoline Derivatives

Homophthalic anhydride 1 reacts with different aromatic amines to produce N‐substituted homophthalimides 2 under microwave irradiation. A rapid microwave‐assisted chemical synthesis of condensed 4‐substituted furo[2,3‐c]isoquinoline‐1,5(2H,4H)‐diones 3 and 5‐substituted‐2,3‐dihydro‐1H‐pyrano[2,3‐c]isoquinoline‐1,6(5H)‐diones 4 involving the condensation of a variety of alkanoyl chlorides with 2‐arylisoquinoline‐1,3‐diones 2 in the presence of base and aprotic solvent is described for the first time. By contrast, the facile ring opening reaction of furo[2,3‐c]isoquinoline‐1,5(2H,4H)‐dione 3 with Vilsmeier–Haack reagent under microwave irradiation yielded the α‐β unsaturated carboxyaldehyde 5 . This novel and clean one‐pot methodology, which is characterized by very short reaction time and easy workup procedure, can be exploited to generate some novel condensed isoquinoline derivatives.     

Thionation of Chalcone and Aurone Derivatives by Lawesson's Reagent

Abstract

The reaction of Lawesson's reagent (LR 5) with chalcones (4a–h) and aurones (12a–h) proceeds in refluxing toluene to give the respective benzofuranylprop-2-en-1-thiones (8a–h) and benzodifuran-3-thiones (13a–h). Correct elemental analyses and spectroscopic data were obtained for the new compounds.     

Two Novel Microwave‐Promoted Reactions between Ethyl 6‐Acetylpyridine‐2‐carboxylate and Aromatic Amine/Aliphatic Amine

The unsymmetric precursor ethyl 6‐acetylpyridine‐2‐carboxylate (3) was synthesized from 2,6‐dipiclinic acid (1). On the basis of this precursor, two distinctively different types of compounds were prepared by microwave irradiation under solvent‐free conditions. One type was mono(imino)pyridine compounds (4a–4f), originating from the Schiff base condensation between a series of aromatic amines and the precursor 3; another type was 6‐acetylpyridine‐2‐carboxamide compounds (5a–5c), which were the products of amidation reactions between a series of aliphatic amines and the same precursor 3.     

Conventional and Microwave-Assisted Facile One-Pot Synthesis of N-Substituted Pyrrole-2,3,4,5-tetracarboxylates Under Neat Conditions

Highly substituted pyrroles 3a,f were prepared conveniently in a reaction of (dimethyl- and diethyl-)acethylenedicarboxylates 1a–b with N-(methyl- and aryl-) hydroxylamines 2a–d in the presence of NaHCO₃ using both conventional heating and microwave irradiation. Excelent yields of the very pure products were isolated under solvent-free conditions both at classical as well as microwave heating.     

A Convenient Route to 1,3,4-Thiadiazoles,Thiazolidinone, Thiazoles,Pyridones, Coumarins,Triazolo[5,1-c]triazines,and Pyrazolo[5,1-c]triazines Incorporating Pyrazolone Moiety and Their Use as Antimicrobial Agents

Condensation of 4-acetyl-5-methyl-2-phenyl-2,4-dihydropyrazol-3-one (1) with hydrazine derivatives (2a–d) afforded hydrazone derivatives (3a–d), which reacted with alkyl halides 4a–c to give bis(alkylthio)methylene derivatives (5a–e). Also, 3a,b reacted with hydrazonyl halides 6a–d to give 1,3,4-thiadiazole (7a–d). Cyclization of 3c with ethyl bromoacetate and haloketones gave thiazolidinone and thiazole derivatives (8, 10a,b) respectively. Treatment of hydrazone (3d) with benzylidine malononitrile 13a,b gave pyridine (14a,b). In addition, cyclocondensation of 3d with phenolic aldehydes furnished coumarin derivatives (16a–c). Coupling of 3d with heterocyclic diazonium salts gave triazol[5,1-c]triazine (20) and pyrazolo[5,1-c]triazine (22). Some of the prepared products showed potent antimicrobial activity.     

Rapid and Efficient Synthesis of (R)-Aryloxypropionic Acid Esters Under Microwave Irradiation

A series of (R)-(+)-ethyl aryloxypropionates (4a–4p) have been synthesized by the reaction of substituted phenols with ethyl (S)-(?)-tosyloxy lactate under the conditions of microwave irradiation and without solvents. The reaction conditions have been optimized. A good method for the preparation of (R)-(+)-ethyl aryloxypropionate was developed, with good yields, high enantiomer excess, short reaction times, easy workup, and simple procedure.     

Regioselective annelation of 3-(prop-2-ynylsulfanyl)-1,2,4-benzotriazine to thiazolo[2,3-c][1,2,4]benzotriazine

Summary Thiosemicarbazide reacted with 1,2-diaminobenzene to give 1,2-dihydro-3-thioxo-1,2,4-benzotriazine (1) in fairly good yield in a solvent free reaction under microwave irradiation.1 was condensed with prop-2ynyl bromide in the presence of sodium methoxide to afford the corresponding 3-(prop-2-ynylsulfanyl)-1,2,4-benzotriazine (5). Transformation of5 to 3-methylidene-2,3-dihydro-9H-thiazolo[2,3-c][1,2,4]benzotriazine (6) was performed in the presence of a palladium salt.

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Regioselektive Anellierung von 3-(prop-2-inylsulfanyl)-1,2,4-benzotriazin zu Thiazolo[2,3-c][1,2,4]benzotriazin

Zusammenfassung Thiosemicarbazid reagierte mit 1,2-Diaminobenzol ohne Lösungsmittel und unter Bestrahlung mit Mikrowellen in guter Ausbeute zu 1,2-Dihydro-3-thioxo-1,2,4-benzotriazin (1), welches in Gegenwart von Natriummethoxid mit Prop-2-inylbromid zum entsprechenden 3-(Prop-2-inylsulfanyl)-1,2,4-benzotriazin (5) kondensiert wurde. Die Umsetzung von5 zu Methyliden-2,3-dihydro-9H-thiazolo[2,3-c] [1,2,4]benzotriazin (6) gelang unter Palladiumkatalyse.

     

A CONVENIENT SYNTHESIS OF 1,3-DISUBSTITUTED-4-(1′,3′-DITHIOLANE/DITHIANE-2′-YLIDENE)-2-PYRAZOLIN-5-ONES

1, 3 - Disubstituted- 4 - (1′, 3′- dithiolane /dithiane - 2′- ylidene) - 2 -pyrazolin-5-one derivatives like (1a–c), (2a–c), (3a–c) have been obtained by condensation of 2-pyrazolin-5-ones (1), (2) and (3) with carbon disulfide in presence of triethylamine followed by the reaction with 1,2-dibromoethane (4a), 1,3-dibromopropane (4b) and 1,3-dibromobutane (4c) respectively.     

SYNTHESIS OF 4,9-DIMETHYL-8- (6-ARYL-2-THIOXO-1,2,3,6-TETRAHYDRO PYRIMIDIN-4-YL)-FURO[2,3-H]CHROMEN-2-ONES AS ANTIMICROBIAL AGENTS UNDER MICROWAVE IRRADIATION

Acrolyl furochromen-2-ones (3a–i) obtained in good yields on microwave irradiation of furochromen-2-one (1) with various simple and substituted aromatic aldehydes (2a–i). 3a–g on cyclo dehydration with thiourea in domestic microwave oven furnished tetrahydro thiaxopyrimidine furochromen-2-ones 4a–i in high yields. The structures of the newly synthesized compounds were established on the basis of analytical and spectral data, IR, and ¹H NMR.