A four-component synthesis of novel spiro[pyrazoloquinoline-oxindoles] under solvent-free conditions

A domino reaction for the rapid and diverse synthesis of spiro[1H-pyrazolo[3,4-b]benzo[h]dihydroquinolin-4,3-indolin-2-ones] is reported. The synthesis represents a thermodynamically-favored four-component reaction between phenylhydrazine, isatins, naphthylamines, and 3-ketoesters giving the novel products in excellent yields under solvent-free conditions. Similar applications of anilines in place of naphthylamines have not led to formation of the expected 4-substituted pyrazolo[3,4-b]quinoline derivatives. The difference was ascribed to lower aromatic character of naphthylamines, with respect to anilines, which enables them to act easier as enamines in reaction with the postulated intermediates formed from condensation of isatins and the in situ generated pyrazolones. Surprisingly, 6-aminouracils in despite of their known enamine properties did not participate in reaction with isatins and pyrazolones, the merit of naphthylamines for this synthesis seems to be met by the favorable balance of their N- and C-nucleophilicity.     

Microwave assisted convenient synthesis of quino[2,3-b][1,5]benzoxazepines

A convenient synthesis of quino[2,3-b][1,5]benzoxazepines from substituted 2-chloroquinoline-3-carbaldehyde and 2-hydroxy-aniline by using stable,non-toxic and inexpensive catalyst 1,8-diazabicyclo-undecan-7-ene (DBU)/silica gel is described.This method affords the quino[2,3-b][1,5]benzoxazepines under the influence of microwave irradiation (360 W) in solvent-free conditions within short reaction times (2-3 min),giving high yields of products (93-96%).     

Microwave assisted synthesis of novel imidazo [2,1-b]thiazole derivative attached to quinoxalinones

3-(6-Phenylimidazo[2,1-b]thiazol-5-yl)quinoxalin-2(1H)-ones (qunoxalinone) (6a-q) have been synthesized by the reaction of ethyl 2-oxo-2-(6-phenylimidazo[2,1-b]thiazol-5-yl)acetates (4a-e) with suitably substituted o-phenylenediamines (5a-f) under microwave heating. The ethyl 2-oxo-2-(6-phenylimidazo[2,1-b]thiazol-5-yl)acetates (4a-e) were prepared by the reaction of 6-phenylimidazo[2,1-b]thiazoles (3a-e) with ethyl chlorooxoacetate in refluxing 1,4-dioxane whereas the thiazoles (3a-e) were synthesized by the reaction of 2-bromo-1-phenylethanones (2a-e) with thiazol-2-amine in refluxing acetone.     

Microwave assisted one-pot synthesis of novel molecular clefts with only one chiral arm based on deoxycholic acid

A rapid, safe, and efficient method for the synthesis of novel molecular clefts based on deoxycholic acid was reported. Seven new molecular clefts have been synthesized in good yields （89-98%）. This method proved to be extremely simple and highly efficient. The structures of these receptors were confirmed by 1H NMR, IR, MS spectra and elemental analysis. 2007 Zhi Gang Zhao. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.     

Microwave assisted,Ca(II)-catalyzed Ritter reaction for the green synthesis of amides

An efficient solvent-free synthesis of amides by Ca(II) catalyzed Ritter reaction has been reported under microwave irradiation. This green protocol tolerates the substrate diversity and delivers the high yielding amides with minimal loading of inexpensive and more abundant Ca(II) catalyst.     

One-pot synthesis of novel spiro 2,3,7,8-tetrahydro-benzo[1,2-b:5,4-b′]dipyran-4,6-dione and 2,3,8,9-tetrahydro-benzo[1,2-b:4,3-b′]dipyran-4,10-dione derivatives

An efficient synthesis of novel spiro 2,3,7,8-tetrahydro-benzo[1,2-b:5,4-b′]dipyran-4,6-dione and 2,3,8,9-tetrahydro-benzo[1,2-b:4,3-b′]dipyran-4,10-dione derivatives in high yields under microwave irradiation is described. The reaction was also studied under conventional heating conditions.     

Microwave assisted synthesis of substituted furan-2-carboxaldehydes and their reactions

A series of 5-unsubstituted and 5-substituted furfurylidenes have been prepared, under thermal and non-thermal microwave irradiation methods, via condensation of furfural and its derivatives with some of active methylene compounds. Furthermore, various condensate products from these furfurylidenes, which contain halogen or sulpher atoms, were also prepared. Structural elucidation of the synthesized compounds were determined on the basis of various spectroscopic methods.     

Microwave versus ultrasound assisted synthesis of some new heterocycles based on pyrazolone moiety

Different pyrazolone derivatives were prepared by microwave irradiation and ultrasound assisted methods besides the traditional ones. They were used for synthesis of some derivatives of spiropiperidine-4,4′-pyrano[2,3-c]pyrazole, dihydropyrano[2,3-c]pyrazole, pyrazole-4-carbothioamide, 4-(2-oxo-1,2-diphenylethylidene)-1H-pyrazol-5(4H)-one, azopyrazole, arylmethylenebis-1H-pyrazol-5-ol and araylidene-1H-pyrazol-5(4H)-one via reactions with different reagents applying the ultrasound method in some cases.     

Addition reactions of fluoroalkanesulfonyl azides to [60] fullerene under thermal or microwave irradiation condition

The reactions of [60] fullerene with excess fluoroalkanesulfonyl azides R_fSO₂N₃ in o-dichlorobenzene under thermal or microwave irradiation condition afforded monoadduct opened [5,6]-bridged azafulleroids. While, similarly treatment of 2,2,2-trifluoroethyl azides CF₃CH₂N₃ with C₆₀ gave two monoadducts, i.e., opened [5,6]-bridged azafulleroids, closed [6,6]-bridged Aziridino-fullerene, and some multi-addition product. A general mechanism for these addition reactions was proposed.     

An efficient synthesis of fluorine-containing substituted spiro[piperidine-4,4′-pyrano[3,2-c]quinoline]-3′-carbonitrile by nonconventional methods

A series of fluorine-containing substituted spiro[piperidine-4,4′-pyrano[3,2-c]quinolines] were synthesized through a rapid one-pot multi-component reaction under microwave irradiation and sonication. The method has the advantages of excellent yields (80-96%) and short reaction time (3-10 min). We provide a series of fluorinated quinoline derivatives interesting for biological screening tests.     

Synthesis of Thia-calix[4]arene Hydroxamic Acids by Microwave Irradiation

Thia-calix[4]arene hydroxamic acids have been synthesized by partial reduction of nitro-thia-calix[4]arenes with hydrazine hydrate, Rn/Ni, and their coupling with benzoyl chloride under the influence of microwave irradiation with 90–95% yield and 3–6 min reaction time.     

Microwave assisted synthesis of nitro phenols from the reaction of phenols with urea nitrate under acid-free conditions

Urea nitrate was found to be an inexpensive, acid-free, and safe nitrating agent that provides mononitration of phenols and substituted phenols in excellent yields with exclusive ortho-selectivity under microwave irradiation. Microwave assisted reactions reduced the reaction times substantially and enhanced the product yields from good to excellent within shorter reaction times.     

Eco-friendly fast synthesis and thermal degradation of optically active polyamides under microwave accelerating conditions

<正>An optically active bulky aromatic diacid chiral monomer,(2S)-4-[(4-methyl-2-phthalimidylpentanoyl-amino) benzoylamino]isophthalic acid(1),containing a rigid phthalimide and flexible L-leucine pendent group was synthesized in five steps.A fast and clean method for direct polyamidation reaction of monomer 1 with various aromatic diamines under microwave irradiation and conventional heating was performed.The polymerization reactions provided optically active polyamides with high yields and inherent viscosities in the range of 0.36-0.74 dL/g.Their thermal properties were evaluated by thermogravimetric analysis(TGA) and differential scanning calorimetry.TGA thermograms show that the polymers are thermally stable,10%weight loss temperatures are in excess of 385℃,and char yields at 800℃are higher than 56%.The data obtained from TGA were used to study the kinetics of thermal decomposition of the resulting polymers. The interpretation of kinetic parameters(E,ΔH,ΔS andΔG) of thermal decomposition stages was evaluated using Coats and Redfern equation.     

Microwave assisted synthesis of the fragrant compound Calone 1951

Calone 1951^®, 7-methyl-benzo[b][1,4]dioxepin-3-one, possesses a strong marine, ozone note with floral nuances and is synthesised via a three-step procedure using microwave irradiation. High yields were obtained, and reaction times reduced to a few minutes, allowing for an efficient and inexpensive synthesis of Calone 1951^®.     

Electron-Rich Phenothiazine Congeners and Beyond: Synthesis and Electronic Properties of Isomeric Dithieno[1,4]thiazines

A series of isomeric dithieno[1,4]thiazines is accessible through an intermolecular–intramolecular Buchwald–Hartwig amination starting from dihalodithienyl sulfides. The electronic properties of dithieno[1,4]thiazine isomers differ conspicuously over a broad range depending on the thiophene–thiazine anellation: a large cathodic (340 mV) or an anodic shift (130 mV) of the redox potentials relative to corresponding phenothiazines is possible. Structure–property relationships of the dithieno[1,4]thiazine constitution derived from DFT calculations and cyclic voltammetry not only reveal increased electron density but also different delocalization of the radical cations that determines the electrochemical properties significantly. In addition, photophysical properties (absorption and emission) qualify dithieno[1,4]thiazines as promising substitutes of phenothiazine and beyond due to increased tunable electron richness.     

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.     

Green chemical multi-component one-pot synthesis of fluorinated 2,3-disubstituted quinazolin-4(3H)-ones under solvent-free conditions and their anti-fungal activity

A rapid one-pot solvent-free procedure has been developed for the synthesis of fluorinated 2,3-disubstituted quinazolin-4(3H)-ones by neat three-component cyclocondensation of anthranilic acid, phenyl acetyl chloride and substituted anilines under microwave irradiation. The experimental methodology and microwave conditions described here are well established, allowing significant rate enhancement and good yields compared to conventional reaction conditions. The reaction is generalized for O, M & P substituted anilines to give quinazolin-4(3H)-ones. Synthesized compounds have been screened for their antifungal activity.     

Microwave-assisted synthesis of new N4-[bi-（4-fluorophenyl）- methyl]-piperazine thiosemicarbazones under solvent-free conditions

Six new N4-[bi-（4-fluorophenyl）-methyl]-piperazine thiosemicarbazones 3a-f have been prepared starting from [bi-（4-fluorophenyl）-methyl]-piperazine in solvent-free condition under microwave irradiation with excellent yields. Their structures have been determined by elemental analysis, IR, MS and 1H NMR data.     

Highly efficient synthesis of triazolo[1,2-a]indazole-triones and novel spiro triazolo[1,2-a]indazole-tetraones under solvent-free conditions

A new, convenient, and high yielding procedure for the synthesis of triazolo[1,2-a]indazole-triones by the condensation reaction between dimedone, aryl aldehydes, and ueazoles in the presence of a catalytic amount of sulfonated polyethylene glycol (PEG-SO₃H) as a highly stable and reusable eco-friendly degradable polymeric catalyst is described under solvent-free conditions. This procedure has also been applied successfully for the synthesis of novel spiro triazolo[1,2-a]indazole-tetraones.     

Green chemical multi-component one-pot synthesis of fluorinated 2,3-disubstituted quinazolin-4(3H)-ones under solvent-free conditions and their anti-fungal activity

A rapid one-pot solvent-free procedure has been developed for the synthesis of fluorinated 2,3-disubstituted quinazolin-4(3H)-ones by neat three-component cyclocondensation of anthranilic acid, phenyl acetyl chloride and substituted anilines under microwave irradiation. The experimental methodology and microwave conditions described here are well established, allowing significant rate enhancement and good yields compared to conventional reaction conditions. The reaction is generalized for o-, m- and p-substituted anilines with electron-donating and -withdrawing groups to give quinazolin-4(3H)-ones. Synthesized compounds have been screened for their anti-fungal activity.