Metal coordination protocol for the synthesis of-2,3-dehydrosilybin and 19-O-demethyl-2,3-dehydrosilybin from silybin and their antitumor activities

An efficient and practical method to access bioactive 2,3-dehydrosilybin and 19-O-demethyl-2,3-dehydrosilybin using naturally abundant flavonolignan silybin in the presence of metal salt as a chelating agent is described. The procedure presented here has several advantages including one-pot, synthetic ease, and products in high yields with no side reactions, and large-scale feasibility. The dehydrogenation and demethylation proceed smoothly via a one-pot process using the AlCl₃/Pyridine system and I₂ as the additive. Furthermore, 2,3-dehydrosilybin and 19-O-demethyl-2,3-dehydrosilybin can inhibit the expression of intracellular mature miRNA-21 with IC₅₀ values of 4.46?μM and 8.25?μM, respectively, and show moderate anticancer activities against HeLa cell lines.     

Microwave-assisted simple, one-pot, four-component synthesis of 2,4,6-triarylpyrimidines under solvent-free conditions

2,4,6-Triarylpyrimidines are synthesized via a simple, one-pot, four-component reaction between aryl methyl ketones, benzaldehydes, aromatic nitriles, and hydroxylamine under microwave irradiation and solvent-free conditions in good to excellent yields.     

Microwave-assisted Suzuki coupling on a KF-alumina surface: synthesis of polyaryls

A range of conjugated polyaryls has been synthesized through one-pot microwave assisted palladium-catalyzed consecutive Suzuki coupling reactions on a KF-alumina surface with notable features including rapid reaction times, solvent-free conditions, high yields, atom economic and air-insensitive reactions.     

Microwave-assisted synthesis of 8-mercapto-3-methyl-7-alkyl xanthines—an improved method

A microwave-assisted synthetic method to prepare novel 8-mercapto-3-methyl-7-alkyl xanthine compounds is reported. Compared to conventional synthetic route, the new method significantly shortened synthetic steps and reaction time.     

Microwave-assisted hydrothermal synthesis of Pt/SnO2 gas sensor for CO detection

In this paper, the Pt/SnO₂ nanostructures were prepared via a facile one-step microwave assisted hydrothermal route. The structure of the introduced Pt/SnO₂ and its gas-sensing properties toward CO were investigated. The results from the TEM test reveal that Pt grows on the SnO₂ nanostructure, which was not found for bulk in this situ method, constructing Pt/SnO₂. The results indicated that the sensor using 3.0 wt% Pt/SnO₂ to 100 ppm carbon monoxide performed a superior sensing properties compared to 1.5 wt% and 4.5 wt% Pt/SnO₂ at 225 °C. The response time of 3.0 wt% sensor is 16 s to 100 ppm CO at 225 °C. Such enhanced gas sensing performances could be attributed to the chemical and electrical factors. In view of chemical factors, the presence of Pt facilitates the surface reaction, which will improve the gas sensing properties. With respect to the electrical factors, the Pt/SnO₂ plays roles in increasing the sensor’s response due to its characteristic configuration. In addition, the one-step in situ microwave assisted process provides a promising and versatile choice for the preparation of gas sensing materials.     

Microwave-assisted tandem reactions for the synthesis of 2-hydrazolyl-4-thiazolidinones

A tandem method for the synthesis of 2-hydrazolyl-4-thiazolidinones (5) from commercially available materials in a 3-component reaction has been developed. The reaction connects aldehydes, thiosemicarbazides, and maleic anhydride, effectively assisted by microwave irradiation. The synthesis of a new type of compound, 2-hydrazolyl-5,5-diphenyl-4-thiazolidinone (7), obtained by treatment of thiosemicarbazone with benzil in basic media is also reported. HOMO/LUMO energies, orbital coefficients, and charge distribution were used to explain the proposed reaction mechanism.     

Microwave-assisted synthesis and characterization of a new metal-free and metallophthalocyanines

Dinitrile monomer (3) was synthesized by nucleophilic aromatic substitution of 4-phenoxyphenol (1) with 4-nitrophthalonitrile (2). The metal-free phthalocyanine (4) was prepared by the reaction of dinitrile monomer (3) with DMAE. Ni(II), Co(II), and Zn(II) metallophthalocyanines were prepared by the reaction of 3 with chlorides of Ni(II), Co(II), and Zn(II) in DMAE. The new compounds were characterized by IR, ¹H- and ¹³C-NMR, UV-Vis, elemental analysis, and MS specral data.     

Microwave-assisted synthesis utilizing supported reagents: a rapid and versatile synthesis of 1,5-diarylpyrazoles

The application of microwave heating to a silica-assisted solution-phase synthesis technique has been utilized to develop a rapid and efficient two-step protocol for the preparation of pyrazoles from aryl methyl ketone and aryl hydrazine monomers.     

Microwave-assisted ring-closing metathesis of diallylamines: a rapid synthesis of pyrrole and pyrroline derivatives

The ring-closing metathesis (RCM) reactions of diallylamines occurred under controlled microwave irradiation. In addition to the high reaction rate, the key features of the reaction are that it can be carried out without deactivation of the substrates and without the use of Lewis acids.     

Reactions of enaminones and related compounds with N,N-dimethylacetamide dimethyl acetal. A simple one-pot metal-free synthesis of polysubstituted benzene derivatives

Herein a simple one-pot metal-free synthesis of alkyl-, aryl-, heteroaryl- and alkoxycarbonyl substituted 1,3-bis(dimethylamino)benzene derivatives is described. The products were prepared from the corresponding methyl ketones or compounds with an α-methylene group in regard to the carbonyl group, using N,N-dimethylacetamide dimethyl acetal (DMADMA) as the reagent.     

Microwave-assisted efficient synthesis of 1,2-diaryldiketones: a novel oxidation reaction of diarylalkynes with DMSO promoted by FeBr3

This paper reports the oxidation of functionalized diarylalkynes with DMSO in the presence of the environmentally friendly FeBr₃ catalyst. This non-toxic procedure is general and has been applied successfully under microwave irradiation leading rapidly to benzil derivatives in good yields.     

Microwave-assisted reactions： Three-component process for the synthesis of 2-amino-2-chromenes under microwave heating

2-Amino-2-chromenes are class of heterocycles that posses considerable interest as pigments,cosmetics,potential agrochemicals and being the main constituents of many natural products.Although,they are generally prepared either under conventional heating,benign reagents or very recently,a three component condensation in poly-ethylene glycol-water in the presence of nanosized magnesium oxide,most of these methods require prolonged reaction time,reagents in stoichiometric amounts and generate moderate yield...     

Microwave-assisted four-component reaction for the synthesis of a monothiohydantoin inhibitor of a fatty acid amide hydrolase

Monothiohydantoin 3a is made in seven steps from 1,4-diiodobenzene and is shown to be an inhibitor of fatty acid amide hydrolase (IC₅₀ = 23.4 ± 1.1 μM). The key step in the sequence involves a microwave-assisted four-component reaction that makes the 5,5′-disubstituted hydantoin nucleus by the sequential formation of two C-C and two C-N bonds.     

Microwave-assisted,one-pot reaction of 7-azaindoles and aldehydes: a facile route to novel di-7-azaindolylmethanes

A novel and highly efficient synthetic method leveraging microwave-assisted organic synthesis (MAOS) to yield di-7-azaindolylmethanes (DAIMs) is reported. Under MAOS conditions, reaction of 7-azaindole with aldehydes resulted predominantly in DAIMs, as opposed to the expected 7-azaindole addition products that form at ambient temperature. Based upon studies of different indoles and azaindoles with various aromatic and aliphatic aldehydes, we herein propose a mechanism where rapid and efficient microwave heating promotes nucleophilicity of 7-azaindoles toward the corresponding alkylidene–azaindolene intermediate to form the DAIM. This sequence provides a versatile approach to efficiently synthesize novel DAIMs that may be useful pharmaceuticals.     

Microwave-assisted chemoselective reaction: a divergent synthesis of pyrazolopyridine derivatives with different substituted patterns

A series of new functionalized pyrazolopyridine derivatives with different substituted patterns were synthesized via microwave-assisted multi-component divergent reactions of aldehydes, 5-aminopyrazoles, and cycloketones by controlling the reaction condition. The procedures are facile, avoiding time-consuming and costly syntheses, tedious work-up, and purifications of precursors as well as protection/deprotection of functional groups. This chemistry provides an efficient and promising synthetic strategy to construction of the pyrazolopyridine skeleton.     

Microwave-assisted synthesis of ethynylarylboronates for the construction of boronic acid-based fluorescent sensors for carbohydrates

A reliable and operationally simple procedure for the synthesis of 2,2-dimethylpropane-1,3-diyl ethynylaryl boronates 4 was developed. The key step is microwave-facilitated selective formation of 2,2-dimethylpropane-1,3-diyl trimethylsilylethynylaryl boronates by Sonogashira reaction from the corresponding bromides. The use of microwave was found to significantly improve the reaction yield and shorten the reaction time. The 2,2-dimethylpropane-1,3-diyl ethynylaryl boronates 4 prepared can be used in the construction of diboronic acid libraries through [2+3] Huisgen cycloaddition for carbohydrate fluorescent sensor development.     

A simple and convenient method for the preparation of diborane from tetrabutylammonium borohydride and benzyl chloride for application in organic synthesis

Diborane is readily generated in situ at 25 °C in toluene using the Bu₄NBH₄/PhCH₂Cl and Bu₄NBH₄/I₂ reagent systems. The reagent prepared in this way is used for the reduction of carbonyl compounds and hydroboration-oxidation of olefins to obtain the corresponding alcohols in good yields.     

General methodology for the chemoselective N-alkylation of (2,2,6,6)-tetramethylpiperidin-4-ol: Contribution of microwave irradiation

A convenient method to access a broad variety of N-alkyl-(2,2,6,6)-tetramethylpiperidin-4-ol compounds is reported. The thermal treatment of a mixture of (2,2,6,6)-tetramethylpiperidin-4-ol and allyl or benzyl bromide derivatives gave the corresponding N–alkylated compounds in good yields while leaving the hydroxyl functional group intact. Whereas 40?h were needed to reach complete conversion, microwave irradiation allowed the reaction time to be reduced (20?min) and improved the yields in most cases.     

A very simple method for the preparation of symmetrical disulfides

A serendipitiously discovered, extremely simple, fast and previously unreported method for the preparation of symmetrical aliphatic, aromatic and heteroaromatic disulfides is reported. Addition of sulfuryl chloride to an alkyl- or arylthiol in a 1:2 ratio under solvent free conditions or in dichloromethane solution produces the corresponding disulfides in nearly quantitative yields with the concomitant elimination of gaseous SO₂ and 2 equiv of HCl. Thus, optimally the reaction needs no work-up at all leaving the disulfide as the sole product in excellent yield. In dichloromethane solution, the reaction is conveniently carried out in a rotary evaporator by mixing the solvent, thiol and SO₂Cl₂ in a round-bottomed flask followed by evaporation of the volatiles.     

Microwave-assisted transition-metal-free intramolecular Ullmann-type O-arylation in water for the synthesis of xanthones and azaxanthones

An efficient, rapid, and green method was developed for the synthesis of xanthones and azaxanthones. Transition-metal-free intramolecular Ullmann-type O-arylation reaction of 2-halo-2′-hydroxybenzophenones in the presence of TBAOH as base under microwave irradiation in water afforded the desired xanthones and azaxanthones in short reaction time in excellent yields.