Solvent-Free Synthesis of Dihydropyridines and Acridinediones via a Salicylic Acid–Catalyzed Hantzsch Multicomponent Reaction

A multicomponent Hantzsch synthesis of 1,4-dihydropyridines and acridinediones from commercially available aldehydes, ammonium acetate, and ethyl acetoacetate or dimedone, in the presence of salicylic acid as an efficient catalyst, in good yield and short reaction time is reported.

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Metal-Free,One-Pot Oxidative Conversion of Aldehydes to Primary Thioamides in Aqueous Media

One-pot tandem reactions of a variety of aldehydes with aqueous ammonia, molecular iodine, and O,O-diethyl dithiophosphoric acid readily afford the corresponding primary thioamides. This is an inexpensive, practical, and metal-free way of accessing various thioamides from aldehydes in aqueous media. The pure products are obtained simply by filtration followed by successive washing with aqueous sodium thiosulfate and water.

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Synthesis of β-Aryl-β-sulfanyl Ketones by a Sequential One-Pot Reaction Using KF/Al2O3 in Glycerol

The title compounds were synthesized by a sequential one-pot reaction of aryl aldehydes, aryl-methyl ketones, and thiols promoted by KF/Al₂O₃. This methodology affords a large number of β-aryl-β-sulfanyl ketone derivatives from aliphatic and aromatic thiols in good yields and is also applicable for solid substrates.

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Mild and Efficient One-Pot Synthesis of 3,5-Disubstituted 1,2,4-Oxadiazoles from Nitriles Mediated by K3PO4

Potassium phosphate, K₃PO₄, has been proved to be a cheap, strong, and efficient reagent for the one-pot synthesis of 3,5-disubstituted-1,2,4-oxadiazoles from nitriles and acid chlorides under mild conditions.

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Green and Reusable Synthetic Procedure for Pyridine N-Oxides Catalyzed by a Lacunary Polyoxometalate

A lacunary Keggin polyoxometalate of K₈[BW₁₁O₃₉H] · 13H₂O was used as an effective and reusable catalyst for pyridine oxidation. Good yields of pyridine N-oxides were obtained in this catalytic system with hydrogen peroxide in water under mild conditions.

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Total Synthesis of (±)-Glabridin

An efficient formal synthesis of (±)-glabridin was accomplished in 10 steps from resorcinol using Raney Ni to reduce carbon–carbon double bonds in α,β-unsaturated carbonyl compound as the key step.

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First Synthesis of Dopamine and Rotigotin Analogue 2-Amino-6,8-dimethoxy-1,2,3,4-tetrahydronaphthalene

The title compound was synthesized starting from 3-(3,5-dimethoxyphenyl)acrylic acid in 11 steps with 30% total yield. The reaction sequence hydrogenation of acrylic acid, reduction of acid to alcohol derivative with LiAlH₄, reaction of alcohol with CBr₄/PPh₃, substitution reaction of alkyl halide to nitrile derivative with NaCN, hydrolysis of nitrile with NaOH, cyclization reaction of acid with PPA to give 1-tetralone, α-carboxylation of tetralone with Me₂CO₃ in the presence of NaH, reduction of ketone group with Et₃SiH, hydrolysis of ester, Curtius rearrangement of acid with diphenylphosphoryl azide followed by conversion to carbamate, and finally hydrogenolysis of carbamate afforded 2-amino-6,8-dimethoxy-1,2,3,4-tetrahydronaphthalene hydrogen chloride salt.

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Silica-Supported 4-OH-TEMPO/NOx: A Novel and Efficient Catalyst for Aerobic Oxidation of Alcohols

Silica-supported 4-OH-2,2,6,6-tetramethylpiperidyl-1-oxy/NO_x (4-OH-TEMPO was immobilized on the surface of silica using the sol-gel method, and then it adsorbed NO_x), as a heterogeneous catalyst, has exhibited good catalytic performance in alcohol oxidation. A broad range of alcohols were oxidized to their corresponding aldehydes or ketones with more than 99% selectivity and 99% conversion rate by such a catalyst system at room temperature in air. NO_x not only acted as an electron bridge between O₂ and 4-OH-TEMPO but also were conducive to the formation of the aldehydes as active component. A possible mechanism for oxidation of alcohols promoted by silica-supported 4-OH-TEMPO/NO_x was supposed.

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Ultrasound-Assisted,One-Pot,Four-Component Synthesis of 1,4,6,8-Tetrahydroquinolines in Aqueous Medium

A series of 2-amino-3-cyano-4-aryl-5-oxo-7,7-dimethyl-1,4,6,8-tetrahydroquinolines were prepared by a one-pot, four-component condensation of aromatic aldehydes, dimedone, malononitrile, and ammonium acetate using K₂CO₃ as a catalyst in aqueous medium under sonic conditions. This protocol, being a single-step reaction, has the advantages of operational simplicity and minimal environmental impact. The synthesized compounds were confirmed through spectral characterization using infrared, ¹H NMR, ¹³C NMR, and CHN analysis.

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Lanthanum Triflate–Catalyzed Rapid Oxidation of Secondary Alcohols Using Hydrogen Peroxide Urea Adduct (UHP) in Ionic Liquid

A convenient and efficient protocol for the oxidation of secondary hydroxyl group to ketone using hydrogen peroxide–urea adduct and catalytic (CF₃SO₃)₃La in ionic liquid has been developed. A number of 1,2-diols, α-hydroxyketones, and other aromatic and aliphatic secondary alcohols have been successfully oxidized to the corresponding ketones using this protocol in good yields and short reaction times.

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Synthesis and Reactions of Novel 2,5-Disubstituted 1,3,4-Thiadiazoles

The desired 1,3,4-thiadiazole compounds bearing different substituents were obtained by the cyclization of the corresponding thiosemicarbazide followed by the reaction with electrophilic reagents, such as aromatic aldehydes, isatin, phenyl isothiocyanate, and carbon disulfide. The newly synthesized 2,5-disubstituted 1,3,4-thiadiazoles were obtained in good yields and their structures were elucidated by spectral data and elemental analysis.

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Unexpected Transformation of Aldehydes into Benzoins with Copper(I)/Samarium

The reductive coupling of aldehydes to afford pinacolic alcohols using all kinds of reducing agents involving samarium is well known. In this report, however, treatment of aromatic aldehydes with Cu(I)/Sm system produces benoins and/or benzils in good yields. A possible mechanism is proposed where Cu(I) not only activates the Sm metal but also promotes the dehydrogenation of the intermediates, during which a Cu(III) species may be involved.

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Reexamination of the Bromination of 2-Nitrobenzaldehyde with NBS or NaBr-NaIO4 in Sulfuric Acid

Two literature procedures for selective bromination of 2-nitrobenzaldehyde using N-bromosuccinimide (NBS) or NaBr-NaIO₄ in sulfuric acid were examined. In contrast to the reports that 4-bromo-2-nitrobenzaldehyde is formed as a single product in good yield, reactions using NBS gave a number of isomeric mono- and dibrominated products identified by spectroscopical methods and by sodium borohydride reduction to the corresponding benzyl alcohol, and reactions using NaBr-NaIO₄ did not furnish any product.

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Palladium-Catalyzed Oxidative Carboacetoxylation of Activated Alkynes with Amino Acids

A palladium-catalyzed intramolecular oxidative carboacetoxylation reaction of alkynes with various amino acids has been demonstrated for the first time, forming pharmaceutically important 3-methyleneindolin-2-one. In the presence of Pd(OAc)₂ and ArI(OAc)₂, N-arylpropiolamides underwent tandem acetoxypalladation/C-H functionalization reactions with various Boc-amino acids to form corresponding methyleneindolin-2-ones bearing amino acid motifs in moderate to excellent yields.

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New Synthetic Route to (1S)-4,5-Dimethoxy-1-[(methylamino)methyl] Benzocyclobutane,a Key Intermediate of Ivabradine

An efficient process for the preparation of (1S)-4,5-dimethoxy-1-[(methylamino)methyl] benzocyclobutane (S)-3 as ivabradine intermediate, which was obtained in 56% yield, is described. The salient feature of this process is the racemization of the undesired (1R)-4,5–dimethoxy-1,2-dihydrocyclobutabenzene-1-carboxylic acid (R)-12, and the overall yield of (S)-12 was improved to 70% by three resolutions of the racemized acid with R-(α)-phenylethanamine. The reduction of amide (S)-13 was achieved with NaBH₄-I₂ in refluxing tetrahydrofuran, giving the corresponding amine (S)-3 in 90% yield. The improved synthetic route described herein is cost-efficient, environmentally friendly and feasibile for scale-up production.

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Free Radical–Mediated Chemoselective Reduction of Enones

A novel methodology has been devised for the chemoselective reduction of enones involving the use of ⁿ Bu₃SnH and azobisisobutyronitrile. The 1,4-reduction of variously substituted α,β-unsaturated cyclic and acyclic enones has been successfully carried out under free radical reaction conditions. The reaction has been determined to proceed via single-electron transfer.

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CuFe2O4 Nanoparticles: A Magnetically Recoverable and Reusable Catalyst for the Synthesis of Coumarins via Pechmann Reaction in Water

The synthesis of coumarins by hydroxyalkylation of phenols with ethyl acetoacetate (via Pechmann reaction) is attempted using magnetically separable and reusable CuFe₂O₄ nanoparticles in water.

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Highly Stereoselective Cyclopropanation of Olefins Catalyzed by a Novel C 3-Symmetric Arsine

A novel C ₃-symmetric arsine was employed in the one-pot cyclopropanation of olefins with carbonyl-stabilized arsonium ylides formed in situ from phenacyl bromide in the presence of NaHCO₃. This new arsine demonstrates good stereoselectivity and activity in the one-pot cyclopropanation of arylidenemalononitrile.

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Highly Efficient Synthesis of 1,3-Dioxanes via Prins Reaction in Brønsted-Acidic Imidazolium Ionic Liquid

The high-yielding synthesis of a wide variety of 1,3-dioxanes via the Prins reaction under mild conditions has been demonstrated using Brønsted-acidic imidazolium ionic liquid [bmim(SO₃H)][OTf] or bmimOTf. The use of ionic liquid makes this synthesis simple, convenient, cost-effective, and environmentally friendly. Furthermore, bmimOTf was conveniently separated from the products and can be easily recycled for the Prins reaction with excellent yields. This method works well with a variety of aliphatic aldehydes including formaldehyde, acetaldehyde, propionaldehyde, and cyclohexanecarboxaldehyde.

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C-S Bond-Forming Reactions of Barbiturylbromide with Isothiocarbamides in Aqueous Media

The C-S cross coupling of pharmaceutically active barbituric acid derivatives has been achieved by the interaction of selective monobromobarbituric acid with thioureas in an aqueous medium. This method is applicable for simple thiourea as well as monosubstituted thioureas, and corresponding products are obtained in good yield.

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