Role of Additives in Chiral Amine-Catalyzed Direct Aldol Reaction

A systematic study of chiral adducts derived from amines as catalysts for aldol reaction revealed that enantioselective outcome depends on the chiral enamine intermediate and not the face-selective activation of aldehyde. A simple addition compound of proline and 8-hydroxy quinoline was found to be a good catalyst.

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Recyclable,Graphite-Catalyzed,Four-Component Synthesis of Functionalized Pyrroles

A facile, convenient, and multicomponent coupling strategy for the synthesis of highly functionalized pyrroles is developed using graphite as a catalyst, but devoid of moisture-sensitive metal catalysts and corrosive acidic reagents. This method involves four-component coupling reactions of ethyl acetoacetate compound or diethyl acetylene dicarboxylate, amines, aromatic aldehydes, and nitromethane without an inert atmosphere. This approach provides easy access to highly substituted pyrroles in good yields via one-pot tandem reaction. The method is very simple, straightforward, and environmentally friendly compared to the existing methods.

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An Expedient Approach for the Synthesis of 1-Alkyl-4-propionylpyrrolidin-2-ones

A simple and useful tandem addition–cyclization reaction of primary amines on a prepared α-functionalized propylvinyl ketone 3 in methanol at reflux is a promising route for the synthesis of a new family of 1-alkyl-4-propionylpyrrolidin-2-ones 4.

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Novel Four-Step Synthesis of Thioxo-quinazolino[3,4-a]quinazolinone Derivatives

A novel synthesis of thioxo-quinazolino[3,4-a]quinazolinone framework was developed through a four-step reaction starting from isatoic anhydride. The resulting 2-aminobenzamides from the reaction of isatoic anhydride and different amines underwent coupling–cyclization reaction with 2-nitrobenzaldehydes, reduction of nitro group, and then cyclization reaction with carbon disulfide (CS₂). All steps were carried out under easy and user-friendly conditions in a short time without using expensive catalysts or reagents.

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PCC-Promoted Dehydration of Aldoximes: A Convenient Access to Aromatic,Heteroaromatic, and Aliphatic Nitriles

A simple and convenient procedure for the synthesis of nitriles by dehydration of aldoximes using a PCC (pyridiniumchlorochromate) has been developed. A variety of aromatic, heteroaromatic, and aliphatic aldoximes are converted.

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One-Pot,Catalyst-Free Synthesis of Spirooxindole and 4H-Pyran Derivatives

The synthesis of biologically valuable spirooxindoles and 4H-pyrans is described under catalyst-free conditions through sequential Knoevenagel–Michael–cyclization reactions from isatin or aromatic aldehyde, malononitrile, and 1,3-dicarbonyl compounds. The reaction conditions are very simple, providing excellent yield.

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Copper bis(2,2,6,6-Tetramethyl-3,5-heptanedionate)–Catalyzed Coupling of Sodium Azide with Aryl Iodides/Boronic Acids to Aryl Azides or Aryl Amines

This work reports an efficient protocol for the coupling reaction of aryl iodides/boronic acids with sodium azide to aryl azides/amines in the presence of copper bis(2,2,6,6-tetramethyl-3,5-heptanedionate) Cu(TMHD)₂ catalyst. The Cu(TMHD)₂ catalyst is a structurally well-defined, O-containing, air- and moisture-stable, transition-metal complex and works at mild reaction conditions. It was observed that aryl azides can be reduced further to corresponding aniline derivatives using the same catalyst under basic reaction conditions for a prolonged period.

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In Situ Demethoxylation,Dechloridation, or Decyanogenation from Coupling Aromatic Compounds Mediated by Potassium Metal

The potassium metal can promote direct arylation of unactivated aromatic C-H bonds under an oxygen atmosphere. Interestingly, in situ demethoxylation, dechloridation, or decyanogenation from the corresponding coupling aromatic compounds mediated by potassium metal was also observed in the radical reaction systems.

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Green and Catalyst-Free One-Pot Synthesis of Anthranilamide Schiff Bases: An Approach Toward Sirtinol

A novel and simple method for the green one-pot synthesis of anthranilamide Schiff bases is described. The reported Schiff bases are obtained via the reaction of isatoic anhydride, amines, and aromatic aldehydes in water at room temperature, without using any catalysts. No cyclization toward 2,3-dihydro-4(1H)-quinazolinones occurred in this method and anthranilamide Schiff bases were produced exclusively. This approach offers a green method to prepare the medicinally important Schiff base sirtinol and other bioactive anthranilamide Schiff bases.

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Efficient Deallylation of Allyl Phenyl Ethers by Molecular Iodine in PEG-400 and Their Utility for Flavone Synthesis

Rapid and efficient deallylation of allyl phenyl ethers by molecular iodine (20 mol%) in polyethylene glycol-400 at 60 °C has been reported. This method has short reaction time, readily available catalyst, and reuse of reaction medium with good yield. The utility of this methodology has been extended to flavone synthesis.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

One-Pot,Two-Step Direct Conversion of Alkenes to Amines Through Tandem Ozonolysis and Ammonia-Borane in Water

An efficient, one-pot, two-step reductive amination of alkenes through tandem ozonolysis using ammonia-borane as a reducing agent is described. The reaction has been carried out in water. This is a highly efficient and mild procedure that is applicable to a wide variety of amine substrates. In particular, this is the first successful manifestation that this type of reaction can be carried out in water with ammonia-borane.

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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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Metal-Free,One-Pot,Rapid Synthesis of Tetrahydropyridines Using Acetic Acid as Solvent and Catalyst at Room Temperature

Acetic acid–promoted, one-pot synthesis of tetrahydropyridines has been developed under metal-catalyst-free conditions via a tandem reaction. High atom economy, good yield, simple procedure, no expensive column chromatography, shorter reaction time, and metal-free and mild reaction conditions are some of the important features of this protocol. The current methodology provides an alternative approach for not only highly substituted tetrahydropyridines (THPs) but also fully substituted tetrahydropyridines (FTHPs) in moderate to good yields. The plausible mechanism for the formation of THPs was greatly promoted by the H⁺ ion coming from acetic acid.

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Surfactant-Catalyzed Addition of Higher Thiols to N-Aryl Substituted Maleimides

The cationic-type surfactant-catalyzed conjugate addition reaction of long-alkyl-chained thiols with N-aryl-substituted maleimides in water as a green reaction medium afforded the corresponding thia-Michael adducts in moderate to good yields.

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Synthesis of N,N-Diethylbenzamides via a Nonclassical Mitsunobu Reaction

The use of the Mitsunobu reaction for the synthesis of N,N-diethylbenzamides affords ortho-, meta-, and para-substituted benzamides containing both electron-donating and electron-withdrawing groups. While the preparation of numerous functional groups has been efficiently demonstrated employing the Mitsunobu reaction, our methodology represents the first application of the Mitsunobu reaction for the construction of benzamides using benzoic acid and amine starting materials. Moreover, this synthetic transformation is believed to proceed via a nonclassical mechanism involving the existence of an acyloxyphosphonium ion.

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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.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications ^® for the following free supplemental resource(s): Full experimental and spectral details.]     

Aldonitrones as Aldehyde Equivalents: An Efficient,Green, and Novel Protocol for the Synthesis of 1,8-Dioxo-octahydroxanthenes

A novel, self-catalyzed, solvent-free, microwave-enhanced, green, and efficient protocol for the synthesis of 1,8-dioxo-octahydroxanthenes and bis-5,5-dimethyl-1,3-cyclohexanediones by condensing aldo-nitrones (imine oxide) and dimedone (5,5-dimethyl-1,3-cyclohexanedione) under microwave irradiation is disclosed. Product formation (viz. xanthenes and bis-5,5-dimethyl-1,3-cyclohexanediones) is dependent on reaction conditions. The entire process is green and sustainable in terms of solvents, chemicals, reaction procedure, and yields. A plausible reaction mechanism of this reaction is also proposed.

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Oxidation of Benzaldehydes to Benzoate Esters Using Household Bleach and Sodium Iodide in Alcohol Solvents

Various substituted benzaldehydes were converted into benzoate esters with household bleach and sodium iodide in an alcohol solvent. The reaction works best with methanol. Only 4-chlorobenzaldehyde, 3-nitrobenzaldehyde, and 4-nitrobenzaldehyde reacted completely with 1-propanol under these conditions.

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AgF-Mediated Homocoupling Reaction of Trialkoxy Aryl Silanes

In this article, we present the direct homocoupling reaction of trialkoxy aryl silanes mediated by AgF in moderate to excellent yields in very mild conditions. It is an important complement for the synthesis of symmetrical biaryls by using homocoupling of trialkoxy silanes. In this reaction, no other catalyst such as Pd or Cu was necessary.

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