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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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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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.

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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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Expeditious Synthesis of Aromatic Cyanodienones Using Neutral Alumina as a Versatile Heterogeneous Catalyst

The work described herein employs neutral alumina as an effective catalyst for ring opening of triarylpyrylium perchlorates to corresponding aromatic cyanodienones, which have main roles in biological activities. The present porous catalyst has several advantages, it is inexpensive, thermally and mechanically stable, nontoxic, and highly resistant against organic solvents. It increases the reaction rate many fold when compared with conventional reaction conditions. Moreover, the recovered alumina can be used several times without serious decrease in activity.

[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.]     

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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Aluminium Chloride–Catalyzed Synthesis of 4-Benzyl Cinnolines from Aryl Hydrazones

An efficient synthesis of 4-benzyl cinnolines from aryl phenylallylidene hydrazone is described. In this report aluminium chloride as a Lewis acid catalyst and toluene as a solvent are used for the synthesis. This method is expected to more advantageous than the other reported methods of synthesis of the cinnoline rings because of its low cost, better yield, and benign reaction conditions.

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Catalysis by Amberlyst A-21: A Greener Approach to 4,5,6,7-Tetrahydro-1H-indazol-3(2H)-ones via Construction of Cyclohexanones

The 4,5,6,7-tetrahydro-1H-indazol-3(2H)-one derivatives have been synthesized in good yields via a two-step method in a single pot. The initial step involved the construction of cyclohexanone ring from aromatic aldehydes and β-ketoester in i-PrOH using an inexpensive and reusable catalyst (i.e., Amberlyst A-21) under mild reaction conditions. The utility of this catalyst has been demonstrated in synthesizing a range of cyclohexanone derivatives. The catalyst can be recovered and recycled, which makes this procedure simple, convenient, economically viable, and environmental friendly.

[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.]     

Boric Acid–Catalyzed One-Pot Access to 7-Aryl-benzopyrano[4,3-b] benzopyran-6,8-diones Under Aqueous Micellar Conditions

A mild protocol for the synthesis of 7-arylbenzopyrano[4,3-b]benzopyran-6,8-diones by three-component reaction of 4-hydroxycoumarin, aromatic aldehyde, and 5,5-dimethylcyclohexane-1,3-dione (dimedone) with boric acid catalyst under aqueous micellar conditions is described. Good to excellent yield, high selectivity, tolerance of several common functional and protecting groups, and green features including avoidance of organic solvent in the reaction as well as isolation stage and use of nontoxic water-compatible mild Lewis acid catalyst are key attractive features of the protocol.

[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.]     

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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Efficient Synthesis of Pyrrolo[1,2-f]phenanthridine Derivatives via Dipolar Cycloaddition of Phenanthridine,Activated Acetylenes,and Ethyl Bromopyruvate

The three-component reactions of phenanthridine, activated acetylenes, and ethyl bromopyruvate through both of simultaneous and stepwise process are surveyed. The reactions afforded the corresponding pyrrolo[1,2-f]phenanthridine derivatives in good yields without using any catalyst and activation.

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Efficient Method for the Synthesis of α,α′-Bis(arylmethylidene) Cycloalkanones Catalyzed by Bromodimethylsulfonium Bromide

Bromodimethylsulfonium bromide (BDMS)–catalyzed crossed aldol condensation between aromatic aldehydes and ketones is reported to access α,α′-bis(arylmethylidene) cycloalkanones at room temperature in good yields within 3–10 min. The salient features of this method are the simplicity of the procedure, the ready accessibility of the catalyst, and greater yields in relatively short reaction times.

[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.]     

Saccharin as an Organocatalyst for Quinoxalines and Pyrido[2,3-b]pyrazines Syntheses

A room-temperature procedure using saccharin as catalyst has been described for the cyclocondensation of different 1,2-arylenediamines with various 1,2-dicarbonyl compounds, yielding either quinoxalines or pyrido[2,3-b]pyrazines. The reactions proceed in very short reaction times in methanol, and the target heterocycles are isolated in quantitative yields after addition of water, filtration, and drying. Substituted pyrido[2,3-b]pyrazines can also be reached regioselectively by reacting α-ketoaldehydes with 2,3-diaminopyridine.

[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.]     

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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Efficient Room-Temperature Synthesis and Antimicrobial Study of Novel 2-Aroylbenzofuran-3-ols from Substituted Methyl Salicylates and Phenacyl Bromides

The article describes a convenient and efficient synthetic route for the construction of 2-aroylbenzofuran-3-ols from readily available diverse methyl salicylates and phenacyl bromides using K₂CO₃ as catalyst in dimethylformamide as solvent at room temperature. The reaction involves two steps, which occur in quick succession within 1 h to deliver the product with reasonably high yields. All the synthesized 2-aroylbenzofuran-3-ols (4a–u) were subjected for their antimicrobial studies, and some of these have shown prominent activity.

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Asymmetric Synthesis of Novel Vicinal Amino Alcohols via Intramolecular Ketone-N-sulfinylimine Pinacol-Type Reductive Coupling Promoted by SmI2

A novel intramolecular asymmetric ketone-N-sulfinylimine pinacol-type reductive coupling reaction induced by SmI₂ was reported. A series of 1-amino-1,2,3,4-tetrahydronaphthalen-2-carbinols were obtained in moderate to good yields with excellent ee and high dr.

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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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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.

[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,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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Convenient Synthesis of Monobenzylated Hydrazides via Aqueous Zinc-Mediated Addition Reactions

Addition of substituted benzyl bromides to dialkyl azodicarboxylates under aqueous zinc-mediated addition conditions occurs readily to afford monobenzylated hydrazides in good to excellent yields. The reaction is tolerant of a variety of substituents on the benzyl bromide ring. Several dialkyl azodicarboxylates were successfully tested under the reaction conditions. The limitations of the reaction are also addressed.

[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.]