p-Toluene Sulfonic Acid–Catalyzed,Solvent-Free Synthesis of Symmetrical Bisamides by Reaction Between Aldehydes and Amides

Reaction between aldehydes and amides catalyzed by p-toluene sulfonic acid in solvent-free conditions provided a simple and efficient one-pot route for the synthesis of symmetrical bisamide derivatives in excellent yields.     

Ionic Liquid–Mediated Knoevenagel Condensation of Meldrum's Acid and Aldehydes

A simple, efficient, and green protocol for Knoevenagel condensation of Meldrum's acid and aldehydes in ionic liquid at room temperature without any catalyst is described. The reaction has been performed in different ionic liquids. The enhancement in the rate is observed in Brönsted acidic ionic liquid 1‐methylimidazolium trifluoroacetate [Hmim]Tfa, which furnishes quantitative yields with 4–30 min in most of the cases. Furthermore, ionic liquid is easily reused without any appreciable loss in activity.     

Chemoselective Condensation of β-Naphthol,Dimethyl Malonate,and Aromatic Aldehydes Promoted by Niobium Pentachloride

A multicomponent reaction of β-naphthol, dimethyl malonate, and aromatic aldehydes in the presence of NbCl₅ as promoter is described. Under similar conditions, aromatic aldehydes with different substituents exhibited different behaviors than β-naphthol and dimethyl malonate. In these MCRs, 4-aryl-3,4-dihydrobenzo[f]coumarins are obtained as the major products (41–93%) and 14-aryl-14H-dibenzo[a,j]xanthenes as the minor products (1–38%).     

A Novel and Efficient Synthesis of α-Aminophosphonates by Use of Triphenyl Phosphite in Acetic Acid Media

Abstract

For the first time, α-aminophosphonates were obtained by a simple and efficient one-pot method from the reaction between aldehyde, aniline, and triphenyl phosphite in the presence of acetic acid as a catalyst and solvent at room temperature.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

GRAPHICAL ABSTRACT     

A Rapid and Convenient Synthesis of Acylals from Aldehydes and Acetic Anhydrides Catalyzed by SnCl_4/SiO_2

Acylals (1, 1-diacetates) are efficient protecting groups for aldehydes as they are stable in neutral and basic media1. Usually, the acylals are prepared from aldehydes and acetic anhydride in the presence of strong protonic acids such as sulfuric acid2, phosphoric acid2, or methanesulfonic acid2, and Lewis acids such as anhydrous zinc chloride3, phosphorus(III) chloride4, and anhydrous ferric(III) chloride5. Recently the use of montmorillonite clay7, TMCS-NaI8, Sc (OTf)39, Cu (OTf)210 …     

Ionic Liquid–Mediated Synthesis of Coumarin-3-carboxylic Acids via Knoevenagel Condensation of Meldrum's Acid with ortho-Hydroxyaryl Aldehydes

A simple, efficient, and green protocol for synthesis of coumarin-3-carboxylic acids is described via Knoevenagel condensation of Meldrum's acid with ortho-hydroxyaryl aldehydes in [Hmim]Tfa ionic liquid, which was found to give better results than other ionic liquids. Furthermore, ionic liquid is easily reused without any appreciable loss in activity.     

Organic Reactions in Ionic Liquids: Ionic Liquid Promoted Knoevenagel Condensation of Aromatic Aldehydes with (2‐Thio)Barbituric Acid

Abstract

The Knoevenagel condensation of aromatic aldehydes with (2‐thio)barbituric acid proceeded efficiently in reusable ionic liquids, EAN, BmimBF₄, and BmimPF₆ at room temperature in the absence of any catalyst with high yields.     

Organic Reactions in Ionic Liquids: Ionic Liquid Ethylammonium Nitrate–Promoted Knoevenagel Condensation of Meldrum's Acid With Aromatic Aldehydes

The Knoevenagel condensation of Meldrum's acid with aromatic aldehydes proceeded efficiently in a reusable ionic liquid, ethylammonium nitrate, at room temperature in the absence of any catalyst with high yields.     

Efficient One-Pot Condensation of β-Naphthol,Aldehydes, and Cyclic 1,3-Dicarbonyl Compounds Catalyzed by p-TSA Under Solvent-Free and Sonication Conditions

A facile and efficient procedure has been developed by one-pot condensation of β-naphthol, aldehydes, and cyclic 1,3-dicarbonyl compounds for the synthesis of 8,9,10,12-tetrahydrobenzo[a]xanthen-11-one or 8,9-dihydrobenzo-[f]cyclopenta[b]chromen-10(11H)-one derivatives catalyzed by p-toluenesulfonic acid under solvent-free and sonication conditions.     

Clean Synthesis in Water：Darzens Condensation Reaction of Aromatic Aldehydes with Phenacyl Chloride

The Darzens condensation reaction of aromatic aldehydes with phenacyl chloride proceeded very efficiently in a water suspension medium in the presence of triethylbenzylammonium chloride and only trans-2,3-epoxy-1,3-diaryl-1-propanones were formed which can be isolated simply by filtration.The structures of these compounds were confirmed by elemental analysis,IR and ^1H NMR spectra.Therir configurations are in agreement with that of the same compounds reported in the literature.Compared to the classical Darzens condensation,this new method has the advantages of good yields,high stereoselectivity,low running cost inexpensive and environmentally benign procedure.     

Synthesis of 3- and 5-Alkyl-6-alkyl(aryl)tetrahydropyran-2,4-diones by the Condensation of β-Oxo Acid Esters with Aldehydes and Ketones

A method is proposed for obtaining 3- and 5-alkyl-6-alkyl(aryl)tetrahydropyran-2,4-diones based on the condensation of the dianion of alkyl(dialkyl)acetoacetic ester with aldehydes and ketones.     

Efficient Synthesis of Dicycloalkenopyridines： One-pot Multicomponent Condensation of Aldehydes with Cyclic Ketones

Under microwave irradiation, the one-pot multicomponent condensation reaction of three moles of aromatic aldehydes with two moles of cyclic ketones having free α,α'-methylene positions such as cyclopentanone or cyclohexanone in the presence of ammonium acetate and acetic acid afforded dicycloalkenopyridines with two α-arylidene groups in high yields. Under the similar reaction condition, the reaction of aromatic aldehydes with 1-tetralone having only one α-methylene position alternatively resulted in 10-ary...     

Reductive Amination of Aldehydes and Ketones Under Heterogeneous and Solvent-Free Conditions Using Sodium-Borohydride and Silica-Gel–Supported Sulfuric Acid

A regioselective and convenient procedure for preparation of amines by reductive amination of aldehydes and ketones using sodium borohydride in the presence of sulfuric acid supported on silica gel as an active, inexpensive, and recoverable catalyst under heterogeneous and solvent-free conditions at room temperature is described.     

Preparation of 5‐Aryl‐3‐Oxo‐δ‐Lactones by the Potassium Carbonate–Promoted Condensation of Aromatic Aldehydes and Ethyl Acetoacetate in Ethanol

5‐Aryl‐3‐oxo‐δ‐lactones (6‐aryl‐dihydro‐2H‐pyran‐2,4(3H)‐diones) were prepared by the potassium carbonate–promoted condensation of aromatic aldehydes and ethyl acetoacetate in absolute ethanol. Benzaldehyde and substituted benzaldehydes bearing an alkoxy group (2 or 3 position), a chlorine atom (2, 3, or 4 position), a nitro group (3 or 4 position), a cyano group (4 position), or an acetyl group (4 position) react in high yields under these conditions.     

Crystal Structures of β-Cyclodextrin Complexes with Formic Acid and Acetic Acid

β-Cyclodextrin (β–CD)-formic acid (1) andβ-CD–acetic acid (2) inclusion complexes crystallizeas β-CD...0.3HCOOH...7.7H₂O andβ-CD...0.4CH₃COOH...7.7H₂O in themonoclinic space group P2₁ with comparable unit cell constants.Anisotropic refinement of atomic parameters against X-ray diffractiondata with F_o ² > 2σ (F_o ²) (986/8563 and 991/8358)converged at R-factors of 0.051 and 0.054 for 1 and 2,respectively. In both complexes, the β-CD molecularconformation, hydration pattern and crystal packing are similar,but the inclusion geometries of the guest molecules are different.The β-CD macrocycles adopt a ``round'' conformationstabilized by intramolecular, interglucose O3(n)...O2(n + 1)hydrogen bonds and their O6–H groups are systematically hydratedby water molecules. In the asymmetric unit, each complex contains oneβ-CD, 0.3 formic acid (or 0.4 acetic acid), and 7.7 water moleculesthat are distributed over 9 positions. Water sites located in theβ-CD cavity hydrogen bond to the guest molecule. In thecrystal lattice, β-CD molecules are packed in a typical ``herringbone'' fashion. In 1, the formic acid (occupancy 0.3) is entirely included in the β-CD cavity such that its C atom is shifted from the O4-plane center to the β-CD O6-side by 2.90 Å and C=O, C–-O bonds point to this side. In 2, the acetic acid (occupancy 0.4) is completely embedded in the β-CD cavity, in which the carboxylic C atom is displaced from the O4-plane centerto the β-CD O6-side by 0.87 Å; the C=O bond directsto the β-CD O6-side and makes an angle of 15°to the β-CD molecular axis. Furthermore, bothdimethyl-β-CD-acetic acid and β-CD-acetic acidcomplexes form a cage structure, showing that the small guestsenclosed entirely in the cavity either in β-CD or indimethyl-β-CD do not affect the packing of the host macrocycles.     

Simple and Efficient One-Pot Synthesis of 2-Substituted Benzimidazoles from θ-Diaminoarene and Aryl Aldehydes

An easy and efficient one-pot condensation method for the synthesis of substituted benzimidazoles from θ-phenylenediamines with aryl aldehydes using urea hydrogen peroxide (UHP) and I₂ in dimethylsulfoxide (DMSO) provides wide substrate scope with good to excellent yields and simple and quick isolation of the products.     

Synthesis of Azaphenanthrene Derivatives by Condensation of 2-Methyleneaminonaphthalene with Cyclic β-Diketones

2-Methyleneaminonaphthalene smoothly reacts with cyclic -diketones to afford azaphenanthrene derivatives in high yield. The dihydropyridine ring in the products can be oxidized to pyridine ring. The oxidation products, unlike their precursors and analogs having an aryl substituent in the -position with respect to the nitrogen atom, react with hydroxylamine at the carbonyl group to give the corresponding oximes and in some cases undergo Knoevenagel condensation with malononitrile. Hydrolysis of the condensation product yields the respective diamide.     

The Condensation of Aromatic Aldehydes with Acidic Methylene Compounds in Water

The condensation of aromatic aldehydes with acidic methylene compounds such as malononitrile, methyl cyanoacetate, cyanoacetamide, 5,5-dimethyl-1,3-cyclohexanedione,bartbituric acid and 2-thiobarbituric acid proceeded very efficiently in water in the presence of triethylbenzylammonium chloride (TEBA) and the products were isolated simply by filtration.     

A Simple Access to Chalcones via Modified Mukaiyama Aldol Condensation Promoted by SmI3／TMSCI

Promoted by SmI3,acetophenones and benzaldehydes can undergo the Mukaiyama type aldol condensation in the presence of TMSCl to form chalcones in good yields.     

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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