Water mediated efficient one-pot synthesis of bis-(4-hydroxycoumarin)methanes

Abstract

Manganous chloride (MnCl₂·4H₂O) has been used as an efficient catalyst for an improved and rapid one-pot synthesis of bis-(4-hydroxycoumarin)methanes in excellent yields using water as a reaction medium. This aqueous mediated reaction of various aromatic and heteroaromatic aldehydes with 4-hydroxycoumarin using catalytic amounts of manganous chloride avoids the use of expensive, corrosive reagents, toxic solvents, and provides operational simplicity.     

Reusable polymer-supported copper catalyst for one-pot synthesis of 1-alkyl- and 1-aryl-1,2,3-triazoles: green,simple, and effective

Abstract

Polymer-supported copper-catalyzed one-pot synthesis of 1,4-disubstituted 1-alkyl- and 1-aryl-1,2,3-triazoles via 1,3-dipolar cycloaddition of alkyl halides or arylboronic acids, sodium azide, and phenylacetylene has been developed. Reactions went smoothly at room temperature using PEG/H₂O or methanol as solvent to afford the corresponding triazoles in good to excellent yields. The catalyst could be recovered by simple filtration and reused several times with slightly decrease in its activity.     

A very high yielding and facile alkaline earth metals homogeneous catalysis of Biginelli reaction: an improved protocol

Abstract

A high yielding and facile Biginelli reaction for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones and thiones, using inexpensive and available alkaline earth metal chlorides (MgCl₂, CaCl₂, SrCl₂ and BaCl₂) and acetic acid as the solvent in a homogeneous catalytic reaction, is reported.     

RuCl3 anchored onto imine functionalized silica for the aerobic oxidation of benzylic alcohols under liquid phase catalysis

Abstract

RuCl₃ anchored onto imine functionalized silica has been developed as a heterogeneous catalyst for the selective oxidation of benzylic alcohols to aldehydes using molecular oxygen as an oxidant. SiO₂-RuCl₃ was found to be highly stable, passes hot filtration test successfully, and could be recycled several times without significant loss of activity. The SiO₂-RuCl₃ was characterized by Fourier Transform Infrared Spectroscopy (FTIR), Thermogavimetric Analysis (TGA), Scanning Electron Microscope (SEM), Transmission Electron Micrographs (TEM), X-Ray Diffractometry (XRD), and Atomic Absorption Spectrophotometric Analysis (AAS).     

Lithium bromide as an efficient,green, and inexpensive catalyst for the synthesis of quinoxaline derivatives at room temperature

Abstract

An efficient, simple, and green procedure for the synthesis of quinoxaline derivatives is described. The condensation of 1,2-diamines with 1,2-diketones using lithium bromide (LiBr) in H₂O/EtOH as a green reaction media at room temperature affords the title compounds in high to excellent yields and in short reaction times.     

PEG-600-mediated,green and efficient,tandem syntheses of N-subtituted-2-styrylquinazolin-4- ones

Polyethylene glycol (PEG)-mediated, green and efficient, tandem syntheses of N-subtituted-2-styrylquinazolinones are being reported. Condensation of anthranilamide (1) with acetic anhydride in PEG-600, at 100°C for 1 hr gave 2-methyl-3H-quinazoline-4-one (2). Treatment of 2 with benzaldehydes in PEG-600, at 100°C for 2–3 hr, gave 2-styrylquinazolinone-4-ones (3) in excellent yields. Treatment of 3 (a–d) either with dimethyl sulfate (DMS), diethyl sulfate (DES), or with Ph-CH₂-Cl, individually in PEG-600, at 100°C for 1–2 hr without using any base, followed by simple processing resulted in N-substituted-2-styrylquinazolin-4-ones 5 (a–l). In an alternative approach, reaction of 4 (a–c) with benzaldehydes in PEG-600, at 100°C for 1–2 hr, without using any base, followed by simple processing resulted in 5 (a–l). 4 (a–c) were prepared by treatment of 2 with either DMS, DES, or with Ph-CH₂-Cl, individually, in the presence of PEG-600 as reaction medium, at 100°C for 1–2 hr without using any base. Both the sequence of reactions, 1 2 3 5 or 1 2 4 5 could be carried out in tandem in an efficient manner in PEG-600 without the isolation of any intermediates. The structures of all the new compounds synthesized in this work have been established on the basis of their spectroscopic data and analytical data.     

Silica supported perchloric acid (HClO4-SiO2): a green,reusable, and highly efficient heterogeneous catalyst for the synthesis of thioethers under solvent-free conditions at room temperature

Abstract

A highly efficient and clean procedure is described for the synthesis of thioethers with excellent yields under solvent-free conditions at room temperature using a catalytic amount of HClO₄-SiO₂. The catalyst is easily prepared, stable, and reusable without much loss of catalytic activity, and is efficient under the reaction conditions.     

An odorless and efficient synthesis of symmetrical thioethers using organic halides and thiourea in Triton X10 aqueous micelles

Abstract

The synthesis of symmetrical thioethers using organic halides and thiourea in Triton X10 aqueous micelles under basic conditions has been described. Primary alkyl, allyl and benzyl halides can be converted efficiently into symmetrical thioethers in high yields. The entire route is an almost odorless process, and the protocol is applicable to large-scale operation without any problem.     

A convenient synthesis of coumarins using reusable ionic liquid as catalyst

Abstract

An efficient and convenient method has been developed for the synthesis of substituted coumarin derivatives using a Brønsted acidic ionic liquid as catalyst under solvent-free conditions. The catalyst can be reused for six consecutive runs without significant loss of activity.     

Brønsted acidic ionic liquid [HMIm]BF4 promoted simple and efficient one-pot green synthesis of isoxazolyl-1,3-benzoxazines at ambient temperature

Abstract

Brønsted acidic ionic liquid [HMIm]BF₄ has been used as a nonvolatile, ecofriendly solvent, and catalytic medium for the one-pot green synthesis of isoxazolyl-1,3-benzoxazines. The reaction afforded excellent yield in short reaction time, and avoids multistep synthesis. The easy of recyclability of the IL makes the reaction economically and potentially viable for commercial applications.     

Novel one-pot synthesis of 1,2,4-triazolidin-3-thiones comprising piperidine moiety

Abstract

A simple synthetic strategy for the synthesis of piperidinyl spiro-1,2,4-triazolidin-3-thiones 11–15 is proposed, exploiting microwave activation coupled with solvent-free reaction conditions catalyzed by NaHSO₄.SiO₂ heterogeneous catalyst is described.     

Solvent-free chemoselective protection of aldehydes on the surface of alumina-sulfuric acid

Abstract

Chemoselective protection of alkyl and aryl aldehydes has been accomplished through the formation of dioxolane on the surface of alumina-sulfuric acid under solvent-free conditions where dialkyl ketones, aryl alkyl ketones, and diaryl ketones remain intact.     

Henry reaction in environmentally benign methods using imidazole as catalyst

Abstract

Imidazole has been found to be an efficient Lewis base catalyst for the synthesis of 2-nitroalkanols from nitro-aldol reaction in aqueous medium as well as using solvent-free grinding methods. In both cases, the products have been found in good to moderate yields without formation of any side product. Recycling of the catalyst is also possible with imidazole containing aqueous phase reaction medium (after extraction of product).     

Non-catalytic condensation of aromatic aldehydes with aniline in high temperature water

Abstract

The synthesis of diamino triphenyl methanes from aniline and aromatic aldehydes was conducted in near critical water and supercritical water. The reaction parameters, such as temperature, density, and reaction time, have been studied. Significant acceleration of the condensation reaction of aniline and aromatic aldehydes can be achieved by using high temperature water, especially near the critical point, in the absence of any acid catalysts. It has been demonstrated that high temperature water act effectively in the place of conventional acid catalysts.     

Efficient and green synthesis of 4H-pyrans and 4H-pyrano[2,3-c] pyrazoles catalyzed by task-specific ionic liquid [bmim]OH under solvent-free conditions

Abstract

A facile and convenient procedure for the synthesis of 4H-pyrans from aldehydes, malononitrile, and ethyl acetoacetate/acetylacetone and also synthesis of 4H-pyrano[2,3-c]pyrazoles from three-component condensation of aldehydes, malononitrile, and pyrazolone or four-component condensation of aldehydes, malononitrile, ethyl acetoacetate, and hydrazine monohydrate using [bmim]OH as task-specific ionic liquid has been described. The protocol proves to be efficient and environmentally benign in terms of high yields, low reaction times, ease of recovery, and reusability of reaction medium.

     

One-pot multicomponent synthesis of polyhydroquinolines under catalyst and solvent-free conditions

Abstract

An efficient one-pot condensation has been developed for the synthesis of polyhydroquinolines via a four component coupling reaction of aldehyde, dimedone, ethyl acetoacetate, and ammonium acetate under catalyst and solvent-free conditions. Non-hazardous experiment procedure, operational simplicity, mild reaction conditions, and the compatibility with various functional groups represent the advantages of the present method.     

Green catalytic synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes using recyclable mesoporous zirconia modified with tungstophosphoric acid

Abstract

A simple and efficient procedure has been developed for the preparation of aryl-14H-dibenzo[a,j]xanthenes by a one-pot condensation of 2-naphthol and aryl aldehydes, in the presence of mesoporous zirconia modified with tungstophosphoric acid (ZrTPA60B_T100), to be used as a heterogeneous catalyst in a solvent-free medium using conventional heating. The present approach offers the advantages of clean reaction, simple methodology, short reaction time, and high yield. The reaction work-up is very simple and the catalyst can be easily separated from the reaction mixture and reused several times in subsequent reactions without appreciable loss of the catalytic activity.     

Concise synthesis of the retinoic acid receptor (RAR) agonist AGN-193836 utilizing a photochemical benzylic oxidation

Abstract

A new, concise synthesis of retinoic acid receptor (RAR)-α agonist AGN-193836 (1) is described which employs a photochemical benzylic methyl oxidation with molecular oxygen as the key step (3 → 2). Further this route explores the application of green photochemistry in the synthesis of drug candidates and avoids a number of toxic or highly pyrophoric reagents that had been described in previous syntheses of 1. In addition, the oxidation proved to be higher yielding when compared to potassium permanganate, a metal oxidant typically used for this –CH₃ to –CO₂H functional group conversion.