无溶剂条件下离子液体催化香豆素衍生物的绿色合成(英文)

Brnsted acidic ionic liquids, namely 2-pyrrolidonium hydrogen sulfate, N-methyl-2-pyrrolidonium hydrogen sulfate, N-methyl-2-pyrrolidonium dihydrogen phosphate, (4-sulfobutyl)tris(4-sulfophenyl)phosphonium hydrogen sulfate, and triphenyl(propyl-3-sulfonyl)phosphonium toluenesulfonate, catalyzed efficient Pechmann condensation of phloroglucinol with β-keto ethyl/ methyl esters. 5,7-Dihydroxy-4-methylcoumarin and 5,7-dihydroxy-4-phenylcoumarin were prepared in good to excellent yields under mild, ambient, and solvent-free conditions. Pyrano[2,3-h] coumarins were then prepared by one-pot three-component reactions of 5,7-dihydroxy-4-subsituted coumarin, malononitrile, and aldehydes in the presence of catalytic amounts of Br nsted basic ionic liquids, namely 2-hydroxyethylammonium formate, 3-hydroxypropanaminium acetate, 1-butyl-3-methylimidazolium hydroxide, pyrrolidinium formate, and pyrrolidinium acetate, under thermal solvent-free conditions. The catalysts are environmentally benign and can be easily prepared, stored, and recovered without significant loss of activity.     

高效可回收催化剂In(OTf)_3用于无溶剂条件下Pechmann缩合反应(英文)

In(OTf)3 plays the role of a Lewis acid catalyst in the Pechmann condensation of phenols with β-ketoesters under solvent-free conditions to give coumarin derivatives. This novel and inexpensive method has advantages such as short reaction time, excellent product yields, and avoids the use of organic solvents in agreement with green chemistry principles. Catalyst loadings can be as low as 1 mol% to give high yields of the corresponding coumarins at 80 °C. The catalyst can be recovered after the reaction, and reused with only a slight decrease in the yield.     

Stereoselective synthesis of piperidinone and quinolinone systems via ring opening reactions using TiCl4/silyl reagents

Titanium(IV) chloride and silyl reagents mediated regio- and chemoselective ring opening reactions of oxa-bridged piperidinone ring systems were demonstrated. This methodology interestingly undergoes the stereoselective ring opening at the C-O bond of oxa-bridged piperidinone ring systems. Study of TiCl₄ with hydride or non-hydride silyl reagents furnished the product with selectivity. This protocol is highly valuable to synthesize a range of stereoselective piperidinones, quinolinones ring systems.     

Selenonium ionic liquid as an efficient catalyst for the synthesis of thioacetals under solvent-free conditions

Acidic ionic liquid butyl ethyl phenyl selenonium tetrafluoroborate, [BEPSe]BF₄, was successfully employed as a catalyst for the synthesis of several dithioacetals in the absence of a solvent. The method is general and selectively afforded thioacetals derived from aldehydes and ketones in good yields.     

ZrCl4 as a mild and efficient catalyst for the one-pot conversion of TBS and THP ethers to acetates

A mild, efficient and chemoselective method has been developed for the direct transformation of tert-butyldimethylsilyl and tetrahydropyranyl protected alcohols into the corresponding acetates with acetic anhydride and zirconium(IV) chloride as the catalyst in acetonitrile, in a one-pot reaction with high yields and short reaction times. This method has been applied to a variety of substrates.     

A solvent-free synthesis of coumarins using a Wells-Dawson heteropolyacid as catalyst

Substituted coumarins are synthesized from phenols and β-ketoesters by the Pechmann reaction, using a Wells-Dawson heteropolyacid (H₆P₂W₁₈O₆₂·24H₂O) as catalyst by a solvent-free procedure. This one requires low reaction times, 130 °C temperature and as little as 1 mol % of Wells-Dawson acid, obtaining good to excellent yields of coumarins. The catalyst showed to be reusable with no differences in the yields. The results are compared with those of the reactions performed in toluene solution. The presented synthetic procedure is a convenient, clean and fast alternative for synthesizing 4-substituted coumarins (17 examples).     

TiCl4/t-BuNH2 as the sole catalyst for a hydroamination-based Fischer indole synthesis

A system comprising TiCl₄ and t-BuNH₂ acts as a catalyst for highly regioselective hydroamination reactions of alkynes using hydrazines and at the same time a Lewis acid in the transformation of the generated hydrazones into indole derivatives, while a 1,3-diyne is converted to pyrroles using the same precatalyst.     

A novel and efficient strategy for the synthesis of various carbamates using carbamoyl chlorides under solvent-free and grinding conditions using microwave irradiation

We present an efficient,fast and simple strategy of generating the intermediate carbamoyl chlorides from secondary amines using stoichiometric amounts of bis(trichloromethyl)carbonate(BTC) in solution and solvent-free conditions with excellent yields.The results obtained showed the yield increasing on whether a base was used.Finally,an efficient and rapid synthesis of variety carbamate derivatives was developed by the reaction with a high variety of different alcohols,phenols,diols and this intermediate at room temperature with grinding and in solvent-free conditions under microwave irradiation.The presence of various safe bases is shown to be effective in reducing the reaction times,increasing the yields and easing purification.The present method does not involve any hazardous phosgene.     

Synthesis of 2,4,5-triaryl and 1,2,4,5-tetraaryl imidazoles using silica chloride as an efficient and recyclable catalyst under solvent-free conditions

An efficient solvent-free synthesis of various 2,4,5-triaryl imidazoles and 1,2,4,5-tetraaryl imidazoles has been developed using silica chloride as a heterogeneous catalyst. The present methodology offers several advantages, such as excellent yields, shorter reaction times, economic availability, and reusability of catalyst.     

Air-stable zirconium (IV)-salophen perfluorooctanesulfonate as a highly efficient and reusable catalyst for the synthesis of 3,4-dihydropyrimidin-2-(1H)-ones/thiones under solvent-free conditions

An air-stable complex of zirconium (IV)-salophen perfluorooctanesulfonate ( 1 ) was successfully synthesized by reacting Zr (salphen)Cl₂ and C₈F₁₇SO₃Ag. Complex 1 was characterized and studied by different techniques (NMR, IR, HRMS, TG-DSC, conductivity and acidity measurements), and was found to be air-stable, water tolerant, thermally stable and strongly Lewis-acidic. Complex 1 exhibited high catalytic efficiency for the synthesis of 3,4-dihydropyrimidin-2-(1H)-ones/thiones via the Biginelli reaction of aldehydes, 1,3-dicarbonyl compounds and urea/thiourea under solvent-free conditions. Furthermore, complex 1 could be reused 5 times with minimal changes in catalytic efficiency. Compared with previously reported methods, the important features of this protocol are the solvent-free conditions, the short reaction times, the wide substrate compatibility, the high efficiency and the good reusability.     

Silica triflate as an efficient reagent for the solvent-free synthesis of coumarins

Silica triflate,as a new silica-based reagent,can be used for the efficient synthesis of 4-substituted coumarins via a Pechmann reaction under solvent-free reaction conditions.All reactions were performed at 80℃in good to high yields.     

One-pot,three-component synthesis of spiroindoloquinazoline derivatives under solvent-free conditions using ammonium acetate as a dual activating catalyst

The one-pot, three-component synthesis of spiroindoloquinazoline derivatives in good to excellent yields via the condensation reaction of tryptanthrin, CH activated carbonyl compounds and malononitrile under solvent-free conditions in the presence of ammonium acetate is reported.     

Xanthan sulfuric acid: An efficient and biodegradable solid acid catalyst for the synthesis of bis(indolyl)methanes under solvent-free conditions

Xanthan sulfuric acid (XSA) is found to be an efficient catalyst for the electrophilic substitution reaction of indole with aromatic aldehydes to afford the corresponding bis(indolyl)methanes at room temperature under solvent-free conditions. The catalyst was characterized for the first time with the help of powder XRD, SEM–EDX and DSC–TGA. The attractive features of this green, new methodology are excellent yield of products, clean reaction profile, reusability of the catalyst, energy sustainable protocol, simple experimental and easier work-up procedures.     

Strontium chloride-catalyzed one-pot synthesis of 4(3H)- quinazolinones under solvent-free conditions

<正>Strontium chloride was used as an efficient and recyclable catalyst in one-pot condensation of anthranilic acid,ortho esters and amines leading to the formation of 4(3H)-quinazolinone derivatives in good yields at room temperature under solvent-free conditions.     

A mild and efficient acetylation of alcohols, phenols and amines with acetic anhydride using La(NO3)3·6H2O as a catalyst under solvent-free conditions

A wide variety of alcohols, phenols and amines are efficiently and selectively converted into the corresponding acetates by treatment with acetic anhydride in the presence of catalytic amounts of La(NO₃)₃·6H₂O under solvent-free conditions at room temperature. The method is compatible with acid sensitive hydroxyl protecting groups such as TBDMS, THP, OBz, OBn, Boc and some isopropylidenes and offers excellent yields of the mono acetates of 1,3-, 1,4- and 1,5-diols.     

An efficient and novel method for the synthesis of sulfinate esters under solvent-free conditions

The present letter describes a reliable one-stage process for the preparation of sulfinate esters from the corresponding sulfinic acid and alcohols in the presence of N,N′-dicyclohexylcarbodiimide (DCC) under solvent-free conditions.     

Microwave assisted synthesis of hydroxychromenes using imidazole-functionalized silica nanoparticles as a catalyst under solvent-free conditions

A microwave-assisted reaction of various salicylaldehydes with dialkyl acetylenedicarboxylates mediated by imidazole-functionalized silica nanoparticles is successfully and rapidly achieved to afford the corresponding hydroxychromenes in high to excellent yields under solvent-free conditions.     

Boric acid as an efficient catalyst for the synthesis of 1,1-diacetate under solvent-free condition

Boric acid (BO₃H₃) is an inexpensive, efficient and mild catalyst for the synthesis of 1,1-diacetate (acylal) from the various aromatic and heteroaryl aldehydes with acetic anhydride at room temperature under solvent-free condition. The present method does not involve any hazardous organic solvents or catalysts. This method gives notable advantages such as excellent chemoselectivity, mild reaction condition, short reaction times and excellent yield.     

Protic guanidinium ionic liquid as a green and highly efficient catalyst for the synthesis of functionalized spirochromenes under solvent-free conditions

A simple and efficient method for the synthesis of functionalized spirochromenes is explained using protic guanidinium ionic liquid as a catalyst under solvent-free conditions at room temperature. This procedure is simple, clean, and excellent yields are obtained in short reaction times.     

One-pot practical method for synthesis of functionalized 4H-chromen-5-one derivatives under catalyst and solvent-free conditions

Abstract

A facile and practical method was described for the synthesis of 4H-chromen-5-ones under catalyst- and solvent-free conditions by one-pot stirring of starting materials at 110?°C. The products were obtained by the reaction between cyclic 1,3-dicarbonyl compounds, aromatic aldehydes and (E)-N-methyl-1-(methylthio)-2-nitroethenamine (NMSM) in short duration with good to excellent yields. This simple and environmentally benign method eliminates the use of expensive, metallic and corrosive catalysts, hazardous organic solvents, and chromatographic separation.