An efficient and solvent-free one-pot synthesis of dihydropyrimidinones under microwave irradiation

An efficient synthesis of 3,4-dihydropyrimidin-2(1H)-one derivatives using formic acid as catalyst, from aldehydes,β-ketoester and urea(thiourea) without solvent under the irradiation of microwave is described. Compared with the classical Biginelli reaction, this new method has the advantage of good yields (77-94% for aromatic aldehydes) and short reaction time (3-8 min).     

Ferric chloride/tetraethyl orthosilicate as an efficient system for synthesis of dihydropyrimidinones by Biginelli reaction

An efficient method for the Biginelli reaction of aldehydes, acetoacetate esters and urea employing tetraethyl orthosilicate in the presence of ferric chloride is described. These improved reaction conditions allow the preparation of a wide variety of substituted dihydropyrimidinones (including sterically encumbered ones) in high yields and purity under mild reaction conditions.     

Heteropoly acid supported on activated natural clay-catalyzed synthesis of 3,4-dihydropyrimidinones/thiones through Biginelli reaction under solvent-free conditions

Dihydropyrimidinones/thiones (DHPM’s) have been prepared by one-pot condensation of methyl acetoacetate, aldehydes, urea/thiourea in the presence of heteropoly-11-tungsto-1-vanadophosphoric acid, H₄[PVW₁₁O₄₀]?·?32H₂O, (HPV) supported on activated natural clay (HPVAC) under solvent-free reaction condition have been proposed. The DHPM derivatives were identified through elemental analysis and melting point measurements and characterized by FT-IR, ¹H-NMR, ¹³C-NMR spectroscopic methods.     

NaIO4-catalyzed one-pot synthesis of dihydropyrimidinones at room temperature under solvent-free conditions

Sodium periodate efficiently catalyzed the three-component Biginelli reaction of an aldehyde, α β-keto ester or β-keto ketone, and urea or thiourea at room temperature under solvent-free conditions and afforded the corresponding 3,4-dihydropyrimidine-2-(1H)-ones in excellent yields.     

An appropriate one-pot synthesis of dihydropyrimidinones catalyzed by heteropoly acid supported on zeolite: An efficient and reusable catalyst for the Biginelli reaction

A mild and efficient catalytic method has been developed for the synthesis of 3,4-dihydropyrimidin-2 (1H)-ones (DHPM) by a one-pot three-component cyclocondensation reaction using molybdophosphoric acid (MPA) supported on Y zeolite in high to excellent yields. The reaction investigated in the presence of molybdophosphoric acid encapsulated in the supercage of zeolite for comparison. In the second method, no appreciable progress was observed due to large size of dihydropyrimidinone compounds towards the supercage dimension of Y zeolite. In addition, the catalyst was recovered and reused for several times without efficient loss in catalytic activity.     

Straightforward and highly efficient catalyst-free one-pot synthesis of dithiocarbamates under solvent-free conditions

[Structure: see text] A highly efficient and simple synthesis of dithiocarbamates is possible based on the one-pot reaction of amines, CS2, and alkyl halides without using a catalyst under solvent-free conditions. The mild reaction conditions, high yields, and broad scope of the reaction illustrate the good synthetic utility of this method. The reaction is a highly atom-economic process for production of S-alkyl thiocarbamates and successfully can be used in high quantities in the pharmaceutical or agrochemical industries.     

An efficient synthesis of quinolines under solvent-free conditions

An efficient synthesis of substituted quinolines has been achieved in a one-pot reaction from o-nitrobenzaldehyde and enolizable ketones using SnCl₂·2H₂O as the reductant under microwave irradiation without any solvent or catalyst     

An efficient and solvent-free one-pot synthesis of 1,4-dihydropyridines under microwave irradiation

An efficient synthesis of 1,4-dihydropyridines using lanthanum oxide as a catalyst from aldehydes,β-ketoester and ammonium acetate without solvent under the irradiation of microwave is described.Compared with the classical Hantzsch reaction,this new method has the advantage of good yield(90-98%) and short reaction time(40-80 s).     

Microwave-assisted efficient synthesis of spiro-fused heterocycles under solvent-free conditions

Spiro-fused heterocycles were synthesized in good to high yields by a pseudo four-component reaction of an aldehyde, urea and a cyclic β-diester or a β-diamide such as Meldrum’s acid or barbituric acid derivatives using microwave irradiation under solvent-free conditions.     

One-pot synthesis of dihydropyrimidones using silica-supported heteropoly acid as an efficient and reusable catalyst: Improved protocol conditions for the Biginelli reaction

An efficient synthesis of 3,4-dihydropyrimidinones or thiones (DHPMs) is described, using silica-supported heteropoly acid H₃PW₁₂O₄₀/SiO₂ (PW/SiO₂) for the first time as the catalyst from an aldehyde, β-keto ester and urea or thiourea in acetonitrile. Compared to the classical Biginelli reaction conditions, this method consistently has the advantage of excellent yields, mild reaction conditions, ease of workup, survival of different functional groups, and short reaction times.     

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.     

An isocyanide based multi-component reaction under catalyst- and solvent-free conditions for the synthesis of unsymmetrical thioureas

A new and efficient method for the synthesis of thiourea derivatives by a sequential one-pot, three-component reaction between aromatic isocyanides, amines, and 1,2-di-tert-butyldisulfane (DTBS) was developed and 27 different examples were synthesized in good to excellent yields. DTBS was identified as an effective sulfur surrogate without the use of both catalysts and solvents. This protocol does not employ any transition metal catalyst or special experimental setup.     

Tungstate sulfuric acid catalyzed one-pot synthesis of a new class of aroylamido coumarins under solvent-free conditions

A one-pot synthesis of novel aroylamido coumarins from the reaction of 4-hydroxycoumarin with aryl glyoxals and benzamides in the presence of a catalytic amount of tungstate sulfuric acid (TSA) is described. The method is operationally simple and provides access to a variety of aroylamido coumarins in good yields.     

TaBr5-catalyzed Biginelli reaction: one-pot synthesis of 3,4-dihydropyrimidin-2-(1H)-ones/thiones under solvent-free conditions

An efficient TaBr₅ (5-10 mol %)-catalyzed Biginelli reaction under solvent-free conditions for one-pot syntheses of 3,4-dihydropyrimidin-2-(1H)-ones (DHPMs) and their thione analogs is reported. The catalyst is stable at room temperature and employed under mild and environmentally friendly conditions.     

A simple and efficient one-pot synthesis of 1,4-dihydropyridines using heterogeneous catalyst under solvent-free conditions

One-pot condensation of β-dicarbonyl compounds with aldehydes and ammonium acetate in the presence of HClO₄–SiO₂ at 80 °C under solvent-free conditions with good to excellent yields. The catalyst is easily prepared, stable, reusable and efficiently used under reaction conditions.