[B(OH)3]0.78[B(OH)2(OSO3H)]0.22 or (BSA) was simply prepared by addition of chlorosulfonic acid to commercial boric acid at room temperature. This cheap and green solid acid was used as an efficient catalyst for synthesis of acylals from aldehydes under solvent-free conditions at room temperature.

Molybdate sulfuric acid (MSA) has been prepared and used as catalyst for the Biginelli synthesis of some quinazolinones/thiones under solvent-free conditions. The catalyst loading is low and it shows recyclability. This method has advantages such as avoidance of the organic solvents, high yield of pure products, short reaction times and operational simplicity.

Silica-bonded n-propyltriethylene-tetramine (SBNPTT) was found as an efficient solid base for the synthesis of 2-amino-5-oxo-5,6,7,8-tetrahydro-4H-chromenes. Chromene derivatives were obtained via the three-component condensation reaction of aromatic aldehydes, malononitrile, and dimedone at 80 oC under solvent-free conditions. The heterogeneous solid base showed much the same efficiency when u...

In the present of methylimidazolium hydrogen sulfate, the synthesis of arylidene heterobicyclic pyrimidinones is studied by condensation of aromatic aldehyde, cyclopentanone, and urea or thiourea. Using solvent-free conditions, non-toxic and inexpensive materials, simple and clean work-up, short reaction times and good yields of the products are the advantages of this method.

A new and efficient synthesis of benzoxanthene drivatives from the three-component condensation reaction ofaryl aldehydes and β-naphthol under solvent-free conditions in the presence of β-cyclodextrin sulfonic acid, as an efficient heterogeneous solid acid catalyst with excellent yields and short reaction time is presented

[B(OH)3]0.78[B(OH)2(OSO3H)]0.22 or (BSA) was simply prepared by addition of chlorosulfonic acid to commercial boric acid at room temperature. This cheap and green solid acid was used as an efficient catalyst for synthesis of acylals from aldehydes under solvent-free conditions at room temperature.

An effective one-pot synthesis of dihydropyrimidinonoes in solvent free conditions using CuCl2 as an inexpensive and readily available reagent through Biginelli condensation reaction of aldehyde derivatives, 1,3-dicarbonyl compounds and urea is described. Excellent yields, short reaction times for formation of the products and simple work-up are attractive features of this green protocol.

Phosphorus pentoxide used on alumina (P2O5/Al2O3) as an inexpensive, eco-friendly and non-toxic acid catalyst for the one-pot synthesis of 1,8-dioxo-octahydroxanthenes via multi-component reactions under solvent-free conditions. The present approach offers several advantages such as short reaction times, high yields, easy purification, recovery and reusability of the catalyst.

Caro’s acid-silicagel was found to be a mild and effective catalyst for the one –pot multicomponent condensation of benzyl, aldehydes and ammonium acetate used for synthesis of 2, 4, 5-trisubstituted imidazole derivatives under solvent–free conditions. This catalyst has several advantages such as simple work-up, low cost and reusability.

A new catalyst was prepared by promoting fly ash with hydrogen peroxide. The catalytic activity of H2O2 promoted fly ash (HPFA) was evaluated by synthesis 5(4H)-oxazolone and imidazolone derivatives under solvent free conditions. The possible mechanisms of synthesis reactions were also suggested. These proposed methods benefit in terms of low-cost catalyst, high yields, ease of workup, survival...