Silica sulfuric acid as an efficient and recoverable catalyst for the synthesis of trisubstituted imidazoles

BF3/nano-sawdust as a green, biodegradable and inexpensive catalyst for one-pot synthesis of tri-substituted imidazoles under solvent free conditions

“…The majority of synthetic routes rely on one-pot condensation of diketones or -hydroxyketones with an aldehyde and ammonium acetate in the presence of catalysts such as silica gel or zeolite [9], alumina [10], molecular iodine [11], neutral ionic liquid [12], L-Proline [13], nano-crystalline Sulfated Zirconia (SZ) [14], DABCO [15], AcOH [16], zeolitesupported reagents [17], silica sulfuric acid [18], PEG-400 [19], InF 3 [20], nanocrystalline magnesium ox- [24], and bioglycerol-based carbon catalyst [25]. Some of these catalysts are ideal choices for the synthesis of 2,4,5-tri-substituted imidazoles and are often used for this purpose.…”

UHP as a mild and efficient catalyst for the synthesis of substituted imidazoles via multicomponent condensation strategy

“…Generally 2,4,5-trisubstituted imidazoles are synthesized by three-component cyclocondensation of 1,2-diketone or α-hydroxyketone or α-ketomonoxime with an aldehyde and ammonium acetate, which comprise the use of ionic liquids [12], refluxing in acetic acid [13], silica supported sulfuric acid [14] [17] and microwave irradiation [18]. Many of the synthetic methods for imidazoles suffer from one or more disadvantages such as low yields, strict reaction conditions, long time period and expensive catalysts and difficult workup.…”

A facile and efficient synthesis of tri- and tetrasubstituted imidazoles with potassium hydrogen sulfate and DB18C6 in an aqueous medium

“…2,4,5-Trisubstituted imidazoles are usually synthesized by a multicomponent reaction involving benzil (or a substituted benzil), an aldehyde, and ammonium acetate as an ammonia source (21), and many catalysts [silica/sulfuric acid (22,23), Yb(OTf) 3 (24), NiCl 2 ×6H 2 O (25), oxalic acid (26), iodine (27), sulfanilic acid (28), tetrabutyl ammonium bromide (29), cerium ammonium nitrate (30), Zr(acac) 4 (22,33,36), or in ionic liquids (37,38). But the synthesis of substituted imidazoles in an aqueous medium is rare.…”