Catalyst-free three-component reaction between 2-aminopyridines (or 2-aminothiazoles), aldehydes, and isocyanides in water

One‐pot Synthesis of 3‐Aminoimidazo[1,2‐a]pyridines Catalyzed by Heteropolyacids

“…16 The reaction of heterocyclic amidines with aldehydes and isonitriles under acid catalysis conditions was first reported in 1998. 17 However, these reactions required long time for completion and the reaction work-ups were complicated.…”

“…Most of the above mentioned syntheses involve harsh or environmentally hazardous reaction conditions. 16 The replacement of these conventional hazardous and polluting corrosive liquid acid catalysts by solid acid catalysts is one of the demands of the societies. Cleaner technology could be possible by making use of environmentally friendly catalysts involving the use of solid acids.…”

ZnO nanorods as an efficient catalyst for the synthesis of imidazo[1,2-a]azines and diazines

“…Although this procedure gave the desired products in good to excellent yields, the application of excessive amounts of sodium bicarbonate and ionic liquid is one of the disadvantages of this procedure [12]. In recent years many procedures for the synthesis of imidazo[1,2-a]azines and diazines have been developed [13]. Various catalysts have been used for the synthesis of imidazo[1,2-a]azines such as p-toluenesulfonic acid [14] and ammonium chloride [15].…”

Tandem approach for the synthesis of imidazo[1,2-a]pyridines from alcohols

“…10 Recently, Adib et al (2011) reported the synthesis of imidazo[1,2-a]pyridine scaffolds by a modified three-component coupling (3-CR) of aromatic amidines, benzyl halides, and isocyanides in the presence of DMSO and K 2 CO 3 (Scheme 1).…”

“…11a Adib et al (2007) reported a catalyst-free, simple, and environmentally friendly approach for the synthesis of imidazo[1,2-a]pyridines 11b using aldehydes as one of the substrates in water at 70°C.…”