One-Pot Synthesis of 2-Phenylimidazo[1,2-α]pyridines from Acetophenone, [Bmim]Br3 and 2-Aminopyridine under Solvent-Free Conditions

Abstract

One-pot synthesis of 2-phenylimidazo[1,2-α]pyridines from acetophenone, [Bmim]Br3 and 2-aminopyridine under solvent-free conditions in the presence of Na2CO3, gave the corresponding 2-phenylimidazo[1,2-α]pyridines in excellent yields ranging from 72% to 89%.

CuI-Catalyzed Aerobic Oxidative α-Aminaton Cyclization of Ketones to Access Aryl or Alkenyl-Substituted Imidazoheterocycles

“…This compound is known. The 1 H and 13 C NMR spectral data are in agreement with the literature data …”

Iodine Promoted Efficient Synthesis of 2-Arylimidazo[1,2-a]pyridines in Aqueous Media: A Comparative Study between Micellar Catalysis and an “On-Water” Platform

“…All the imidazo­[1,2- a ]­pyridine derivatives were thoroughly characterized by 1 H NMR, 13 C NMR, and HRMS analysis. The 1 H and 13 C NMR spectra were in good agreement with the reported values of the known compounds. ,,− The newly reported compounds were also in good agreement with their expected spectral characteristic peaks. A 1 H singlet peak in the range δ 7.60–8.00 ppm is the signature peak of the imidazole moiety.…”

“…Attributing to its vast applications, this field received tremendous research interest to develop clean and efficient synthetic methodologies for imidazo­[1,2- a ]­pyridines. ,− The classical methods for the synthesis of imidazo­[1,2- a ]­pyridines involve cyclocondensation of 2-aminopyridines with α-haloketones or their equivalents, and α,β-unsaturated carbonyl compounds in conventional reaction media . Other notable two-component strategies include reactions between 2-aminopyridines with various coupling partners such as metal-catalyzed oxidative addition of alkynes, nitroalkenes by tandem reactions, oxidative coupling of 1,3-dicarbonyl compounds, and so on .…”

“…Relooking at the current literature for the synthesis of imidazo­[1,2- a ]­pyridines, we felt interested in dehydrogenetive heteroannulation between 2-aminopyridine and arylketo compounds to afford this heterocycle with an aryl group at C-2 (Scheme ). ,− In this direction, various methods have been developed in conventional media, which include metal-catalyzed C–H functionalization (e.g., Cu­(OAc) 2 in dichlorobenzene, CuI in dimethylformamide (DMF), CuI in 1,4-dioxane, CuI–In­(OTf) 3 in N -methyl-pyrrolidone (NMP)), in situ α-iodination followed by Ortoleva–King-type reaction in the presence of catalytic or stoichiometric amount of iodine (e.g., I 2 in dimethyl sulfoxide (DMSO), I 2 –NH 4 OAc in CHCl 3 , I 2 –FeCl 3 in chlorobenzene), and few others . Apart from developing new strategies, efforts are also directed toward the development of practical and scalable methods for the synthesis of imidazo­[1,2- a ]­pyridine-based drug candidates. ,,,, However, these methods have one or more shortcomings like the requirement of dry conditions, use of hazardous organic solvents, Lewis acids, high temperature, and so forth.…”

Recent Developments in the Synthesis of Imidazo[1,2-a]pyridines

“…From this perspective, great advances have been made over the last decade in the traditional cyclocondensation procedure 8 by using efficient alternatives; for example, α-halo carbonyl compounds were replaced with environmentally benign reagents such as α-tosyloxy ketones 9 or αdiazo ketones 10 to give imidazo[1,2-a]pyridines in good yields. On the other hand, carbonyl compounds can be activated in situ through reagents such as [Bmim]Br 3 11 or hypervalent iodine agents, 12 and then treated with 2-aminopyridines to obtain the imidazo[1,2-a]pyridines. In some cases flow chemistry has been applied to the synthesis of these pharmacologically potent motifs starting from readily available materials.…”