3-Substituted 2-trifluoromethylimidazo [1,2-a] pyridines

3-Fluoro-2-trifluoromethylimidazo[1,2-a]pyridines were obtained by reactions of hexafluoroacetone 2-pyridylimines with trimethyl phosphite and studied in reactions with sodium methoxide. This gave the corresponding 3-methoxy-2-trifluoromethylimidazo[1,2-a]pyridines.     

Ionic liquid promoted one-pot synthesis of 3-aminoimidazo[1,2-a]pyridines

3-Aminoimidazo[1,2-a]pyridines have been synthesized in good to excellent yields in the presence of the ionic liquid 1-butyl-3-methylimidazolium bromide [bmim]Br, the reaction workup is simple and the ionic liquid can be easily separated from the product and reused.     

Microwave-assisted synthesis of 3-formyl substituted imidazo[1,2-a]pyridines

An efficient, metal-free method for the synthesis of 3-formyl imidazo[1,2-a]pyridines is reported. The method utilises commercially available substrates and features a broad substrate scope. The intermediate enamine was isolated and a plausible reaction mechanism proposed.     

Selective C-acylation of 2-aminoimidazo[1,2-a]pyridine: application to the synthesis of imidazopyridine-fused [1,3]diazepinones

A series of 20 optically pure 3,4-dihydro-5H-pyrido[1',2':1,2]imidazo[4,5-d][1,3]diazepin-5-ones which form a new family of azaheterocycle-fused [1,3]diazepines were synthesized in four steps with 17-66% overall yields. The key step consists of a selective C-acylation reaction of easily accessible 2-aminoimidazo[1,2-a]pyridine at C-3.     

Regiospecific synthesis of 3-substituted imidazo[1,2-a]pyridines,imidazo[1,2-a]pyrimidines,and imidazo[1,2-c]pyrimidine

3-Substituted imidazo[1,2-a]pyridines, imidazo[1,2-a]pyrimidines, and imidazo[1,2-c]pyrimidine were obtained regiospecifically in yields of 35-92% in one pot by reaction of 2-aminopyridines or 2-(or 4-)aminopyrimidines, respectively, with 1,2-bis(benzotriazolyl)-1,2-(dialkylamino)ethanes.     

New multi-component reaction accessing 3-aminoimidazo[1,2-a]pyridines

The novel one step solution phase synthesis of an array of 3-aminoimidazo[1,2-a]pyridines is reported. Reactions were performed in methanol by mixing a α-amino-pyridine, aldehyde and trimethylsilylcyanide (TMSCN) to give the desired product. Mediated by microwave irradiation and catalyzed by scandium triflate, the methodology represents the first one pot preparation of 3-aminoimidazo[1,2-a]pyridines that avoids the use of an isonitrile and subsequent de-protection strategy. The reaction is an example of a formal three-centre-three-component multi-component reaction.     

Phosphorylated imidazo[1,2-a]pyridines

The reaction of phosphorus(III) halides with imidazo[1,2-a]pyridines in the presence of bases leads to the formation of 3-phosphorylated imidazo[1,2-a]pyridines. The reaction proceeds in high yield and requires no catalysts. In the compounds obtained, in contrast to phosphorylated indolizines, the phosphorus–heterocycle bond is stable and not cleaved by dry hydrogen chloride, alcohols, or water. Imidazo[1,2-a]pyridines with the phosphinic and phosphinous groups can be alkylated both at the phosphorus and at the nitrogen atom of the heterocycle, the alkylation direction being dependent on the strength of the alkylation reagent used. © 1995 John Wiley & Sons, Inc.     

Easy access to novel substituted 6-aminoimidazo[1,2-a]pyridines using palladium- and copper-catalyzed aminations

Convenient and efficient methods for the preparation of novel 6-aminoimidazo[1,2-a]pyridine derivatives are reported that utilized palladium- or copper-catalyzed methodology. The crystal structure for 6-N-methylanilinoimidazo[1,2-a]pyridine 10 is also described.     

Ammonium chloride catalyzed one-pot synthesis of imidazo[1,2-a]pyridines

Ammonium chloride as a very inexpensive and readily available reagent efficiently catalyzes one-pot, three-component Groebke condensation reactions of aldehydes, isocyanides, and 2-aminopyridines or 2-aminopyrimidines in methanol to afford the corresponding imidazo[1,2-a]pyridines in high yields at room temperature. Correspondence: Ahmad Shaabani, Department of Chemistry, Shahid Beheshti University, PO Box 19396-4716, Tehran, Iran.     

Synthesis of 6-alkylthioimidazo[1,2-a]pyridines

A number of 6-alkylthio(and sulfonyl)-substituted imidazo[1,2-a]pyridines were synthesized by the reaction of 5-alkylthio- and 5-alkylsulfonyl-2-aminopyridines with -bromoacetophenone and -chlorocyclohexanone in order to search for new compounds that have fungicidal activity. 5-Alkylthio-2-aminopyridines were obtained from the double salt of 5-mercapto-2-aminopyridine with SnCl₂ and HCl by reaction with alkyl halides or tert-C₄H₉OH and 75% H₂SO₄. 5-tert-Butylthio-2-aminopyridine was oxidized by means of KMnO₄ to 5-tert-butylsulfonyl-2-aminopyridine. A double salt was synthesized from 2-aminopyridine-5-sulfonic acid.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 634–638, May, 1979.     

Efficient syntheses of imidazolo[1,2-a]pyridines and -[2, 1-a]isoquinolines

2-Aminopyridines 1a-c and 1-aminoisoquinoline with 1-chloromethylbenzotriazole give 2-amino-1-[alpha-benzotriazol-1-ylmethyl]pyridinium chlorides 2a-c and 1-amino-2-(alpha-benzotriazol-1-ylmethyl)isoquinolinium++ + chloride 12, respectively. Compounds 2a-c and 12 react with aryl aldehydes 3a-h to afford imidazolo[1,2-a]pyridines 7a-k and imidazolo[2, 1-a]isoquinolines 13a,b in good yields.     

Green synthesis of pyrido[2,1-a]isoquinolines and pyrido[1,2-a]quinolins using Fe3O4-MNPs as efficient nanocatalyst: Study of antioxidant activity

In this work, synthesis of pyrido[2,1-a]isoquinolines and pyrido[1,2-a]quinolins in excellent yield using multicomponent reaction of phthalaldehyde, methyl amine, methyl malonyl chloride, alkyl bromides, and triphenylphosphine in the presence of catalytic amount of Fe₃O₄-MNPs with aqueous sodium hydroxide at 80°C was investigated. The reduction of ferric chloride solution with Clover Leaf water extract caused to synthesis of magnetic iron oxide nanoparticles (Fe₃O₄-MNPs) as a green method. As well, antioxidant activity was studied for the some newly synthesized compounds such as 6a , 6c , 9b , and 9c using the DPPH radical trapping and reducing of ferric ion experiments and comparing results with synthetic antioxidants (TBHQ and BHT). As a result, compounds 6a , 6c , 9b , and 9c show good DPPH radical trapping and excellent reducing strength of ferric ion.     

Regioselective two step synthesis of 3-substituted 2-aminoimidazo[1,2-a]pyrimidines

A two step procedure for the regioselective synthesis of 3-substituted-2-aminoimidazo[1,2-a]pyrimidines is described. The key step is a Dimroth rearrangement of a mixture of 2 and 3-substituted aminoimidazo[1,2-a]pyrimidines that yields quantitatively one regioisomer. Reaction screening for the rearrangement step is reported. A multicomponent isocyanide based reaction is chosen as the preferred way for the synthesis of the precursors. Elucidation of regiochemistry has been done by X-ray determination of some representative compounds.     

Solvent and catalyst-free synthesis of imidazo[1,2-a]pyridines by grindstone chemistry

The present work describes the solvent and catalyst-free synthesis of imidazo[1,2-a]pyridines in excellent to nearly quantitative yields from 2-aminopyridines and a wide variety of ω-bromomethylketones using a grindstone procedure at 25°C to 30°C for 3 to 5 minutes. The absolute structure of the compound, 2-(3-bromophenyl)-7-methylimidazo[1,2-a]pyridine is determined by X-ray crystallography. This green strategy has several noteworthy advantages such as wide spread substrate scope, short reaction times, water work up and the products do not require any chromatographic purification. Moreover, the method does not require any specialized equipment and is highly economical, environmentally benign and easy to carry out in any laboratory. Hence, the developed method meets the concept of “benign by design” and is greener alternative to the reported procedures for the synthesis of imidazo[1,2-a]pyridines.     

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

Condensation of aldehydes, isonitriles and 2‐aminopyridines in the presence of H₃PMo₁₂O₄₀ affords different derivatives of 3‐aminoimidazo[1,2‐a]pyridine in good to excellent yields.     

Transformations of the pyrido[1,2-a]pyrazine ring system into imidazo[1,2-a]pyridines,imidazo[1,2-a]pyrimidines and 2-oxa-6a, 10c-diazaaceanthrylenes

Transformations of methyl 3-dimethylamino-2-(1-methoxycarbonyl-4-oxo-4H-pyrido[1,2-a]pyrazin-3-yl)acrylate with some cyanomethylenecarbonyl group containing compounds or cyanamide into imidazo-[1,2-a]pyridines, irmdazo[1,2-a]pyrimidines and 2-oxa-6a, 10c-diazaaceanthrylenes are described.     

New catalytic system for the synthesis of imidazo[1,2-a]pyridines by the Ugi reaction

A combination of N-hydroxysuccinimide and p-toluenesulfonic acid is proposed as an efficient catalyst for the preparation of a great variety of imidazo[1,2-a]pyridine derivatives by three-component condensation of aromatic isocyanides, aldehydes, and 2-aminopyridine. The advantages of this procedure are high yields of the target products and the absence of side reactions. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1768–1772, October, 2006.