One-pot Copper Nanoparticle-catalyzed Synthesis of Imidazo[1,2-α]pyridines Under Solvent-free Conditions

A direct and efficient approach to synthesize imidazo[1,2-α]pyridines through three-component one-pot reaction of 2-aminopyridine,aldehyde and terminal alkyne catalyzed by Cu-nanoparticles under solvent-free conditions has been developed.This method provides a rapid access to substituted imidazo[1,2-α]pyridines with good yields（up to 85％）.     

Pd-Cu–Mediated Synthesis of 2-Substituted Imidazo[1,2-α]pyridines in Water

The reaction of 2-amino-1-(2-propynyl)pyridinium bromide with various iodobenzenes, catalyzed by Pd-Cu, in the presence of sodium lauryl sulfate as the surfactant and cesium carbonate as the base, in water, leads to the formation of 2-substituted imidazo[1,2-α]pyridines.     

Rapid Synthesis of 3‐Aminoimidazo[1,2‐a]Pyridines and Pyrazines

p‐Toluenesulfonic acid catalyzed the one‐pot, three‐component synthesis of 3‐aminoimidazo[1,2‐a]pyridines and pyrazines through a condensation reaction of a 2‐aminoazine, an aldehyde, and an isocyanide at room temperature. This methodology affords a number of 3‐aminoimidazo[1,2‐a]pyridines in reasonable yields and short reaction times without any significant optimization of the reaction conditions.     

Novel syntheses of hexahydro-1H-pyrrolo[1,2-a]ĭmidazoles and Octahydroimidazo[1,2-a]pyridines

1-Phenyl-5-(benzotriazol-1-yl)hexahydro-1H-pyrrolo[1,2-a]?midazole (18) and 1-phenyl-5-benzotriazolyloctahydroimidazo[1,2-a]pyridine (27) were readily prepared from succindialdehyde or glutaraldehyde, benzotriazole, and N-phenylethylenediamine. Synthons 18 and 27 reacted with Grignard reagents, allylsilanes, silyl ethers, and triethyl phosphite to produce 1-phenyl-5-substituted-hexahydro-1H-pyrrolo[1,2-a]?midazoles 20a-f, 22, 24a,b, and 25 and 1-phenyl-5-substituted-octahydroimidazo[1, 2-a]pyridines 28a-e, 32, 33a,b, and 34 in good to excellent yields. The configurations of 20, 22, 24, and 25 were determined to be cis isomers by NOE experiment, while the configurations and conformations of 28a-e, 32, 33a,b, and 34 were elucidated by (1)H-(1)H COSY and (1)H-(13)C COSY.     

Crystal structure of 1,2‐[4‐butoxybenzoyloxy‐4′‐pentyl]diphenylethane

The crystal structure of 1,2‐[4‐butoxybenzoyloxy‐4′‐pentyl]diphenylethane (C₃₀H₃₆O₃) has been determined by direct methods using single crystal X‐ray diffraction data. It crystallizes in the monoclinic system with space group P2₁/a and Z?=?4. The unit cell parameters are: a?=?8.098(1), b?=?10.926(1), c?=?29.643(2)?Å and β?=?94.01(1)°. The final reliability factor is R?=?0.073 and the goodness of fit is equal to 1.027. The molecular arrangement is very typical, with molecules associated in dimers very closely parallel to the Oz axis. In a given dimer, the backbones of the two molecules run alongside each other; this association can be attributed to strong dipole–dipole interactions through the polar ester and ether groups. In addition these dimers are connected to neighbours via dipole–dipole interactions along the Oy direction. There are numerous very weak van der Waals interactions, particularly between the terminal aliphatic chains.     

An Improved Synthesis of 2-Chlorinated Imidazo[1,2-α]-pyridines and the Application of this Procedure for the Synthesis of Several New Polychlorinated Imidazo[1,2-α]Pyridnes.

Polychlorinated imidazo[1,2-α]pyridines were synthesized as analogs of certain chlorinated benzimidazoles. The imidazo[1,2-α]pyridines were obtained by a condensation of ethyl bromoacetate and chlorinated 2-aminopyridines. These condensation products were treated with an ion exchange resin to effect an exchange of hydrobromide salts with hydrochloride salts. These compounds were subsequently treated with POCl₃ to convert the imidazo[1,2-α]pyridin-2-ones into 2-chloroimidazo[1,2-a]pyridines.     

Synthesis of 1-｛ Imidazo[ 1,2-a ] pyridin-2-yl ｝ guaiazulenes

以1-氯乙酰基愈创兰烃奠和取代2-氨基吡啶为原料,一锅法合成了一系列未见文献报道的1-{2-咪唑[1,2-a]吡啶基}愈创兰烃薁衍生物,收率47％ ～ 74％,其结构经1H NMR,IR和元素分析表征.     

Anomeric Stereoauxiliary Cleavage of the C−N Bond of d-Glucosamine for the Preparation of Imidazo[1,5-a]pyridines

The targeted cleavage of the C−N bonds of alkyl primary amines in sustainable compounds of biomass according to a metal-free pathway and the conjunction of nitrogen in the synthesis of imidazo[1,5-a]pyridines are still highly challenging. Despite tremendous progress in the synthesis of imidazo[1,5-a]pyridines over the past decade, many of them can still not be efficiently prepared. Herein, we report an anomeric stereoauxiliary approach for the synthesis of a wide range of imidazo[1,5-a]pyridines after cleaving the C−N bond of d -glucosamine (α-2° amine) from biobased resources. This new approach expands the scope of readily accessible imidazo[1,5-a]pyridines relative to existing state-of-the-art methods. A key strategic advantage of this approach is that the α-anomer of d -glucosamine enables C−N bond cleavage via a seven-membered ring transition state. By using this novel method, a series of imidazo[1,5-a]pyridine derivatives (>80 examples) was synthesized from pyridine ketones (including para-dipyridine ketone) and aldehydes (including para-dialdehyde). Imidazo[1,5-a]pyridine derivatives containing diverse important deuterated C(sp²)−H and C(sp³)−H bonds were also efficiently achieved.     

One‐Pot and Convenient Conversion of 5‐Azidopyrazole‐4‐carboxaldehyde to Pyrazolo[3,4‐b]pyridines

A one‐pot and convenient synthesis of multisubstituted pyrazolo[3,4‐b]pyridines in moderate to high yields has been achieved by a two‐step reaction: diazo‐transfer of 5‐azido‐1‐phenylpyrazole‐4‐carboxaldehydes to ketones in ethanolic KOH to give 5‐amino‐1‐phenylpyrazole‐4‐carboxaldehyde and subsequent Friedlaender reaction of 5‐amino‐1‐phenylpyrazole‐4‐carboxaldehyde with ketones.     

Synthesis of Benzo[4,5]furo[3,2-b]thieno[2,3-d]pyridines —Derivatives of a New Heterocyclic System

Russian Journal of Organic Chemistry - Methyl 2-(bromomethyl)thiophene-3-carboxylates reacted with substituted 2-hydroxybenzonitriles to give methyl...     

Synthesis of Some New N‐Substituted Pyrroles,Pyrrolo[1,2‐a]quinazoline,and Diaza‐as‐indacene Derivatives

2‐Phenyl‐1,1,3‐tricyano‐3‐bromopropene 1 reacts with the aromatic amines 2a–f and 6a–c to afford the N‐substituted pyrroles 4a–d, the pyrrolo[1,2‐a]quinazoline derivatives 5a, b, and the diaza‐as‐indacene derivatives 7a–c and 8a–c, presumably via elimination of hydrogen bromide followed by cyclization of the formed acyclic intermediates. All structures are confirmed by analytical and spectral data.     

Intramolecular Ullmann-type C−N coupling for the synthesis of substituted benzo[4,5]imidazo[1,2-a]pyrrolo[3,4-c]pyridines

An efficient CuI catalyzed intramolecular Ullmann-type C−N coupling reaction is described here. Newly substituted 1H-benzo[4,5]imidazo[1,2-a]pyrrolo[3,4-c]pyridine-1,3,5(2H, 11H)-trione has been easily synthesized from ortho halogenated N-substituted pyrrolo[3,4-c]pyridine-1,3,6(5H)-triones in presence of CuI catalyst and K₂CO₃ base without any ligand. This procedure is based on intramolecular Ullmann-type reaction and provides a proficient method of making fused tetracyclic heterocycles.     

Rapid and efficient one-pot microwave-assisted synthesis of 2-phenylimidazo[1,2-a]pyridines and 2-phenylimidazo[1,2-a]quinoline in water–PEG-400

An effective, expeditious, environmentally benign one-pot synthesis of 2-phenylimidazo[1,2-a]pyridines and 2-phenylimidazo[1,2-a]quinoline from easily available starting materials as aromatic carbonyl compound, 2-amino pyridine, succinamide, and in situ generated α-iodo acetophenone in combination with green solvent PEG-400 and water (2:1) under microwave irradiation. The newly developed protocol with excellent yield of product in very short time of reaction by avoiding the use of lachrymatric α-chloro and α-bromocarbonyl compounds, volatile, toxic organic and hazardous solvents, reagents is the advantage of this research work. The final products were confirmed by their characterization data such as ¹H NMR, ¹³C NMR, high resolution mass spectrometry (HRMS) and were compared with its reported method.     

Synthesis of Functionalized Pyrano[3,2‐c]pyridines and Their Transformations to 4‐Hydroxy‐3[(1E)‐N‐hydroxyalkanimidoyl]pyridones

Reaction of 4‐hydroxy‐6‐methyl‐2(1H)‐pyridones 1a and 4‐hydroxy‐1,6‐dimethyl‐2(1H)‐pyridones 1b with diethyl malonates 2a–e leads to the formation of pyrano[3,2‐c]pyridines 4a–j. Degradation of 4a–i affords the corresponding ketones 6a–i. Condensation of ketones 6a–i with hydroxyl amine or phenyl hydrazine hydrochloride is described.     

Transition-metal-free,visible-light-mediated regioselective C–H trifluoromethylation of imidazo[1,2-a]pyridines

A transition-metal-free, visible-light-induced trifluoromethylation of imidazo[1,2-a]pyridines has been developed at mild conditions by employing cheap and commercially available anthraquinone-2-carboxylic acid (AQN-2-CO₂H) as the photo-organocatalyst, and Langlois reagent as the trifluoromethylating reagent. A series of 3-(trifluoromethyl)imidazo[1,2-a]pyridine derivatives with broad functionalities could be conveniently and efficiently obtained by direct regioselective functionalization.     

Glycosylation of 4‐Aryl‐1‐thioxo[1,2,4] triazolo[4,3‐a] quinazolin‐5(4H)‐one

Reaction of 4‐aryl‐1‐thioxo [1,2,4] triazolo [4,3‐a] quinazolin‐5 (4H)‐ones (2a,b) with acetylated glycosyl bromides 3a–c under alkaline conditions afforded the corresponding S‐glycoside derivatives 4, 5 and N‐glycoside derivatives 6, 7. Oxidation of S‐glycosyl derivatives 4, 5 with m‐chloroperbenzoic acid yielded the corresponding sulphones 8, 9, whereas the N‐glycosyl derivatives 6, 7 yielded 1‐oxo derivatives 10, 11. However their O‐deacetylation with sodium methoxide in methanol caused cleavage of the S‐glycosyl residue and gave N ²‐glycosylated analogues 12, 13, 14 and 15.     

TBAI-catalyzed oxidative coupling of aminopyridines with β-keto esters and 1,3-diones-synthesis of imidazo[1,2-a]pyridines

TBAI could catalyze the direct oxidative C-N coupling of 2-aminopyridines with β-keto esters and 1,3-diones, which affords imidazo[1,2-a]pyridines as the products. The reaction was realized under metal-free conditions by using tert-butyl hydroperoxide (TBHP) as the oxidant.     

Synthesis of Substituted Pyrido[1,2-a]benzimidazoles by Ruthenium-Catalyzed C−H Bond Activation and Tandem Cyclization of 2-Arylimidazo[1,2-a]pyridines with Iodonium Ylides

Ruthenium-catalyzed C−H bond activation and tandem cyclization of 2-arylimidazo[1,2-a]pyridines with iodonium ylides proceed efficiently. For the first time, the easily available iodonium ylides and inexpensive ruthenium complex were employed to synthesize pyrido[1,2-a]benzimidazole derivatives in good yields under simple and easy-to-operate conditions. Several primary mechanism investigations and synthetic applications involving gram-scale preparation, derivatization reactions and the transformation of iodonium ylide generated in situ have also been conducted.     

Cyclization of alk-4-ynals with o-diaminoarenes as a selective one-pot synthesis of arylmethylidene-substituted 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazoles and 7,8-dihydro-6H-pyrrolo[1’,2’:1,2]imidazo[4,5-b]pyridines

Russian Chemical Bulletin - A one-pot synthesis of arylmethylidene-substituted 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazoles based on the reaction of alk-4-ynals with 1,2-diaminobenzenes in DMSO at...     

Synthesis of 11-aryl-11H-indeno[1′,2′:4,5]imidazo[1,2-a]pyridines via dehydrative cyclization of aryl(2-arylimidazo[1,2-a]pyridin-3-yl)methanols

A series of 11-aryl-11H-indeno[1′,2′:4,5]imidazo[1,2-a]pyridines was obtained via AlCl₃-promoted, dehydrative cyclization of the corresponding aryl(2-arylimidazo[1,2-a]pyridin-3-yl)methanols in moderate to good yields. The synthesized compounds can be considered as conformationally restricted, privileged aza-heterocyclic scaffold bearing triarylmethane analogs.