| 85% |
With sodium hydrogencarbonate; In ethanol; for 9h;Reflux; |
2,4'-Dibromoacetophenone in an amount of 15 g (54 mmoles) was dissolved into 100 ml of ethanol. To the obtained solution, 7.0 g of sodium hydrogencarbonate and 5.2 g (55 mmoles) of 2-aminopyridine were added and the resultant mixture was heated for 9 hours under the refluxing condition. After the reaction was completed, the mixture was cooled at the room temperature. The formed crystals were separated by filtration and washed with water and ethanol and 12.5 g (the yield: 85%) of Intermediate Compound (A) was obtained. |
| 82% |
In ethanol; for 12h;Heating / reflux; |
Synthesis of Intermediate 1d; 3.39 g of 2-aminopyridine (35.98 mmol) and 10 g of 2,4'-dibromo acetophenone (35.98 mmol) were dissolved in 150 ml of ethanol, and the mixture was refluxed for 12 hours. The mixture was cooled to room temperature to obtain a white solid. The obtained white solid was washed with a saturated NaHCO3 solution. Moisture remaining in the organic layer was removed with anhydrous MgSO4, dried under reduced pressure, and then recrystallized (dichloromethane/normal hexane) to obtain 8.02 g of Intermediate 1d having a plate crystalline form (yield 82%). |
| 82% |
In ethanol; for 12h;Heating / reflux; |
Synthesis of Intermediate 1d; 3.39 g of 2-aminopyridine (35.98 mmol) and 10 g of 2,4'-dibromo acetophenone (35.98 mmol) were dissolved in 150 ml of ethanol, and the mixture was refluxed for 12 hours. The mixture was cooled to room temperature to obtain a white solid. The obtained white solid was washed with a saturated NaHCO3 solution. Moisture remaining in the organic layer was removed with anhydrous MgSO4, dried under reduced pressure, and then recrystallized (dichloromethane/normal hexane) to obtain 8.02 g of Intermediate 1d having a plate crystalline form (yield 82%). |
| 82% |
In ethanol; for 12h;Reflux; |
2-aminopyridine (3.39g) and 2,4-dibromoacetophenone (10g) were melted in the ethanol 150ml and it refluxed for 12 hours. In a room temperature, the white solid cooling and was generated was washed with the NaHCO3saturated aqueous solution. It recrystallized as the dichloromethane / hexane solution and the intermediate A was obtained with 8.02g (yield 82%). |
| 76% |
With sodium hydrogencarbonate; In ethanol; at 80℃; for 6h; |
1.0 g (11 mmol) of 2-aminopyrid]ine, 3.0 g (11 mmol) of 4-bromophenacyl bromide, and 1.9 g (14 mmol) of sodium hydrogen carbonate were put in a 50 mL three-neck flask, and the air in the flask was replaced with nitrogen. This mixture was added with 10 mL of ethanol, and then heated and stirred at 80 C for six hours. After the stirring, the mixture was added with water and subjected to suction filtration to give a solid The obtained solid was washed with water and methanol in this order, whereby 2.3 g of the target white solid was obtained in a yield of 76 %. |
| 76% |
With sodium hydrogencarbonate; In ethanol; for 2h;Reflux; |
General procedure: To a solution of 2-aminopyridine (1.0 equiv.) in EtOH (15 mL) was added the appropriate 10a-10f or10h (1.0 mmol) with NaHCO3 (0.5 equiv.). The solution was refluxed about 2 h. After completion ofthe reaction (monitored by TLC), the formed precipitate was filtered off and washed with acetone (15mL). The aqueous phase was extracted with DCM (3 × 20 mL). The combined organic layers weredried on Na2SO4, filtered and concentrated) under vacuum to give the pure imidazo[1,2-a]pyridine13a-13g. 6, 7 |
| 50% |
In ethanol; for 18h;Reflux; |
Synthesis of Intermediate 1; 10 g (36 mmol) of 2-bromo-1-(4-bromo-phenyl)-ethanone and 3.4 g (36 mmol) of pyridine-2-amine were dissolved with 50 mL of ethanol and the mixture was stirred for 18 hours at a reflux temperature. The reaction solution was cooled to room temperature and the generated white solid was filtered and washed with ethanol and ethylether, thereby obtaining 5 g (Yield: 50%) of Intermediate 1. The generated compound was identified using high-resolution mass spectra (HR-MS). C13H9BrN2 calc.: 271.9949; found 271.99450 |
| 43% |
In acetone; at 25℃; |
General procedure: To a solution of 2-aminopyridine (1 equiv.) in acetone was added the appropriate alpha-bromoketone (1 equiv.). The solution was stirred at 25 C with reaction times ranging from 2 to 6 hours. After completion of the reaction (monitored by LC-MS), the formed precipitate was filtered off and washed with acetone (15 mL). The solid was neutralized with a saturated NaHCO3 or ammonia solution. The aqueous phase was extracted with DCM (3 x 20 mL). The combined organic layers were dried on Na2SO4, filtered and concentrated) under vacuum to give the pure imidazo[1,2-a]pyridine. |
|
|
A slurry of 2-aminopyridne (7.52 g, 80.0 mmol) and 2,41~dibromalphaace-alphapheno?e (22.24 g, 80.0 mmol) in EtOH (80 mL) was heated at reflux for 8 h. NaHCO3 (3.36 g, 40.0 mmol) was added to the resulting solution. Gas evolution was observed. After an additional 14 h of refluxi?g, more NaHCO3 (3.36 g, 40.0 mmol) was added. The reaction mixture was refluxed for another 2 h, cooled to 0 0C for one hour, filtered and rinsed with EtOH and Et2O to provide 2-(4-bromo-phenyl)-imidazo[1,2-a]pyridne (17.3 g) as an off-white solid. MS: (M*) 273, 275. 1H NMR (400 MHz, CDCI3): delta 8.09 (dt, 1, J = 6.8, 1.1), 7.79-7.83 (m, 3), 7.60 (d, I1 J = 9.1), 7.52-7.56 (m, 2), 7.14-7.19 (m, 1), 6.75-6.79 (m. 1). |
|
In ethanol; acetone; for 3h;Inert atmosphere; Reflux; |
Synthesis (D1-3); Under an Ar atmosphere, into a 300 ml flask, 3.4 g of 2-aminopyridine was weighed, and 40 ml of ethanol and 40 mL of acetone were added thereto and were dissolved. 10 g of 4-bromophenacyl bromide was added thereto and was heated under reflux. After 3 hours, heating was stopped and the mixture was cooled to room temperature. After the solvent was removed under reduced pressure, the mixture was heated and dissolved in 1 liter of methanol, and after the insoluble impurities were removed by filtration, concentrated and precipitated resultant was recovered.As a result, 8 g of a target compound as white solid (2-(4-bromophenyl)-imidazo[1,2-a]pyridine) was obtained. |
|
In ethanol; for 6h;Reflux; |
General procedure: 4-substituted phenacylbromide (2a-c, 0.1 mol) was added to a solution of substituted 2-amino pyridine (1a-c, 0.1 mol) in 15 mL of ethanol, and the reaction mixture was stirred at reflux temperature for 6 h. The progress of the reaction was checked by TLC. After completion of the reaction, the mixture was cooled, and the solid was separated, filtered, and dried in vacuum to obtain analytically pure productin good yields. |
|
With polyethylene glycol (PEG-400); In water; at 80℃;Microwave irradiation; Green chemistry; |
General procedure: A mixture of aromatic acetophenones (5 mmol) and NBS (5.5 mmol) in PEG-400 and water (1:2) (5 ml) was irradiated for 30 min at 300 W, 80-85 C. The formation of alpha-bromoacetophenone was monitored by TLC. After completion of bromination, 2-amino pyridine (5 mmol) was added to the reaction mixture and the reaction mass was further irradiated for 3-5 min at 300 W at 80-85 C. The progress of reaction was monitored by TLC. After completion of reaction, 10 ml of ethyl acetate was added and stirred for 20 min. This process was repeated twice. The combined ethyl acetate phase was removed under reduced pressure to obtain imidazo[1,2-a]pyridines (4a-j). |
|
|
A 100 mL three-neck round-bottomed flask was charged with 2,4'-dibromoacetophenone 17 (6.08 g, 21.9 mmol), 2-aminopyridine 16 (1.1 equiv, 2.31 g, 24.5 mmol) and degassed acetone (45 mL). The reaction flask was fitted with a reflux condenser and the reaction mixture was heated at 80 C for 3 h. Additional acetone (20 mL) was added during this time. The reaction mixture was subsequently allowed to cool to room temperature and transferred to a 250 mL one-neck round-bottomed flask. The solvent was removed in vacuo and HBr (45 mL) and MeOH (90 mL) was added to the reaction mixture. The reaction flask was again fitted with a reflux condenser and the reaction mixture was heated at 80 C for 1 h. The reaction mixture was cooled to 0 C by means of an ice-bath. The white precipitate was then filtered through a sinter funnel, washed with distilled H20 and dried under vacuum to afford the crude title compound 18 (5.69 g, 20.8 mmol, 95 %) (Rf = 0.36, 40 % EtOAc/Hexane) as a white solid which was not further purified. |
| 8 g |
In ethanol; for 3h;Inert atmosphere; Reflux; |
Under Ar, 300 ml flask weighed 2 - aminopyridine 3.4 g, 40 ml 40 ml acetone added thereto was dissolved in ethanol. 10 g 4 - [buromohuenashiruburomido[buromohuenashiruburomido] added thereto was heated to reflux. 3 hours, heating is stopped and cooling to room temperature. After removing the solvent under reduced pressure, dissolved in 1 liter of methanol heated, after removal of the insoluble impurities by filtration, it was concentrated to precipitate was recovered. Therefore, an object (2 - (4 - bromophenyl) - 1, 2 a-a-imidazo: pyridine) 8 g of white solid was obtained. |
| 11.33 g |
With sodium hydrogencarbonate; In ethanol; at 20 - 80℃; for 6h; |
To a 250 mL round bottom flask was added B1 (5.00 g, 53.13 mmol), B2 (14.77 g, 53.13 mmol) and sodium hydrogen carbonate (NaHCO3)(5.36 g, 63.76 mmol) was dissolved in ethanol (200 mL), stirred at room temperature for 4 hours, stirred at 80 C in a bath for 2 hours,After removing ethanol, it was extracted with dichloromethane and water, distilled under reduced pressure, and separated by column using ethyl acetate and n-hexane. after, Dichloromethane and petroleum ether were used to make the precipitate,Filtration afforded compound B3 (11.33 g, 41.48 mmol). |
|
With sodium hydrogencarbonate; at 20℃; for 6h; |
General procedure: Method A1a: To an ethanol solution containing 2-bromoacetophenones (1.0 equiv) and 2-aminopyridines (1.25 equiv) was added NaHCO3 (1.56 equiv). The reaction mixture was stirred at room temperature for 6 hours. After completion of the reaction, the resulting mixture was diluted with water and extract with ether. The combined organic layer was washed with brine, dried with anhydrous MgSO4, concentrated under vacuum to give the crude product, which was purified by silica gel column with petroleum ether/EtOAc as the eluent to give the analytical pure 2-arylimidazo[1,2-a]pyridine (1a-1r). |
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