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With 1,3-dibromo-5,5-dimethylhydantoin; anhydrous sodium carbonate In dimethyl sulfoxide at 50℃; for 1h; Sealed tube;
5 Synthesis of 3-bromo-6-fluoro-2-phenylimidazo[1,2-α]pyridine:
The substrate 53mg (0.25mmol) 6-fluoro-2-phenylimidazo[1,2-α]pyridine, 71.5mg (0.25mmol) dibromohydantoin, catalyst 53.0mg (0.5mmol) Na2CO3 and 2.0mL DMSO Add 30mL sealed tube under air environment, then put the sealed tube into an ultrasonic cleaning machine (Jiekang ultrasonic cleaning machine, ultrasonic power is 70W, heating power is 60W, ultrasonic frequency is 40KHz), the reaction temperature is 50 , The reaction was performed for 1 h. After the reaction was completed, the reaction solution was cooled to room temperature, 10 mL of saturated saline was added, extracted three times with 15 mL of ethyl acetate, and the organic layers were combined. The organic layer was dried over anhydrous sodium sulfate, filtered, and the solvent was removed under reduced pressure. The residue was separated by silica gel column chromatography (ethyl acetate/petroleum ether: 1/4 as eluent),61.86 mg of yellow solid was obtained with a calculated yield of 85%.
83%
With anhydrous sodium carbonate; pyridinium hydrobromide perbromide In N,N-dimethyl-formamide at 25 - 43℃; for 0.5h; Sonication; Schlenk technique; Green chemistry; regioselective reaction;
3-Bromo-2-phenylimidazo[1,2-a]pyridine (3a); Typical Procedure
General procedure: A mixture of 2-phenylimidazo[1,2-a]pyridine (1a; 38.8 mg, 0.20 mmol), pyridinium tribromide (2a; 63.9 mg, 0.20 mmol) and Na2CO3 (21.2 mg, 0.2 mmol) in DMF (2.0 mL) in a Schlenk tube at r.t. was subjected to ultrasonic irradiation JP-120ST(Skymen) for 30 min. After the reaction was complete, the mixture was extracted with EtOAc (3 5 mL). The combined organic extracts were washed with brine (10 mL), dried over Na2SO4 and filtered. The solvent was removed under reduced pressure and the residue was purified by flash column chromatography (silica gel, 200-300 mesh) to give desired product 3a.
82%
With carbon tetrabromide; tetra-n-butylammonium tetrafluoroborate In methanol; acetonitrile Inert atmosphere; Heating; Electrochemical reaction;
76%
With carbon tetrabromide; [4,4'-bis(1,1-dimethylethyl)-2,2'-bipyridine-N1,N1']bis[2-(2-pyridinyl-N)phenyl-C]iridium(III) hexafluorophosphate In dimethyl sulfoxide at 20℃; for 13h; Inert atmosphere; Irradiation; Green chemistry;
General procedure for the photocatalytic bromination of 2-arylimidazo[1,2-a]pyridines
General procedure: An oven-dried flask was equipped with a magnetic stir bar, 2-arylimidazo[1,2-a]pyridines1 (0.1 mmol), carbon tetrabromide (2, 49.7 mg, 0.15 mmol), Ir(ppy)2(dtbbpy)PF6(1.8 mg, 0.002 mmol), and DMSO (1mL) under N2 atmosphere. The reaction mixture was then stirred for 7-21 h under irradiation using 5W blue LEDs (kmax 455 nm).Upon completion of the reaction, the mixture was concentrated in vacuum and purified by chromatography on silica gel (ethyl acetate:n-hexane 1:5) to afford 3-bromo-2-arylimidazo[1,2-a]pyridines 3.
72%
With oxygen; copper(II) bromide In N,N-dimethyl-formamide at 120℃; for 6h; regioselective reaction;
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