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With N-iodo-succinimide In acetonitrile at 0 - 20℃;
EXAMPLES Example 1 3-iodo-imidazo-[1 ,2-a]pyridineA solution of 11.61 g (98.27 mmol) of imidazopyridine in 100 ml. of acetonitrile was placed in a 250 ml. three-neck round-bottom flask equipped with a magnetic stirrer, thermocouple, nitrogen bleed, and cooling ice bath. A total of 24.32g (108.1 mmol, 1.1 eg.) of solid N-iodosuccinimide was added portion-wise to the flask at O0C, and the resulting yellow suspension was allowed to warm to room temperature overnight. The solvent was removed on rotavap to give the dark solid (39.2 g). This residue was re-dissolved in 0.5 L of dichloromethane and washed with 10percent KOH (2 x 250 ml_). The organic phase was separated, washed with water (200 ml_), and dried over Na2SO4. The solvent was removed on rotavap, and the remaining dark material was re-crystallized from boiling ethyl acetate upon the addition of hexane. The precipitated solid was filtered, washed with 40 ml. of hexane, and dried under nitrogen flow until constant weight. The yield was 20.8 g (86percent) of white solid with Rf = 0.42 (in EtOAc/hexane = 1 :1 ).H1 NMR (CDCI3), δ: 8.12 (d, 1 H, J=6.8 Hz), 7.69 (s, 1 H), 7.62 (d, 1 H, J=6.8 Hz), 7.24 (t, 1 H, J=6.8 Hz), 6.94 (t, 1 H, J=6.8 Hz).13C NMR (CDCI3), δ: 147.52, 140.02, 126.08, 125.23, 1 17.76, 113.43, 60.91.LC-MS (ESI) for C7H5N2I m/z 245 [M+H]+.
76%
With N-iodo-succinimide In N,N-dimethyl-formamide at 20℃; Cooling with ice
The imidazo [l, 2-a] pyridine (1.18 g, 0.1 mol) was dissolved in N, N-dimethylformamide (10 mL), and under ice cooling was added portionwise N-iodosuccinimide (2.7 g, 0.12 mol), addedafter continued at room temperature overnight.Completion of the reaction, thereaction mixture was added to saturated sodium bicarbonate solution (20 mL) toquench the reaction, stirring was continued for 1 hour, a yellow solid wasprecipitated, the solid was collected by filtration under reduced pressure, thesolid washed with distilled water, and dried to give 3-iodoimidazo[1,2-a]pyridine(yellow solid, 1.85 g),
76%
With N-iodo-succinimide In N,N-dimethyl-formamide at 20℃; Cooling with ice
Imidazo[1,2-a]pyridine (1.18 g, 0.1 mol) was dissolved in N,N-dimethylformamide (10 mL).N-iodosuccinimide (2.7 g, 0.12 mol) was added portionwise under ice-cooling, and stirring was continued at room temperature overnight.After completion of the reaction, a saturated sodium hydrogencarbonate solution (20 mL) was added to the reaction mixture, and the mixture was stirred and stirred for 1 hour, and a yellow solid was precipitated. The solid was collected by filtration under reduced pressure, and the solid was washed with distilled water and dried.The intermediate 3-iodo-imidazole [1,2-a]pyridine is obtained.(Yellow solid, 1.85 g), yield 76percent.
72%
With N-iodo-succinimide In acetonitrile at 20℃; for 8 h;
A mixture of imidazo[1,2-a]pyridine (7a) (10.00 g, 84.71 mmol) and NIS (22.86 g, 101.65 mmol) in acetonitrile (100 ml) was stirred at room temperature for 8 h. The reaction mixture was poured into water (150 ml) and then extracted with EtOAc (3×150 ml). The combined organic phase dried over anhydrous Na2SO4 and concentrated under reduced pressure. The resulting crude was purified by flash chromatography(eluent petroleum ether – EtOAc, 1:1) to give the desired product.
69%
With 4-(3-methylimidazolium)butanesulfonate; iodine In water at 20℃; for 2 h; Sealed tube; Green chemistry
General procedure: To a mixture of 2-phenylimidazo[1,2-a]pyridine (1a, 39 mg, 0.2 mmol), molecular I2 (50 mg, 1 equiv), and 4-(3-methylimidazolium)butane-1-sulfonate (I, 9 mg, 20 molpercent) in a sealed tube was added water (2 mL) and the mixture was stirred at r.t. for 2 h. After completion of the reaction (TLC), the mixture was extracted with EtOAc (20 mL). The organic phase was dried (anhyd Na2SO4) and concentrated under reduced pressure give the crude residue which was purified by column chromatography (silica gel, 60–120 mesh, petroleum ether/EtOAc, 9:1) to afford 2a as a white solid: yield: 58 mg (91percent); mp 132–134 °C.
47.3%
With N-iodo-succinimide In tetrahydrofuran at 0 - 20℃; for 1 h; Inert atmosphere
In a 250 mL single-necked flask,Under nitrogen protection and 0 ° C,A solution of imidazo [1,2-a] pyridine (6.0 g,50.8 mmol) was dissolved in THF (80 mL)NIS (13.7 g, 60.9 mmol) was added in batches,Room temperature reaction 1h.Reaction is completed,To the reaction solution was added 100 mL of water,Ethyl acetate extraction (150 mL x 3),Saturated brine (100 mL x 3)Dried over anhydrous magnesium sulfate,The solvent was evaporated to dryness under reduced pressure to give 5.9 g of yellow solid 3-iodoimidazo [1,2-a] pyridine in 47.3percent yield.
Reference：
[1] Journal of Organic Chemistry, 2000, vol. 65, # 20, p. 6572 - 6575
[2] Patent: WO2010/33978, 2010, A2, . Location in patent: Page/Page column 26-27
[3] Patent: CN103420977, 2016, B, . Location in patent: Paragraph 0241-0244
[4] Patent: CN104341425, 2018, B, . Location in patent: Paragraph 0137; 0139; 0140; 0141
[5] Chemistry of Heterocyclic Compounds, 2018, vol. 54, # 5, p. 568 - 571[6] Khim. Geterotsikl. Soedin., 2018, vol. 54, # 5, p. 568 - 571,4
[7] Synthesis (Germany), 2016, vol. 48, # 22, p. 4009 - 4015
[8] Patent: CN107163042, 2017, A, . Location in patent: Paragraph 0021; 0022; 0032; 0033; 0043; 0044; 0054; 0055
[9] Letters in Organic Chemistry, 2016, vol. 13, # 7, p. 519 - 525
2
[ 274-76-0 ]
[ 516-12-1 ]
[ 307503-19-1 ]
Yield
Reaction Conditions
Operation in experiment
45.5%
at 20℃; for 1 h;
To thesolution of imidazo[1,2-a]pyridine (6.50 g, 0.055 mol) in 80mLof THF was added 1-iodopyrrolidine-2,5-dione (14.85 g,0.066 mol) slowly. The reaction mixture was stirred for 1 h atroom temperature and extracted by ethyl acetate. The organicphase was collected and the solvent was evaporated to affordthe yellow solid (6.10 g, 45.5percent).
Reference：
[1] Patent: CN107163042, 2017, A,
[2] Chemistry Letters, 2017, vol. 46, # 6, p. 848 - 850
4
[ 307503-19-1 ]
[ 1066-54-2 ]
[ 943320-53-4 ]
Yield
Reaction Conditions
Operation in experiment
72%
With copper(l) iodide; bis(triphenylphosphine)palladium(II) dichloride; triethylamine In acetonitrile for 3 h; Inert atmosphere; Reflux
In a 500 mL three-necked flask,Under nitrogen protection conditions,3-iodoimidazo [1,2-a] pyridine (10.0 g, 41.0 mmol)PdCl2 (pph3) 2 (0.6 g, 0.8 mmol),CuI (0.2 g, 0.8 mmol) was successively added to anhydrous acetonitrile (200 mL)Then Et3N (12.4 g, 122.9 mmol)And trimethylsilylacetylene (12.1 g, 122.9 mmol)Reflux reaction 3h. Reaction is completed, suction filter,The filtrate was evaporated under reduced pressure,The residue was dissolved in methanol (150 mL)Anhydrous potassium carbonate (22.7 g, 163.9 mmol) was added at room temperature for 30 min,Filter, the filtrate vacuum distillation solvent was crude,The crude product was subjected to silica gel column (mobile phase: PE: EA = 20: 1) to give 4.2 g of 3-acetimidazo [1,2-a] pyridine as a white solid in 72percent yield.
Reference：
[1] Patent: CN107163042, 2017, A, . Location in patent: Paragraph 0023; 0024; 0025; 0034; 0035; 0036; 0045; 0046
With N-iodo-succinimide; In acetonitrile; at 0 - 20℃;
EXAMPLES Example 1 3-iodo-imidazo-[1 ,2-a]pyridineA solution of 11.61 g (98.27 mmol) of imidazopyridine in 100 ml. of acetonitrile was placed in a 250 ml. three-neck round-bottom flask equipped with a magnetic stirrer, thermocouple, nitrogen bleed, and cooling ice bath. A total of 24.32g (108.1 mmol, 1.1 eg.) of solid N-iodosuccinimide was added portion-wise to the flask at O0C, and the resulting yellow suspension was allowed to warm to room temperature overnight. The solvent was removed on rotavap to give the dark solid (39.2 g). This residue was re-dissolved in 0.5 L of dichloromethane and washed with 10% KOH (2 x 250 ml_). The organic phase was separated, washed with water (200 ml_), and dried over Na2SO4. The solvent was removed on rotavap, and the remaining dark material was re-crystallized from boiling ethyl acetate upon the addition of hexane. The precipitated solid was filtered, washed with 40 ml. of hexane, and dried under nitrogen flow until constant weight. The yield was 20.8 g (86%) of white solid with Rf = 0.42 (in EtOAc/hexane = 1 :1 ).H1 NMR (CDCI3), delta: 8.12 (d, 1 H, J=6.8 Hz), 7.69 (s, 1 H), 7.62 (d, 1 H, J=6.8 Hz), 7.24 (t, 1 H, J=6.8 Hz), 6.94 (t, 1 H, J=6.8 Hz).13C NMR (CDCI3), delta: 147.52, 140.02, 126.08, 125.23, 1 17.76, 113.43, 60.91.LC-MS (ESI) for C7H5N2I m/z 245 [M+H]+.
76%
With N-iodo-succinimide; In N,N-dimethyl-formamide; at 20℃;Cooling with ice;
The imidazo [l, 2-a] pyridine (1.18 g, 0.1 mol) was dissolved in N, N-dimethylformamide (10 mL), and under ice cooling was added portionwise N-iodosuccinimide (2.7 g, 0.12 mol), addedafter continued at room temperature overnight.Completion of the reaction, thereaction mixture was added to saturated sodium bicarbonate solution (20 mL) toquench the reaction, stirring was continued for 1 hour, a yellow solid wasprecipitated, the solid was collected by filtration under reduced pressure, thesolid washed with distilled water, and dried to give 3-iodo<strong>[274-76-0]imidazo[1,2-a]pyridine</strong>(yellow solid, 1.85 g),
76%
With N-iodo-succinimide; In N,N-dimethyl-formamide; at 20℃;Cooling with ice;
Imidazo[1,2-a]pyridine (1.18 g, 0.1 mol) was dissolved in N,N-dimethylformamide (10 mL).N-iodosuccinimide (2.7 g, 0.12 mol) was added portionwise under ice-cooling, and stirring was continued at room temperature overnight.After completion of the reaction, a saturated sodium hydrogencarbonate solution (20 mL) was added to the reaction mixture, and the mixture was stirred and stirred for 1 hour, and a yellow solid was precipitated. The solid was collected by filtration under reduced pressure, and the solid was washed with distilled water and dried.The intermediate 3-iodo-imidazole [1,2-a]pyridine is obtained.(Yellow solid, 1.85 g), yield 76%.
72%
With N-iodo-succinimide; In acetonitrile; at 20℃; for 8h;
A mixture of <strong>[274-76-0]imidazo[1,2-a]pyridine</strong> (7a) (10.00 g, 84.71 mmol) and NIS (22.86 g, 101.65 mmol) in acetonitrile (100 ml) was stirred at room temperature for 8 h. The reaction mixture was poured into water (150 ml) and then extracted with EtOAc (3×150 ml). The combined organic phase dried over anhydrous Na2SO4 and concentrated under reduced pressure. The resulting crude was purified by flash chromatography(eluent petroleum ether - EtOAc, 1:1) to give the desired product.
69%
With 4-(3-methylimidazolium)butanesulfonate; iodine; In water; at 20℃; for 2h;Sealed tube; Green chemistry;
General procedure: To a mixture of 2-phenyl<strong>[274-76-0]imidazo[1,2-a]pyridine</strong> (1a, 39 mg, 0.2 mmol), molecular I2 (50 mg, 1 equiv), and 4-(3-methylimidazolium)butane-1-sulfonate (I, 9 mg, 20 mol%) in a sealed tube was added water (2 mL) and the mixture was stirred at r.t. for 2 h. After completion of the reaction (TLC), the mixture was extracted with EtOAc (20 mL). The organic phase was dried (anhyd Na2SO4) and concentrated under reduced pressure give the crude residue which was purified by column chromatography (silica gel, 60-120 mesh, petroleum ether/EtOAc, 9:1) to afford 2a as a white solid: yield: 58 mg (91%); mp 132-134 C.
62%
With sodium iodide; In acetonitrile; at 20℃; for 4h;Electrochemical reaction;
General procedure: An undivided cell was equipped with a platinum plate (1.00.7 cm2) as the anode anda platinum plate (1.00.7 cm2) as the cathode and connected to a DC regulated powersupply. A mixture of <strong>[274-76-0]imidazo[1,2-a]pyridine</strong> 1 (0.1 mmol) and NaI (2a, 0.2 mmol) in acetonitrile (3.0 mL) was added to an undivided cell. The reaction mixture was stirredand electrolyzed at a constant current of 5mA under room temperature for 4 h. Whenthe reaction was completed, electrodes were washed with ethanol (EtOH). The combinedorganic solvent was removed in vacuo. The residue was purified by flash chromatography(EtOAc:Hex, 1:5) to afford 3-iodo <strong>[274-76-0]imidazo[1,2-a]pyridine</strong> 3.
47.3%
With N-iodo-succinimide; In tetrahydrofuran; at 0 - 20℃; for 1h;Inert atmosphere;
In a 250 mL single-necked flask,Under nitrogen protection and 0 C,A solution of imidazo [1,2-a] pyridine (6.0 g,50.8 mmol) was dissolved in THF (80 mL)NIS (13.7 g, 60.9 mmol) was added in batches,Room temperature reaction 1h.Reaction is completed,To the reaction solution was added 100 mL of water,Ethyl acetate extraction (150 mL x 3),Saturated brine (100 mL x 3)Dried over anhydrous magnesium sulfate,The solvent was evaporated to dryness under reduced pressure to give 5.9 g of yellow solid 3-iodoimidazo [1,2-a] pyridine in 47.3% yield.
To thesolution of imidazo[1,2-a]pyridine (6.50 g, 0.055 mol) in 80mLof THF was added 1-iodopyrrolidine-2,5-dione (14.85 g,0.066 mol) slowly. The reaction mixture was stirred for 1 h atroom temperature and extracted by ethyl acetate. The organicphase was collected and the solvent was evaporated to affordthe yellow solid (6.10 g, 45.5percent).
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