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(Reference Example 2-2) 5-Fluoro-3-nitropyridine-2-amine (2.66 g) suspended in concentrated hydrochloric acid (35 ml) was cooled to -15C, and an aqueous solution (7 ml) of sodium nitrite (2.57 g) was added dropwise over 10 minutes. After stirring at -10C for 1 hour, and further stirring at room temperature for 1 hour, under ice cooling a 30% aqueous sodium hydroxide solution was added for neutralization. The insolubles were collected by filtration, washed with water, air-dried, and then redissolved in ethyl acetate, before the insolubles were filtered off. The filtrate was concentrated under reduced pressure to afford 2-chloro-5-fluoro-3-nitropyridine (1.41 g). 1H NMR (400 MHz, CDCl3) delta: 8.03 (dd, 1H, J = 6.6, 2.7 Hz), 8.55 (d, 1H, J = 2.7 Hz).
With sodium azide; copper(ll) sulfate pentahydrate; sodium carbonate; sodium L-ascorbate; L-proline; In water; dimethyl sulfoxide; at 70℃; for 24h;
In a high-pressure reactor, 85 g (0.5 mol) of 2,3-dichloro-5-fluoropyridine was added to 200 mL of ammonia water.Set the temperature to 180 C, high pressure reaction 24h,TLC detects the reaction of the raw material completely.The solvent was evaporated to give 2-chloro-5-fluoro-3-aminopyridine 65 g;2-chloro-5-fluoro-3-aminopyridine 65 g (0.45 mol)Placed in 900 mL round bottom flask in acetonitrile,Aqueous buffer solution 450mL (0.6M K2CO3-4x10-4M EDTA disodium salt) was added successively,Acetonitrile 350mL (3mol) and 30% H2O2 in water290mL (3mol),The reaction mixture was stirred at room temperature for 1 hour and extracted with ethyl acetate (3 x 300 mL).Combine organic layers,Dry with anhydrous Na2SO4,Remove the solvent under vacuum to obtain the product of sufficient purity <strong>[136888-21-6]2-chloro-5-fluoro-3-nitropyridine</strong>65g;To a solution of <strong>[136888-21-6]2-chloro-5-fluoro-3-nitropyridine</strong> 65 g (0.35 mol) in DMSO/H2O (9:1, 3500 mL) was added L-Proline 230g (2mol),Na2CO3 210g (2mol),NaN3 230g (3.5mol),Sodium ascorbate 350g (1.75mol) andCuSO4·5H2O500g (2 mol);The mixture was stirred in an oil bath at 70 C for 24 hours.Then pour the mixture into 10,000 mL of ice water.The solid product was filtered and crystallized to obtain 47 g of 2-amino-5-fluoro-3-nitropyridine.
With sodium azide; copper(ll) sulfate pentahydrate; sodium carbonate; sodium L-ascorbate; L-proline; In water; dimethyl sulfoxide; at 70℃; for 24h;
In a high-pressure reaction vessel, 2,3-dichloro-5-fluoropyridine 85g (0.5 mol) was added to 200 mL of ammonia water, and the temperature was set at 180 C., and the reaction under high pressure was performed for 24 h. The reaction of the starting material was complete by TLC, and the solvent was swirled to obtain 2- Chloro-5-fluoro-3-aminopyridine 65g;Place 2-chloro-5-fluoro-3-aminopyridine 65 g (0.45 mol) in a 900 mL round-bottomed flask in acetonitrile, and add 450 mL of water buffer solution (0.6 M K2CO3-4×10-4 M EDTA disodium salt). 350 mL (3 mol) of acetonitrile and 290 mL (3 mol) of a 30% H2O2 aqueous solution, and the reaction mixture was stirred at room temperature for 1 hour and extracted with ethyl acetate (3 x 300 mL). The organic layers were combined and dried over anhydrous Na2SO4. The solvent was removed to give a sufficiently pure product, <strong>[136888-21-6]2-chloro-5-fluoro-3-nitropyridine</strong>, 65 g;To a solution of 65 g (0.35 mol) of <strong>[136888-21-6]2-chloro-5-fluoro-3-nitropyridine</strong> in DMSO/H2O (mass ratio 9:1, 3500 mL) was added L-proline 230 g (2 mol), Na2CO3 210 g (2 mol), NaN3 230 g (3.5 mol), sodium ascorbate 350 g (1.75 mol) and CuSO4.5H2O 500 g (2 mol); the mixture was stirred in an oil bath at 70C for 24 hours, and then the mixture was poured into 5000 mL of ice water to give a solid product. Filter and crystallize to obtain 47g of 2-amino-5-fluoro-3-nitropyridine; add 2-amino-5-fluoro-3-nitropyridine to the aqueous solution of sulfuric acid, add a certain amount of chloroacetic acid, and heat to 120C. After TLC monitored the reaction of the raw materials, the reaction mixture was extracted with methylene chloride. The pH of the organic phase was adjusted to 7-8 with a saturated sodium carbonate solution, and the organic phase was concentrated to obtain 2-amino-5-fluoro-pyridine.
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