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With sulfuric acid; water; sodium nitrite; at 10℃; for 0.666667h;Green chemistry;
In a 25 ml reaction flask, first add 3.4 ml of a solution consisting of 17 ml of H2O and 17 ml of concentrated sulfuric acid (50%, volume fraction), then add 1 g (0.01 mol) of 2-amino-5-chloropyridine and cool with an ice salt bath. Below 10 C, after stirring for a few minutes, the reaction solution turned white.Then, a solution consisting of (1.72 g of NaNO2 and 3 mL of H 2 O) was slowly added dropwise, and when it was added dropwise, an irritating gas was generated. After the dropwise addition, the reaction solution became a pale yellow solution, and TCL (thin layer chromatography) was monitored until the reaction was completed ( About 40min).Then, 8 mL of H2O was added, and the reaction was stirred under reflux for 15 min, cooled, and anhydrous Na2CO3 was added under stirring to make the reaction liquid neutral (a yellow-brown solid was produced), filtered, and the obtained filtrate was dried, and then filtered and dissolved with absolute ethanol. The obtained filtrate was dried to give a yellow-brown solid, 5-chloro-2(1H)pyridone, 0.70 g.
A mixture of 5-CHLORO-2-HYDROXYPYRIDINE (20.1 g, 155.4 MMOL) and bromine (11.9 ml) in acetic acid (250 m) was stirred at r. t. for 2 hours. Then, the solvent was evaporated in vacuo and ethyl acetate (600 ML) and saturated sodium bicarbonate (300 ML) were added. The organic layer was washed with saturated sodium bicarbonate (2X200 ML), brine and was dried (NA2SO4) and concentrated to give a solid that was crystallized from hexane/ diethyl ether. The solid 3-bromo-<strong>[4214-79-3]5-chloro-2-hydroxypyridine</strong> (21.3 g, 66percent) so obtained was used in the subsequent reaction.
With bromine; In water; acetic acid;
Step 1: 3-Bromo-<strong>[4214-79-3]5-chloro-2-hydroxypyridine</strong> A mixture of <strong>[4214-79-3]5-chloro-2-hydroxypyridine</strong> (100 g) and bromine (40.1 mL) in acetic acid (400 mL) was stirred at r.t. for 1 h. The mixture was poured into 3 L of water and stirred for 30 min then filtered. The residual solid was washed with 2 L of cold water, air dried and then coevaporated with toluene three times and with benzene two times. The white solid (81 g) so obtained was used in the subsequent reaction.
With bromine; In water; acetic acid;
Step 1 3-Bromo-<strong>[4214-79-3]5-chloro-2-hydroxypyridine</strong> A mixture of <strong>[4214-79-3]5-chloro-2-hydroxypyridine</strong> (100 g) and bromine (40.1 mL) in acetic acid (400 mL) was stirred at r.t. for 1 h. The mixture was poured into 3 L of water and stirred for 30 min then filtered. The residual solid was washed with 2 L of cold water, air dried and then coevaporated with toluene three times and with benzene two times. The white solid (81 g) so obtained was used in the subsequent reaction.
4.4 g
With bromine; acetic acid; at 20℃;
To a stirred solution of <strong>[4214-79-3]5-chloropyridin-2-ol</strong> (4 g, 31 mmol) in acetic acid (35 mL) at room temperature was added bromine (2.55 mL, 49.6 mmol) dropwise. After stirring the reaction mixture for overnight at room temperature, water was added and the mixture was extracted twice with ethyl acetate (2 x 150 mL). The organic layer was washed with water, dried over anhydrous sodium sulfate and was concentrated under reduced pressure to afford crude product. The crude product was purified by column chromatography by using silica (100-200 mesh) using 22percent EtOAc-hexane as eluent to afford the 3-bromo-<strong>[4214-79-3]5-chloropyridin-2-ol</strong> (4.4 g) as yellow solid.
With bromine; In acetic acid; at 20℃; for 48h;
5-CHLORO-2-PYRIDINOL (5.18g, 40MMOL) was dissolved in glacial acetic acid (50ml) and bromine (7. 51 G, 2. 41ml, 47mmol) added. The mixture was stirred at room temperature for 48 hours. Ethyl acetate and water were added and the organic layer washed with water (*3), dried (MGS04) and evaporated. The residue was triturated with diethyl ether and the buff solid filtered and dried (5.59g). 1H NMR (CDCI3) 7.52 (1 H, d J=3Hz), 7.87 (1 H, d J=3Hz).
With bromine; In acetic acid; at 20℃;
At room temperature, bromine (1.2 mL, 24 mmol) was added dropwise to a solution of <strong>[4214-79-3]5-chloro-2-pyridinol</strong> (2.9 g, 20 mmol) in glacial acetic acid (25 mL). After stirred at room temperature overnight, ethyl acetate and water were added. The organic layer was washed with water, dried and concentrated. The residue was triturated with diethyl ether and the precipitate was filtered and dried to give the title compound (1.5 g).
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