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With sodium hydroxide; In water; for 72.0h;Inert atmosphere;
5-Chloro-2-nitrobenzoic acid (32.00 g, 0.159 mol),Dissolved in 15% aqueous sodium hydroxide solution,The reaction was refluxed under N2 for 72h.After completion of the reaction, the pH of the solution was adjusted to 1.0, extracted with ethyl acetate, the combined ethyl acetate layers were dried over anhydrous sodium sulfate,The solvent was distilled off under reduced pressure to give 28.05 g of 5-hydroxy-2-nitrobenzoic acid in a yield of 96.5%.
90%
With potassium hydroxide; In water; for 24.0h;Reflux;
Step 1: (0332) Potassium hydroxide aqueous solution (13.8 g, 248 mmol, 40 ml) was added into 5-chloro-2-nitrobenzoic acid 11-a (5 g, 24.8 mmol) and the mixture was stirred at reflux for 24 hours. The pH value of the reaction mixture was adjusted to 2 with concentrated hydrochloric acid under ice-cooling, the precipitated solid was filtered and dried to give 11-b as a white solid (4.1 g, yield: 90%).
With sodium hydroxide; In water; for 18.0h;Heating / reflux;
124.6 g (0.618 mol) of 5-chloro-2-nitro-benzoic acid (Fluka Buchs, Switzerland) are heated under reflux in an aqueous sodium hydroxide solution [197.8 g (4.94 mol) of NaOH in 1. 231 water] for 18 h. The cold reaction mixture is extracted several times with ether-ethyl acetate, washed with brine and dried over sodium sulfate. The raw material is crystallized from iso- propyl ether-hexane. The crystals are filtered off and dried at 50C (high-vacuum). mp: 167- 171 C ; MS: 182 (M+-1) ; HPLC: tut=6. 315 min (Grad 1).
With hydrogenchloride; sodium hydroxide; In water;
EXAMPLE 45 Preparation of 5-hydroxy-2-nitrobenzoic acid A mixture of 5.0 l. of water, 800 g. of sodium hydroxide and 504 g. of 5-chloro-2-nitrobenzoic acid was refluxed for 24 hours. The solution was cooled and acidified with 1.75 l. of concentrated hydrochloric acid. The acidic aqueous mixture was extracted three times with 1.5 l. of ether. The combined ether extracts were dried over anhydrous magnesium sulfate, filtered through Celite and evaporated to a light yellow solid (473 g.). This material was recrystallized from ether-petroleum ether to yield 298 g. of 5-hydroxy-2-nitrobenzoic acid, mp 167-169 (65.2%).
With potassium hydroxide; potassium hydrogencarbonate; In water; dimethyl sulfoxide;
Step 1. 5-Hydroxy-2-nitrobenzoic acid. 5-Chloro-2-nitrobenzoic acid (100 g) in 800 ml dimethylsulfoxide was treated with 112 g powdered KOH with cooling, 170 ml anhydrous alcohol added and the mixture stirred 2 hours at 25 and then left overnight. The mixture was kept at 28 for about 8 hours, then overnight at 0, warmed to room temperature and 3.5 liters of water added. The mixture was acidified with HCl, 1 kg NaCl added and extracted with ethyl acetate. The extract was washed with water, dried, 50 g KHCO3 in 500 ml water added, diluted to 2 liters, and the ethyl acetate blown off with a stream of nitrogen. The solution was acidified and filtered to give 56 g product, m.128-30.
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