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Step 1: Methyl quinoxaline-6-carboxylate (237a) [0385] To a stirred solution of 3, 4-DIAMINO-BENZOIC acid methyl ester (236,2 g, 12.03 mmol) in isopropanol (50 mL) was added oxaldehyde as a 40% solution in water (13.23 MMOL, 1.52 mL). The reaction mixture was heated at 80C for 2 hours, the solvent was removed under reduced pressure and the residue was dried under vacuum to yield 237a as a yellow solid (2.09 g, 93% yield NMR: (DMSO) 6 9.01 (s, 2H), 8.54 (d, J=1.6 Hz, 1H), 8.23 (dd, J=8.6, 2.0 Hz, 1H), 8.14 (dd, J=8. 6,0. 6 Hz, 1H), 3.35 (s, 3H).
Preparation Example I-1. Quinoxaline-6-carboxylic acid To a solution of quinoxaline-6-carboxylic acid methyl ester (2084mg, 11.07mmol) in ethanol (25mL) was added an aqueous solution of 1 N sodium hydroxide (25mL), and the solution was stirred for 4 hours under reflux. 1 N Hydrochloric acid was added to the reaction mixture to adjust the pH to 4, then, the precipitated solid was collected by filtration, washed with water and isopropanol, then dried to obtain the title compound (1477mg, 8.479mmol, 76.6%) as a solid. 1H-NMR Spectrum (DMSO-d6) δ (ppm): 8.18 (1 H, d, J=8.4Hz), 8.29 (1H, dd, J=8.4, 1.2Hz), 8.61 (1 H, d, J=1.2Hz), 9.00-9.07 (2H, m).
76.6%
To a solution of quinoxaline-6-carboxylic acid methyl ester (2084mg, 11.07mmol) in ethanol (25mL) was added an aqueous solution of 1 N sodium hydroxide (25mL), and the solution was stirred for 4 hours under reflux. 1 N Hydrochloric acid was added to the reaction mixture to adjust the pH to 4, then, the precipitated solid was collected by filtration, washed with water and isopropanol, then dried to obtain the title compound (1477mg, 8.479mmol, 76.6%) as a solid. 1H-NMR Spectrum (DMSO-d6) δ(ppm) : 8.18 (1H, d, J=8.4Hz), 8.29 (1H, dd, J=8.4, 1.2Hz), 8.61 (1 H, d, J=1.2Hz), 9.00-9.07 (2H, m).
To a solution of <strong>[23088-23-5]methyl quinoxaline-6-carboxylate</strong> (500 mg, 2.66 mmol) in 10 mL of THF was added sodium hydroxide (5N, 2.5 mL, 12.5 mmol) followed by methanol (2.5 mL). The reaction was stirred at room temperature overnight and then concentrated in vacuo to remove THF/MeOH. The resulting aqueous mixture was acidified with IN HCl until the pH was slightly acidic (pH = 5). The resulting solution was extracted with EtOAc (3x), and the combined organic layers were then washed with brine, dried over anhydrous MgSO4, filtered and concentrated in vacuo. The resulting white solid was used without further purification. LC-MS: 3.50 min. (M+H) = 175.16
With hydrogenchloride; sodium hydroxide; In methanol; water; ethyl acetate;
The 6-quinoxalinylcarbonyl chloride used as a starting material was prepared as follows: A 2N aqueous sodium hydroxide solution (7.95 ml) was added to a solution of <strong>[23088-23-5]methyl quinoxaline-6-carboxylate</strong> (1 g) in a mixture of methanol (30 ml) and water (5 ml) and the mixture was stirred at ambient temperature for 16 hours. The reaction mixture was evaporated and the residue was dissolved in water. The solution was acidified to pH3.5 by the addition of dilute aqueous hydrochloric acid and extracted with ethyl acetate. The organic extracts were evaporated and the residue was triturated under a mixture of ethyl acetate and isohexane. There was thus obtained quinoxaline-6-carboxylic acid a solid (0.5 g); NMR Spectrum: (DMSOd6) 8.16 (d, 1H), 8.28 (d, 1H), 8.59 (s, 1H), 9.02 (s, 2H).
With hydrogenchloride; In tetrahydrofuran; diethyl ether; water;
Step 1: 2-(2-Chloro-4-methoxy-phenyl)-1-quinoxalin-6-yl-ethanone A 2M solution of tert-butylmagnesium chloride (CAS Reg. No. 677-22-5) in diethyl ether (5.9 ml) was added to 2-chloro-4-methoxyphenylacetic acid (1.173 g, CAS Reg. No. 91367-09-8) in THF (10 ml). The mixture was stirred at room temperature for 30 min. A solution of methyl 6-quinoxalinecarboxylate (1 g, CAS Reg. No. 23088-23-5) in THF (3 ml) was added and the resulting mixture was stirred overnight. Aqueous HCl (25%, 1.5 ml) and water (30 ml) were added and extracted with EtOAc. The combined organic layers were dried over Na2SO4 and then concentrated to an oil. The residue was purified by flash chromatography (SiO2, EtOAc/heptane 1:2) to give the title compound (480 mg) as a light brown solid. MS (m/e)=313.2 [M+H+].
Take a 100ml single-mouth bottle,Add 3,4-diaminobenzoic acid methyl ester (2) 3.32 g (0.02 mol),And added 30 ml of N,N-dimethylformamide, and dissolved by stirring.Then, [1,4]dioxane-2,3-diol (a) 3.6 g (0.03 mol) was added.Stir at 90 C for 8 hours.Then extracted, washed,Drying to give methyl quinoxaline-6-carboxylate (3)3.64 g, yield 96.7%.
With sodium tetrahydridoborate; In methanol; at 90.0℃; for 2.0h;
Take a 100 ml single-mouth bottle, add quinoxaline-6-carboxylic acid methyl ester (3) 3.76 g (0.02 mol), add 50 ml of methanol, stir to dissolve,Then, 3.02 g (0.08 mol) of sodium borohydride was slowly added.The reaction was carried out at 90 C for 2 hours.After the reaction is completed, excess methanol is distilled off under reduced pressure.Then, it is extracted and dried to obtain 3.24 g of methyl 1,2,3,4-tetrahydroquinoxaline-6-carboxylate (4).The yield was 87%.
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