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Step 2 The preparation of 3-chloro-2-methyl-5-nitropyridine. Ethyl alpha-ethoxycarbonyl-3-chloro-5-nitropyridine-2-acetate (3.56 g) was heated in concentrated sulphuric acid (70 ml) and water (35 ml) at 180 C. for 4 hours. After cooling, the mixture was poured into ice and water, and extracted with ethyl acetate. The organic layer was washed with water, dried over magnesium sulphate and evaporated to yield the desired product as a red-brown liquid (1.40 g); 1 H-NMR (CDCl3,270 Mhz) delta: 2.78(3H,s), 8.45(1H,d), 9.22(1H,s) ppm.
2
[ 51984-62-4 ]
3-chloro-5-nitropyridine-2-carboxaldehyde[ No CAS ]
Yield
Reaction Conditions
Operation in experiment
With selenium(IV) oxide; In 1,4-dioxane;
Step 3 The preparation of 3-chloro-5-nitropyridine-2-carboxaldehyde. <strong>[51984-62-4]3-chloro-2-methyl-5-nitropyridine</strong> (1.109 g) was refluxed with selenium dioxide (0.909 g) in dry 1,4-dioxan (35 ml) under nitrogen, for 30 hours. The reaction mixture was then cooled to room temperature, filtered through celite, poured into water and extracted with ethyl acetate. The organic layer was dried over magnesium sulphate and evaporated to give a reddish-brown liquid which consisted of a mixture containing 85% of the desired aldehyde and 15% of the starting material, which was used without purification; 1 H-NMR (CDCl3,270 Mhz) delta: 8.65(1H,d), 9.49(1H,d), 10.34(1H,s) ppm.
With tetrakis(triphenylphosphine) palladium(0); caesium carbonate; In 1,4-dioxane; at 100.0℃; for 6.0h;
Cesium carbonate (338 mg), methylboronic acid (47 mg), and tetrakis(triphenylphosphine)palladium (60 mg) were added to a 1,4-dioxane (3 ml) solution containing 2,3-dichloro-5-nitropyridine (100 mg), followed by stirring at 100C for 6 hours. The reaction solution was adjusted to room temperature, and water was added, followed by extraction with ethyl acetate. The resultant was washed with saturated saline and dried over anhydrous sodium sulfate, the solvent was distilled away under reduced pressure, and 3-chloro-2-methyl-5-nitropyridine (344 mg) was thus obtained.
With iron; ammonium chloride; In ethanol; water; at 90.0℃; for 1.0h;
Water (1 ml), iron powder (344 mg), and ammonium chloride (172 mg) were added to an ethanol solution (5 mL) containing the crude product (344 mg) obtained in the 1st step, followed by stirring at 90C for 1 hour. The reaction solution was adjusted to room temperature, water and ethyl acetate were added, and insoluble matter was removed by filtration. The obtained organic layer was washed with saturated saline and dried over anhydrous sodium sulfate, and the solvent was distilled away under reduced pressure. The obtained residue was purified by silica gel chromatography (hexane : ethyl acetate = 4:1 to 1:1), and yellow oily matter of 5-chloro-6-methylpyridin-3-amine (53 mg) was thus obtained. MS (ESI m/z): 143, 145 (M+H) RT (min): 0.42
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