反应详情

A mixture of dimethyl acetone-1,3-dicarboxylate (200 g, 1.15 mol), cyanamide (48.3 g, 1.15 mol), and Ni(acac)2 (14.75 g, 0.0574 mol) in dioxane (200 mL) was heated to reflux for 16 h and then cooled to room temperature. The precipitate was filtered off, and the solid was mixed with methanol (200 mL) and stirred for 30 min and filtered again to give 93 g product (44% yield). In a 1 L flask with a reflux condenser was added the product from step one (93.0 g, 0.505 mol) and POCl3 (425 mL) and the reaction mixture was heated to reflux for 35 min. POCl3 (300 mL) was evaporated under vacuum. The residue was poured into ice and water (400 mL), which was neutralized with KOH to pH 6-7. The precipitate was filtered off and extracted with ethyl acetate (2×300 mL). The organic solution was concentrated and purified by column chromatography to give methyl 2-amino-4,6-dichloropyridine-3-carboxylate (22.5 g, 20.1%). In a 500 mL flask with reflux condenser was added methyl 2-amino-4,6-dichloropyridine-3-carboxylate (22.5 g, 0.101 mol) and 25 wt % sodium methoxide in methanol (88 mL, 0.407 mol), together with methanol (20 mL). The mixture was heated to reflux for 5 h then cooled to room temperature. Acetic acid (15 mL) was added to the mixture and the pH was adjusted to ˜7.0. Methanol was removed and the residue was poured into water (100 mL). The precipitated solid was filtered off and rinsed with water (3×200 mL) to give methyl 2-amino-4,6-dimethoxypyridine-3-carboxylate (18.5 g, 86.4%). In a 500 mL flask with a reflux condenser was added methyl 2-amino-4,6-dimethoxypyridine-3-carboxylate (18.5 g, 0.0872 mol), potassium hydroxide (19.5 g, 0.349 mol) in water (80 mL) and ethanol (100 mL). The mixture was heated to 80° C. for 16 h. The solvent was removed and aqueous HCl was used to adjust pH to 6.0. The water was removed by lyophilization. The obtained solid was extracted with methanol to yield 2-amino-4,6-dimethoxy-nicotinic acid in quantitative yield. 2-Amino-4,6-dimethoxy-nicotinic acid (17.2 g, 0.0872 mol) was added to THF (110 mL). 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide hydrochloride (21.73 g, 0.113 mol), 1-hydroxybenzotriazole hydrate (12.96 g, 0.0959 mol) and 4-methyl morpholine (9.7 g, 0.0959 mol) were then added to the suspension. After stirring for 10 min at room temperature, 50% v/v ammonium hydroxide (18.3 g, 0.262 mol) was added. The reaction mixture was kept at room temperature for 16 h. THF was removed and the residue was poured into cold water (100 mL). The precipitate was filtered off and further washed with cold water to yield 5.3 g of the pure desired compound. The aqueous solution was further extracted with dichloromethane (3×150 mL) to yield 8.4 g crude product, which was further purified by column chromatography to give a total of 10.8 g (62.8%) of 2-amino-4,6-dimethoxy-nicotinamide.

1. temperatureIn a 500 mL flask with reflux condenser
2. temperatureThe mixture was heated
3. temperatureto reflux for 5 h
4. customMethanol was removed
5. additionthe residue was poured into water (100 mL)
6. filtrationThe precipitated solid was filtered off
7. washrinsed with water (3×200 mL)