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With hydrogen bromide; In ethanol; water; at 50 - 60℃; for 13 - 38h;Product distribution / selectivity;
Example 1; Ethanol (10 ml) suspension of N-{1,4-dioxo-3-[(pyrazin-2-ylmethyl)amino]-1,4-dihydronaphthalen-2-yl}-N-(2-methoxyethyl)acetamide (2.0 g) was mixed with 47% hydrobromic acid (1 ml) and stirred at 50C for 38 hours. After completion of the reaction, the reaction mixture was cooled to room temperature to find precipitation of crystals. This was stirred for 5 hours, and then the crystals were collected by filtration, washed with ethanol and dried to obtain the bromide (alpha-form Crystal) (2.01 g) as orange crystals.; Example 2; Ethanol (680 ml) suspension of N-{1,4-dioxo-3-[(pyrazin-2-ylmethyl)amino]-1,4-dihydronaphthalen-2-yl}-N-(2-methoxyethyl)acetamide (170 g) was mixed with 47% hydrobromic acid (85 ml) and stirred by heating at 60C for 13 hours. At the time of completing the reaction, a small amount of insoluble matter was formed. When this was heat-dissolved by adding ethanol (170 ml) and then spontaneously cooled, crystals were precipitated. They were stirred at room temperature for 24 hours and then collected by filtration and washed with ethanol to obtain 185 g (wet weight) of crude crystals. The crude crystals were recrystallized using a mixed solvent of ethanol (850 ml) and water (85 ml) to obtain the bromide (alpha-form Crystal) (104.80 g). The residue (53.6 g) obtained by concentrating the recrystallization mother liquor was mixed with water (250 ml) and dissolved therein at room temperature. The thus formed insoluble matter was removed by filtration, and the filtrate was concentrated under a reduced pressure to obtain a yellow crystalline residue (53.5 g). The residue was mixed with ethanol (250 ml), suspended and stirred at 50C for 1 hour and then stirred at room temperature for 21 hours. The crystals were collected by filtration and then washed with ethanol and dried to obtain the bromide (beta-form Crystal) (47.34 g).
With hydrogen bromide; In methanol; water; for 5h;Heating / reflux;
Example 3; Methanol (25 ml) suspension of N-{1,4-dioxo-3-[(pyrazin-2-ylmethyl)amino]-1,4-dihydronaphthalen-2-yl}-N-(2-methoxyethyl)acetamide (5 g) was mixed with 47% hydrobromic acid (2.5 ml) and heated under reflux for 5 hours. After completion of the reaction, methanol (15 ml) was evaporated under ordinary pressure. When the residue was spontaneously cooled, crystals were precipitated. They were stirred at room temperature for 15 hours and then mixed with ethyl acetate (40 ml) and further stirred at room temperature for 7 hours. The crystals were collected by filtration, washed and dried to obtain the bromide (P-form Crystal) (4.61 g) as yellow crystals.
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