反应详情

A solution of 2-hydroxyethylhydrazine (15.2 g, 200 mmol) in ethanol (50 mL) was added over a period of 30 minutes to a solution of ethyl 2,4-dioxopentanoate (31.6 g, 200 mmol) in ethanol (200 mL). The reaction mixture was stirred for an additional 20 minutes and then concentrated under reduced pressure to provide 45 g of ethyl 1-(2-hydroxyethyl)-5-methyl-1H-pyrazole-3-carboxylate a light brown oil. A portion (31.1 g) of this material was combined in a Parr vessel with methanol (25 mL) and concentrated ammonium hydroxide (25 mL). The vessel was sealed and the mixture was heated for 12 hours. The reaction mixture was concentrated under reduced pressure to provide a brown resin. The resin was stirred with a mixture of chloroform and methanol until a solid appeared. The solid was isolated by filtration and then recrystallized from isopropanol to provide 7.01 g of 1-(2-hydroxyethyl)-5-methyl-1H-pyrazole-3-carboxamide as a white solid. The rest of the ester was purified by IFC (silica gel eluting with a gradient of 50 to 100% ethyl acetate in hexanes) to provide 6.6 g of a pale yellow oil. This material was dissolved in concentrated ammonium hydroxide (25 mL) and allowed to stand at ambient temperature for 48 hours. A precipitate was isolated by filtration, rinsed with water, and dried to provide 3.74 g of 1-(2-hydroxyethyl)-5-methyl-1H-pyrazole-3-carboxamide as white needles, mp 170-172° C. Anal. Calcd for C7H11N3O2: C, 49.70; H, 6.55; N, 24.84. Found: C, 49.59; H, 6.65; N, 24.92.

1. concentrationconcentrated under reduced pressure