Sodium borohydride → Diethyl 4-(4-chloro-2-aminobenzoyl)-1H-pyrazole-3,5-dicarboxylate

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

Alternatively, the title compound can be prepared as follows: A mixture of nickel acetate (444 g, 1.78 moles) and water (6.6 L) was cooled to 8° C. with stirring under nitrogen; then a solution of sodium borohydride (271 g, 7.16 moles) in water (3.55 L) was added dropwise over 1.5 hours maintaining the reaction temperature between 8° C. and 12° C. The reaction mixture was then stirred for 1.5 hours at 8-12° C. The reaction mixture was filtered through a coarse scintered glass filter funnel, keeping the black filter cake wet (Caution: this black powder may be pyrophoric if allowed to dry.). The filter cake was washed first with water (6×2 L), then with ethanol (2×2 L) and finally with methanol (1 L). The methanol wet filter cake (Ni2B, pyrophoric) was transferred to a 22 L flask with methanol (8 L) . A solution of diethyl 4-(4-chloro-2-nitrobenzoyl)-1H-pyrazole-3,5-dicarboxylate (111.0 g, 0.28 mole) in hydrochloric acid (2.52 L) was added. The reaction mixture was heated to 64° C. and was kept at 64° C. for 6 hours; then was allowed to cool to room temperature and was filtered through CELITE™. The CELITE™ layer was washed with methanol (2×2 L). The filtrate and wash liquors were combined and the methanol was distilled off under water aspirator vacuum. Water (1 L) was added to the reaction and the mixture was filtered. The filter cake was washed with water (2×500 m L) and dried under vacuum at 40° C. to give the title compound as a yellowish solid (98.81 g, 96%).

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