Water → 6-(4-Tert-butyl-phenyl)-4-oxo-4,5-dihydro-pyrazolo[1,5-a]pyrazine-2-carboxylic acid ethyl ester

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Reaction Steps

A solution of 1.04 g (2.71 mmol) 1-[2-(4-tert-butyl-phenyl)-2-oxo-ethyl]-1H-pyrazole-3,5-dicarboxylic acid diethyl ester and 2.08 g (27.1 mmol) ammonium acetate in 20 ml acetic acid is stirred for 44 hours at 110° C. The reaction mixture is cooled to room temperature and excess water is added. The resulting precipitate is filtered off, and washed with water. The residue is chromatographed on a silica gel column with dichloromethane/methanol as eluent to give 6-(4-tert-butyl-phenyl)-4-oxo-4,5-dihydro-pyrazolo[1,5-a]pyrazine-2-carboxylic acid ethyl ester as colourless crystals; HPLC/MS 2.41 (A), [M+H] 340.

Provenance & Evidence