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In 1,4-dioxane; ethanol; for 17.5h;Cooling with ice; Reflux;
Stage 3Ethyl 1-pyrimidin-2-yl-5-trifluoromethyl-1H-pyrazole-4-carboxylate An amount of 6.5 g (27 mmol) of ethyl 2-[1-ethoxymethylidene]-4,4,4-trifluoro-3-oxobutyrate was dissolved in ethanol/dioxane and the solution was admixed with 2.99 g (27.1 mmol) of 2-hydrazinopyrimidine with ice-bath cooling. The mixture was stirred at RT for 16 hours and then heated at reflux for a further 1.5 hours, and then evaporated, and the residue was purified by chromatography (cyclohexane/acetone).Yield: 6.08 g (77% of theory) 1H-NMR (D6-DMSO) 1.3 (t, 3H), 4.35 (q, 2H), 7.85 (t, 1H), 8.4 (s, 1H), 9.1 (d, 2H)