Tert-butyl 2-acetyl-3-(dimethylamino)acrylate → tert-butyl 1-(4-chloropyridin-2-yl)-5-methyl-1H-pyrazole-4-carboxylate

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Reaction Conditions

Reaction Steps

1-(4-Chloropyridin-2-yl)-5-methyl-1H-pyrazole-4-carboxylic acid: To a solution of tert-butyl 2-((dimethylamino)methylene)-3-oxobutanoate (0.032 g, 0.148 mmol) in acetonitrile (2 mL) was added TEA (0.021 mL, 0.148 mmol) and Intermediate 42A (0.024 g, 0.133 mmol). The dark brown solution was heated to 85° C. for 1 h. The reaction mixture was concentrated, and water (1 mL) and CH2Cl2 (1 mL) were added. The organic layer was concentrated and purified by silica gel chromatography to give tert-butyl 1-(4-chloropyridin-2-yl)-5-methyl-1H-pyrazole-4-carboxylate (12 mg, 27%) as yellow oil. MS(ESI) m/z: 294.2 (M+H)+. To the oil was added 4 N HCl in dioxane (2 mL). The reaction was stirred at rt for 4 h, and the clear orange solution was evaporated to dryness followed by coevaporation with toluene (2×) to give the desired product as sticky pink solid. MS(ESI) m/z: 238.2 (M+H)+.

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