Triethylamine → tert-butyl 1-(3-fluoro-4-methylpyridin-2-yl)-5-methyl-1H-pyrazole-4-carboxylate

Participants

Reaction Conditions

Reaction Steps

1-(3-Fluoro-4-methylpyridin-2-yl)-5-methyl-1H-pyrazole-4-carboxylic acid: To a solution of tert-butyl 2-((dimethylamino)methylene)-3-oxobutanoate (0.123 g, 0.575 mmol) in acetonitrile (2 mL) was added TEA (0.080 mL, 0.575 mmol) and Intermediate 43A (0.073 g, 0.517 mmol). The orange solution was heated to 85° C. for 1 h. Additional tert-butyl 2-((dimethylamino)methylene)-3-oxobutanoate (0.160 mL) and Et3N (0.080 mL) were added into the solution and the reaction was heated at 85° C. for 1 h. The reaction mixture was concentrated and purified by silica gel chromatography to give tert-butyl 1-(3-fluoro-4-methylpyridin-2-yl)-5-methyl-1H-pyrazole-4-carboxylate as yellow oil. MS(ESI) m/z: 292.1 (M+H)+. 1H NMR (400 MHz, CDCl3) δ 8.26 (d, J=4.8 Hz, 1H), 8.02 (s, 1H), 7.29 (t, J=4.8 Hz, 1H), 2.54 (s, 3H), 2.43 (d, J=1.5 Hz, 3H), 1.58 (s, 9H). To the oil was added 4 N HCl in dioxane (2 mL) and the reaction was stirred at rt for 4 h. The clear orange solution was evaporated to dryness followed by coevaporation with toluene (2×) to give the desired product (15 mg, 11%) as sticky pink solid. MS(ESI) m/z: 236.1 (M+H)+.

Provenance & Evidence