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

Participants

Reaction Conditions

Reaction Steps

1-(4-Chloro-3-fluoropyridin-2-yl)-5-methyl-1H-pyrazole-4-carboxylic acid: To a solution of tert-butyl 2-((dimethylamino)methylene)-3-oxobutanoate (0.045 g, 0.211 mmol) in acetonitrile (2 mL) was added TEA (0.030 mL, 0.215 mmol) followed by Intermediate 41B (0.038 g, 0.19 mmol). The dark brown solution was stirred for 1 h at 85° C. The reaction was concentrated, and water (1 mL) and CH2Cl2 (1 mL) were added. The organic layer was concentrated and purified by silica gel chromatography to provide tert-butyl 1-(4-chloro-3-fluoro-pyridin-2-yl)-5-methyl-1H-pyrazole-4-carboxylate as brown oil. MS(ESI) m/z: 312.1 (M+H). 1H NMR (400 MHz, CDCl3) δ 8.39-8.25 (m, 1H), 8.04 (s, 1H), 7.51 (t, J=5.0 Hz, 1H), 2.57 (s, 3H), 1.48 (s, 9H). The oil was stirred with 4 N HCl in dioxane (2 mL) for 12 h at rt. The solution was evaporated to dryness followed by coevaporation with toluene (2×) to give the desired product (12 mg, 22%). MS(ESI) m/z: 256.1 (M+H)+.

Provenance & Evidence