Reacción #10791

Ecuación de reacción

2,4-dimethoxy-5-bromo-benzaldehye

4-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-pyrazole-1-carboxylic acid tert-butyl ester

potassium fluoride

potassium fluoride

→

4-(5-formyl-2,4-dimethoxy-phenyl)-pyrazole-1-carboxylic acid tert-butyl ester

Rendimiento 40.0%

Disolventes

water

Condiciones de reacción

Tratamiento posterior

1. 1
   workup.ADDITIONwas added
2. 2
   Otrodegassed tetrahydrofuran (15 mL)
3. 3
   OtroThe reaction was then quenched by water
4. 4
   ExtracciónThe aqueous solution was extracted with ethyl acetate
5. 5
   LavadoThe solution of ethyl acetate was washed with saturated solution of sodium bicarbonate, brine
6. 6
   Secadodried over sodium sulfate
7. 7
   Concentraciónconcentrated
8. 8
   OtroThe crude product was purified by flash chromatography
9. 9
   LavadoElution with ethyl acetate (50%, v/v, in hexane)

Procedimiento

Ex-74B: To a mixture of 2,4-dimethoxy-5-bromo-benzaldehye (0.28 g, 1.13 mmol), 4-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-pyrazole-1-carboxylic acid tert-butyl ester (Ex-76A, 0.61 g, 1.70 mmol), bis(tri-tert-butylphosphine)palladium (43 mg, 0.085 mmol) and potassium fluoride (0.24 g, 4.08 mmol) was added degassed tetrahydrofuran (15 mL). The reaction mixture was heated at 60° C. for one day. Additional potassium fluoride (0.24 g, 4.08 mmol) and water (20 μL) were added. The reaction mixture continued to stir at 60° C. for another 8 hours. The reaction was then quenched by water. The aqueous solution was extracted with ethyl acetate. The solution of ethyl acetate was washed with saturated solution of sodium bicarbonate, brine, dried over sodium sulfate and concentrated. The crude product was purified by flash chromatography. Elution with ethyl acetate (50%, v/v, in hexane) afforded 4-(5-formyl-2,4-dimethoxy-phenyl)-pyrazole-1-carboxylic acid tert-butyl ester (0.15 g, 40%) as white solid. 1H NMR (CDCl3) δ 10.35 (s, 1H), 8.43 (s, 1H), 8.09 (s, 1H), 8.02 (s, 1H), 6.52 (s, 1H), 4.02 (s, 3H), 3.99 (s, 3H), 1.68 (s, 9H). MS m/z=333 ([M+H]+, 100%).

Fuente