Reaktion #716442

Reaktionsgleichung

acetic acid

1-(4-fluorophenyl)-1H-pyrazole

n-butyl lithium

2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane

→

title compound

Ausbeute 51.0%

1-(4-Fluoro-phenyl)-5-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-1H-pyrazole

Ausbeute 51.0%

Lösungsmittel

THF

hexane

Reaktionsbedingungen

Aufarbeitung

1. 1
   workup.STIRRINGthe mixture was stirred for 1.5 h at −78° C
2. 2
   workup.WAITto reach room temperature within 1 h
3. 3
   FiltrationThe mixture was filtered
4. 4
   Waschenwas washed with ethyl acetate
5. 5
   Sonstigethe filtrate was evaporated to dryness
6. 6
   SonstigeThe crude product (4.36 g, light brown solid) was purified by flash chromatography on silica gel (heptane/ethyl acetate, 10-50%)

Vorschrift

To a stirred solution of commercially available 1-(4-fluorophenyl)-1H-pyrazole [CAS No 81329-32-0] (2.27 g, 14.0 mmol) in THF (100 ml) was added drop wise at −78° C. under argon atmosphere n-butyl lithium (1.6N in hexane, 10.5 ml, 16.8 mmol. The reaction mixture was allowed to stir for 1 h at −78° C. Afterwards commercially available 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2.84 g, 3.12 ml, 15.0 mmol) was added drop wise at −78° C., and the mixture was stirred for 1.5 h at −78° C. The mixture was allowed to reach room temperature within 1 h, and acetic acid (0.925 g, 881 μl, 15.4 mmol) was added. The mixture was filtered using a Celite pad, which was washed with ethyl acetate, and the filtrate was evaporated to dryness. The crude product (4.36 g, light brown solid) was purified by flash chromatography on silica gel (heptane/ethyl acetate, 10-50%) to yield the title compound as an off-white solid (2.04 g, 51%), MS (ISP) m/z=289.5 [(M+H)+], mp 133° C.

Quelle