2,2,6,6-Tetramethylpiperidine → 1-(4-chlorophenyl)-5-tributylstannyl-1H-pyrazole

Temperature

-76 °C

In a dry flask, 2,2,6,6-tetramethylpiperidine (0.30 mL, 1.8 mmol) in anhydrous THF (10 mL) under argon was treated with a 1.6M solution of n-butyllithium in hexanes (1.1 mL, 1.8 mmol) at −76° C. during 2 minutes. After stirring for 5 minutes at −76° C., a solution of 1-(4-chlorophenyl)-1H-pyrazole (0.21 g, 1.1 mmol) in anhydrous THF (2 mL) was added over 4 minutes. After stirring for 20 minutes at −76° C., tributyltin chloride (0.30 mL, 1.11 mmol) was added all at once. The resulting mixture was stirred at −76° C. for 10 minutes and at ambient temperature for 5 minutes, then quenched by addition of methanol (1 mL). The mixture was concentrated by rotary evaporation, the residue was taken up in water (20 mL) and washed with ethyl acetate (20 mL). The organic phase was separated, washed with brine (10 mL), dried over anhydrous sodium sulfate, filtered and concentrated by rotary evaporation. Purification of the crude product by flash chromatography on silica with ethyl acetate/n-heptane (1:7) as eluent gave 1-(4-chlorophenyl)-5-tributylstannyl-1H-pyrazole (0.20 g, 40%) as a colourless oil.

1. stirringAfter stirring for 20 minutes at −76° C.
2. stirringThe resulting mixture was stirred at −76° C. for 10 minutes and at ambient temperature for 5 minutes
3. customquenched by addition of methanol (1 mL)
4. concentrationThe mixture was concentrated by rotary evaporation
5. washwashed with ethyl acetate (20 mL)
6. customThe organic phase was separated
7. washwashed with brine (10 mL)
8. dry with materialdried over anhydrous sodium sulfate
9. filtrationfiltered
10. concentrationconcentrated by rotary evaporation
11. customPurification of the crude product by flash chromatography on silica with ethyl acetate/n-heptane (1:7) as eluent

ORD record

ord-c13470c16e4a43a080669129858743c5

Source dataset

uspto-grants-2013_06

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08466284B2