Diisopropylamine → tert-butyl 4-((trimethylsilyl)ethynyl)-1H-pyrazole-1-carboxylate

Participants

Reaction Conditions

Reaction Steps

tert-Butyl 4-iodo-1H-pyrazole-1-carboxylate (2) (4.67 g 15.9 mmole) and trimethylsilyl acetylene (2.18 g, 22.2 mmole) were dissolved in DMF (22 mL) and placed under argon. Diisopropylamine (2.9 mL, 2.08 g, 20.7 mmole), copper(I) iodide (197 mg, 1.03 mmole), triphenylphosphine (832 mg, 3.18 mmole) and palladium acetate (239 mg, 1.06 mmole) were added and the flask was flushed again with argon. The reaction was heated at 60° C. for 1.25 hours. The reaction was cooled and added to water (220 mL). The product was extracted with ether (3×60 mL). The combined extracts were washed with water (3×50 mL) and with brine, then dried and evaporated. The crude product was flash chromatographed (silica, eluting with 10% ethyl acetate in cyclohexane) to give the title compound (3.88 g, 92%). 1H-NMR (CDCl3, 500 MHz): δ 0.25 (s, 6H), 1.67 (s, 9H), 7.77 (d, J=0.63 Hz, 1H), 8.20 (d, J=0.63 Hz, 1H).

Provenance & Evidence