Pyrazole → tert-Butyl 4-(4-bromo-1H-pyrazol-1-yl)piperidine-1-carboxylate

Participants

Reaction Conditions

Reaction Steps

To a stirred solution of 4-bromo-pyrazole (10.44 g, 71.03 mmol) in anhydrous DMF (96 mL), cooled to 0° C., was slowly added NaH (60% in mineral oil) (3.13 g, 78.133 mmol). The solution was stirred for 1 hour at 0° C. 4-Methanesulfonyloxy-piperidine-1-carboxylic acid tert-butyl ester (19.82 g, 71.03 mmol) was added slowly and the reaction was heated to 100° C. overnight or until consumption of the pyrazole by NMR. The reaction was cooled to room temperature and water added (20 mL) followed by extraction with EtOAc. The combined extracts were washed with saturated aqueous NaCl (4×20 mL), dried with Na2SO4 and concentrated to afford 4-(4-bromo-pyrazol-1-yl)-piperidine-1-carboxylic acid tert-butyl ester as an orange oil. The oil was purified using silica gel chromatography eluting with 10% EtOAc/hexanes to 25% EtOAc/hexanes to provide 4-(4-bromo-pyrazol-1-yl)-piperidine-1-carboxylic acid tert-butyl ester as a white solid (10.55 g, 45% yield) with a Rf=0.4 (25% EtOAc/hexanes, using iodine as the stain). 1H NMR (CDCl3, 400 MHz) δ 7.46 (s, 1H), 7.43 (s, 1H), 4.23 (m, 3H), 2.88 (m, 2H), 2.10 (m, 2H), 1.88 (m, 2H), 1.47 (s, 9H).

Provenance & Evidence