Cesium carbonate → tert-butyl 4-[4-(tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazol-1-yl]piperidine-1-carboxylate

Participants

Reaction Conditions

Reaction Steps

A mixture of 4-(4,4,5,5-tetramethyl[1,3,2]dioxaborolan-2-yl)-1H-pyrazole (30.0 g, 154 mmol), 4-methanesulfonyloxypiperidine-1-carboxylic acid tert-butylester (52.5 g, 200 mmol) and cesium carbonate (80.1 g, 246 mmol) in anhydrous DMF (400 mL) was heated to 100° C. for 24 h. DMF was removed under high vacuum. The residue was then diluted with water (200 mL) and extracted with EtOAc (3×200 mL). The combined organic phases were washed with water (3×50 mL) and brine (100 mL), dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. To the orange-brown oily residue was added diisopropyl ether (300 mL), and the mixture was stirred at 0° C. for 2 h. Colorless crystals separated out that were filtered off and dried in vacuo to give a 1st crop of the title compound. The filtrate was then concentrated in vacuo, the residue was mixed with diisopropyl ether (100 mL), a small amount of the 1st crop was added as a seed, and the mixture was stirred overnight. The resulting white precipitate was filtered and dried in vacuo as 2nd crop of the title compound. 1H NMR (300 MHz, CDCl3): δ=1.33 (s, 12H), 1.48 (s, 9H), 1.85-1.93 (m, 2H), 2.15-2.18 (m, 2H), 2.83-2.92 (m, 2H), 4.23-4.39 (m, 3H), 7.76 (s, 1H), 7.84 (s, 1H).

Provenance & Evidence