Trifluoroacetic acid → 1-(oxan-2-yl)-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole

Participants

Reaction Conditions

Reaction Steps

3,4-Dihydro-2H-pyran (5.6 g, 67 mmol) and trifluoroacetic acid (1.17 g, 10.3 mmol) were added to a solution of 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole (10.0 g, 51.5 mmol) in toluene (200 mL), and the reaction mixture was heated to 90° C. for 2 hours. After cooling to room temperature, the reaction mixture was partitioned between ethyl acetate (200 mL) and saturated aqueous sodium bicarbonate solution (100 mL), and the aqueous layer was extracted with ethyl acetate (100 mL). The combined organic layers were washed with saturated aqueous sodium chloride solution (100 mL), dried over sodium sulfate, filtered, and concentrated in vacuo. Silica gel chromatography (Gradient: 10% to 50% ethyl acetate in petroleum ether) provided the product as a white solid. Yield: 13.4 g, 48.2 mmol, 94%. 1H NMR (400 MHz, CDCl3) δ 7.94 (s, 1H), 7.83 (s, 1H), 5.41 (dd, J=9.5, 2.5 Hz, 1H), 4.01-4.08 (m, 1H), 3.65-3.74 (m, 1H), 1.98-2.18 (m, 3H), 1.6-1.76 (m, 3H), 1.32 (s, 12H).

Provenance & Evidence