3-FLUORO-5-(4,4,5,5-TETRAMETHYL-[1,3,2]DIOXABOROLAN-2-YL)PYRIDINE

73183-34-3

462652-75-1

719268-92-5

5-Fluoropyridin-3-yl trifluoromethanesulfonate (3.67 g, 15.0 mmol), potassium acetate (2.94 g, 30.0 mmol), bis(pinacolato)diboron (4.18 g, 17.0 mmol), and dichloro[1,1'-bis(diphenylphosphino)ferrocene]palladium(II) dichloromethane (0.37 g, 0.45 mmol) were used in a 45 ml of 1,4-dioxane containing 1% dimethyl sulfoxide, the mixture was degassed with nitrogen for 1 hr and then heated at 90 °C for 14 hrs for the reaction. After completion of the reaction, it was cooled to room temperature and subsequently concentrated under vacuum. To the residue was added 2N sodium hydroxide solution (300 ml), stirred for 10 minutes and filtered. The filtrate was extracted with ether (2 x 200 ml) and the organic phase was discarded. The aqueous phase was cooled to 0°C and the pH was adjusted to 5 by slow dropwise addition of 36% hydrochloric acid over a period of 15 min. The resulting precipitate was allowed to stand at 0°C for 2 h. It was filtered and washed with ice water. The obtained sand-colored solid was dried under vacuum at 300 mmHg in the presence of phosphorus pentoxide to afford 3-fluoro-5-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)pyridine (3.0 g, 90% yield) as a yellow oil. Its NMR hydrogen spectrum (400 MHz, CDCl3) data were as follows: δH 1.25 (12H, s), 7.75 (1H, dd, J=5Hz and 1Hz), 8.52 (1H, d, J=3Hz), 8.74 (1H, s).