Synthesis
(b) 2,2,6,6-tetramethyl-4-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-3,6-dihydro-2H-pyran-1-yl 1,2,2,3,3,4,4,4-ninafluorobutane-1-sulfonate (43.8 g, 0.100 mol) was dissolved in anhydrous dimethoxyethane (DME, 500 mL ), bis(pinacolato)diboron (27.9 g, 0.109 mol), 1,1'-bis(diphenylphosphino)ferrocene (1.60 g, 2.90 mmol), and potassium acetate (KOAc, 29.4 g, 0.30 mol) were added sequentially. After degassing by sonication under argon protection, a 1:1 complex of [1,1'-bis(diphenylphosphino)-ferrocene]-palladium(II) dichloride with dichloromethane (2.19 g, 2.68 mmol) was added. The reaction mixture was heated and stirred at 80 °C overnight. After completion of the reaction, it was cooled to room temperature and filtered through a diatomaceous earth pad. The filtrate was concentrated under reduced pressure and the resulting residue was purified by silica gel column chromatography (eluent: 0-2% ethyl acetate/hexane) to afford (2,2,6,6-tetramethyl-3,6-dihydro-2H-pyran-4-yl)boronic acid pinacol ester as a white solid (17 g, 64% yield).1H-NMR (CDCl3; 400 MHz): δ 6.40 (t, 1H, J = 1.8 Hz), 1.97 (d, 2H, J = 1.8 Hz), 1.21 (s, 12H), 1.18 (s, 6H), 1.13 (s, 6H).
