Step 1: Synthesis of methyl 2-(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)acetate
Methyl 2-(3-bromophenyl)acetate (5.00 g, 21.8 mmol), bis(pinacolato)diboron (11.1 g, 43.7 mmol), and potassium acetate (6.43 g, 65.5 mmol) were dissolved in dioxane (43.7 mL) and degassed by bubbling nitrogen. PdCl2 (dppf)-CH2Cl2 adduct (0.446 g, 0.546 mmol) was added and the reaction mixture was heated to 85 °C and stirred for 4 hours. After completion of the reaction, the reaction mixture was diluted with ethyl acetate (30 mL) and filtered through diatomaceous earth. The organic layer was separated, washed with brine and dried over anhydrous sodium sulfate. The solvent was evaporated under reduced pressure and the residue was purified by silica gel column chromatography (220 g silica gel column, elution gradient 0 to 40% ethyl acetate/hexanes) to afford the target product 3-(2-methoxy-2-oxoethyl)phenylboronic acid pinacol ester (6.00 g, 100%) as a colorless oil. The structure of the product was confirmed by 1H NMR (400 MHz, CDCl3): δ 7.74 (s, 1H), 7.72 (s, 1H), 7.40 (t, J=1.7 Hz, 1H), 7.38-7.33 (m, 1H), 3.70 (s, 3H), 3.65 (s, 2H), 1.36 (s, 12H). lcmS (M+H) = 277.3; HPLC retention time = 0.99 min (column: BEH C18 2.1×50 mm; mobile phase A: water containing 0.05% TFA; mobile phase B: acetonitrile containing 0.05% TFA; gradient: 2-8% B in 1.6 min; flow rate: 0.8 mL/min).
