A suspension of zinc (8.04 g, 123 mmol) in THF (80 mL) was added TMSCl (2.31 ml, 18.2 mmol) at 40° C. The temperature was increased to 55° C. over 30 min. Then, the temperature was lowered to 37° C. and ethyl 2-bromoacetate (12.6 mL, 114 mmol) was added slowly. The resulting solution was stirred for 30 min and cooled from 45° C. to room temperature and stood by for 1 h. The top clear layer (25 mL) was added to a solution of 2-methoxymethyl-4-(tetrahydro-pyran-2-yloxy)-6-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-benzaldehyde (3.56 g, 9.46 mmol) in THF (50 ml) at −78° C. After the addition, the reaction was warmed to 0° C. using an ice bath and stirred at 0° C. 30 min. The reaction mixture was quenched with aqueous NH4Cl and extracted with ethyl acetate. The organic phase was separated, dried (Na2SO4), and concentrated. The residue was purified by the flash column chromatography (silica, hexanes/ethyl acetate=2:1) to afford the title compound (2.30 g, 67%). 1H NMR (300 MHz, CDCl3) δ 7.33 (s, 1H), 7.11 (s, 1H), 5.73-5.70 (m, 1H), 5.46-5.44 (m, 1H), 4.54-4.39 (m, 2H), 4.21-4.16 (q, 2H), 3.94-3.90 (m, 1H), 3.66-3.60 (m, 1H), 3.38 (s, 3H), 3.18-3.11 (m, 1H), 2.43-2.34 (m, 1H), 1.88-1.85 (m, 2H), 1.70-1.61 (m, 4H), 1.26 (t, 3H).
